Unsteady Boundary Layers : (1st Report, Theory of the Boundary Layer on a Symmetrical Body in a Fluctuating Main Stream)

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  • 非定常境界層の研究 : 第1報, 主流速度が変動する対称物体の境界層の理論
  • ヒテイジョウ キョウカイソウ ノ ケンキュウ 1

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Abstract

A theory is presented for the calculation of unsteady laminar boundary layers in an incompressible fluid about a two-dimensional body. Fluid velocity in the main stream just outside the boundary layer, expressed as a power series of the distance x measured along the body surface, is assumed to fluctuate about its mean value. The magnitude and frequency of the fluctuation are assumed to be small. Velocity fluctuation in the boundary layer is also expressed as a power series of x, whose coefficients are functions of the non-dimensional distance measured normal to the surface. These coefficient functions are universal and can be tabulated once and for all. Functions corresponding to the main stream velocities of third order polynomial and frequencies up to second order are actually computed and tabulated. As an example, the movement of the boundary layer separation point on a circular cylinder is calculated. The movement, although it increases with frequency, is rather small.

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