FORMATION AND EVOLUTION OF THE STREAMWISE VORTICES IN MIXING LAYERS

摘要

The evolution of the three-dimensional time-developing mixing layeris simulated numerically using the pseudo-spectral method.The initial perturba-tions used in this study consisted of the two-dimensional fundamental wave and thestreamwise-invariant three-dimensional disturbance.A comparison of the formationsof the streamwise vortices with different amplitude functions for three-dimensionaldisturbances is made.In one case the results are similar to that of Rogers & Moser~[1],whereas a different way in which the quadrupole forms and sudden expansion of therib are observed in another case.The simulation also confirms that the stretching bythe forming roller rather than Rayleigh centrifugal instability is responsible for theformation of the rib.Finally,numerical flow visualization results are presented.