Numerical Investigation And Wind Tunnel Test On Hypersonic Aero-thermo-elasticity

Due to the complex flow phenomena such as shock layer,entropy layer,boundary layer,complex wave system interference,shock-viscous interference and high temperature gas effect in hypersonic flow,the flutter problem is more complicated than low speed flow.For such problems,in addition to careful theoretical and numerical analysis,it is necessary to conduct corresponding experimental research to validate the foregoing analysis.One of the important contents is the ground wind tunnel flutter test.Due to the difficulty in reaching high-altitude conditions in the wind tunnel and the short blowing time,the aerodynamic heat generation phenomenon in high-altitude flight is difficult to reproduce.Therefore,the ground wind tunnel test can only evaluate the aeroelastic problem other than aerodynamic heat.What’s more,in designing the wind tunnel model,it is necessary to take into account the impact on the model during starting or stopping the wind tunnel.In addition,the safety technology of the hypersonic wind tunnel flutter test is not mature enough.These all put forward higher design requirements for hypersonic wind tunnel flutter tests.Aiming at above problems,this paper mainly does the following work from the aspects of hypersonic flow simulation,grid processing,hypersonic aero-thermoelastic multi-field coupling method,aero-thermoelastic scaling design and hypersonic wind tunnel flutter experiments.Fast and accurate numerical simulation of the flow field is inseparable from the correct and efficient mesh processing.In computational fluid dynamics,the overlapping grid method has been widely used in numerical simulation of complex configuration flow fields and relative motion of multiple bodies,such as the separation of boosters for hypersonic aspirated aircraft.This paper has studied the explicit and implicit assembly methods of unstructured overlapping grids and made a series of improvements,including the improved hole mapping method,improved donor search method based on cut-paste and neighbor to neighbor searching,and the improved implicit grid assembly strategy as well as the local donor search method based on Cartesian grid mapping.Compared with traditional methods,these improved methods have higher computational efficiency,and provide a guarantee for fast and efficient numerical simulation of hypersonic flow fields.In order to verify the fluid-structure coupling calculation method in this paper,a hypersonic rudder model of an aluminum alloy plate was designed,and a hypersonic wind tunnel flutter experiment under the condition of Mach 5 was completed.Typical flutter phenomena were successfully observed.In order to avoid model flutter damage and potential risks to wind tunnel facilities,a passive flutter suppression system including collision is proposed.When the incoming flow pressure is higher than the model’s flutter pressure,the model oscillates in the form of a limit cycle within a certain amplitude range due to the impact of the model.A nonlinear aeroelastic numerical simulation platform including a flutter suppression system is established.The platform is based on the CFD / CSD coupling to take into account the nonlinear characteristics of collision.The good agreement between the numerical simulation and the final wind tunnel test results verifies the accuracy of the simulation platform.The Euler,N-S equation and ZAERO software were used to calculate the hypersonic flutter of the wind tunnel model,and the results were compared.All three results were in good agreement with test results.In addition,for this experimental model,the linear aerodynamic method can already provide good engineering accuracy.An aero-thermoelastic scaling method was developed based on the “hot mode,cold model”concept.Firstly,the “hot mode” of the model after aerodynamic heating under high-altitude conditions was obtained by static aero-thermoelastic trimming,and the aeroelastic response analysis of the model was used to obtain the flutter speed of the model after considering thermal effects.Secondly,the modal data of the target model was calculated based on the aeroelastic similarity theory based on the “hot mode”.Then take the stiffness and frequency of the target model as the target and optimize it separately to get the final scaled model.A typical hypersonic model was scaled down and the flutter speed of the scaled model was calculated,which matched the flutter speed of the air model well.