Direct Numerical Simulation of Low Re_m Compressible Magnetohydrodynamic Isotropic Turbulence

摘要

Since the magnetohydrodynamics (MHD) flow control was proposed in 1990s, the MHD control is regarded as a highly potential technology in the applications of hypersonic vehicles. In typical hypersonic cruising flight conditions with MHD control, the low magnetic Reynolds number (Re_m) magnetohydrodynamic turbulence exists in the flow field, which is different from the turbulence without magnetic field and the high Re_m magnetohydrodynamic turbulence. This paper investigated the low Re_m compressible magnetohydrodynamic isotropic turbulence via the Direct Numerical Simulation (DNS). The free decaying turbulence in different Taylor-microscale Reynolds number (Re_λ) and magnetic interaction parameter per unit length (N) conditions are studied. Results indicate that the external magnetic field causes the anisotropic characteristics of the turbulence, the velocity and the normal Reynolds stress in the direction perpendicular to the magnetic field are both suppressed and decrease. Moreover, the velocity gradient in the turbulence is also anisotropic when the external magnetic field exists. Besides, the Joule dissipation caused by the coupling effect of the magnetic field and the turbulence transforms the kinetic energy of the flow to the internal energy, and then the turbulent kinetic energy decays faster.