Numerical Investigations Of Supersonic Magnetohydrodynamic Flows Over A Semispherical Body

Magnetohydrodynamic flow control is a kind of new flow control mode by applying electromagnetic field, which is different from the traditional air flow by contacting the aircraft surface, and its most advantage is that not changing the aircraft aerodynamic shape. Therefore, the MHD flow control has the very deep development space and great application prospect in the aerospace field.The thesis aim at the problems of supersonic aircraft flying in the air will generate high heat,high pressure and will be resisted by drag force. The existing researches show that changing the front flow field of vehicle, especially changing the structure of the bow shock, which will improve the above problems effectively. For the purpose, the paper mainly study the influence of the flow field of typical hemisphere sphere under several categories of magnetic fields, and discuss the methods of the magnetohydrodynamic control in supersonic aircraft. In this paper, the flow field over the hemisphere sphere in supersonic situation be numerically simulated by solving three dimensional magnetohydrodynamic equations, the aerodynamic characteristics and the flow field in cases of uniform magnetic field, the dipole magnetic field and with Angle of attack are researched respectively. The concrete content includes:Firstly, the thesis study the interaction between different strengths of the dipole magnetic field and the flow field, mainly analyzed the flow field structure under different conditions, the status parameters on extension line of the stagnation point and the change of drag coefficient. The results showed that the different flow fields of cross sections are symmetry. With magnetic field intensity increasing, the bow shock standoff distance is increased, the drag coefficient is decreased. And the pressure, density and temperature on both sides of the semispherical body between shock layer and body surface are gradually reduced.Secondly, the paper study the influence of flow fields around the hemisphere sphere under different uniform magnetic field intensity. The results showed that within a certain range, with the increase of uniform magnetic field intensity, both sides of the bow shock gradually are widened, the bow shock standoff is increased and the drag coefficient is decreased, when the magnetic field strength is larger, drag coefficient is decreased mostly by 20%. In addition, the pressure and density are decreased at stationary point on the head of the body.Finally, the flow field structures of the semispherical body in different Angle of attack were simulated under different dipole magnetic fields. Results showed that when the body is in the same Angle of attack, with the increasing of magnetic field intensity, the shock standoff distance is increased and the drag coefficient is reduced linearly. When the body is under the same magnetic field intensity, with the increasing of Angle of attack, bow shock is inclined, drag coefficient is decreases gradually, and the status parameters on the extension line of stagnation point are varied irregularly.The above study complement the numerical simulation of MHD flow control research, which will provide a certain of reference data for further application in aerospace field, therefore it has a certain theoretical and practical significance.