Numerical Simulation of Airfoil-Vortex Interaction in Tandem Airfoils

Aerodynamic noise generation from aircraft and wind turbines is one of the pertinent problems in the aeronautical industry. The fluid flow over an airfoil generates noise because of various phenomena such as vortex-shedding and flow separation. The vortex shedding from the upstream object interacts with the object placed in the wake and generates noise, called body-vortex interactions (BVI). Tandem airfoil arrangements were used to analyze the BVI effect on noise generation. The hybrid RANS-LES method was used for simulation. The noise generated in the two airfoils case showed a slight increase. The acoustic level depended on the interference pattern between the acoustic waves radiated from the trailing edge of both airfoils and the interaction of the shed vortices with the second airfoil. It was found that the flow pattern and the resultant acoustic field depend on the distance between the airfoils. An increase in the inlet velocity shifted the peak SPL amplitudes to higher frequencies. The modal analysis provided insight into the broadband spectrum. The trailing edge of the airfoil was observed to generate pressure waves of a broadband nature containing multiple frequencies. Different dominating modes were found in the two airfoil cases, which resulted in a modified acoustic field.