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AngularMom0 Command

The AngularMom0 command sets the initial angular momentum for all particles in the current region. In 2D simulations, the command takes one argument:

AngularMom0 (Lp0z)

while for 3D simulations, it takes 3 arguments:

AngularMom0 (Lp0x),(Lp0y),(Lp0z)

(Lp0x), (Lp0y), and (Lp0z) are numerical values or user-defined functions of particle position that give the initial angular momentum per unit mass in (length units)2/time units. The initial values apply to all particles in the current region, including particles created in shape commands before the AngularMom0 command.

Notes

  1. This initial setting only has an effect for simulations that track particle spin.
  2. This command is setting angular momentum and not angular velocity. The setting to get a particular angular velocity (ω radians per sec) depends are particle locations and dimensions. For particles at typical starting positions, the angular momentum for given ω would be: where Δx and Δy are cell dimensions for the grid cell containing the particle. For 3D simulations, the equations are the same except may involve all three axes. The equation for each axis (e.g., Lp,x) depends on cell dimensions in the other two directions (e.g., Δy and Δz).
  3. Simulations with more particles per cell would need to set different angular momenta for different particle locations, which is currently not possible. One alternative is to use an average value noting that the fraction in the above angular momenta will range from 1/8 to 1/4 depending on particle location.
  4. The AngularMom0 command is only allowed within Region blocks of MPM analyses.