Numerical Analysis Of Magnetofluiddynamic Control On The Hypersonic Inlet Flow

To realize the wide speed range flight of hypersonic aircraft,how to ensure the performance of the inlet in the off-design flight conditions is very important.Compared with the traditional control method,the electromagnetic flow control is a new concept active flow control technology,this flow control system has so many advantages that it is reusable,easy to be switched on-off and does no harm to the aerodynamic configuration of the object aircraft.Moreover,the feedback control can be realized according to different flight conditions.All of these advantages have warranted popular interest in this subject area in recent years.In this research,focusing on the hypersonic inlet with application of electromagnetic flow control,combined methods of theoretical analysis and numerical simulation are utilized in this paper.In order to explore the interaction mechanisms between the hypersonic flow field and the electromagnetic field,physical models and CFD methods of the hypersonic flow field coupled with electromagnetic field are developed.By applying the numerical codes written in this paper,hypersonic flow structures,flow principles as well as the electromagnetic control mechnisms after coupling the electromagnetic field are detailedly analyzed and clearly revealed,which provide theoretical and design tool support for further mechanism analysis of active flow control technology for hypersonic inlet.Numerical calculation model is constructed for solving the three-dimensional perfect gas laminar and turbulence flow coupled with electromagnetic fields based on the low magneto-Reynolds assumption.Common conductivity models are given,including thermal ionization gas conductivity model and artificial ionization gas conductivity model.Multiple types of applied electric and magnetic field models are established.Results indicate that the simulation result in this work is in good agreement with experimental data and calculation results provided by the references,and can be used as a reliable tool for the research of electromagnetic flow control mechanism.By analyzing the role of Lorentz force in the fixed geometry shock control technologies,the mechanism of electromagnetic shock control and separation control have been revealed.The numerical simulation of simplified flow models have been conducted by application of an external electromagnetic field,which provides basic examples and basic data for the research of the hypersonic electromagnetic control inlet.Based on the numerical calculation method of coupling external electromagnetic field and the laminar flow field.The effects of external magnetic fields on the shock wave configuration at hypersonic plasma flow field are investigated in this paper.A series of numerical simulations over a blunt body have been conducted by varying the applied magnetic field under different freestream conditions.Results show that,for the bow shock control,the function of two components of Lorentz force is different that the counter-flow one decelerates the flow and increases the shock-wave standoff distance,while the normal one squeezes the oblique shock and deflects the streamlines.The bow shock standoff distance is dependent on the distribution of counter-flow Lorentz force right after shock in the stagnation region.Based on the numerical calculation method of coupling external electromagnetic field and the turbulent flow field,a series of numerical simulations over a fixed-geometry inlet forbody,have been conducted by varying the applied electromagnetic field.The required electrical conductivity in air is supposed to be created by electron beams injected into the air.The effects of deceleration/acceleration control systems on the oblique shock of hypersonic inlet are clarified.Results show that the magnetofluiddynamic deceleration system could bring shocks back to the cowl lip under the effect of counter-flow Lorentz force.The inlet forebody shock electromagnetic acceleration system not only has the positive effect of Lorentz force accelerating the local flow field,but also has the negative effect of energy release.All in all,the electromagnetic acceleration system have little effect on the ability of shock controlled.The fixed geometry hypersonic inlet can be designed with a low design Mach number,and the magnetofluiddynamic deceleration control system bring shocks back to the cowl lip at high Mach number flight,and significantly improve the basic performance of the hypersonic inlet.A new type of hypersonic compression corner separation electromagnetic control system is established.The electromagnetic control mechnisms of typical compression corner shock boundary layer separated flow have been conducted.Conclusions can be summarized as follows: 1)For the compression corner flow deceleration magnetofluiddynamic control system,the performance of boundary layer flows control is mainly determined by the Lorentz force in the counter-flow direction by application of an external magnetic field.With an external magnetic field applied,the fluid in the boundary layer can be dccelerated,and the ability of the boundary layer to resist separation have been reduced.Moreover,the Lorentz force in the counter-flow direction reduced the turbulent skin friction coefficients and increased the static temperature locally.The location for the magnetofluiddynamic zone has a great influence on the control of the ramp-induced separation.When the excitation location before the separation point and after the reattachment point,the separation zone of the flow field is obviously enlarged.However,when the excitation position is located in part of the separation bubble,the separation zone of the flow field is reduced,saturation effect exists in the process of magnetofluiddynamic separation mitigation.2)For the compression corner flow acceleration electromagnetic control system,the performance of electromagnetic boundary layer flows control is mainly determined by the Lorentz force in the streamwise direction by application of an external electromagnetic field.With an external electromagnetic field applied,the low velocity fluid in the boundary layer can be accelerated and the ability of boundary layer to resist separation have been enhanced.The closer the electromagnetic interaction area is to the separation area,the smaller the pressure platform area becomes,the platform pressure gradually increases,and the size of the separation area decreases.In addition,The Joule heating term always brings negative effects on the electromagnetic separation flow control and increases the static pressure locally,where the electromagnetic field is applied.3)The electromagnetic control effect of turbulent flow is mainly reflected in the influence of Lorentz force on the flow parameters in the turbulent boundary layer.Compared with hypersonic laminar flow,the magnetic interaction parameters of hypersonic turbulent flow field are smaller,and the stronger external electromagnetic field and flow conductivity are required to achieve the same control result.The numerical simulation of hypersonic inlet have been conducted by application of an external electromagnetic field.The shock induced boundary layer separation electromagnetic control have been conducted.Moreover,the unstarted hypersonic inlet is studied and the electromagnetic control for inlet start is investigated based on the inlet.The analytical model of separated flow control in the electromagnetic controlled inlet is established.In the experimental case of low Reynolds number and low turbulence intensity,the electromagnetic control technique could move the separation point downstream,diminish the separation bubble,and then alleviate or even eliminate the shock-induced separation.The basic flow field structure of the unstarted hypersonic inlet is studied,and the electromagnetic control for inlet start is investigated based on the inlet.The results show that the Lorentz force directed in the streamwise direction can reduce the self-starting Mach number of the background inlet.