For Static Structural analysis only, use the Fluid Penetration Pressure loading condition to simulate surrounding fluid or air penetrating into a contact interface. You can apply this load to flexible-to-flexible or rigid-to-flexible contact pairs.
Fluid pressure along normal directions can penetrate into the contact interface from one or multiple locations. The penetrating path can propagate and vary, and it is determined iteratively.
The initial starting points are user-defined locations that are exposed to the fluid pressure. Among the starting points, fluid penetrating points are locations where the contact status is open or lost, or where the contact pressure is smaller than the user-defined pressure penetration criterion. For fluid penetrating points, its nearest neighboring nodes are considered to be the starting points which are exposed to the fluid pressure as well.
This page includes the following sections:
Analysis Types
This loading condition is only available for a Static Structural analysis.
Dimensional Types
The supported dimensional types for the Fluid Penetration Pressure boundary condition include:
3D Simulation
2D Simulation
Geometry Types
The Fluid Penetration Pressure boundary condition does not support geometry types like most other boundary conditions. The application applies this pressure on contact pairs (scoped to a Contact Region object).
Topology Selection Options
You scope the Fluid Penetration Pressure boundary condition to a Contact Region object.
Define By Options
For this boundary condition, the Define By property is read-only and set to Normal To.
Applying a Fluid Penetration Pressure Boundary Condition
To apply a Fluid Penetration Pressure:
Before inserting the loading condition, verify your desired units of measure.
On the Environment Context tab, open the Loads drop-down menu and select . Alternatively, right-click the Environment tree object or in the Geometry window and select > .
Select the desired contact interface (Contact Region).
Specify the Pressure Update Frequency. Options include Each Iteration (default) and Each Substep.
Specify the Penetration History Dependency: Options include History Dependent (default) and History Independent.
Using the options of the Starting Point property, select desired geometric entities for the initial points exposed to the fluid and potentially subjected to the penetration pressure.
Use the Define By property of the Pressure Penetration Criterion category to define criterion penetration pressure. Options include and . If you select , the Criterion Value property displays. Use this property to enter a pressure value. See the property descriptions below for more information.
Based on how you specify criterion, additional display categories and properties display. See below for more information.
Details Pane Properties
The selections available in the Details pane are described below.
| Category | Property/Options/Description |
|---|---|
|
Scope |
Scope Method: Read-only property set to . Contact Region: Drop-down list of available objects. |
|
Definition |
Type: Read-only property set to . Define By: Read-only property set to . Magnitude: Define the magnitude of the fluid/air pressure applied normal to the contact interface. Define the magnitude of boundary condition as a (default), , or as a . Pressure Update Frequency: Options include Each Iteration (default) and Each Substep. When you select , the application applies the fluid-pressure-penetration load to the contact and target elements based on the contact status at the beginning of each substep and remains constant over that substep even if the contact status changes during iterations. When select , the application varies the load during each iteration based on the current contact status. In certain cases, this can cause an unstable convergence pattern because the contact status and the resulting applied fluid penetration load continue to change during iterations. Penetration History Dependency: Options include (default) and . When you select , any contact detection point that was previously exposed to the fluid pressure remains in the condition of “penetrating” unless a closed contact condition is reestablished. The penetrating load could be cut-off in the middle of the path. If you select , the application always newly applies the load from the initial starting points regardless of the history of “penetrating” conditions. Therefore, the penetrating path is continuous following any starting point. Suppressed: Options include (default) and . Select whether to suppress of unsuppress the object. |
|
Starting Point |
Define By: Read-only property set to . Scoping Method: Options include (default) and . Supported geometric entities include faces (3D only), vertices, edges, and nodes. Geometry: Use selection filters to pick geometry, click in the Geometry field, then click Apply. Named Selection: Select a desired Named Selection from the drop-down menu. |
|
Pressure Penetration Criterion |
Define By: Use this property to specify how the criterion is applied, either by the application or manually. Options include and . Criterion Value: This property displays when you select the option for the above Define By property. The Criterion Value is a pressure value. When the contact pressure is less than the criterion, the starting point turns into the penetrating point. That is, fluid pressure starts to penetrate. Therefore, a higher criterion value allows the fluid to penetrate more easily. When the contact pressure is greater than the criterion, fluid penetration is cut off. By default, the penetration criterion is zero (). In this case the fluid penetration occurs only when the contact is open, and the cutoff of fluid penetration occurs only when the contact is reestablished. You specify the Criterion Value as a (default), , or as a . |
|
Tabular Data[a] |
Independent Variable: Use this property to specify how the load varies with either (default), load , or in the , , or (3D only) spatial direction. Note: When you set the Criterion Value property set to or , is the only supported option. Coordinate System:This property displays if you specify the Independent Variable in a spatial direction (X, Y, or Z). Use this property to select a coordinate system. |
|
Tabular Data and Graph Display |
Selection: Options include Pressure Penetration Criterion (default) and Fluid Penetration Pressure. These are display selections for the information presented in the Graph and Tabular Data windows. |
|
Function[b] |
Unit System: Read-only property indicating the units of measure specified when you inserted the Fluid Penetration Pressure object. Angular Measure: Read-only property indicating the unit for angular measure that was selected when you inserted the Fluid Penetration Pressure object. |
|
Graph Controls[a] |
X-Axis: This property displays if you specify the Independent Variable in a spatial direction. Options include , , and (3D only). Number of Segments: The function is graphed with a
default value of |
[a] See the Tabular Loads section for more information.
[b] See the Mathematical Function Loads section for more information.
Mechanical APDL References and Notes
See the Applying Fluid-Pressure-Penetration Loads section of the Mechanical APDL Contact Technology Guide.