Upper Velocity Function Constants#

Upper Velocity Function Constants = {model_name} <floatlist>

Description / Usage#

This card takes the specification of the upper-wall velocity function for the confined channel lubrication capability, or the lub_p equation. This function specifies the velocity of the upper 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

  • <float1> is the velocity component in the x-direction. L/t.

  • <float2> is the velocity component in the y-direction. L/t

  • <float3> is the velocity component in the z-direction. L/t (NOTE: this is usually taken as zero as it is set in the Upper Wall Height Function model)

ROLL

This model invokes a wall velocity which corresponds to a rolling-motion. This model takes nine constants ???? :

  • <float1> Roll radius, L.

  • <float2> x-coordinate of axis origin, L.

  • <float3> y-coordinate of axis orgin, L.

  • <float4> z-coordinate of axis origin, L.

  • <float5> Direction angle 1 of rotation axis

  • <float6> Direction angle 2of rotation axis

  • <float7> Direction angle 3of rotation axis

  • <float8> Squeeze rate

  • <float9> rotation rate

TANGENTIAL_ROTATE

his model allows a velocity that is always tangential to a shell surface, not necessarily aligned along the coordinate directions. It requires three specifications. First, a vector (v) that is always non-colinear to the normal vector of the shell must be specified. This is used to make unique tangent vectors. The last two specifications are the two tangential components to the velocity. The first velocity is applied in the direction of t1 = v×n. The second velocity is then applied in the t = t ×n direction.

  • <float1> vx

  • <float2> vy

  • <float3> vz

  • <float4> velocity in the t1 direction

  • <float5> velocity in the t2 direction

CIRCLE_MELT

Model which allows a converging or diverging height that is like a circle. Also works for melting.

  • <float1> - x-location of the circle center (circle is in x-y plane)

  • <float2> - radius of circle

  • <float3>- minimum height of circle

Examples#

Following is a sample card:

Upper Velocity Function Constants = CONSTANT {v_x= -0.001} {vy=0.00} {vz=0}

This card results in an upper wall speed of -0.001 in the x-direction which is tangential to the substrate, thus generating a Couette component to the flow field.

Technical Discussion#

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.