境界層の乱流遷移におけるトリッピングワイヤ効果とワイヤ後流の測定 : 全頂角の異なるくさび形物体

概要

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Experiments were conducted on the effect of a tripping-wire on the laminar-turbulent transition of boundary layers over wedges of 15, 30 and 60 degrees with a pressure gradient. The results obtained are as follows : (1) the transition Reynolds number R_t=U_∞x_t/ν at the most effective condition is given as the formula R_t=1.06R_k+1.33×10^4 for the range of the wedge angle between 15゜ and 60゜, where R_k (=U_∞x_k/ν) is the wire Reynolds number, U_∞ the free-stream velocity, x_k and x_t the location of the wire and the transition point measured from the apex of the wedge, respectively, k the wire diameter, and ν the kinematic viscosity of the fluid. (2) The minimum transition Reynolds number R_<tm> is a function of the ratio of the height of the roughness element k to the displacement thickness δ* of the boundary layer at the location of the element, and R_<tm> decreases with increasing k/δ*. R_<tm> increases with an increasing wedge angle at the same value of k/δ*.
1989-08-25