Lower Height Function Constants#

Lower Height Function Constants = {model_name} <floatlist>

Description / Usage#

This card takes the specification of the lower-height function for the confined channel lubrication capability, or the lub_p equation. This function specifies the height of the channel versus distance and time. Currently three models for {model_name} are permissible:


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> the separation velocity (rate) in units of length/time

  • <float2> the initial wall separation in units of length

  • <float3> An OPTIONAL parameter which scales the addition of an external field called “HEIGHT” which is read in using the External Field or External Pixel Field capabilities. If this field is present, the value of it is added to the height calculated with this model.


This model invokes a squeeze/separation velocity in a hinging-motion along one boundary. The model is best explained with the figure in the technical discussion section. The equation for the gap h as a function of time and the input parameters (floats) is as follows:

  • <float1> is x0 in units of length

  • <float2> is hlow in units of length

  • <float3> is h Δ, in units of length

  • <float4> is the verticle separation velocity (if negative then squeeze velocity) in units of length/time

  • <float5> is the length of the plate, L.



This model is used for a roll coating geometry. This option requires 8 floats:

  • <float1> x-coordinate of origin, L.

  • <float2> y-coordinate of orgin, L.

  • <float3> z-coordinate of origin, L.

  • <float4> Direction angle 1 of rotation axis

  • <float5> Direction angle 2 of rotation axis

  • <float6> Direction angle 3 of rotation axis

  • <float7> rotation speed L/t.

TABLE <integer1> <character_string1> {LINEAR | BILINEAR} [integer2] [FILE = filenm]

Please see discussion at the beginning of the material properties Chapter 5 for input description and options. Most likely character_string1 will be LOWER_DISTANCE This option is good for inputing table geometry versus distance. Specifically, an arbitrary lower height function model is input as a function of the x-direction coordinate of the Lower Velocity Function model. This option in turn requires the use of SLIDER_POLY_TIME lower velocity function model. See example below.


Following is a sample card:

Lower Height Function Constants = CONSTANT_SPEED {v_sq = -0.001} {h_i=0.001}

This results in an lower wall speed of 0.001 in a direction which reduces the gap, which is initial 0.001.

In another example:

Lower Height Function Constants = TABLE 2 LOWER_DISTANCE 0 LINEAR FILE=shell.dat

where shell.dat is a table with 2 columns, the first the position, the second the height.

Technical Discussion#

The material function model ROLL_ON prescribes the squeezing/separation motion of two non-parallel flate plates about a hinge point, as shown in the figure below.