抄録
The stability of fluid flow in a circular pipe to infinitesimal disturbances is investigated by making use of a method of eigenfunction expansion, taking into account the three-dimensional variation of disturbance velocities. It is shown by numerical computations that the Poiseuille flow becomes unstable beyond a critical Reynolds number which depends on azimuthal wave numbers considered. The minimum critical Reynolds number corresponds to the rotationally symmetric spiral mode of oscillations and it is found to be 1320 when use is made of twenty coordinate functions. Non-symmetric disturbances become growing for the Reynolds numbers larger than 8600. Discussions are made concerning the physical reasonings of discrepancy with the results of previous investigations according to which the Poiseuille flow has been considered to be stable to small disturbances.
