This command is used to define initial velocities and initial angular velocities, applying to nodes and to soil particles (see PARTICLE_SOIL). The command is additive and multiple velocity definitions are summed up to form a total velocity.

An initial velocity term of a node or a soil particle at coordinate $(x,y,z)$ is defined as:

$\left\{ \begin{array}{c} v_x \\ v_y \\ v_z \end{array} \right\} = \left\{ \begin{array}{c} v_{x0} \\ v_{y0} \\ v_{z0} \end{array} \right\} + \left\{ \begin{array}{c} x-x_0 \\ y-y_0 \\ z-z_0 \end{array} \right\} \times \left\{ \begin{array}{c} \omega_x \\ \omega_y \\ \omega_z \end{array} \right\} + \left\{ \begin{array}{c} \delta v_x (x-x_0) \\ \delta v_y (y-y_0) \\ \delta v_z (z-z_0) \end{array} \right\}$

Initial velocity

The command below initializes the spin of rigid body with part id 333. The axis of rotation is defined from the spin vector (10,20,0) and the point (1,2,3).

Initial velocity field using fcn

Complete command file of a rubber sheet that has been assigned a linear velocity field.

Linear variation of velocity in x-direction