203 低レイノルズ数正方形ダクト乱流における渦構造(2)(OS2-1 壁乱流の計測と制御,OS2壁乱流の計測と制御)

概要

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Spectral direct numerical simulations of fully developed turbulent flow in a straight square duct were performed in order to investigate flow structures at low Reynolds numbers. It was found that turbulence can be maintained for values of the bulk Reynolds number above approximately 1100, and the minimum value for the streamwise period of the computational domain is around 190 wall units, which is roughly independent of the Reynolds number. The flow state at marginal Reynolds numbers exhibits a 4-vortex secondary flow structure alternating in time, whereas the fully turbulent one presents the usual 8-vortex pattern. It is shown that buffer layer coherent structures play a crucial role in the appearance of secondary flow of Prandtl's second kind at the marginal Reynolds numbers. The coherent structures are observed to affect the mean primary and secondary flow even at higher Reynolds numbers.
一般社団法人日本機械学会の論文
2007-11-17