Hydromechanics of low - Reynolds - number flow . Part 4

The problem of a uniform transverse flow past a prolate spheroid of arbitrary aspect ratio a t low Reynolds numbers has been analysed by the method of matched asymptotic expansions. The solution is found to depend on two Reynolds numbers, one based on the semi-minor axis b, Rb = Ublv, and the other on the semi-major axis a, Ra = Ualv (U being the free-stream velocity at infinity, which is perpendicular to the major axis of the spheroid, and v the kinematic viscosity of the fluid). A drag formula is obtained for small values of R, and arbitrary values of R,. When Ra is also small, the present drag formula reduces to the Obcrbeck (1876) result for Stokes flow past a spheroid, and it gives the Oseen (1910) drag for an infinitely long cylinder when Ra tends to infinity. This result thus provides a clear physical picture and explanation of the 'Stokes paradox' known in viscous flow theory.