讲座时间 2016-09-29
讲座地点 东三楼东汽报告厅
讲座人 Thomas B. Gatski

应能动学院王秋旺教授邀请,美国Old Dominion University(欧道明大学)Thomas B. Gatski教授将于2016年9月29日来访交流并做学术报告,欢迎大家积极参加。


报告人:Thomas B. Gatski 报告摘要:
It has been well-known for over six decades that the addition of minute amounts of long polymer chains to organic solvents, or water, can lead to significant turbulent drag reduction. However, it has only been the last twenty-five years that the full utilization of direct numerical simulation of such turbulent viscoelastic flows has been achieved. The unique characteristics of viscoelastic fluid flow are dictated by the nonlinear differential relationship between the flow strain rate field and the extra-stress induced by the additive polymer. Some basic features of such constitutive relationships are presented that delineate among the various types of non-Newtonian and viscoelastic fluids.
 A primary motivation for the analysis of these turbulent fluid flows is the understanding of the effect on the dynamic transfer of energy in the turbulent flow due to the presence of the extra-stress field induced by the presence of the viscoelastic polymer chain. Such analyses utilize direct simulation data of fully developed channel flow for the FENE-P (Finite Extendable Nonlinear Elastic – Peterlin approximation) fluid model, and results at a moderately high friction Reynolds number of order 103 at both medium (30%) and high (58%) drag reduction levels are presented. The transfer of energy is analyzed in physical space through a sequence of energetic budgets that include the mean and turbulent kinetic energy, and the mean polymeric and elastic potential energies. For channel flow in spectral space, a two-dimensional spectrum is formed with a spatial dependency in the wall-normal direction. In addition to allowing for an assessment of energetic content over a broad spectral range, it also allows for an assessment of energetic interchange within the plane of shear. It is shown that the primary effect of the interaction between the turbulent and polymeric fields is to transfer energy from the turbulence to the polymer, and that the magnitude of this transfer does not change between the low and high drag reduction flows.
 As with the turbulent flow of a Newtonian fluid, the traditional approach of Reynolds-averaged Navier-Stokes (RANS) model development can be extended to the turbulent flow of a viscoelastic fluid. Such models require some form of closure of the extra-stress contribution of the viscoelastic fluid to the turbulence dynamics. Such approaches are relatively new and have been primarily based on phenomenological extensions of the Newtonian fluid models.



Tom received his academic degrees [B.S.(70), M.S. (72)and Ph.D. (76)] from Penn State University in the Department of Aerospace Engineering where he worked on (M.S. and Ph.D.) viscoelastic constitutive equations under John Lumley. In 1976 he went to Brown University as a post-doctoral research associate to investigate large scale coherent structures in turbulent shear flows and their role in aerodynamic noise generation.
He joined NASA Langley Research Center in 1977 in the aeroacoustics group where he continued his research and its application to aerodynamic sound. In the early 1980s, his research focus moved to drag reduction on aerodynamic surfaces where he investigated a wide range of phenomena including: effects of embedded cavities on surfaces, vortex breakdown dynamics and the interaction of (deterministic) disturbances with a random turbulent field. This latter work was the subject of his Fellowship (Floyd Thompson Fellow, NASA LaRC Award) to the University of Cambridge, England (1987-88) in the Department of Engineering During this fellowship year, he was also a Visiting Scholar at Wolfson College, Cambridge. After returning from Cambridge to LaRC, Tom became active in turbulence modeling research. An area he now leads at LaRC. Over the last decade, he has taught several short courses on turbulence modeling and has been a scientific visitor at many international institutions. These include: EPFL (Switzerland); Isaac Newton Institute (Cambridge, U.K.); Les Houches School of Physics (France); University of Tokyo; Hong Kong Polytechnic University; and the University of Rome "la Sapienza." He has also served as an outside examiner for Ph.D. candidates domestically and internationally. In addition to these activities, he has also edited 4 books related to the subjects of transition and turbulence and currently serves on the Editorial Board of the ASME Journal of Fluids Engineering and the journal Theoretical and Computational Fluid Dynamics. He has been actively involved in organizing summer programs at ICASE and is currently involved in a NATO RTA research project with Greece.
Tom has also been active in community service as the United Way of Greater Williamsburg liaison to the Combined Federal Campaign and, in addition to serving as committee chair for several UW committees, he has also served as Board President. Tom is also a member of the Rotary Club of Williamsburg, where he has also served as Club President.

讲座视频 暂无视频

(转载文章,请注明出处: 西安交通大学学术资源平台