Simulation of Initially Forced Mixing Layers

Two-dimensional, turbulent mixing layers with initial periodic forcing are simulated by a vortex blob method. The motions of up to 2600 vortices and 3000 marker particles are followed by the use of the direct summation method. The first-order accurate Euler scheme is employed as a time-integral scheme. Forcing frequencies higher than the first subharmonic of the predominant, frequency of an unforced mixing layer are applied. It is shown that the development of a turbulent mixing layer depends much on forced disturbances and that turbulence suppression or amplification occurs depending on forcing frequencies. The results are consistent with experiments.