Masanori Matsumura

Incoherent turbulence structure in the near wake of a normal plate

In this paper experimentally studied characteristics of various frequency components of incoherent velocity fluctuations in the near wake behind a thin normal plate immersed in a uniform flow are described. Measurements were made at a position 8 plate heights downstream of the plate where the wake had a marked periodicity, so that coherent vortices shed from the plate are expected to have a small dispersion in streamwise spacing, transverse location, strength and shape. Shearing stress associated with the incoherent fluctuations is mainly contributed by components with frequencies around half of the vortex-shedding frequency f s on one side of the wake. The ½ f s frequency component appears to be caused by the spanwise locations of ribs, which are connected to the coherent vortices, being different from vortex to vortex. A probable spanwise arrangement of the ribs is suggested.

Turbulence structure in intermediate wake of a circular cylinder.

本論文は,中間領域における円柱後流中の速度変動を位相平均することによって,大規模な組織的渦構造とこれに重畳された小規模構造との関係を実験的に調べたものである.大規模構造内における流線,渦度,速度ベクトル,相関の分布を求めるとともに,小規模構造による変動エネルギ,相関,乱流間欠係数の空間的分布を示した.また,この結果にもとづいて大規模構造による連行および渦度の拡散に対する一機構を明らかにすることができた.