純粋ポアズイユ，純粋クエツトおよびクエツト・ポアズイユ型バックステップ乱流の回復域の乱流構造

摘要

Turbulence statistics in velocity recovery region of pure Poiseuille, pure Couette and CouettePoiseuille type turbulent channel flows over a backward-facing step are measured and investigated experimentally. The flows are turbulent channel flows between moving and stepside stationary walls with different non-dimensional upstream pressure gradients β_0 (flow type parameter). The channel expansion ratio is 1.50. The upstream Reynolds number based on the friction velocity and upstream channel half width is about 300. Regions for the logarithmic and half power velocity laws in the backward-facing step flows were specified in the last report. In this study, velocity profiles are measured by using X-type hot-wire anemometry at several sections and turbulence statistics at the sections are estimated. The region for the logarithmic velocity law appears in the regions aside the production predominant region. On the other hand, the region for the half power velocity law appears in the region where the turbulent diffusion term is comparable with the production term.%バックステップ乱流は，はく離点がステップ角部でrn固定されるため，はく離・再付着を伴う乱流の中でも最rnも基本的なものである．著者らは前報においrnて，ステップ上流が完全発達平行平板間乱流，つまりrn純粋ポアズイユ流，純粋クエツト流およびクエツトポrnアズイユ流である場合について，壁面の静圧測定およrnびI型熱線流速計による平均速度場の計測を行った．