Analysis Of Maneuvering Impact On Cavity Aerodynamic Characteristic

The buried weapon bay is an essential technology in the design of modern fighter.It can meet the requirements of modern war,such as stealth,supersonic flight and so on.But there are some new issues because of its complex internal flow field,such as the separation of flow,the movement of shear-layer,the generation and development of vortex,the shedding of vortices,the interference between vortexes and waves,etc.Especially under the condition of supersonic speed,there are strong flow phenomena such as shock waves and self-sustained oscillation in the buried weapon bay.The complex flow field in the buried weapon bay produces serious pressure oscillation and harsh noise,which cause fatigue damage to the weapon control system and related equipments,and then affecting the launch of weapons and the safe flight of fighters.In the actual situation,with the change of the fighter's attitude in the air,the flow field in the buried weapon bay will become more complex and more threatening to the fighter's safety.The research on the aerodynamic characteristics of the buried weapon bay during the maneuver flight is more close to the actual situation,which should be more comprehensively explored.In this paper,the sliding mesh model is used to realize the dynamic change process of the angle of attack of the buried weapon bay.First of all,the numerical simulation is carried out under the same conditions as the wind tunnel test when the angle of attack of the missile cabin remains unchanged.Then the results are compared with the results of wind tunnel test,which prove that the numerical simulation method in this paper can accurately solve the aerodynamic noise problem of the buried weapon bay.Then,using the numerical simulation method,has been proved correct,to study the dynamic process of changing the angle of attack with different angular velocity under the condition of transonic and supersonic flow.By analyzing the dynamic phenomena of flow field and the dynamic data,which includes velocity contour,vortical contour,overall sound pressure level distribution diagram,sound pressure level spectrum and so on,revealing the influence of changing the angle of attack of the buried weapon bay on the aerodynamic and acoustic characteristics under the condition of transonic and supersonic speed.The numerical simulation results show that the numerical simulation method adopted in this paper is relatively accurate to simulate the flow field changes in the buried weapon bay.Under the condition of transonic flow,the increase of the angle of attack will make the shear layer intrude into the bay early and cause more violent collision with the rear wall.However,when the angle velocity increases to a certain extent,the shear layer will collide with the bottom first,so that the flow in the bay is no longer a typical flow of open buired weapon bay;when the angular velocity is within 5rad/s,the greater the angular velocity of the bay,the flow will more easier to lose its opening characteristics.In the first 0.15 s,the modal frequency is not greatly affected by the rotation,but after0.15 s,the first and third order modal frequencies are reduced by about 50 Hz.Compared with the transonic condition,the aerodynamic characteristics of the buried weapon bay are more easily affected by the change of attack angle.