Crow instability effects on the exhaust plume mixing and condensation

Three-dimensional direct numerical simulation is performed to study the interaction of two engine jets with a pair of trailing vortices. First of all, a test panel of selected flux limiter has permitted to suppress spurious oscillations of the passive scalar and to enforce its positivity. Then, contours of a passive scalar (or a tracer concentration) are used to investigate the mixing and entrainment processes when the vortex pair goes through sinusoidal instability. The present results show that the dilution of the exhaust plume is less efficient when the flow undergoes this perturbation. However, the rate of mixing appears insensitive to the development of the Crow instability. Furthermore, in order to study condensation process, results are presented involving the calculation of the saturation with respect to liquid water. This is performed by post-processing solution fields which provide a qualitative indicator where the condensation occurred in the aircraft wake.