A 1ST APPROXIMATION TO THE EFFECTS OF MEAN FLOW ON SOUND-PROPAGATION THROUGH CYLINDRICAL CAPILLARY TUBES

It is shown, with reference to assumed isentropic disturbances, that radial velocity terms have negligible influence upon the axial wave propagation in capillary tubes. A variational solution of the problem of non-isentropic wave propagation in a cylindrical tube in the presence of a convecting steady flow is then presented. The manner in which the flow influences the attenuation and the phase velocity of the forward and backward propagating acoustic waves is deduced. It is also shown that a third wave of hydrodynamic type is generated when steady flow is present.