Numerical Investigation on Aerodynamic and Electromagnetic Influence of Shape of The Grilles in a Rectangular Duct

Abstract

The electromagnetic scattering characteristics of the inlet with grilles are calculated to verify the feasibility to reduce the radar cross section by installation of grilles. The Method of Moment (MOM) is used to calculate the models. According to its complicated structures, the inlet with grilles is simplified and the structured mesh is applied to specify the minor features of a large quantity of grilles to obtain aerodynamic characteristics of these models. The SST k-ω turbulence model based on the RANS method is utilized to simulate the air flow through the inlet. A clear duct with the geometric parameters (180mm 180mm 400mm) as well as the duct with grilles involving different parameters (shapes, thickness) is applied for the numerical simulation at the speed of 0.6 Mach at a certain range of angles of attack. Grilles in different parameters are simulated separately and compared with the clear inlet and the inlet with grilles, to find an approximate but simple method to estimate the aerodynamic influence taken by the different grilles. The results implicate that grille installation in the inlet has a significant positive influence on electromagnetic stealth performance. RCS drops by 4.80dBsm at an angle of attack of 0°. Meanwhile, substantial RCS reduction at range of angle of attack from 0°to 20° is found. Thickness and shape have remarkable influence on aerodynamic performance instead of electromagnetic scattering characteristics (f=1GHz, VV). The couple of grilles and inlet duct shows a little effect on aerodynamic characteristics compared with the single-element grille. It is acceptable to simulate grilles with inlet by numerically calculating the single-element grille.