Effects of Microjets in Flow Over a Backward-Facing Step

Large eddy simulation is used to study the flow over a backward-facing step interacting with a periodic array of streamwise microjets emenating from the step at a 45° angle to the step face. Averaged streamwise velocity profiles are in good agreement with experimental data. A well defined turbulent inlet profile for the microjet is found to be important to obtain correct streamwise normal fluctuations near the step. To simulate cases as per the experimental setup a microjet inlet pipe section is necessary for the simulations. The studies with passive scalars need to be conducted to quantify scalar mixing. The monotonicity problem of simulating passive scalar can be overcome by simply clipping the unbounded values. This technique works because the volume occupied by overshoot values of passive scalar are small compared to the total volume of the backward-facing step geometry.