振動流中の正方形柱周りの流れの三次元数値解析(流体工学,流体機械)

概要

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Flow around a square cylinder in oscillatory flow was studied by a numerical simulation using a finite-volume method. The computations were carried out by assuming 3-dimensional (3-d), unsteady, incompressible and viscous flow through Keulegan-Carpenter number (KC) in the range of 2.5≦KC≦25 at Stokes number (β)=95. The region in KC≦4, "longitudinal vortex pairs" periodically arranged in span-direction were found out as well as in the case of circular cylinder. On the other hand, KC≧5, the flow patterns called "transverse-vortex street", "double-pair" which appeared in the case of the circuler cylinder at KC = 12 and KC = 16, respectively, were not formed. The drag and inertia coefficients of the Morison equation C_D and C_M were estimated and it was found that decreasing of C_D as KC increases in the region 2.5≦KC≦12 is caused by the change in the position of rolling up of the flow in the wake. By calculating spanwise correlation, the effect of 3-D flow structures on the transvers force were investigated. The effect remarkably appears in the range of 2.5≦KC≦8 in which the "longitudinal vortex pairs" are formed.
社団法人日本機械学会の論文
2008-03-25