正方形断面管路内乱流におけるストリーク構造 : 低速ストリークを伴う壁付近の組織的構造

抄録

Streaky structures have been studied in a fully developed turbulent square-duct flow by using combined dye flow visualization-LDV velocity measurement techniques. Velocity fluctuations were characterized both by topological properties of low-speed streaks, such as coalescing and branching, and by the transverse location λ of the visually identified low-speed streaks. Near-wall coherent structures are discussed for each topological type of low-speed streak in terms of the dependence of the most probable values of the velocity fluctuations on λ. It is shown that without coalescing and branching, a spanwise symmetric pair of counter-rotating quasi-streamwise vortices is, statistically speaking, associated with one low-speed streak. However, upstream of the coalescing point and downstream of the branching point of low-speed streaks, an asymmetric single quasi-streamwise vortex may be associated with one low-speed streak.