円弧型溝による円柱の抗力低減のメカニズム(流体工学,流体機械)

概要

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The mechanism of drag reduction in a circular cylinder with arc grooves is investigated. The circular cylinders with grooves have thirty-two arc grooves of different depth on the cylinder surface. The pressure distributions of cylinders with grooves, velocity of boundary layer and Karman vortices in the wake area are measured and the flow of cylinders surface are visualized in experiment. The following results are clarified by these experiments. The separation bubbles are generated inside the grooves. These separation bubbles transform the laminar boundary layer into the turbulent boundary layer. Therefore, the separation point of cylinder with grooves shift to further downstream side and the drag coefficient of the cylinder with grooves take a smaller value than that of a smooth cylinder. As the grooves are deeper, the critical region shifts to lower Reynolds number side. In the supercritical region, the spectrum of Karman vortices for the cylinder with shallower grooves is very small. However, as the depth of groove increases, the cycle of Karman vortices become clear.
一般社団法人日本機械学会の論文
2004-09-25