Helical vortices
Valery L. Okulov
Department of Wind Energy, Technical University of Denmark,
DK-2800 Lyngby, Denmark
报告时间：2017年9月28日(周四)下午4:00
报告地点：北航流体所214会议室
报告摘要：The main applications of 2D dynamics of helical vortices embedded in flows with helical symmetry are addressed.
The fundamentals of the 2D helical vortex dynamics lie in
(i) 2D algebraical expression of Biot-Savart law for helical filament;
(ii) analytical solution for self-induced motion of the helical vortex cores;
(iii) Goldstein’s solution for circulation of equilibrium of helical vortex sheets;
(iv) Generalization of Kelvin’s problem on point vortex N-gon stability to helix etc.
The primary assumption of the 2D theory is the hypothesis of helical symmetry that has been carefully tested in swirling flows in different kinds of swirlers and vortex generators. Both right- and left-handed helical symmetries were found in these real flows and hypothesis of existence of possible transitions between the different types of the vortex structures have been put forward. The change in axial velocity distribution from a jet-like profile to a wake-like during vortex breakdown has been investigated from this point of view and the associated transition from right- to left-handed helical symmetry of the vorticity field has been confirmed from experimental data and numerical simulations. Various vortex models for far wakes behind rotors are analyzed.
报告人简介：
Prof. Valery Okulov works in DTU, Denmark more than 10 years but before that he worked long time in Institute of Thermophysics, SB RAS, Russia. He obtained his degrees of D.Sc. (1994) and PhD (1985) in Fluid Dynamics. His research area is focused on aerodynamic and acoustic of turbo machines and wind turbines; hydrodynamics and physical processes in swirl flows; vortex dynamic, resonances and hydrodynamics instability in power-engineering devices. His scientific works are awarded diplomas and prizes: JSPS invitation fellowships (Japan), Diploma of TsAGI, Medal of G.I. Petrov for outstanding results in hydrodynamical stability and turbulence, Diploma of the Russian Academy of Sciences for outstanding scientific results, Otto Mønsted professorships (Denmark), Fellowship for young D.Sc. granted by the President of the Russian Federation etc.
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