ANALYSIS OF SYNTHETIC JETS INFLUENCE ON PRES-SURE PULSATIONS AND FLOW IN THREE-DIMENSIONAL CAVITY FOR SUBSONIC AND SUPERSONIC EXTERNAL FLOW USING RANS/ILES METHOD

摘要

The effect of synthetic jets (SJs) and the influence of an external speed on the flow features were investigated using RANS/ILES method for the cavity M219. The numerical simulations were performed on a grid containing 2.5 million cells at Mach M_0 0.85 and 1.5. The method was approved by the comparison with the experiment and results of other authors. More precisely, the accuracy of the method is comparable to the accuracy of LES for a mesh with the number of cells twice as large. SJs were simulated using the modified boundary wall condition, which is well-proved in the calculations of SJs and permits to avoid time-consuming simulation of flow in the SJ generator. During the calculations there were used various SJ characteristics, such as their number (1 or 4), position (in front of a cavity, inside on the front wall and inside on the back wall), frequency f (100Hz, 200Hz, 300Hz, 1000Hz) and amplitude q (50m/s, 100m/s). It was shown that the jet inside the cavity acts as a turbulator of the flow and the jet in front of the cavity has a barrier character. For a subsonic external flow SJ located in front of a cavity for q=100 m/s and f=200Hz reduce peak pressure pulsations at the cavity back wall by 24%. The same jet located at the back wall increases peak pressure pulsations in 2 times. Spectral characteristics of the flow were obtained for M_0 0.85 and 1.5. Simulation results have shown good agreement with the experimental data and Rossiter's formula. It was found that on the back wall SJs decrease the second and the third modes of pressure fluctuations for subsonic flow and the first, the third and the fourth in the supersonic case.