2D Magnetohydrodynamic Rotor - SFG-CUHK/scorpio-test-cases GitHub Wiki

The rotor problem is one of the standard problems to test the propagation of Alfven waves with a strong torsional component and is closely related to star formation. It was first published by [Balsara and Spicer, 1999(https://ui.adsabs.harvard.edu/abs/1999JCoPh.149..270B/abstract). The parameters of the test case are listed below.

Parameter Setting Parameter Setting
x, y [0, 1] Nx, Ny 201
Gamma 1.4 CFL 0.4
Solver HLLD Flux-limiter minmod
tend 0.15 P 1
B Bvec r0 0.1
r1 0.115 v0 2

Where x, y are the dimension of the domain, Nx, Ny are the number of cells in the two directions. The initial magnetic field is uniform following B. The density and velocity of the gas are separated into three layers.

  1. Core of the rotor, rleqr0:
    • density rho=10
    • x-velocity vx1
    • y-velocity vy1

  1. Outer shell of the rotor, r0<r<r1:
    • density rho=1+9fr
    • x-velocity vx2
    • y-velocity vy2

  1. Ambient fluid,rgeqr1:
    • density rho=1
    • velocity vx=vy=0

Where fr The dense rapidly spinning cylinder (the rotor) locates at the center of ambient fluid. The rapidly spinning rotor cases torsional Alfven waves to be launched into the ambient fluid. The magnetic field around the rotor is strong enough and the high magnetic pressure around the rotor compresses the fluid in the rotor, thus giving an oblong shape. Torsional Alfven waves transfer angular momentum from the rotor to the ambient fluid as shown in the figure below.

Result of the 2D MHD rotor, simulated with Scorpio.

The result is comparable to Balsara and Spicer, 1999, and the FLASH test case.

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