Study On Drag And Heat Reduction Characteristics Induced By Spike And Jet In Hypersonic Flows Based On Conjugate Heat Transfer Approach

The hypersonic vehicle technology has high-efficiency penetration and rapid response capability,and its great strategic value in the military field has been widely concerned by the world's military powers.When the aircraft cruises in the adjacent space at hypersonic speed,it will face huge aerodynamic drag and severe aerodynamic heating environment.When the thermal protection design is unreasonable,the ablation caused by severe aerodynamic heating will change the hypersonic vehicle's aerodynamic shape,which even leads to failure of the flight.On the other hand,the huge aerodynamic drag will require higher demand for propulsion power and limit the further increase in cruising speed.Therefore,once concerning the engineering application of hypersonic vehicle,thermal protection and drag reduction have always been the key technologies.In this paper,based on the research background of drag and heat reduction technology in the field of hypersonic vehicle and employing the computational fluid dynamics approach as the research method,an in-house code using high resolution numerical scheme for conjugate heat transfer is developed based on finite volume method.Based on that,the mechanisms of drag and heat reduction for hypersonic vehicle and its influencing factors have been thoroughly studied,and a new type of drag and heat reduction strategy has been proposed for hypersonic vehicle.The main work is illustrated as follows:(1)For the hypersonic flow field,based on the Reynolds-Averaged Navier-Stokes equations and the coupling approach is applied to solve the structure heat conduction equation,the code for simulating the fluid-thermal interaction between the structure and hypersonic flow is developed.For the Navier-Stokes equations of fluid domain,the code employs finite volume method to solve the fluid governing equations based on the multi-block structured grids using high resolution numerical scheme and SST turbulence model,and the code also has the ability to simulate the two-dimensional,axisymmetric and three-dimensional flow field.To obtain the structure thermal response,the structure heat conduction equation is solved by the central difference scheme simultaneously based the conjugate heat transfer approach.(2)The developed code for fluid-thermal interaction in hypersonic flow field has been through validated by several classical experiments.Firstly,considering the flow features in hypersonic flow field,including shock waves,expansion waves,reattachment shock,shockshock and shock-boundary interaction and so on,classical experiments with different flow characteristics were selected to validate the accuracy and reliability of current code for simulating the hypersonic flow field.Then,the accuracy and reliability of current code for computing the structure heat conduction was validated by the case with analytical solution.Finally,the accuracy and reliability of the code for predicting the fluid-thermal interaction in hypersonic flow field was validated by widely-used and classical coupled heat transfer experiment.(3)A reliable and reasonable coupled heat transfer model for drag and heat reduction induced by the combinational spike and lateral jet concept is established.The turbulent flow field structure and the mechanism of the drag and heat reduction induced by the combinational spike and lateral jet concept in hypersonic flows are thoroughly studied.The numerical results present the high-resolution flow field structure,and the heat transfer characteristics of solid structure induced by the aerodynamic heating are also obtained.Based on that,the influences of spike length,lateral jet pressure ratio and lateral jet location on the flow field and the drag and heat reduction are numerically investigated.The obtained results give the variations of flow structure and drag and heat reduction performance following the change of these factors.(4)In order to further enhance the drag and heat reduction performance induced by the drag and heat reduction system,a novel non-ablative dual-jets strategy has been proposed.Compared with conventional drag and heat reduction system,this novel strategy employs the opposing jet at the spike head,which can protect the spike head from severe aerodynamic heating.On the other hand,the opposing jet employs low mass flow rate,so the drag induced by the opposing jet can be significantly reduced.The obtained results indicate that this strategy can achieve excellent thermal protection,which significantly reduce the heat flux along the blunt body and spike rod surfaces.Also,the drag reduction efficiency of this strategy is remarkable.Subsequently,the effects of the spike length and multi-jet conditions on the flow field and drag and het reduction are numerically analyzed.The computed results give clear flow features and the drag and heat reduction characteristics.(5)The unsteady development process of the flow field induced by the jet opening is numerically studied.The obtained results obtained clear development process of jet flow and the whole filed field unsteady characteristics.The variations of pressure and temperature along the blunt body and spike surfaces as well as aerodynamic drag are also obtained.Based on that,the influences of lateral jet location,spike length and jet pressure ratio on the flow development process are thoroughly investigated.In summary,the flow structure and the mechanism of drag and heat reduction induced by the combinational spike and jet strategy in hypersonic flows are thoroughly studied by means of computational fluid dynamics,and the influences of different factors on the flow field and the performance of drag and heat reduction are numerically investigated in detail.The current research is of significant for drag reduction and thermal protection system designs in the field of hypersonic vehicles.The in-house code is successful in simulating fluid-thermal interaction in hypersonic flows,which can provide clear and high-resolution flow structure and reveal the mechanisms of flow field and coupled heat transfer.