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Velocity Command

The Velocity command sets velocity conditions to all nodes near the line specified by the GridBC Command that encloses it or creates a moving wall boundary near those nodes:

Velocity (dir),(style),<(value)>>,<(time)>

where

Moving Wall Velocity Conditions

A moving wall boundary condition models a wall moving through the grid normal to the x, y, or z axis with any provided velocity. This condition sets velocity on the wall surface and will include as many nodes on either side of wall as needed for optimal results. This condition can also set velocity gradient at the wall. These conditions are created with the Velocity command but using more arguments:

Velocity (dir),"gradient",(velFxn),0,(depth),<(gradFxn)>,<(dispFxn)>

where

Skewed Velocity Conditions

Setting the velocity along two direction is not the same as setting the velocity in a direction of that resultant vector. To set a single velocity in a direction that is not along a cartesian axes, you can use:

Velocity (skewDir),(style),(value),(time),(angle1),<(angle2)>

where

When using more than one velocity boundary condition on a node, you should create non-skewed conditions first and then create skewed ones. Skewed conditions are only allowed if they are orthogonal to other velocity condition on that node.

Notes

  1. You can use GlobalArchive command to archive reaction forces at nodes with velocity boundary conditions. To archive reaction forces at only selected boundary conditions, you can assign those conditions a boundary condition ID and use that ID in the GlobalArchive command for reaction forces.