静止流体中の回転円筒まわりの乱流せん断流 : 流れの可視化とうず塊のスケール

抄録

An experimental study has been performed on the structure of turbulent flow around a cylinder spinning in a quiescent fluid. The visualization using smoke wires and the method of thermal tuft have revealed that the reverse flow exists not in the internal region but in the external region of the cylinder. The reverse flow occurs in the same region as the eddies which can be found by scattering aluminum powder. It has been found that the eddies displayed by the picture of aluminum powder, which was taken by a rotating camera grew larger and larger in propagation to the distance from the cylinder. Also the mixing length grows longer and longer just as above. The radial length of eddies almost agrees with the mixing length. Furthermore, the turbulent diffusion of the instantaneous spot in the dropping of dyes has been examined. The examination has shown that the scale of diffusion has a strong correlation with that of the peripheral length of eddies.