B-233 乱流中の DNS, GS 及び SGS 速度場における Coherent 渦構造の性質

概要

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Characteristics of coherent structures (CS) in homogeneous isotropic turbulence are investigated by using DNS (Direct Numerical Simulation), GS (grid-scale) and SGS (subgrid-scale) velocity fields to perform a priori test. GS and SGS fields are obtained by filtering the DNS database up to Re_λ=87.9 using two classical filters : Gaussian and sharp cutoff for LES. The filter width, Δ is considered as the length of Kolmogorov microscale (η) in the DNS field with a constant multiplication. Visualization of flows revealed that GS and SGS fields itself contain lots of distinct tube-like structures somewhat similar to the structures in the DNS field, but shows strict coherency, which can be defined as CS in turbulence. The characteristics of the CS in GS and SGS field are likewise similar to the structures in the DNS field, which indicate that the DNS field may contain small-scale and large-scale structures together in turbulence.
日本流体力学会の論文
2003-07-28