+publisher:"Clemson University" +contributor:("Dr. Xiangchun Xuan")

Clemson University

1. Wright, James Ray, III. Static Pressure Recovery Effects of Conical Diffusers with Swirling Inlet Flow.

Degree: MS, Mechanical Engineering, 2020, Clemson University

URL: https://tigerprints.clemson.edu/all_theses/3363

► Conical diffusers are used in hundreds of engineering applications in various industries. Some of the operating conditions that they operate under cause swirling flow… (more)

Subjects/Keywords: Mechanical Engineering

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APA (6^th Edition):

Wright, James Ray, I. (2020). Static Pressure Recovery Effects of Conical Diffusers with Swirling Inlet Flow. (Masters Thesis). Clemson University. Retrieved from https://tigerprints.clemson.edu/all_theses/3363

Chicago Manual of Style (16^th Edition):

Wright, James Ray, III. “Static Pressure Recovery Effects of Conical Diffusers with Swirling Inlet Flow.” 2020. Masters Thesis, Clemson University. Accessed January 22, 2021. https://tigerprints.clemson.edu/all_theses/3363.

MLA Handbook (7^th Edition):

Wright, James Ray, III. “Static Pressure Recovery Effects of Conical Diffusers with Swirling Inlet Flow.” 2020. Web. 22 Jan 2021.

Vancouver:

Wright, James Ray I. Static Pressure Recovery Effects of Conical Diffusers with Swirling Inlet Flow. [Internet] [Masters thesis]. Clemson University; 2020. [cited 2021 Jan 22]. Available from: https://tigerprints.clemson.edu/all_theses/3363.

Council of Science Editors:

Wright, James Ray I. Static Pressure Recovery Effects of Conical Diffusers with Swirling Inlet Flow. [Masters Thesis]. Clemson University; 2020. Available from: https://tigerprints.clemson.edu/all_theses/3363

Clemson University

2. Dhingra, Devakar. Thermo-physical Property Models and Effect on Heat Pipe Modelling.

Degree: ME, Mechanical Engineering, 2014, Clemson University

URL: https://tigerprints.clemson.edu/all_theses/2052

► Heat transfer devices find applications in various aspects of life. Be it residential, commercial or industrial application, efficient heat transfer is a challenge to… (more)

▼ Heat transfer devices find applications in various aspects of life. Be it residential, commercial or industrial application, efficient heat transfer is a challenge to all. Other than geometric design considerations and wick selection, the optimization of heat transfer in the heat pipe also depends on fluid selection. Heat pipe technology has proven to work efficiently with properly selected thermal fluid, from cryogenic temperatures to very high temperatures. Higher heat transfer ability through small temperature differences makes the heat pipe an efficient technology. Hence, it can be stated that selecting a proper working fluid enhances the heat transfer performance of a heat pipe. For selecting the working fluid, important thermo-physical properties to be considered are density, viscosity, surface tension, latent heat of vaporization and vapor saturation pressure at every working temperature. The operating range of the working fluid starts from the triple point and till the critical point. The performance of the working fluid is not optimum at both ends of the operating range of temperature. At critical temperature, it is impacted by low surface tension and latent heat of vaporization, whereas near the triple point low vapor density and high viscosity affects the performance. One of the first indices for evaluating the performance of the working fluid is called 'Merit Number' This merit number considers a single pressure gradient, i.e. the liquid pressure drop. Later, substantial works have been done to implement the same idea in a system utilizing multiple pressure gradients (losses). In all the methods comparing the merit number of the fluids, the higher the merit number, better is the heat transfer capacity of the pipe. For theoretical calculations and geometrical design considerations, thermo-physical property data of the working fluid at every operating temperature is not available and if available, the reliability of this data is a reason of concern. The present work constitutes of dividing the working fluids into two main categories polar fluids (i.e. ammonia, water and methanol) and nonpolar fluids (i.e. ethane) and thus validating the methods used for formulating these thermo-physical properties as a function of temperature. As per conventional available data (in several reliable resources), these thermo-physical properties are formulated as a polynomial function of the temperature. The main problem though with such formulation is the data reliability outside the specified temperature range. This work tries to formulate such properties as a function of intensive properties and molecular structure of the working fluid. Thereafter the most useful method for thermo-physical property formulation was chosen after calculating the error percentage (relating to the experimental data obtained from various sources) The latter part of this work focuses on the uncertainty of the value about the mean obtained from the methods used and thereafter the percent deviation (between the mean obtained and the experimental… Advisors/Committee Members: Dr. Jay M. Ochterbeck, Dr. Xiangchun Xuan, Dr. Chenning Tong.

Subjects/Keywords: Mechanical Engineering

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APA (6^th Edition):

Dhingra, D. (2014). Thermo-physical Property Models and Effect on Heat Pipe Modelling. (Thesis). Clemson University. Retrieved from https://tigerprints.clemson.edu/all_theses/2052

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Chicago Manual of Style (16^th Edition):

Dhingra, Devakar. “Thermo-physical Property Models and Effect on Heat Pipe Modelling.” 2014. Thesis, Clemson University. Accessed January 22, 2021. https://tigerprints.clemson.edu/all_theses/2052.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7^th Edition):

Dhingra, Devakar. “Thermo-physical Property Models and Effect on Heat Pipe Modelling.” 2014. Web. 22 Jan 2021.

Vancouver:

Dhingra D. Thermo-physical Property Models and Effect on Heat Pipe Modelling. [Internet] [Thesis]. Clemson University; 2014. [cited 2021 Jan 22]. Available from: https://tigerprints.clemson.edu/all_theses/2052.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Dhingra D. Thermo-physical Property Models and Effect on Heat Pipe Modelling. [Thesis]. Clemson University; 2014. Available from: https://tigerprints.clemson.edu/all_theses/2052

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Clemson University

3. Quinones, Matthew. Numerical Analysis of Scramjet Cavity Flameholders at Varying Flight Mach Numbers.

Degree: MS, Mechanical Engineering, 2018, Clemson University

URL: https://tigerprints.clemson.edu/all_theses/3010

► Various types of air breathing engines are used as propulsion devices in aviation. At high flight velocities, the use of a ramjet or supersonic combustion… (more)

Subjects/Keywords: Flame holder; Flame stability; Ramjet; Scramjet

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APA (6^th Edition):

Quinones, M. (2018). Numerical Analysis of Scramjet Cavity Flameholders at Varying Flight Mach Numbers. (Masters Thesis). Clemson University. Retrieved from https://tigerprints.clemson.edu/all_theses/3010

Chicago Manual of Style (16^th Edition):

Quinones, Matthew. “Numerical Analysis of Scramjet Cavity Flameholders at Varying Flight Mach Numbers.” 2018. Masters Thesis, Clemson University. Accessed January 22, 2021. https://tigerprints.clemson.edu/all_theses/3010.

MLA Handbook (7^th Edition):

Quinones, Matthew. “Numerical Analysis of Scramjet Cavity Flameholders at Varying Flight Mach Numbers.” 2018. Web. 22 Jan 2021.

Vancouver:

Quinones M. Numerical Analysis of Scramjet Cavity Flameholders at Varying Flight Mach Numbers. [Internet] [Masters thesis]. Clemson University; 2018. [cited 2021 Jan 22]. Available from: https://tigerprints.clemson.edu/all_theses/3010.

Council of Science Editors:

Quinones M. Numerical Analysis of Scramjet Cavity Flameholders at Varying Flight Mach Numbers. [Masters Thesis]. Clemson University; 2018. Available from: https://tigerprints.clemson.edu/all_theses/3010

Clemson University

4. Deshpande, Saurabh Satish. Measurement of Slip Velocity and Lift Coefficient for Laterally Focused Particles in an Inertial Flow through a Spiral Microfluidic Channel.

Degree: MS, Mechanical Engineering, 2016, Clemson University

URL: https://tigerprints.clemson.edu/all_theses/2477

► Microfluidic channels with a spiral geometry are extensively researched for their use in particle focusing, separation and identification. Instead of using electrophoresis, magnetophoresis, etc., spiral… (more)

▼ Microfluidic channels with a spiral geometry are extensively researched for their use in particle focusing, separation and identification. Instead of using electrophoresis, magnetophoresis, etc., spiral channel takes advantage of the Inertial Lift Force along with the Viscous Drag to achieve size based separation of particles. Inertial microfluidic channel can have high throughput and are much safer to use for live cell separation and other physiological fluids processing. A particle flowing freely in a spiral microchannel at low Reynolds number inertial flow, attains lateral equilibrium due to balance of Inertial Lift force and the viscous Dean Drag. The inertial lift forces are primarily due to the wall effect and the shear gradient of the fluid flow profile. Much theoretical research has been done in this field to explain the lateral migration of a particle in an inertial fluid flow. Notable contributions were made by Saffman (1965), Ho and Leal (1974) and later Vasseur and Cox (1976) in explaining the lift force on a particle theoretically. All these and many other theoretical models developed in the last few decades discuss Lift force being dependent on the particle slip velocity. Additionally many models including the one developed by Saffman predicts a linear dependence of Lift force on the slip velocity of particle. But it seems that the microfluidic community has ignored this dependence with the result that several hypotheses and models exist in which the slip velocity is nonexistent. The measurement of slip velocities for particles has never been done in the field of microfluidics. The current study aims to do so and bridge the gap in understanding the Lift force responsible for the lateral migration of particles. The focused particle’s velocity when it passes through the outer arm of the spiral microfluidic device is measured experimentally followed by a computational study (using COMSOL Multiphysics) to obtain the undisturbed fluid flow velocity through the spiral arm. To calculate the slip velocity, identification of focusing positions in the horizontal and vertical plane of the channel is necessary. Identification in horizontal plane is easy by simply observing the channel under microscope. To identify the vertical focusing positions, a high speed camera (Photron SA-4) coupled with a Nikon microscope and a 50x objective lens (depth of focus = 0.9 um) is used. The narrow depth of focus of objective lens coupled with the precise movement of microfluidic device in the vertical plane is used to identify the height of focused particles from the channel bottom. A focus-measure of all the acquired images is calculated (using a Matlab script which calculates the global variance of an image as a focus-measure) followed by its statistical distribution to obtain the particle’s vertical location within an error of ±5 um. Velocity of the particles for all the focused positions is now calculated using a Matlab script which detects the particles from the acquired images and traces it across successive frames. At the… Advisors/Committee Members: Dr. Phanindra Tallapragada, Committee Chair, Dr. Xiangchun Xuan, Dr. Melur Ramasubramanian.

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Deshpande, S. S. (2016). Measurement of Slip Velocity and Lift Coefficient for Laterally Focused Particles in an Inertial Flow through a Spiral Microfluidic Channel. (Masters Thesis). Clemson University. Retrieved from https://tigerprints.clemson.edu/all_theses/2477

Chicago Manual of Style (16^th Edition):

Deshpande, Saurabh Satish. “Measurement of Slip Velocity and Lift Coefficient for Laterally Focused Particles in an Inertial Flow through a Spiral Microfluidic Channel.” 2016. Masters Thesis, Clemson University. Accessed January 22, 2021. https://tigerprints.clemson.edu/all_theses/2477.

MLA Handbook (7^th Edition):

Deshpande, Saurabh Satish. “Measurement of Slip Velocity and Lift Coefficient for Laterally Focused Particles in an Inertial Flow through a Spiral Microfluidic Channel.” 2016. Web. 22 Jan 2021.

Vancouver:

Deshpande SS. Measurement of Slip Velocity and Lift Coefficient for Laterally Focused Particles in an Inertial Flow through a Spiral Microfluidic Channel. [Internet] [Masters thesis]. Clemson University; 2016. [cited 2021 Jan 22]. Available from: https://tigerprints.clemson.edu/all_theses/2477.

Council of Science Editors:

Deshpande SS. Measurement of Slip Velocity and Lift Coefficient for Laterally Focused Particles in an Inertial Flow through a Spiral Microfluidic Channel. [Masters Thesis]. Clemson University; 2016. Available from: https://tigerprints.clemson.edu/all_theses/2477

Clemson University

5. Lu, Xinyu. Particle Transport Phenomena in Non-Newtonian Microfluidics.

Degree: PhD, Mechanical Engineering, 2016, Clemson University

URL: https://tigerprints.clemson.edu/all_dissertations/1716

► In the past two decades, microfluidic devices have become attractive platforms for many chemical and biomedical applications due to their enhanced efficiency and accuracy at… (more)

▼ In the past two decades, microfluidic devices have become attractive platforms for many chemical and biomedical applications due to their enhanced efficiency and accuracy at a reduced cost. Many of the fluids encountered in these applications exhibit non-Newtonian behaviors. However, the majority of current particle transport studies have been limited in Newtonian fluids only. Very little work has been done on particle transport in non-Newtonian fluids. This dissertation presents experimental and numerical studies of particle transport phenomena in both electric field- and pressure-driven flows in non-Newtonian fluids through microchannels. In the first part, electrokinetic transport phenomena are investigated in viscoelastic polymer solutions though a constricted microchannel. The first experimental study of particle electrophoresis shows an oscillatory particle motion in the constriction region. This oscillatory motion is affected by the electric field magnitude, particle size and fluid elasticity (i.e., polymer concentration). Then the viscoelastic effect on electrokinetic particle focusing is presented via the study of particle charge effect. The particle focusing trend observed is opposite to that in a Newtonian fluid when the electric field varies. Particle aggregation phenomena are also found at high electric fields. These phenomena are speculated to be a consequence of the fluid viscoelasticity effects. Inspired by the interesting electrokinetic particle transport phenomena, the flow visualization study in the viscoelastic fluid is conducted by using small fluorescent particles as trackers. It is showed that the small particle trajectories, which represent the electroosmotic flow streamlines, are significantly different from those in the Newtonian fluid at the upstream of the microchannel constriction due to the viscoelastic instability. The 2D numerical result of Oldroyd-B model obtains a smaller flow rate than the Newtonian one, but fails to predict the deflected particle trajectories via Lagrangian particle tracking method. In the second part, comprehensive studies are performed for particle transport in pressure driven flows through straight rectangular microchannels. A continuous size-based separation is achieved via elasto-inertial pinched flow fractionation (eiPFF). The separation is found to be affected by the flow rate, polymer concentration and channel aspect ratio significantly. Then elasto-inertial particle focusing is studied, which also demonstrates a sheath-free particle separation. An interesting trend has been observed that the particle size (blockage ratio) plays a less significant role on the particle equilibrium position with the increase of channel aspect ratio. Shear-thinning effect is studied in Polyvinylpyrrolidone (PAA) solutions of varied glycerol concentrations in a near-slit channel, which has been demonstrated to inhibit the elastic lift and deflect particles towards the walls. The 2D numerical studies of the particle motion via Oldroyd-B and Giesekus models are qualitatively… Advisors/Committee Members: Dr. Xiangchun Xuan, Committee Chair, Dr. Donald Beasley, Dr. Richard Figliola, Dr. Chenning Tong.

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Lu, X. (2016). Particle Transport Phenomena in Non-Newtonian Microfluidics. (Doctoral Dissertation). Clemson University. Retrieved from https://tigerprints.clemson.edu/all_dissertations/1716

Chicago Manual of Style (16^th Edition):

Lu, Xinyu. “Particle Transport Phenomena in Non-Newtonian Microfluidics.” 2016. Doctoral Dissertation, Clemson University. Accessed January 22, 2021. https://tigerprints.clemson.edu/all_dissertations/1716.

MLA Handbook (7^th Edition):

Lu, Xinyu. “Particle Transport Phenomena in Non-Newtonian Microfluidics.” 2016. Web. 22 Jan 2021.

Vancouver:

Lu X. Particle Transport Phenomena in Non-Newtonian Microfluidics. [Internet] [Doctoral dissertation]. Clemson University; 2016. [cited 2021 Jan 22]. Available from: https://tigerprints.clemson.edu/all_dissertations/1716.

Council of Science Editors:

Lu X. Particle Transport Phenomena in Non-Newtonian Microfluidics. [Doctoral Dissertation]. Clemson University; 2016. Available from: https://tigerprints.clemson.edu/all_dissertations/1716

Clemson University

6. Liu, Xuchen. Particle Separation Using Electrokinetically-Driven Deterministic Lateral Displacement: A Computational Study.

Degree: MS, Mechanical Engineering, 2016, Clemson University

URL: https://tigerprints.clemson.edu/all_theses/2458

► Electrokinetically-driven deterministic lateral displacement (e-DLD) is a recently proposed technique for continuous, two-dimensional fractionation of particle suspensions in microfluidic platforms. It utilizes the negative dielectrophoretic… (more)

▼ Electrokinetically-driven deterministic lateral displacement (e-DLD) is a recently proposed technique for continuous, two-dimensional fractionation of particle suspensions in microfluidic platforms. It utilizes the negative dielectrophoretic force that is induced by the DC electric field gradients formed around an array of regularly spaced posts. While e-DLD devices have been demonstrated to be able to separate particles by size, a fundamental understanding of the separation process and the factors that affect the separation is still lacking. This thesis is aimed to answer these questions using a computational study of electrokinetic particle transport and separation in e-DLD devices. We first numerically prove a continuous, two-dimensional separation of 5 μm, 10 μm and 15 μm-diameter rigid circular particles in an e-DLD device. These particles can be viewed as good mimics of red blood cells, white blood cells and tumor cells, respectively, in blood. A number of features are observed in the kinetics of particles, including directional locking and sharp transitions between migration angles upon variations in the direction of the force, which are advantageous for high-resolution two-dimensional separation.We then discuss several factors that affect the separation of particles in the proposed e-DLD device, such as electric field, forcing angle, post gap ratio, post shape and particle shape. We find that the electric field influences the particle separation by affecting the electric field gradient. The larger electric field, the larger electric field gradient will be. We also investigate the orientation of the driving field with respect to the array of posts and find that, at specific forcing-angles, particles of different sizes migrate in different directions, enabling continuous, two-dimensional separation in electrokinetic flow. Moreover, we study the effect of the post gap ratio on particle separation. The smaller the ratio, the larger the electric field gradient will be around the posts, so particles will more easily get deflected away from the posts due to the enhanced negative dielectrophoretic force. In addition, we find that the shape of posts plays an important role in particle separation. Using equilateral triangular posts, we are able to separate smaller particles as compared to the traditional circular posts under the same conditions. We also look into the effect of particle shape on separation in e-DLD. It is found that an elliptic particle behaves like a smaller sized circular particle due to its preferred orientation in electric field. Therefore, we can easily achieve the separation of circular and elliptic particles with an equal surface area. In the end, we compare e-DLD with the traditional pressure-driven DLD. With the same geometry, e-DLD device is capable of separating much smaller particles. Alternatively, pressure-driven DLD requires a smaller gap size and/or a smaller forcing angle to implement the same particle separation which will… Advisors/Committee Members: Dr. Xiangchun Xuan, Committee Chair, Dr. Lonny Thompson, Dr. Rodrigo Martinez-Duarte.

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6^th Edition):

Liu, X. (2016). Particle Separation Using Electrokinetically-Driven Deterministic Lateral Displacement: A Computational Study. (Masters Thesis). Clemson University. Retrieved from https://tigerprints.clemson.edu/all_theses/2458

Chicago Manual of Style (16^th Edition):

Liu, Xuchen. “Particle Separation Using Electrokinetically-Driven Deterministic Lateral Displacement: A Computational Study.” 2016. Masters Thesis, Clemson University. Accessed January 22, 2021. https://tigerprints.clemson.edu/all_theses/2458.

MLA Handbook (7^th Edition):

Liu, Xuchen. “Particle Separation Using Electrokinetically-Driven Deterministic Lateral Displacement: A Computational Study.” 2016. Web. 22 Jan 2021.

Vancouver:

Liu X. Particle Separation Using Electrokinetically-Driven Deterministic Lateral Displacement: A Computational Study. [Internet] [Masters thesis]. Clemson University; 2016. [cited 2021 Jan 22]. Available from: https://tigerprints.clemson.edu/all_theses/2458.

Council of Science Editors:

Liu X. Particle Separation Using Electrokinetically-Driven Deterministic Lateral Displacement: A Computational Study. [Masters Thesis]. Clemson University; 2016. Available from: https://tigerprints.clemson.edu/all_theses/2458

Clemson University

7. Zhao, Yu. An Integrative Approach to Elucidating the Governing Mechanisms of Particles Movement under Dielectrophoretic and Other Electrokinetic Phenomena.

Degree: PhD, Bioengineering, 2017, Clemson University

URL: https://tigerprints.clemson.edu/all_dissertations/1956

► Dielectrophoresis (DEP) has been a subject of active research in the past decades and has shown promising applications in Lab-on-Chip devices. Currently researchers use the… (more)

▼ Dielectrophoresis (DEP) has been a subject of active research in the past decades and has shown promising applications in Lab-on-Chip devices. Currently researchers use the point dipole method to predict the movement of particles under DEP and guide their experimental designs. For studying the interaction between particles, the Maxwell Stress Tensor (MST) method has been widely used and treated as providing the most robust and accurate solution. By examining the derivation processes, it became clear that both methods have inherent limitations and will yield incorrect results in certain occasions. To overcome these limitations and advance the theory of DEP, a new numerical approach based on volumetric-integration has been established. The new method has been proved to be valid in quantifying the DEP forces with both homogeneous and non-homogeneous particles as well as particle-particle interaction through comparison with the other two methods. Based on the new method, a new model characterizing the structure of electric double layer (EDL) was developed to explain the crossover behavior of nanoparticles in medium. For bioengineering applications, this new method has been further expanded to construct a complete cell model. The cell model not only captures the common crossover behavior exhibited by cells, it also explains why cells would initiate self-rotation under DEP, a phenomenon we first observed in our experiments. To take a step further, the new method has also been applied to investigate the interaction between multiple particles. In particular, this new method has been proved to be powerful in elucidating the underlying mechanism of the tumbling motion of pearl chains in a flow condition as we observed in our experiments. Moreover, it also helps shed some new insight into the formation of different alignments and configurations of ellipsoidal particles. Finally, with the consideration of the Faradic current from water electrolysis and effect of pH, a new model has been developed to explain the causes for the intriguing flow reversal phenomenon commonly observed (but not at all understood) in AC-electroosmosis (ACEO) with reasonable outcomes. Advisors/Committee Members: Dr. Guigen Zhang, Committee Chair, Dr. Bruce Gao, Dr. Rodrigo Martinez-Duarte, Dr. Xiangchun Xuan.

Subjects/Keywords: AC-electroosmosis; Dielectrophoresis; Electric double layer; Self-rotation of cell; Tumbling motion; Volumetric-integration method

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APA (6^th Edition):

Zhao, Y. (2017). An Integrative Approach to Elucidating the Governing Mechanisms of Particles Movement under Dielectrophoretic and Other Electrokinetic Phenomena. (Doctoral Dissertation). Clemson University. Retrieved from https://tigerprints.clemson.edu/all_dissertations/1956

Chicago Manual of Style (16^th Edition):

Zhao, Yu. “An Integrative Approach to Elucidating the Governing Mechanisms of Particles Movement under Dielectrophoretic and Other Electrokinetic Phenomena.” 2017. Doctoral Dissertation, Clemson University. Accessed January 22, 2021. https://tigerprints.clemson.edu/all_dissertations/1956.

MLA Handbook (7^th Edition):

Zhao, Yu. “An Integrative Approach to Elucidating the Governing Mechanisms of Particles Movement under Dielectrophoretic and Other Electrokinetic Phenomena.” 2017. Web. 22 Jan 2021.

Vancouver:

Zhao Y. An Integrative Approach to Elucidating the Governing Mechanisms of Particles Movement under Dielectrophoretic and Other Electrokinetic Phenomena. [Internet] [Doctoral dissertation]. Clemson University; 2017. [cited 2021 Jan 22]. Available from: https://tigerprints.clemson.edu/all_dissertations/1956.

Council of Science Editors:

Zhao Y. An Integrative Approach to Elucidating the Governing Mechanisms of Particles Movement under Dielectrophoretic and Other Electrokinetic Phenomena. [Doctoral Dissertation]. Clemson University; 2017. Available from: https://tigerprints.clemson.edu/all_dissertations/1956

Clemson University

8. Wang, Tianwei (Thomas). Investigation of Advanced Engine Cooling Systems - Optimization and Nonlinear Control.

Degree: PhD, Mechanical Engineering, 2016, Clemson University

URL: https://tigerprints.clemson.edu/all_dissertations/1647

► Advanced automotive engine cooling systems can positively impact the performance, fuel economy, and reliability of internal combustion engines. A smart engine cooling system typically features… (more)

▼ Advanced automotive engine cooling systems can positively impact the performance, fuel economy, and reliability of internal combustion engines. A smart engine cooling system typically features multiple real time computer controlled actuators: a three way linear smart valve, a variable speed coolant pump, and electric radiator fan(s). In this dissertation, several innovative comprehensive nonlinear control and optimization operation strategies for the next generation smart cooling application will be analyzed. First, the optimal control has been investigated to minimize the electric energy usage of radiator fan matrix. A detailed mathematical model of the radiator fan(s) matrix operation and the forced convection heat transfer process was developed to establish a mixed integer nonlinear programming problem. An interior points approach was introduced to solve the energy consumption minimization problem. A series of laboratory tests have been conducted with different fan configurations and rotational shaft speed combinations, with the objective to cool a thermal loaded engine. Both the mathematical approach and the laboratory test results demonstrated the effectiveness of similar control strategies. Based on the tests data and mathematical analysis, an optimization control strategy reduced the fan matrix power consumption by up to 67%. Second, a series of experimental laboratory tests were implemented to investigate the contributions of each electro-mechanical device in automotive thermal management system. The test results established a basis for several key operating conclusions. The smart valve and variable speed pump impacted the engine temperature by adjusting the heat transfer rate between the engine and the radiator through coolant redirection and/or coolant flow rate. On the other hand, the radiator fan(s) operation affects the engine's temperature by modifying the heat rejection rate of the radiator which can influence the entire cooling system. In addition, the smart valve's operation changes the engine's temperature magnitude the greatest amount followed by the radiator fan(s) and the coolant pump. Furthermore, from a power consumption aspect, the radiator fan(s) consumes the most engine power in comparison to the two other actuators. Third, a Lyapunov based nonlinear control strategy for the radiator fan matrix was studied to accommodate transient engine temperature tracking at heavy heat load. A reduced order mathematical model established a basis for the closed-loop real time feedback system. Representative numerical and experimental tests demonstrated that the advanced control strategy can regulate the engine temperature tracking error within 0.12Â°C and compensate the unknown heat load. The nonlinear controller provided superior performance in terms of power consumption and temperature tracking as evident by the reduced magnitude when compared to a classical proportional integral with lookup table based controller and a bang bang controller. Fourth, a nonlinear adaptive… Advisors/Committee Members: Dr. John Wagner, Committee Chair, Dr. Georges Fadel, Dr. Xiangchun Xuan, Dr. Todd Schweisinger.

Subjects/Keywords: Energy Conservation; Experimental Test; Nonlinear Control; Optimization Control; Powertrain Cooling System; Thermal Management

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APA (6^th Edition):

Wang, T. (. (2016). Investigation of Advanced Engine Cooling Systems - Optimization and Nonlinear Control. (Doctoral Dissertation). Clemson University. Retrieved from https://tigerprints.clemson.edu/all_dissertations/1647

Chicago Manual of Style (16^th Edition):

Wang, Tianwei (Thomas). “Investigation of Advanced Engine Cooling Systems - Optimization and Nonlinear Control.” 2016. Doctoral Dissertation, Clemson University. Accessed January 22, 2021. https://tigerprints.clemson.edu/all_dissertations/1647.

MLA Handbook (7^th Edition):

Wang, Tianwei (Thomas). “Investigation of Advanced Engine Cooling Systems - Optimization and Nonlinear Control.” 2016. Web. 22 Jan 2021.

Vancouver:

Wang T(. Investigation of Advanced Engine Cooling Systems - Optimization and Nonlinear Control. [Internet] [Doctoral dissertation]. Clemson University; 2016. [cited 2021 Jan 22]. Available from: https://tigerprints.clemson.edu/all_dissertations/1647.

Council of Science Editors:

Wang T(. Investigation of Advanced Engine Cooling Systems - Optimization and Nonlinear Control. [Doctoral Dissertation]. Clemson University; 2016. Available from: https://tigerprints.clemson.edu/all_dissertations/1647

Clemson University

9. Korucu, Ayse. Analysis of High Pressure H2/O2, H2/AIR AND KEROSENE/AIR Reacting Shear Flows.

Degree: PhD, Mechanical Engineering, 2016, Clemson University

URL: https://tigerprints.clemson.edu/all_dissertations/1837

► Direct Numerical Simulation (DNS) data for high pressure H₂/O₂ and H₂/Air flames using the compressible flow formulation, detailed kinetics, a real fluid equation of state,… (more)

▼ Direct Numerical Simulation (DNS) data for high pressure H₂/O₂ and H₂/Air flames using the compressible flow formulation, detailed kinetics, a real fluid equation of state, and generalized diffusion are analyzed. The DNS is filtered over a range of filter widths to provide exact terms in the Large Eddy Simulation (LES) governing equations, including unclosed terms. The filtered heat flux vector is extensively compared with the heat flux vector calculated as a function of the filtered primitive variables (i.e. the exact LES term is compared with its form available within an actual LES). The difference between these forms defines the subgrid heat flux vector. The analyses are done both globally across the entire flame, as well as by conditionally averaging over specific regions of the flame; including regions of large subgrid kinetic energy, subgrid scalar dissipation, subgrid temperature variance, flame temperature, etc. In this work, both the subgrid heat flux vector and its divergence are found to be substantially larger in reacting flows in comparison with mixing due to the associated larger temperature gradients. However, the divergence of the subgrid heat flux vector tends to be significantly smaller than other unclosed terms in the energy equation with decreasing significance with increasing Reynolds number. Then a reduced (29 step, 10 species) Kerosene/Air mechanism including a semi-global soot formation/oxidation model associated with an optically thin medium radiative heat flux model has been added to the same code to investigate soot formation/oxidation processes in a temporarily developing hydrocarbon flame operating at both atmospheric and elevated pressures for both a real gas law (RGL) and the ideal gas law (IGL) equations of state (EOS). Btoh 3D the RGL and the IGL EOS predictions of the soot formation/oxidation processes good agreement with the limited literature of atmospheric pressure flames [45, 46, 96] has been achieved. High values of the soot volume fraction have been shown to be independent from high temperature flame regions by occupying the flame volumes whose temperature varies from 1300 K to 1800 K. Additionally, the soot number density has been shown to be highly dependent on the temperature, while the soot volume fraction is dominated by local flow characteristics which is also in good agreement with Ref. [96]. Lignell et al. [46, 45] have reported two distinct behaviors of soot mass fraction: I- the slow soot nucleation process has caused the soot mass fraction to be widely scattered in the flame, and II - turbulent transportation has carried the soot to the fuel rich region emphasizing the importance of the turbulence transportation in sooting flames. Similar behavior has also been observed in the current work. The soot generation rate has been shown to have a similar trend with soot mass fraction, while Lignell et al. [45, 46] have observed a high dependency on flame temperature for the soot generation rate. … Advisors/Committee Members: Dr. Richard S. Miller, Committee Chair, Dr. Donald E. Beasley, Dr. Richard S. Figliola, Dr. Xiangchun Xuan.

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APA (6^th Edition):

Korucu, A. (2016). Analysis of High Pressure H2/O2, H2/AIR AND KEROSENE/AIR Reacting Shear Flows. (Doctoral Dissertation). Clemson University. Retrieved from https://tigerprints.clemson.edu/all_dissertations/1837

Chicago Manual of Style (16^th Edition):

Korucu, Ayse. “Analysis of High Pressure H2/O2, H2/AIR AND KEROSENE/AIR Reacting Shear Flows.” 2016. Doctoral Dissertation, Clemson University. Accessed January 22, 2021. https://tigerprints.clemson.edu/all_dissertations/1837.

MLA Handbook (7^th Edition):

Korucu, Ayse. “Analysis of High Pressure H2/O2, H2/AIR AND KEROSENE/AIR Reacting Shear Flows.” 2016. Web. 22 Jan 2021.

Vancouver:

Korucu A. Analysis of High Pressure H2/O2, H2/AIR AND KEROSENE/AIR Reacting Shear Flows. [Internet] [Doctoral dissertation]. Clemson University; 2016. [cited 2021 Jan 22]. Available from: https://tigerprints.clemson.edu/all_dissertations/1837.

Council of Science Editors:

Korucu A. Analysis of High Pressure H2/O2, H2/AIR AND KEROSENE/AIR Reacting Shear Flows. [Doctoral Dissertation]. Clemson University; 2016. Available from: https://tigerprints.clemson.edu/all_dissertations/1837

10. Hasabnis, Nilesh Sudhir. Inertial Focusing in Spiral Microchannels.

Degree: MS, Mechanical Engineering, 2015, Clemson University

URL: https://tigerprints.clemson.edu/all_theses/2127

► The ability to control and manipulate the motion of particles or bio-cells from a complex mixture has been the center of attention since the beginning… (more)

Subjects/Keywords: Inertial Flow; Microfluidics; Particle Separation; Spiral Microchannels

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APA (6^th Edition):

Hasabnis, N. S. (2015). Inertial Focusing in Spiral Microchannels. (Masters Thesis). Clemson University. Retrieved from https://tigerprints.clemson.edu/all_theses/2127

Chicago Manual of Style (16^th Edition):

Hasabnis, Nilesh Sudhir. “Inertial Focusing in Spiral Microchannels.” 2015. Masters Thesis, Clemson University. Accessed January 22, 2021. https://tigerprints.clemson.edu/all_theses/2127.

MLA Handbook (7^th Edition):

Hasabnis, Nilesh Sudhir. “Inertial Focusing in Spiral Microchannels.” 2015. Web. 22 Jan 2021.

Vancouver:

Hasabnis NS. Inertial Focusing in Spiral Microchannels. [Internet] [Masters thesis]. Clemson University; 2015. [cited 2021 Jan 22]. Available from: https://tigerprints.clemson.edu/all_theses/2127.

Council of Science Editors:

Hasabnis NS. Inertial Focusing in Spiral Microchannels. [Masters Thesis]. Clemson University; 2015. Available from: https://tigerprints.clemson.edu/all_theses/2127

11. Mitra, Arnab. Asynchronous propulsion of the three sphere micro-swimmer using perturbed magnetic field.

Degree: MS, Mechanical Engineering, 2018, Clemson University

URL: https://tigerprints.clemson.edu/all_theses/2998

► In recent years much effort have been placed on development of microscale devices capable of propulsion in low Reynold number environment. These devices have potential… (more)

Subjects/Keywords: 3-sphere swimmer; Asynchronous; Micro-swimmers

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APA (6^th Edition):

Mitra, A. (2018). Asynchronous propulsion of the three sphere micro-swimmer using perturbed magnetic field. (Masters Thesis). Clemson University. Retrieved from https://tigerprints.clemson.edu/all_theses/2998

Chicago Manual of Style (16^th Edition):

Mitra, Arnab. “Asynchronous propulsion of the three sphere micro-swimmer using perturbed magnetic field.” 2018. Masters Thesis, Clemson University. Accessed January 22, 2021. https://tigerprints.clemson.edu/all_theses/2998.

MLA Handbook (7^th Edition):

Mitra, Arnab. “Asynchronous propulsion of the three sphere micro-swimmer using perturbed magnetic field.” 2018. Web. 22 Jan 2021.

Vancouver:

Mitra A. Asynchronous propulsion of the three sphere micro-swimmer using perturbed magnetic field. [Internet] [Masters thesis]. Clemson University; 2018. [cited 2021 Jan 22]. Available from: https://tigerprints.clemson.edu/all_theses/2998.

Council of Science Editors:

Mitra A. Asynchronous propulsion of the three sphere micro-swimmer using perturbed magnetic field. [Masters Thesis]. Clemson University; 2018. Available from: https://tigerprints.clemson.edu/all_theses/2998

12. Kalkhanda, Abhinav. Joule Heating Enabled Electrokinetic Trapping of Submicron Particles in Ratchet Microchannels Using Depth Modelling.

Degree: MS, Mechanical Engineering, 2017, Clemson University

URL: https://tigerprints.clemson.edu/all_theses/2704

► Microfluidic devices have been increasingly used for diverse particle manipulations in various chemical and biological applications. Fields such as water quality control, environmental monitoring and… (more)

▼ Microfluidic devices have been increasingly used for diverse particle manipulations in various chemical and biological applications. Fields such as water quality control, environmental monitoring and food safety require the continuous trapping and concentration of particles (either bio- or non-bio) for enhanced detection and analysis. To achieve this, various microfluidic techniques have been developed using electric field as well as other fields including magnetic, optical, acoustic, hydrodynamic, gravitational and inertial. Among these methods, electrokinetic manipulation of particles is the most often used due to its advantages over other methods such as simple operation and easy integration etc. It transports fluids and controls the motion of the suspended particles via electroosmosis, electrophoresis and dielectrophoresis. However, there is an inevitable phenomenon accompanying electrokinetic devices, i.e., Joule heating due to the passage of electric current through the conductive suspending medium. Previous studies indicate a negative impact of Joule heating on the trapping and concentration of micron-sized particles in insulator-based dielectrophoretic microdevices. We demonstrate in this thesis that the Joule heating-induced electrothermal flow can actually enhance the electrokinetic manipulation, leading to the otherwise impossible trapping and concentration of submicron particles in ratchet microchannels. We fabricated ratchet microchannels with polydimethylsiloxane and used them to study the transport and control of submicron particles in a moderately conductive phosphate buffer solution. Our research group did the experiments previously. We developed a numerical multiphysics depth average model, which can predict the observed particle trapping in the ratchet region. The numerical model consists of coupled electric current, fluid flow, heat transfer and mass transport equation. A depth average analysis of these governing equations was done to develop a 2D model on the horizontal plane of the microchannel, which gives us numerical results that are as good as a full-scale 3D model developed previously, but with much less computational resources. Numerical analysis of the developed model predicts the formation of two counter rotating electrothermal vortices at the ratchet tips. Moreover, particles can be seen trapped inside these vortices and the concentration of particles trapped in electrothermal vortices can be observed to increase with time. Further, on doing the parametric study we found out that with increase in voltage the size of these vortices increases. We also changed the shape of the ratchet, but that does not seem to affect particle trapping in a significant manner. These obtained numerically predicted results are found to be in good agreement with our experimental observations, which further validates our numerical modelling. Advisors/Committee Members: Dr. Xiangchun Xuan, Committee Chair, Dr. Xin Zhao, Dr. Ethan Kung.

Subjects/Keywords: Joule heating; Microfluidics

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APA (6^th Edition):

Kalkhanda, A. (2017). Joule Heating Enabled Electrokinetic Trapping of Submicron Particles in Ratchet Microchannels Using Depth Modelling. (Masters Thesis). Clemson University. Retrieved from https://tigerprints.clemson.edu/all_theses/2704

Chicago Manual of Style (16^th Edition):

Kalkhanda, Abhinav. “Joule Heating Enabled Electrokinetic Trapping of Submicron Particles in Ratchet Microchannels Using Depth Modelling.” 2017. Masters Thesis, Clemson University. Accessed January 22, 2021. https://tigerprints.clemson.edu/all_theses/2704.

MLA Handbook (7^th Edition):

Kalkhanda, Abhinav. “Joule Heating Enabled Electrokinetic Trapping of Submicron Particles in Ratchet Microchannels Using Depth Modelling.” 2017. Web. 22 Jan 2021.

Vancouver:

Kalkhanda A. Joule Heating Enabled Electrokinetic Trapping of Submicron Particles in Ratchet Microchannels Using Depth Modelling. [Internet] [Masters thesis]. Clemson University; 2017. [cited 2021 Jan 22]. Available from: https://tigerprints.clemson.edu/all_theses/2704.

Council of Science Editors:

Kalkhanda A. Joule Heating Enabled Electrokinetic Trapping of Submicron Particles in Ratchet Microchannels Using Depth Modelling. [Masters Thesis]. Clemson University; 2017. Available from: https://tigerprints.clemson.edu/all_theses/2704

13. Liu, Qi. Modeling and Performance Analysis of A Sloshing Ferrofluid Based Electromagnetic Energy Harvester.

Degree: PhD, Mechanical Engineering, 2018, Clemson University

URL: https://tigerprints.clemson.edu/all_dissertations/2207

► Computational modeling and performance analysis are carried out for a ferrofluid based electromagnetic energy harvester which converts ambient vibratory energy into electromotive force through sloshing… (more)

▼ Computational modeling and performance analysis are carried out for a ferrofluid based electromagnetic energy harvester which converts ambient vibratory energy into electromotive force through sloshing motion of a ferrofluid. The system consists of a tank partially filled with ferrofluid, magnets placed on the opposite sides of the tank and a copper coil wound around the tank. In the presence of an external magnetic field, magnetic dipoles in the ferrofluid rotate and produce a net magnetic moment aligned in the direction of the field. When the device is subjected to an external excitation, the ferrofluid in the tank undergoes a sloshing motion which induces a time-varying magnetization in the fluid, causing a time-varying magnetic flux and electromotive force in the copper coil according to Faraday's law of induction. Compared to traditional solid-state vibratory energy harvesters, this liquid-state harvester provides better conformability, sensitivity, tunability and response bandwidth. This study provides useful insights for designing high performance ferrofluid based energy harvesters and is divided into three sections. First, A continuum level finite element model is developed and implemented for the multi-physics computational analysis of the energy harvester. The model solves the coupled magnetic scalar potential equation and Navier-Stokes equations for the dynamic behavior of the magnetic field and fluid motion. The model is validated against experimental results for eight configurations of the system. The validated model is then employed to study the underlying mechanisms that determine the electromotive force of the energy harvester. Furthermore, computational analysis is performed to test the effects of several modeling aspects, such as three-dimensional effect, surface tension and type of the ferrofluid-magnetic field coupling, on the accuracy of the model prediction. Second, a series of numerical simulations are performed to investigate the influence of several design parameters on the electromotive force of the energy harvester. From the eight configurations used for model validation, two configurations that give the highest electromotive forces are chosen for further performance analysis. The design parameters considered in this investigation include the device's geometric parameters, external excitation amplitude and material properties of the ferrofluid, which affect either the magnetic flux in the device or the sloshing behavior of the ferrofluid. Third, non-equilibrium molecular dynamics (NEMD) simulations are employed to obtain an understanding of the dynamic magnetization behavior of the ferromagnetic nano-particles and microscopic structures of the ferrofluid. The results from the continuum level numerical simulations reveal that the magnetic susceptibility/magnetization of ferrofluid greatly influences the performance of the energy harvester. Since the ferrofluid in the energy harvester undergoes sloshing motion under external mechanical excitations, it is also expected… Advisors/Committee Members: Dr. Gang Li, Committee Chair, Dr. Mohammed Daqaq, Dr. Lonny Thompson, Dr. Xiangchun Xuan.

Subjects/Keywords: Energy harvesting; Ferrofluid; Finite element method; Molecular dynamics; Sloshing

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APA (6^th Edition):

Liu, Q. (2018). Modeling and Performance Analysis of A Sloshing Ferrofluid Based Electromagnetic Energy Harvester. (Doctoral Dissertation). Clemson University. Retrieved from https://tigerprints.clemson.edu/all_dissertations/2207

Chicago Manual of Style (16^th Edition):

Liu, Qi. “Modeling and Performance Analysis of A Sloshing Ferrofluid Based Electromagnetic Energy Harvester.” 2018. Doctoral Dissertation, Clemson University. Accessed January 22, 2021. https://tigerprints.clemson.edu/all_dissertations/2207.

MLA Handbook (7^th Edition):

Liu, Qi. “Modeling and Performance Analysis of A Sloshing Ferrofluid Based Electromagnetic Energy Harvester.” 2018. Web. 22 Jan 2021.

Vancouver:

Liu Q. Modeling and Performance Analysis of A Sloshing Ferrofluid Based Electromagnetic Energy Harvester. [Internet] [Doctoral dissertation]. Clemson University; 2018. [cited 2021 Jan 22]. Available from: https://tigerprints.clemson.edu/all_dissertations/2207.

Council of Science Editors:

Liu Q. Modeling and Performance Analysis of A Sloshing Ferrofluid Based Electromagnetic Energy Harvester. [Doctoral Dissertation]. Clemson University; 2018. Available from: https://tigerprints.clemson.edu/all_dissertations/2207

14. Sudarsanam, Senbagaraman. Particle Manipulation in Viscous Flows: Singularity Models and Phase Space Boundaries.

Degree: PhD, Mechanical Engineering, 2018, Clemson University

URL: https://tigerprints.clemson.edu/all_dissertations/2181

► This dissertation develops a modeling framework to address the problem of particle manipulation in low Reynolds number fluid flows. This framework combines singularity methods in… (more)

Subjects/Keywords: Chaos; Dynamical systems; Inertial Particles; Microfluidics; Mixing; Singularity methods

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APA (6^th Edition):

Sudarsanam, S. (2018). Particle Manipulation in Viscous Flows: Singularity Models and Phase Space Boundaries. (Doctoral Dissertation). Clemson University. Retrieved from https://tigerprints.clemson.edu/all_dissertations/2181

Chicago Manual of Style (16^th Edition):

Sudarsanam, Senbagaraman. “Particle Manipulation in Viscous Flows: Singularity Models and Phase Space Boundaries.” 2018. Doctoral Dissertation, Clemson University. Accessed January 22, 2021. https://tigerprints.clemson.edu/all_dissertations/2181.

MLA Handbook (7^th Edition):

Sudarsanam, Senbagaraman. “Particle Manipulation in Viscous Flows: Singularity Models and Phase Space Boundaries.” 2018. Web. 22 Jan 2021.

Vancouver:

Sudarsanam S. Particle Manipulation in Viscous Flows: Singularity Models and Phase Space Boundaries. [Internet] [Doctoral dissertation]. Clemson University; 2018. [cited 2021 Jan 22]. Available from: https://tigerprints.clemson.edu/all_dissertations/2181.

Council of Science Editors:

Sudarsanam S. Particle Manipulation in Viscous Flows: Singularity Models and Phase Space Boundaries. [Doctoral Dissertation]. Clemson University; 2018. Available from: https://tigerprints.clemson.edu/all_dissertations/2181

15. Islam, Monsur. Advanced Manufacturing of Lightweight Porous Carbide Shapes Using Renewable Resources.

Degree: PhD, Mechanical Engineering, 2018, Clemson University

URL: https://tigerprints.clemson.edu/all_dissertations/2138

► This dissertation presents an origami-inspired manufacturing and an additive manufacturing platform for the fabrication of 3D shapes of porous carbide material using renewable biopolymers as… (more)

Subjects/Keywords: Additive Manufacturing; Carbide; Lightweight; Origami; Porous; Renewable biopolymer

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APA (6^th Edition):

Islam, M. (2018). Advanced Manufacturing of Lightweight Porous Carbide Shapes Using Renewable Resources. (Doctoral Dissertation). Clemson University. Retrieved from https://tigerprints.clemson.edu/all_dissertations/2138

Chicago Manual of Style (16^th Edition):

Islam, Monsur. “Advanced Manufacturing of Lightweight Porous Carbide Shapes Using Renewable Resources.” 2018. Doctoral Dissertation, Clemson University. Accessed January 22, 2021. https://tigerprints.clemson.edu/all_dissertations/2138.

MLA Handbook (7^th Edition):

Islam, Monsur. “Advanced Manufacturing of Lightweight Porous Carbide Shapes Using Renewable Resources.” 2018. Web. 22 Jan 2021.

Vancouver:

Islam M. Advanced Manufacturing of Lightweight Porous Carbide Shapes Using Renewable Resources. [Internet] [Doctoral dissertation]. Clemson University; 2018. [cited 2021 Jan 22]. Available from: https://tigerprints.clemson.edu/all_dissertations/2138.

Council of Science Editors:

Islam M. Advanced Manufacturing of Lightweight Porous Carbide Shapes Using Renewable Resources. [Doctoral Dissertation]. Clemson University; 2018. Available from: https://tigerprints.clemson.edu/all_dissertations/2138

16. Li, Wei. Effects of Mean Shear and Scalar Initial Length Scale on Three-Scalar Mixing in Turbulent Coaxial Jets.

Degree: PhD, Mechanical Engineering, 2016, Clemson University

URL: https://tigerprints.clemson.edu/all_dissertations/1717

► The eﬀects of the velocity and length scale ratios of the annular ﬂow to the center jet on three-scalar mixing in turbulent coaxial jets are… (more)

▼ The eﬀects of the velocity and length scale ratios of the annular ﬂow to the center jet on three-scalar mixing in turbulent coaxial jets are investigated. In this ﬂow a center jet and an annular ﬂow, consisting of acetone-doped air and ethylene respec-tively, are mixed with the co-ﬂow air. Simultaneous planar laser-induced ﬂuorescence and Rayleigh scattering are employed to measure the mass fractions of the acetone-doped air and ethylene. The velocity ratio alters the relative mean shear rates in the mixing layers between the center jet and the annular ﬂow and between the annular ﬂow and the co-ﬂow, modifying the scalar ﬁelds through mean-ﬂow advection, turbu-lent transport, and small-scale mixing. The length scale ratio determines the degree of separation between the center jet and the co-ﬂow. The results show that while varying the velocity ratio can alter the mixing characteristics qualitatively, varying the annulus width only has quantitative eﬀects. Increasing the velocity ratio and the annulus width always delays the evolution of the scalar ﬁelds. The evolution of the mean scalar proﬁles are dominated by the mean-ﬂow advection, while the shape of the joint probability density function (JPDF) is largely determined by the turbulent transport and molecular diﬀusion. The JPDF for the higher velocity ratio cases is bimodal at some locations while it is unimodal for the lower velocity ratio cases. The diﬀusion velocity streamlines in scalar space representing the conditional diﬀusion generally converge quickly to a manifold along which they continue at a lower rate. The curvature of the manifold is signiﬁcantly larger for the higher velocity ratio cases. Predicting the mixing path along the manifold as well as its dependence on the velocity and length scale ratios presents a challenging test for mixing models. The three-scalar subgrid-scale (SGS) mixing in the context of large eddy simu-lation and its dependence on the velocity and length scale ratios are also investigated. The analysis reveals two SGS mixing regimes depending on the SGS variance value of the center jet scalar. For small SGS variance the scalars are well mixed with uni-modal ﬁltered joint density function (FJDF) and the three-scalar mixing conﬁguration is lost. For large SGS variance, the scalars are highly segregated with bimodal FJDFs at radial locations near the peak of the mean SGS variance of the center jet scalar. Two competing factors, the SGS variance and the scalar length scale, are important for the bimodal FJDF. For the higher velocity ratio cases, the peak value of the SGS variance is higher, thereby resulting in stronger bimodality. For the lower velocity ratio cases, the wider mean SGS variance proﬁles and the smaller scalar length scale cause bimodal FJDFs over a wider range of physical locations. The diﬀusion stream-lines ﬁrst converge to a manifold and continue on it toward a stagnation point. The curvature of the diﬀusion manifold is larger for the larger velocity ratio cases. The manifold provides a SGS mixing path for the center… Advisors/Committee Members: Dr. Chenning Tong, Committee Chair, Dr. Richard Miller, Dr. Jay Ochterbeck, Dr. Xiangchun Xuan.

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APA (6^th Edition):

Li, W. (2016). Effects of Mean Shear and Scalar Initial Length Scale on Three-Scalar Mixing in Turbulent Coaxial Jets. (Doctoral Dissertation). Clemson University. Retrieved from https://tigerprints.clemson.edu/all_dissertations/1717

Chicago Manual of Style (16^th Edition):

Li, Wei. “Effects of Mean Shear and Scalar Initial Length Scale on Three-Scalar Mixing in Turbulent Coaxial Jets.” 2016. Doctoral Dissertation, Clemson University. Accessed January 22, 2021. https://tigerprints.clemson.edu/all_dissertations/1717.

MLA Handbook (7^th Edition):

Li, Wei. “Effects of Mean Shear and Scalar Initial Length Scale on Three-Scalar Mixing in Turbulent Coaxial Jets.” 2016. Web. 22 Jan 2021.

Vancouver:

Li W. Effects of Mean Shear and Scalar Initial Length Scale on Three-Scalar Mixing in Turbulent Coaxial Jets. [Internet] [Doctoral dissertation]. Clemson University; 2016. [cited 2021 Jan 22]. Available from: https://tigerprints.clemson.edu/all_dissertations/1717.

Council of Science Editors:

Li W. Effects of Mean Shear and Scalar Initial Length Scale on Three-Scalar Mixing in Turbulent Coaxial Jets. [Doctoral Dissertation]. Clemson University; 2016. Available from: https://tigerprints.clemson.edu/all_dissertations/1717

17. Padmanabhan, Neelakantan. On High Pressure Real Gas Turbulent Mixing Jets.

Degree: PhD, Mechanical Engineering, 2017, Clemson University

URL: https://tigerprints.clemson.edu/all_dissertations/1981

► A database of direct numerical simulation (DNS) of spatially evolving turbulent mixing slot jets of Heptane-Air and Heptane-Oxygen is developed. The formulation includes the compressible… (more)

▼ A database of direct numerical simulation (DNS) of spatially evolving turbulent mixing slot jets of Heptane-Air and Heptane-Oxygen is developed. The formulation includes the compressible form of the governing equations, a generalized multicomponent diffusion model with Soret and Dufour effects, a cubic real gas equation of state and realistic property models. Simulations are conducted over a wide range of initial pressures (1 atm < P0 < 100 atm) and jet width based Reynolds numbers of 850 and 1300. High order explicit finite difference schemes in combination with low order boundary closures and Runge-Kutta time integration schemes are used to approximate the spatial and temporal derivatives. Non-reflecting inflow and outflow boundary conditions in combination with absorbing zones are applied for proper convection of flow structures and acoustic waves with minimal reflection of numerical waves. Low level disturbances are imposed on the laminar inflow near the nozzle to initiate instability for development of turbulence. The simulations are run until a statistically stationary state of the flow is achieved. The mean velocity, variance, centerline velocity excess decay, and downstream growth of normal Reynolds stresses are calculated and compared with various experimental results. For subgrid analysis, a spatial filtering operation is applied to the DNS. The filtered mass density function (FMDF) of mixture fraction at various filter widths is obtained from the simulation at several spatial locations within the flow. The conditional scalar diffusion (CSD) term in the exact transport equation of FMDF is calculated from the DNS. A parametric study of variation of CSD with time, spatial location, Reynolds number, pressure and diffusion models is conducted. An a priori analysis of Interaction by Exchange of Mean (IEM), Modified Curl (MC) and Mapping Closure (MAPPING) mixing models for CSD is conducted. Performance of mixing models at various pressures with the generalized and Fickian diffusion models, with real and ideal gas equations of state is evaluated. The significance of mixing frequency used in the models and the errors associated with calculation of mixing frequency in simulations with the generalized diffusion model is studied. A parametric study of variation of the mixing frequency and its parameters with pressures, diffusion models and Reynolds number is performed. New model constants for mixing frequency applicable to the LES with generalized diffusion models at various pressures are proposed. Conditionally averaged mixing frequency for the IEM model is determined and compared with the conditionally averaged second invariant of the strain tensor to study the effects of flow physics (viscous dissipation) on the mixing time. Mean turbulent kinetic energy and mean dissipation rates are calculated from the DNS and their ratios are compared with mixing frequencies at various pressures. The model constants for various pressures are determined and an alternative expression for determination of mixing frequency in… Advisors/Committee Members: Dr. Richard S. Miller, Committee Chair, Dr. Donald E. Beasley, Dr. Xiangchun Xuan, Dr. John R. Wagner.

Subjects/Keywords: Computational Fluid Dynamics; Direct Numerical Simulations; High pressure mixing jets; RSM modeling in RANS; SGS modeling in LES; Spatially evolving mixing jets

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APA (6^th Edition):

Padmanabhan, N. (2017). On High Pressure Real Gas Turbulent Mixing Jets. (Doctoral Dissertation). Clemson University. Retrieved from https://tigerprints.clemson.edu/all_dissertations/1981

Chicago Manual of Style (16^th Edition):

Padmanabhan, Neelakantan. “On High Pressure Real Gas Turbulent Mixing Jets.” 2017. Doctoral Dissertation, Clemson University. Accessed January 22, 2021. https://tigerprints.clemson.edu/all_dissertations/1981.

MLA Handbook (7^th Edition):

Padmanabhan, Neelakantan. “On High Pressure Real Gas Turbulent Mixing Jets.” 2017. Web. 22 Jan 2021.

Vancouver:

Padmanabhan N. On High Pressure Real Gas Turbulent Mixing Jets. [Internet] [Doctoral dissertation]. Clemson University; 2017. [cited 2021 Jan 22]. Available from: https://tigerprints.clemson.edu/all_dissertations/1981.

Council of Science Editors:

Padmanabhan N. On High Pressure Real Gas Turbulent Mixing Jets. [Doctoral Dissertation]. Clemson University; 2017. Available from: https://tigerprints.clemson.edu/all_dissertations/1981

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