Prediction of splitting airfoils horizontal spacing effects on loss distribution in an array distortion generator based on comparison of RANS, URANS and DES

The ability to reproduce a given distribution of total pressure loss by horizontal arrangement of splitting airfoils has been evaluated numerically in this research. This array arrangement is a proposal design for a new distortion generator mechanism. Due to significant differences between steady-state simulation based on RANS turbulence models and reference experimental test results, unsteady simulation was performed with vortex shedding frequency- proportional time step. The 90-degree airfoil reference test measurements show that maximum loss zones from primary downstream stations to fully developed wake region switch from vertical placement to horizontal; this distinctive feature was not seen in the unsteady RANS results. Detailed simulation of downstream turbulent mixing based on DDES hybrid model, predicts above switching well. The repeatability studies of single splitting airfoil loss pattern in airfoils horizontal arrangement combined pattern, led to necessity of 90-degree airfoil downstream flow structure correction that is a destructive factor of pattern predictability. This correction can be achieved by changing the airfoil aspect ratio.