非定常境界層の研究 : 第4報, 級数解法による任意形状物体の境界層計算法

抄録

A method of calculating the unsteady laminar boundary layer is presented. Two-dimensional flow of an incompressible fluid is assumed. The case of an oscillating outer flow, about a time-mean value, with a small amplitude and at relatively low frequency, is considered. By the use of a power-series expansion method, boundary layer around a body with an arbitrary shape and with a wedge-shaped nose of arbitrary angle, can be calculated. The solution is obtained as a linear combination of a set of universal functions. Velocity fluctuations in the boundary layer, of second order in magnitude, are taken into account. The time-mean velocity at a point in the boundary layer shifts as the amplitude of outside flow oscillation is increased. At the same time, the second harmonic fluctuation is produced. The method of calculation is applied to the boundary layer of a circular cylinder, and it is found that the influence of the second order velocity change is rather small, even at the outside velocity fluctuation 0.5 times the mean velocity.