The stability of axisymmetric free shear layers

Abstract

The stability of laminar axisymmetric jets and wakes, the two prominent examples of free shear layers, is investigated with respect to linear azimuthally periodic disturbances. The complete viscous disturbance equations are integrated numerically and the eigenvalues are obtained by matching the numerically advanced solutions to the asymptotic solutions at a large radius. Both spatial and temporal stability are examined for inviscid and viscid flows. It is found that the critical Reynolds number for the jet and the wake are not much different while the amplification rates for the wake become considerably greater than those for the jet as the Reynolds number increases. The axisymmetric shear-layer flows also seem to be more stable than the corresponding plane flows.