Numerical investigation to wind-tunnel-blockage effects on aerodynamic noise measurements of a landing gear

In order to provide a basis and some references for experimental study on aerodynamic noise of landing gears, a numerical simulation is carried out for a four-wheel rudimentary landing gear (RLG) model using the delayed detached eddy simulation (DDES) based on the S-A turbulent model. Slip wall boundary condition with different section areas are used to mimic wind tunnels with different sizes, and the non-wind-tunnel case is simulated with far field boundary conditions for the side walls and the floor. The blockage ratio β is varied from 0 to 8.8%. Time-averaged surface pressure coefficient and surface sound pressure level (SPL) are calculated from the simulated unsteady flow field. The results show that the mean surface SPL decreases with increasing β in general. There is a threshold β ranged of roughly 4%~5%. The mean surface SPL varies sharply when β is within this range, and is insensitive with β when it is out of this range. The most β-sensitive part is the front wheel, while the most insensitive is the back wheel. This demonstrates a close relation between the aeroacoustic properties and mean flow properties at different blockage ratios.