THE SOUND FIELD GENERATED BY A PAIR OF CIRCULAR CYLINDERS MOVING IN UNSTEADY RECTILINEAR MOTION

摘要

Two parallel circular cylinders with equal radii a_0 move with variable speed through an inviscid compressible fluid. Their centres are at ( ± h, 0), where h varies with time, so that they move along a common straight line with equal and opposite speeds. The acoustic velocity potential is determined asymptotically when the typical speed u_0 of the cylinders is small compared with the mean sound speed c_0 and the separation function h varies on a time scale t_0 = a_0/u_0. Inner and outer asymptotic approximations are matched and the distant sound field is expressed in terms of line sources of monopole and quadrupole type.