Ks. Peat, A 1ST APPROXIMATION TO THE EFFECTS OF MEAN FLOW ON SOUND-PROPAGATION THROUGH CYLINDRICAL CAPILLARY TUBES, Journal of sound and vibration, 175(4), 1994, pp. 475-489
It is shown, with reference to assumed isentropic disturbances, that r
adial velocity terms have negligible influence upon the axial wave pro
pagation 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 i
s present.