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INITIAL_VELOCITY

Initial conditions

*INITIAL_VELOCITY
entype, enid, $v_{x0}$, $v_{y0}$, $v_{z0}$, $\omega_x$, $\omega_y$, $\omega_z$
$x_0$, $y_0$, $z_0$, $\delta v_x$, $\delta v_y$, $\delta v_z$, csysid

Parameter definition

Variable
Description
entype
Entity type
options: N, NS, P, PS, ALL, G, DP, SPH
enid
Entity identification number
$v_{x0}$
Initial velocity in x-direction
options: constant, fcn
default: 0
$v_{y0}$
Initial velocity in y-direction
options: constant, fcn
default: 0
$v_{z0}$
Initial velocity in z-direction
options: constant, fcn
default: 0
$\omega_x$, $\omega_y$, $\omega_z$
Initial angular velocity vector
default: (0,0,0)
$x_0$, $y_0$, $z_0$
Center of rotation
default: (0,0,0)
$\delta v_x$, $\delta v_y$, $\delta v_z$
Gradient of velocity field
default: (0,0,0)
csysid
Optional local coordinate system ID
default: not used

Description

This command is used to define initial velocities and initial angular velocities, applying to nodes and particles (PARTICLE_SOIL or PARTICLE_SPH). 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 particle at coordinate $(x,y,z)$ is defined as:

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

Example

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 P, 333, 0.0, 0.0, 0.0, 10.0, 20.0, 0.0 1.0, 2.0, 3.0
Initial velocity field using fcn

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

*UNIT_SYSTEM SI *TIME 0.01 *COMPONENT_BOX 1, 1, 10, 5, 1 -0.1, 0, 0, 0.1, 0.1, 0.001 *CHANGE_P-ORDER ALL, 0, 3 *MAT_MOONEY_RIVLIN 1, 2000.0, 1.0e9 2.0e5, 2.0e5 *PART "rubber sheet" 1, 1 *INITIAL_VELOCITY P, 1, fcn(22) *FUNCTION 22 100*x *END
Linear variation of velocity in x-direction
Linear variation of velocity in x-direction