Investigation of flow characteristics over the fuselage airbrake

This paper studies the characteristics of the hinge moment of the fuselage airbrake at the opening angle of 60° with the fuselage angles of attack from 0° to 70°,analyzes the flow structures on the windward side and the leeward side of the airbrake.The experimental results show that the characteristics of the hinge moment can be classified into three regions with α.In the constant region (α=0°~16°),the hinge moment of the airbrake changes little with α increasing,because the positive pressure decreases on the windward side of the airbrake and the negative pressure increases on the leeward side of the airbrake with α increasing,two opposite trends counteract with each other.In the nonlinear increasing region (α=16°~32°),the hinge moment of the airbrake increases greatly with α increasing,because the hinge moment is mainly contributed from the leeward side of the airbrake and the negative pressure increases markedly on the leeward side of the airbrake with α increasing due to the enhanced couple vortices on the leeward side of the airbrake.In the nonlinear decreasing region (α=32°~70°),the hinge moment of the airbrake decreases greatly in the range of 32°~36° because the vortices flow on the leeward side of the airbrake turns to a low speed reattachment flow at α=36°; the hinge moment of the airbrake increases in the range of 36°~44° because the positive pressure on the windward side of the airbrake increases greatly due to the enhanced forebody vortices flow; the hinge moment of the airbrake decreases gradually in the range of 44°~70° because the pressure values on the windward side of the airbrake decreases gradually due to the weakened forebody vortices flow.