NONAXISYMMETRIC INSTABILITY IN SLOWLY SWIRLING JET FLOWS

作者：FOSTER MR^*

来源：Physics of Fluids. A, Fluid Dynamics, 1993, 5(12): 3122-3135.

DOI：10.1063/1.858721

Very small, amounts of swirl are shown to strongly destabilize a round jet flow to large n inertial modes, where (k,n) are, respectively, the axial and azimuthal wave numbers of the disturbance. This mechanism is operative if the scale of the small swirl, epsilon, is O(n(-1)) for k=O(1). Further, viscosity is shown to exert a stabilizing influence on these modes if the Reynolds number is no larger than O(n(3)), hence, neutral curves have been obtained for a particular example-the slowly swirling Squire jet. For this case, there is a very broad range of unstable wave numbers-all k between epsilon n/2 and n. It is further determined that in the context of an initial-value problem for such a weak vortex on which is imposed a concentrated initial disturbance, the entire vortex is temporally unstable downstream of the initial disturbance.

• 出版日期1993-12