*PRESSURE PENETRATION

Required parameters

MAIN: Set this parameter equal to the name of the main surface of the contact pair used in the pressure penetration analysis.
SECONDARY: Set this parameter equal to the name of the secondary surface of the contact pair used in the pressure penetration analysis.

Optional parameters

AMPLITUDE

Set this parameter equal to the name of the amplitude curve that defines the variation of the fluid pressure during the step. If this parameter is omitted, the reference magnitude is applied immediately at the beginning of the step or ramped up linearly over the step, depending on the value assigned to the AMPLITUDE parameter on the STEP option (see Defining an Analysis).

OP

Set OP=MOD (default) for existing pressure penetration loads to remain, with this option modifying existing pressure penetration loads or defining additional pressure penetration loads.

Set OP=NEW if all existing pressure penetration loads applied to the model should be removed. New pressure penetration loads can be defined.

PENETRATION TIME

Set this parameter equal to a time period over which the fluid pressure on newly penetrated contact surface segments is ramped up to the current magnitude. The default penetration time period is chosen to be 0.001 of the current step time. This parameter will be neglected in a linear perturbation analysis, in which case the current fluid pressure will be applied immediately once the pressure penetration criterion is satisfied.

WETTED FRONT

This parameter only applies to two dimensional elements.

Set WETTED FRONT=NODE (default) to indicate the fluid pressure loading is applied only to the wetted region until the front penetrated node.

Set WETTED FRONT=MID ELEMENT to indicate that the fluid pressure loading is ramped down and also applied to the unwetted front element region beyond the front penetrated node.

Optional, mutually exclusive parameters for matrix generation and steady-state dynamics analysis (direct or modal)

IMAGINARY: Include this parameter to define the imaginary (out-of-phase) part of the loading.
REAL: Include this parameter (default) to define the real (in-phase) part of the loading.

Data lines to define the pressure penetration loads

First line

A node or node set on the secondary surface that is exposed to the fluid. If a node set label is given, it can contain only one node for two dimensional models; while for three dimensional models, it can contain any number of nodes.
A node or node set on the main surface that is exposed to the fluid. If a node set label is given, it can contain only one node for two dimensional models; while for three dimensional models, it can contain any number of nodes. This field should be left blank if the main surface is an analytical rigid surface. This field can be also left blank for a three-dimensional model even if the main surface is not an analytical rigid surface.
Fluid pressure magnitude.
Enter the critical contact pressure below which fluid penetration starts to occur. The higher this value, the easier the fluid penetrates. The default is zero, in which case fluid penetration occurs only if contact is lost.

Repeat this data line as often as necessary to define fluid penetrations from different locations on the surface, possibly with different fluid pressure magnitudes. Alternatively, the PRESSURE PENETRATION option can be repeated (if, for example, a different amplitude reference is needed).