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**Lower Velocity Function Constants**
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::
Lower Velocity Function Constants = {model_name}
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**Description / Usage**
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This card takes the specification of the Lower-wall velocity function for the confined
channel lubrication capability, or the lub_p equation. This function specifies the
velocity of the Lower channel wall as a function of time. Currently two models for
{model_name} are permissible:
+--------------------------+-------------------------------------------------------------------------------------+
|**CONSTANT** |This model invokes a squeeze/separation velocity uniformly across the entire material|
| |region, viz. the two walls are brought together/apart at a constant rate. This option|
| |requires two floating point values |
| | |
| | * is the velocity component in the x-direction. L/t |
| | * is the velocity component in the y-direction. L/t |
| | * is the velocity component in the z-direction. L/t (NOTE: this is usually |
| | taken as zero as it is set in the Lower Wall Height Function model) |
+--------------------------+-------------------------------------------------------------------------------------+
|**SLIDER_POLY_TIME** |This model implements a spatially-uniform velocity in the x-direction that is |
| |specified as a polynomial in time. The value of time may be scaled by a given scaling|
| |factor and the polynomial may have an unlimited number of terms. |
| | |
| | * is the time scaling factor |
| | * are the coefficients in front of the t^(i-2) term |
+--------------------------+-------------------------------------------------------------------------------------+
.. figure:: /figures/490_goma_physics.png
:align: center
:width: 90%
+--------------------------+-------------------------------------------------------------------------------------+
|**ROLL** |This model invokes a wall velocity which corresponds to a rolling-motion. This model |
| |takes nine constants ???? : |
| | |
| | * Roll radius, L. |
| | * x-coordinate of axis origin, L. |
| | * y-coordinate of axis orgin, L. |
| | * z-coordinate of axis origin, L. |
| | * Direction angle 1 of rotation axis |
| | * Direction angle 2of rotation axis |
| | * Direction angle 3of rotation axis |
| | * Squeeze rate. |
| | * rotation rate |
+--------------------------+-------------------------------------------------------------------------------------+
|**TANGENTIAL_ROTATE** |This model allows a unique specification of tangential motion in a lubrication shell |
| |element. Previous implementations allowed specification only in terms of coordinate |
| |direction, but this option can be used to rotate a cylinder. Five floats are required|
| | |
| | * x-comnponent of a vector tangential to the shell. This vector must never |
| | be normal to the shell. It is then projected onto the shell. |
| | * y-comnponent of a vector tangential to the shell. |
| | * z-comnponent of a vector tangential to the shell. |
| | * U1, or scalar speed of wall velocity in a direction determined by the |
| | cross product ot the tangent vector and the normal vector to the shell. (L/t) |
| | * U2 scalar speed component in direction normal to U1. (L/t) |
+--------------------------+-------------------------------------------------------------------------------------+
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**Examples**
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Following is a sample card:
::
Lower Velocity Function Constants = CONSTANT {v_x= -0.001} {vy=0.00} {vz=0}
This card results in an Lower wall speed of -0.001 in the x-direction which is tangential
to the substrate, thus generating a Couette component to the flow field.
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**Technical Discussion**
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For non-curved shell meshes, most of the time they are oriented with the x-, y-, or zplane.
This card is aimed at applying a tangential motion to that plane, and so one of
the three components is usually zero.