subject:(Droplet impact dynamics)

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Iowa State University

1. Li, Haixing. Experimental studies on the dynamics of in-flight and impacting water droplets pertinent to aircraft icing phenomena.

Degree: 2017, Iowa State University

URL: https://lib.dr.iastate.edu/etd/15564

► Aircraft icing is widely recognized as a significant hazard to aircraft operations in cold weather. When an aircraft or rotorcraft fly in a cold climate,… (more)

▼ Aircraft icing is widely recognized as a significant hazard to aircraft operations in cold weather. When an aircraft or rotorcraft fly in a cold climate, some of the super-cooled water droplets would impact and freeze on the exposed aircraft surfaces to form ice shapes, which can degrade the aerodynamic performance of an airplane significantly by decreasing lift while increasing drag, and even lead to the aircraft crash. In the present study, a series of experimental investigations were conducted to investigate dynamics and thermodynamics of in-flight and impinging water droplets in order to elucidate the underlying physics of the important microphysical process pertinent to aircraft icing phenomena. A novel lifetime-based molecular tagging thermometry technique (MTT) is developed to achieve simultaneous measurements of droplet size, flying velocity and transient temperature of in-flight water droplets to characterize the dynamic and thermodynamic behaviors of the micro-sized in-flight droplets pertinent to aircraft icing phenomena. By using high-speed imaging and infrared thermal imaging techniques, a comprehensive experimental study was conducted to quantify the unsteady heat transfer and phase changing processes as water droplets impinging onto frozen cold surfaces under different test conditions (i.e., with different Weber numbers, Reynolds numbers, and impact angles of the impinging droplets, different temperature, hydrophobicity and roughness of the test plates) to simulate the scenario of super-cooled water droplets impinging onto the frozen cold wing surfaces. A novel digital image projector (DIP) technique was also developed to achieve time-resolved film thickness measurements to quantify the dynamic impinging process of water droplets (i.e., droplet impact, rebounding, splashing and freezing process). An impact droplet maximum spreading diameter model and a damped harmonic oscillator model was proposed based on precise measurement of the impact droplet 3D shape. A better understanding of the important micro physical processes pertinent to aircraft icing phenomena would lead to better ice accretion models for more accurate prediction of ice formation and accretion on aircraft wings as well as develop more effective and robust anti-/de-icing strategies for safer and more efficient operation of aircraft in cold weather.

Subjects/Keywords: 3-D shape reconstruction of impact droplet; Aircraft icing; Droplet impact dynamics; Droplet impact on super-hydrophobic surface; In-flight droplets temperature measurement; Aerospace Engineering

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APA (6^th Edition):

Li, H. (2017). Experimental studies on the dynamics of in-flight and impacting water droplets pertinent to aircraft icing phenomena. (Thesis). Iowa State University. Retrieved from https://lib.dr.iastate.edu/etd/15564

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):

Li, Haixing. “Experimental studies on the dynamics of in-flight and impacting water droplets pertinent to aircraft icing phenomena.” 2017. Thesis, Iowa State University. Accessed March 03, 2021. https://lib.dr.iastate.edu/etd/15564.

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

MLA Handbook (7^th Edition):

Li, Haixing. “Experimental studies on the dynamics of in-flight and impacting water droplets pertinent to aircraft icing phenomena.” 2017. Web. 03 Mar 2021.

Vancouver:

Li H. Experimental studies on the dynamics of in-flight and impacting water droplets pertinent to aircraft icing phenomena. [Internet] [Thesis]. Iowa State University; 2017. [cited 2021 Mar 03]. Available from: https://lib.dr.iastate.edu/etd/15564.

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

Council of Science Editors:

Li H. Experimental studies on the dynamics of in-flight and impacting water droplets pertinent to aircraft icing phenomena. [Thesis]. Iowa State University; 2017. Available from: https://lib.dr.iastate.edu/etd/15564

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

Clemson University

2. He, Ping. Fluid Dynamics of Cell Printing.

Degree: PhD, Mechanical Engineering, 2011, Clemson University

URL: https://tigerprints.clemson.edu/all_dissertations/727

► Cell printing is an emerging technology that uses droplets to deliver cells to desired positions with resolution potentially comparable to the size of single… (more)

▼ Cell printing is an emerging technology that uses droplets to deliver cells to desired positions with resolution potentially comparable to the size of single cells. In particular, ink–jet based cell printing technique has been successfully used to build simple bio–constructs and has shown a promise in building complex bio–structures or even organs. Two important issues in ink–jet based cell printing are the moderate survival rate of delicate cells and the limited cell placement resolution. Resolving these issues is critical for the ink–jet based cell printing techniques to realize their full potential. In this work, we use numerical simulations to reconstruct the impact of a droplet loaded with a single cell onto a pool of viscous fluids to gain insights into the droplet and cell dynamics during cell printing. We developed a mathematical model for this process: the droplet, pool and air are modeled as Newtonian fluids, and their flow is modeled as a laminar flow governed by the Navier–Stokes equation. The cell is modeled as an axisymmetric solid object governed by the neo–Hookean law and also has a shear viscosity that is the same as that of its host droplet. To numerically solve the coupled fluid and cell motion, we used a hybrid method in which fluid flow is solved on a fixed Cartesian grid and the deformation of solid body is solved on a Lagrangian mesh. We also developed a new full Eulerian method, termed the solid level set (SLS) method, to simulate cell printing. The key idea is to track the deformation of the solid body using four level set functions on a fixed Cartesian grid instead of using a Lagrangian mesh. The SLS method is easy to implement and addresses several challenges in simulations of fluid–tructure interactions using hybrid Eulerian/Lagrangian meshes. Using codes developed based on the above methods, we systematically investigated the fluid and cell dynamics during the cell printing process. We studied how the droplet penetration depth, droplet lateral spreading, cell stress and cell surface area change are affected by printing conditions such as impact velocity, pool depth, and cell stiffness. Our simulations indicate that cell experiences significant stress (∼20kPa) and local surface area dilation (∼100%) during the impact process. The latter suggests that cell membrane is temporally ruptured during the printing process, and is consistent with the gene transfection observed during cell printing. We speculate that the survival of cell through the rather violent cell printing process may be related to the briefness of the impact process, which only lasts about 0.1 milliseconds. Based on our simulation results, several strategies have been proposed to reduce the stress and membrane dilation of cells during cell printing. Advisors/Committee Members: Qiao, Rui, Tong , Chenning, Miller , Richard S, Zumbrunnen , David A.

Subjects/Keywords: cell printing; computational fluid dynamics; droplet impact; fluid struture interactions; multi-phase flow; Mechanical Engineering

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APA (6^th Edition):

He, P. (2011). Fluid Dynamics of Cell Printing. (Doctoral Dissertation). Clemson University. Retrieved from https://tigerprints.clemson.edu/all_dissertations/727

Chicago Manual of Style (16^th Edition):

He, Ping. “Fluid Dynamics of Cell Printing.” 2011. Doctoral Dissertation, Clemson University. Accessed March 03, 2021. https://tigerprints.clemson.edu/all_dissertations/727.

MLA Handbook (7^th Edition):

He, Ping. “Fluid Dynamics of Cell Printing.” 2011. Web. 03 Mar 2021.

Vancouver:

He P. Fluid Dynamics of Cell Printing. [Internet] [Doctoral dissertation]. Clemson University; 2011. [cited 2021 Mar 03]. Available from: https://tigerprints.clemson.edu/all_dissertations/727.

Council of Science Editors:

He P. Fluid Dynamics of Cell Printing. [Doctoral Dissertation]. Clemson University; 2011. Available from: https://tigerprints.clemson.edu/all_dissertations/727

Indian Institute of Science

3. Umashankar, Viverjita. Edge Effect of Semi-Infinite Rectangular Posts on Impacting Drops.

Degree: MSc Engg, Faculty of Engineering, 2018, Indian Institute of Science

URL: http://etd.iisc.ac.in/handle/2005/3644

► The inhibiting effect of a sharp edge on liquid spreading is well observed during drop interaction with textured surfaces. On groove-textured solid surfaces comprising unidirectional… (more)

▼ The inhibiting effect of a sharp edge on liquid spreading is well observed during drop interaction with textured surfaces. On groove-textured solid surfaces comprising unidirectional parallel grooves, the edge effect of posts results in the squeezing of drop liquid in the direction perpendicular to the grooves and the stretching of drop liquid along the grooves leading to anisotropy in drop flow, popularly known as wetting anisotropy which has been employed in several engineering applications. A recent study observed that the energy loss incurring at the edges of posts via contact angle hysteresis is primarily responsible for the anisotropic spreading of impacting drops on groove-textured surfaces. The present study aims to elucidate the role of edges on the spreading and receding dynamics of water drops. The experiments of drop impact are carried out on semi-infinite rectangular post comprising a pair of parallel 90-deg edges separated by a distance (post width) comparable to the diameter of impacting drop. The equilibrium shape of drops on the semi-infinite rectangular post is analyzed using open source computational tool Surface Evolver to optimize the ratio of initial droplet diameter to post width. Quantitative measurements of drop impact dynamics on semi-infinite rectangular posts are deduced by analysing high speed videos of impact process captured under three different camera views during experiments. Based on the role of post edges on impacting drops, different regimes of the impacting drops are characterized in terms of drop Weber number and the ratio of diameter of impacting drop to post width. Characteristic features of impact dynamics in each of the regimes are identified and discussed. It is seen that edges play a pivotal role on all stages of impact dynamics regardless of Weber number. Impacts in the regime of completely pinned drops on narrow posts are further analyzed to reveal characteristics of post-spreading oscillations. Advisors/Committee Members: Sivakumar, D (advisor).

Subjects/Keywords: Surface Evolver; Liquid Drop Impact Phenomena; Anisotropic Spreading; Interfacial Oscillations; Droplet Impact; Liquid Drop Impact; Semi-infinite Target Surfaces; Liquid Drop Generator; Semi-infinite Rectangular Post; Impact Dynamics; Aerospace Engineering

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APA (6^th Edition):

Umashankar, V. (2018). Edge Effect of Semi-Infinite Rectangular Posts on Impacting Drops. (Masters Thesis). Indian Institute of Science. Retrieved from http://etd.iisc.ac.in/handle/2005/3644

Chicago Manual of Style (16^th Edition):

Umashankar, Viverjita. “Edge Effect of Semi-Infinite Rectangular Posts on Impacting Drops.” 2018. Masters Thesis, Indian Institute of Science. Accessed March 03, 2021. http://etd.iisc.ac.in/handle/2005/3644.

MLA Handbook (7^th Edition):

Umashankar, Viverjita. “Edge Effect of Semi-Infinite Rectangular Posts on Impacting Drops.” 2018. Web. 03 Mar 2021.

Vancouver:

Umashankar V. Edge Effect of Semi-Infinite Rectangular Posts on Impacting Drops. [Internet] [Masters thesis]. Indian Institute of Science; 2018. [cited 2021 Mar 03]. Available from: http://etd.iisc.ac.in/handle/2005/3644.

Council of Science Editors:

Umashankar V. Edge Effect of Semi-Infinite Rectangular Posts on Impacting Drops. [Masters Thesis]. Indian Institute of Science; 2018. Available from: http://etd.iisc.ac.in/handle/2005/3644

Northeastern University

4. Gao, Fei. Numerical simulation of the droplet-surface impact using interFoam.

Degree: MS, Department of Mechanical and Industrial Engineering, 2016, Northeastern University

URL: http://hdl.handle.net/2047/D20194500

► Droplet dynamics involves multi-scale forces from inertia body force, interior viscous shear stress to surface tension. The main purpose of this thesis is to simulate… (more)

▼ Droplet dynamics involves multi-scale forces from inertia body force, interior viscous shear stress to surface tension. The main purpose of this thesis is to simulate the normal impact of a liquid droplet on a hydrophobic surface by solving for the Navier[nil]Stokes equations. The numerical results obtained is used to evaluate the effects of variable parameters on the droplet deformation evolution. The numerical simulation also works as a complimentary part of the experimental exploration, by the group members in the Droplet-Surface Impact Project in Northeastern University.; The computational tool used is OpenFOAM, an open source CFD software package licensed and distributed by the OpenFOAM Foundation. The specific solver used is interFoam for this two phase problem. Water is modeled as a representative of the Newtonian fluids, while blood is modeled to represent non-Newtonian fluids. Multiple variables of the droplet-surface impact are investigated numerically: initial velocity, droplet diameter, transport properties, all of which contributes to a variation of the Weber number.; The numerical results obtained for water droplets are supported by experimental data and also semi-empirical correlations. The spreading behavior and generation of ripples are in good agreement with that observed in the experimental tests. As the capillary effects become more dominant in the recoiling period, a discrepancy starts to show by a pre-maturely generated secondary droplet in simulation. Possible reasons are speculated for this discrepancy between numerical and experimental results.; In the numerical comparison between water and blood droplets, a resemblance of droplet behavior in the initial spreading process is observed, while the recoiling process shows differences: blood droplets rebound in an "irregular" way compared to water droplets. The difference in deformation behaviors caused by varied transport properties leads to a way of distinguishing liquids by simple droplet-surface impact tests.

Subjects/Keywords: droplet impact; hydrophobic surface; simulation; Drops; Fluid dynamics; Simulation methods; Computational fluid dynamics; Water; Fluid dynamics; Simulation methods; Blood; Fluid dynamics; Simulation methods; Hydrophobic surfaces; Shear (Mechanics)

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

APA (6^th Edition):

Gao, F. (2016). Numerical simulation of the droplet-surface impact using interFoam. (Masters Thesis). Northeastern University. Retrieved from http://hdl.handle.net/2047/D20194500

Chicago Manual of Style (16^th Edition):

Gao, Fei. “Numerical simulation of the droplet-surface impact using interFoam.” 2016. Masters Thesis, Northeastern University. Accessed March 03, 2021. http://hdl.handle.net/2047/D20194500.

MLA Handbook (7^th Edition):

Gao, Fei. “Numerical simulation of the droplet-surface impact using interFoam.” 2016. Web. 03 Mar 2021.

Vancouver:

Gao F. Numerical simulation of the droplet-surface impact using interFoam. [Internet] [Masters thesis]. Northeastern University; 2016. [cited 2021 Mar 03]. Available from: http://hdl.handle.net/2047/D20194500.

Council of Science Editors:

Gao F. Numerical simulation of the droplet-surface impact using interFoam. [Masters Thesis]. Northeastern University; 2016. Available from: http://hdl.handle.net/2047/D20194500

Indian Institute of Science

5. Gupta, Rahul. Influence of Chemical Coating on Droplet Impact Dynamics.

Degree: MSc Engg, Faculty of Engineering, 2018, Indian Institute of Science

URL: http://etd.iisc.ac.in/handle/2005/3262

► Dynamic behavior of impacting water drops on superhydrophobic solid surfaces provides important details on the stability/durability of such solid surfaces. Multi-scale surface roughness combined with… (more)

▼ Dynamic behavior of impacting water drops on superhydrophobic solid surfaces provides important details on the stability/durability of such solid surfaces. Multi-scale surface roughness combined with a layer of low energy chemical is an essential surface modification process followed to create superhydrophobic capabilities on solid surfaces. The present work aims at studying the effect of low energy surface coating on droplet impact dynamics by carrying out experiments of water drop impacts on rough solid surfaces with and without chemical modification. A group of six aluminium alloy (Al6061) surfaces (three pairs) are prepared. Roughness, characterized in terms mean surface roughness, Ra, is introduced to these metallic surfaces using sand-paper polishing, electric discharge machining (EDM), and chemical based surface etching process. Low energy surface layer is laid on the rough surfaces by coating NeverWet hydrophobic solution, octadecyl-trichloro-silane (OTS), and perfluorodecyltricholorosilane (FAS-17). The impact dynamics of water drops is analyzed by capturing high speed videos for a range of drop Weber number from 1 to 570 and the salient features of drop impact process on the coated rough surfaces are compared with the corresponding uncoated rough surfaces. A one-to-one comparison on the spreading, fingering, receding, and final equilibrium of impacting drops on the coated and uncoated target surfaces is presented. Upon coating NeverWet, the original surface features of the base aluminium surface are completely covered by the hydrophobic coating material resulting in a fresh top surface layer. The outcomes as well as the bounce-off characteristics of impacting water drops on the coated surface are comparable to those observed on lotus leaf. The surface morphology features of rough aluminium surfaces coated with OTS and FAS-17 are comparable to those of the corresponding uncoated surfaces. The quantitative measurements on primary spreading and maximum spread factor of impacting drops are largely unaffected by the presence of low energy chemical coating. The dominant effect of surface coating is seen on the receding of impacting drops and hence the final drop configuration. This behavior is more prominently seen on EDM fabricated rough surface (larger Ra) combined with OTS coating than that on etching based rough surface (smaller Ra) combined with FAS-17 coating highlighting the dependence of coating effect with roughness features. Advisors/Committee Members: Sivakumar, D (advisor).

Subjects/Keywords: Droplet Impact Dynamics; Low Energy Surface Coating; Surface Modification; Chemical Coating; Liquid Drop Impact; Solid Surfaces - Liquid Drop Impact; Aluminium Alloy Surfaces; Water Drop Impacts - Solid Surfaces; Superhydrophobic Surface; Water Droplets Impacting; Superhydrophobic Solid Surfaces; FAS-17; Impacting Water Drops; Drop Impact Dynamics; Aerospace Engineering

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

APA (6^th Edition):

Gupta, R. (2018). Influence of Chemical Coating on Droplet Impact Dynamics. (Masters Thesis). Indian Institute of Science. Retrieved from http://etd.iisc.ac.in/handle/2005/3262

Chicago Manual of Style (16^th Edition):

Gupta, Rahul. “Influence of Chemical Coating on Droplet Impact Dynamics.” 2018. Masters Thesis, Indian Institute of Science. Accessed March 03, 2021. http://etd.iisc.ac.in/handle/2005/3262.

MLA Handbook (7^th Edition):

Gupta, Rahul. “Influence of Chemical Coating on Droplet Impact Dynamics.” 2018. Web. 03 Mar 2021.

Vancouver:

Gupta R. Influence of Chemical Coating on Droplet Impact Dynamics. [Internet] [Masters thesis]. Indian Institute of Science; 2018. [cited 2021 Mar 03]. Available from: http://etd.iisc.ac.in/handle/2005/3262.

Council of Science Editors:

Gupta R. Influence of Chemical Coating on Droplet Impact Dynamics. [Masters Thesis]. Indian Institute of Science; 2018. Available from: http://etd.iisc.ac.in/handle/2005/3262

6. Dhiman, Rajeev. Splashing and Breakup of Droplets Impacting on a Solid Surface.

Degree: 2009, University of Toronto

URL: http://hdl.handle.net/1807/17753

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Two new mechanisms of droplet splashing and breakup during impact have been identified and analyzed. One is the internal rupture of spreading droplet film through… (more)

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Two new mechanisms of droplet splashing and breakup during impact have been identified and analyzed. One is the internal rupture of spreading droplet film through formation of holes, and the other is the splashing of droplet due to its freezing during spreading. The mechanism of film rupture was investigated by two different methods. In the first method, circular water films were produced by directing a 1 mm diameter water jet onto a flat, horizontal plate for 10 ms. In the second method, films were produced by making 0.6 mm water droplets impact a solid surface mounted on the rim of a rotating flywheel. Substrate wettability was varied over a wide range, including superhydrophobic. In both cases, the tendency to film rupture first increased and then decreased with contact angle. A thermodynamic stability analysis predicted this behavior by showing that films would be stable at very small or very large contact angle, but unstable in between. Film rupture was also found to be promoted by increasing surface roughness or decreasing film thickness. To study the effect of solidification, the impact of molten tin droplets (0.6 mm diameter) on solid surfaces was observed for a range of impact velocities (10 to 30 m/s), substrate temperatures (25 to 200°C) and substrate materials (stainless steel, aluminum and glass) using the rotating flywheel apparatus. Droplets splashed extensively on a cold surface but on a hot surface there was no splashing. Splashing could be completely suppressed by either increasing the substrate temperature or reducing its thermal diffusivity. An analytical model was developed to predict this splashing behavior. The above two theories of freezing-induced splashing and film rupture were combined to predict the morphology of splats typically observed in a thermal spray process. A dimensionless solidification parameter, which takes into account factors such as the droplet diameter and velocity, substrate temperature, splat and substrate thermophysical properties, and thermal contact resistance between the two, was developed. Predictions from the model were compared with a wide range of experimental data and found to agree well.

PhD

Advisors/Committee Members: Chandra, Sanjeev, Mechanical and Industrial Engineering.

Subjects/Keywords: Fluid Dynamics; Heat Transfer; Droplet Impact; Droplet Splashing; Thermal Spray Coating; Water Jet Impact; 0548

…generator �� .27 Figure 2.11: A schematic diagram of the droplet impact apparatus… …30 Figure 2.13: A typical sequence of droplet impact, Do =600 μm, Vo =10 m/s �� .32… …hole due to the impact of a droplet onto an otherwise stable water film on smooth wax surface… …Figure 4.7: Modeling droplet impact on a solid surface: (a) before impact, t=0, (… …thin film created by droplet impact will rupture as a function of receding liquid-solid…

10 more images…

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

APA (6^th Edition):

Dhiman, R. (2009). Splashing and Breakup of Droplets Impacting on a Solid Surface. (Doctoral Dissertation). University of Toronto. Retrieved from http://hdl.handle.net/1807/17753

Chicago Manual of Style (16^th Edition):

Dhiman, Rajeev. “Splashing and Breakup of Droplets Impacting on a Solid Surface.” 2009. Doctoral Dissertation, University of Toronto. Accessed March 03, 2021. http://hdl.handle.net/1807/17753.

MLA Handbook (7^th Edition):

Dhiman, Rajeev. “Splashing and Breakup of Droplets Impacting on a Solid Surface.” 2009. Web. 03 Mar 2021.

Vancouver:

Dhiman R. Splashing and Breakup of Droplets Impacting on a Solid Surface. [Internet] [Doctoral dissertation]. University of Toronto; 2009. [cited 2021 Mar 03]. Available from: http://hdl.handle.net/1807/17753.

Council of Science Editors:

Dhiman R. Splashing and Breakup of Droplets Impacting on a Solid Surface. [Doctoral Dissertation]. University of Toronto; 2009. Available from: http://hdl.handle.net/1807/17753

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