Command manual

Command list

INITIAL_VELOCITY

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

Parameter definition

VariableDescription
entype Entity type
options: N, NS, P, PS, ALL, G
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)

Description

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:

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

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