INITIAL DRAG ON A CYLINDER

The short-time solutions for the flows past a circular cylinder which starts from rest with several different prescribed motions at finite Reynolds numbers have been obtained by previous workers who have used boundary-layer approximations. In the present work, the initial stage of the unsteady flow past a circular cylinder which starts from rest with an arbitrary translation along a line perpendicular to the axis of the cylinder is determined. The solution to this problem is shown to be equivalent to the solution of the one-dimensional heat equation with an unsteady boundary condition, for which a solution is given. Numerical results for the unsteady drag force on a cylinder are given for two examples. The first example demonstrates the accuracy of the present results in comparison with the known approximate solution, and the second example illustrates how readily hitherto unavailable results can be derived from the general solution given herein.