*********************************** **Upper Height Function Constants** *********************************** :: Upper Height Function Constants = {model_name} ----------------------- **Description / Usage** ----------------------- This card takes the specification of the upper-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: +--------------------------+-------------------------------------------------------------------------------------+ |**CONSTANT_SPEED** |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 | | | | | | * the separation velocity (rate) in units of length/time | | | * the initial wall separation in units of length | | | * 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. | +--------------------------+-------------------------------------------------------------------------------------+ |**ROLL_ON** |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: | | | | | | * is x0 in units of length | | | * is hlow in units of length | | | * is h Δ, in units of length | | | * is the verticle separation velocity (if negative then squeeze velocity) | | | in units of length/time | | | * is the length of the plate, L. | +--------------------------+-------------------------------------------------------------------------------------+ .. figure:: /figures/486_goma_physics.png :align: center :width: 90% +--------------------------+-------------------------------------------------------------------------------------+ |**ROLL** |This model is used for a roll coating geometry. This option requires 8 floats: | | | | | | * x-coordinate of origin, L. | | | * y-coordinate of orgin, L. | | | * z-coordinate of origin, L. | | | * Direction angle 1 of rotation axis | | | * Direction angle 2of rotation axis | | | * Direction angle 3of rotation axis | | | * rotation speed L/t. | +--------------------------+-------------------------------------------------------------------------------------+ |**FLAT_GRAD_FLAT** |This model used two arctan functions to mimic a flat region, then a region of | | |constant slope, then another flat region. The transitions between the two regions are| | |curved by the arctan function. This currently on works for changes in the x | | |direction. This option requires five floating point values | | | | | | * x location of the first transition (flat to grad) | | | * height of the first flat region | | | * x location of the second transition (grad to flat) | | | * height of the second flat region | | | * parameter controlling the curvature of the transitions | +--------------------------+-------------------------------------------------------------------------------------+ |**POLY_TIME** |This time applies a time-dependent lubrication height in the form of a polynomial. It| | |can take as many arguments as GOMA can handle, and the resulting height function is | | | | | | * value of Ci | +--------------------------+-------------------------------------------------------------------------------------+ .. figure:: /figures/487_goma_physics.png :align: center :width: 90% +--------------------------+-------------------------------------------------------------------------------------+ |**JOURNAL** |This model simulates a journal bearing. It is intended to be run on a cylindrical | | |shell mesh aligned along the z axis and centered at (0,0). It could be extended to be| | |more flexible, but this is all it is currently capable of. The height is defined by | | | | | |h(θ ) = C(1+ε cos(0)) | | | | | |Where C is the mean lubrication height and is the eccentricity of the two cylinders, | | |with the smallest gap in the –y direction. | | | | | | * C | | | * ε | +--------------------------+-------------------------------------------------------------------------------------+ |**EXTERNAL_FIELD** |Not recognized. Oddly, this model is invoked with the extra optional float on the | | |CONSTANT_SPEED option. | +--------------------------+-------------------------------------------------------------------------------------+ :: External Field = HEIGHT Q1 name.exoII (see this card) ------------ **Examples** ------------ Following is a sample card: :: Upper Height Function Constants = CONSTANT_SPEED {v_sq = -0.001} {h_i=0.001} This results in an upper wall speed of 0.001 in a direction which reduces the gap, which is initial 0.001. ------------------------- **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.