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【8月13日15:00】北京大学工学校特聘研究员谢金翰:Theory for structure functions of turbulence: Beyond the inertial range

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  • 报告题目:Theory for structure functions of turbulence: Beyond the inertial range
  • 人:谢金翰 特聘研究员
  • 报告时间:2020年8月13日(星期四),15:00-16:30
  • 报告地点:祁连堂322报告厅
  • 人:王国华
报告人简介

 Jin-Han Xie is an Assistant Professor at the Department of Mechanics, College of Engineering, Peking University. He was a Courant Instructor at the Courant Institute of Mathematical Sciences, New York University. Before that, he was a postdoctoral researcher at the physics department of the University of California, Berkeley. He obtained his PhD degree in Applied Math at the mathematics department of the University of Edinburgh. Jin-Han Xie's research focuses on fluid dynamics, in particular, geophysical fluid dynamics, turbulence, magnetohydrodynamics and microfluid dynamics.

报告摘要

  In 1941, Kolmogorov proposed the 4/5 law for three-dimensional isotropic turbulence, which links measurable third-order structure functions with energy transfer. It is only after around 60 years later that this theory is generalized to two-dimensional turbulence, then the theory is applied to quantify the direction and magnitude of energy transfer. However, the applicability of these theories is limited for several reasons: (i) they are derived for the inertial range, so they do not cover the forcing and dissipation scales; (ii) they apply to scenarios with unidirectional energy transfer, while the geophysical turbulence is known to transfer energy to both large and small scales simultaneously. To overcome these two obstacles, we derive a forcing-scale-resolving global theory that expresses different inertial ranges in one formula and captures the bidirectional energy transfer. Therefore it is well applicable to geophysical fluid data to obtain the information of energy transfer, and it applies to a broader range of the measured data by avoiding the artificial choice of inertial ranges. Also, the new theory brings about qualitative improvement by the ability to detect the scales of energy input, which was impossible before. Applying the new theory to oceanic drifter data we find bidirectional energy transfer and energy injection scales. We also apply the theory to the data of atmospheric surface layer and find energy transfer to small scale.

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