Advanced search options

Advanced Search Options 🞨

Browse by author name (“Author name starts with…”).

Find ETDs with:

in
/  
in
/  
in
/  
in

Written in Published in Earliest date Latest date

Sorted by

Results per page:

Sorted by: relevance · author · university · dateNew search

You searched for subject:(Shear induced convection). Showing records 1 – 2 of 2 total matches.

Search Limiters

Last 2 Years | English Only

No search limiters apply to these results.

▼ Search Limiters


NSYSU

1. Yu, Chun-Hung. Mechanism of bottom convection and upwelling over continental shelf.

Degree: Master, Department of Oceanography, 2018, NSYSU

Turbulence, current, and stratification were measured in the northern section of Penghu Channel (PHC) during September 2015 and April 2016. Two datasets of current profiles and bottom temperature from bottom-mounted ADCP in summer and winter of 1999 at about 10 km north of PHC were used for bottom Ekman layer and eddy viscosity analysis. Our results indicate that the cycle of turbulence in the bottom boundary layer has a semi-diurnal period. Dissipate rate of turbulent kinetic energy, ε, is higher during the flood phase and reaches a maximum value of 2.29Ãã10ã^(-5) W ãkgã^(-1). Turbulent layer extends from the bottom to a height of 40 m, is produced primarily by vertical shear of tidal currents. Density profiles show that stratification is eroded within depths of 80-105 m during the flood, and the bottom layer becomes well mixed during the ebb. Temperature observations from the bottom-mounted ADCP reveal periodic occurrence of temperature decrease of 2-3â during the flood, implying shear-induced convective cooling near the bottom during the upslope flow. This phenomenon is more prominent in the summer which contributes to the along-channel upwelling in the PHC. Ekman veering of the current profiles near the bottom occurs periodically with tidal oscillation and is more obvious when the flow speed is less than 1 m s-1 during the summer. A comparison of the profiles of estimated eddy viscosity and observed eddy diffusivity indicates that the orders of magnitude of these two quantities are close. Eddy viscosity has a maximum value at the bottom and decreases upward. In summary, the combining effect of along-channel, shear-induced convection and the cross-channel, bottom Ekman dynamics will act sequentially and periodically to promote upwelling in the PHC. Advisors/Committee Members: Ruo-Shan Tseng (committee member), Yiing-Jang Yang (chair), Jian-Ming Liau (chair), Guan-Yu Chen (chair).

Subjects/Keywords: Ekman transport; Eddy viscosity; Coastal upwelling; Penghu channel; Shear-induced convection; Bottom boundary layer

Record DetailsSimilar RecordsGoogle PlusoneFacebookTwitterCiteULikeMendeleyreddit

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

APA (6th Edition):

Yu, C. (2018). Mechanism of bottom convection and upwelling over continental shelf. (Thesis). NSYSU. Retrieved from http://etd.lib.nsysu.edu.tw/ETD-db/ETD-search/view_etd?URN=etd-0429118-150531

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

Chicago Manual of Style (16th Edition):

Yu, Chun-Hung. “Mechanism of bottom convection and upwelling over continental shelf.” 2018. Thesis, NSYSU. Accessed October 22, 2019. http://etd.lib.nsysu.edu.tw/ETD-db/ETD-search/view_etd?URN=etd-0429118-150531.

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

MLA Handbook (7th Edition):

Yu, Chun-Hung. “Mechanism of bottom convection and upwelling over continental shelf.” 2018. Web. 22 Oct 2019.

Vancouver:

Yu C. Mechanism of bottom convection and upwelling over continental shelf. [Internet] [Thesis]. NSYSU; 2018. [cited 2019 Oct 22]. Available from: http://etd.lib.nsysu.edu.tw/ETD-db/ETD-search/view_etd?URN=etd-0429118-150531.

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

Council of Science Editors:

Yu C. Mechanism of bottom convection and upwelling over continental shelf. [Thesis]. NSYSU; 2018. Available from: http://etd.lib.nsysu.edu.tw/ETD-db/ETD-search/view_etd?URN=etd-0429118-150531

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


Virginia Tech

2. Sen, Debamoy. Coupled Field Modeling of Gas Tungsten Arc Welding.

Degree: PhD, Mechanical Engineering, 2012, Virginia Tech

Welding is used extensively in aerospace, automotive, chemical, manufacturing, electronic and power-generation industries. Thermally-induced residual stresses due to welding can significantly impair the performance and reliability of welded structures. Numerical simulation of weld pool dynamics is important as experimental measurements of velocities and temperature profiles are difficult due to the small size of the weld pool and the presence of the arc. From a structural integrity perspective of welded structures, it is necessary to have an accurate spatial and temporal thermal distribution in the welded structure before stress analysis is performed. Existing research on weld pool dynamics simulation has ignored the effect of fluid flow in the weld pool on the temperature field of the welded joint. Previous research has established that the weld pool depth/width (D/W) ratio and Heat Affected Zone (HAZ) are significantly altered by the weld pool dynamics. Hence, for a more accurate estimation of the thermally-induced stresses it is desired to incorporate the weld pool dynamics into the analysis. Moreover, the effects of microstructure evolution in the HAZ on the mechanical behavior of the structure need to be included in the analysis for better mechanical response prediction. In this study, a three-dimensional model for the thermo-mechanical analysis of Gas Tungsten Arc (GTA) welding of thin stainless steel butt-joint plates has been developed. The model incorporates the effects of thermal energy redistribution through weld pool dynamics into the structural behavior calculations. Through material modeling the effects of microstructure change/phase transformation are indirectly included in the model. The developed weld pool dynamics model includes the effects of current, arc length, and electrode angle on the heat flux and current density distributions. All the major weld pool driving forces are included, namely surface tension gradient, plasma drag force, electromagnetic force, and buoyancy. The weld D/W predictions are validated with experimental results. They agree well. The effects of welding parameters (like welding speed, current, arc length, etc.) on the weld D/W ratio are documented. The workpiece deformation and stress distributions are also highlighted. The transverse and longitudinal residual stress distribution plots across the weld bead and their variations with welding speed and current are also provided. The mathematical framework developed here serves as a robust tool for better prediction of weld D/W ratio and thermally-induced stress evolution and distribution in a welded structure by coupling the different fields in a welding process. Advisors/Committee Members: Tafti, Danesh K. (committee member), Battaglia, Francine (committee member), Hendricks, Robert W. (committee member), Ball, Kenneth S. (committeecochair), Pierson, Mark A. (committeecochair).

Subjects/Keywords: Residual Stress; Thermal Stress; Buoyancy; Electromagnetic Force; Plasma Induced Shear; Marangoni Convection; Material Modeling; Structural Analysis; Weld Pool Dynamics; Gas Tungsten Arc Welding

Record DetailsSimilar RecordsGoogle PlusoneFacebookTwitterCiteULikeMendeleyreddit

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

APA (6th Edition):

Sen, D. (2012). Coupled Field Modeling of Gas Tungsten Arc Welding. (Doctoral Dissertation). Virginia Tech. Retrieved from http://hdl.handle.net/10919/38820

Chicago Manual of Style (16th Edition):

Sen, Debamoy. “Coupled Field Modeling of Gas Tungsten Arc Welding.” 2012. Doctoral Dissertation, Virginia Tech. Accessed October 22, 2019. http://hdl.handle.net/10919/38820.

MLA Handbook (7th Edition):

Sen, Debamoy. “Coupled Field Modeling of Gas Tungsten Arc Welding.” 2012. Web. 22 Oct 2019.

Vancouver:

Sen D. Coupled Field Modeling of Gas Tungsten Arc Welding. [Internet] [Doctoral dissertation]. Virginia Tech; 2012. [cited 2019 Oct 22]. Available from: http://hdl.handle.net/10919/38820.

Council of Science Editors:

Sen D. Coupled Field Modeling of Gas Tungsten Arc Welding. [Doctoral Dissertation]. Virginia Tech; 2012. Available from: http://hdl.handle.net/10919/38820

.