Fluid Load
Add a Fluid Load node to describe loads from the fluid on the pipe. Three types of loads can be entered: Internal pressure, drag force from the fluid, and centrifugal forces in pipe bends.
When computing the effect of the pressure loads, only the internal gauge pressure is important, as discussed in Effects of Internal Pressure. You can thus use two approaches:
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Enter the gauge pressure as internal pressure, and set the external pressure to zero. This is a common approach when the Pipe Mechanics interface is used standalone.
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Enter absolute pressures for both the internal and external pressures. When combining with the Pipe Flow interface this is the common case, since the pressure in that interface is often interpreted as being absolute.
Since pressure loads are almost invariably part of a piping analysis, one Fluid Load node with all edges selected is included as default when the physics interface is created. It is however not mandatory to use it, and it will not give any contributions to the solution unless you have entered data in it. You can add any number of Fluid Load nodes.
Fluid Loads
Enter the Internal pressure, pi. The list contains any pressure variables announced by other physics interfaces, as well as the option User defined. For User defined, enter a value or an expression for the internal pressure.
Select a method for entering the External pressure, po, — User defined or Common model input.
For User defined, enter a value or an expression for the external pressure.
Select a method for entering the Drag force per unit length, Fd. The choice User defined is always available, in which case you enter a value or expression in the text field. A positive load acts in the same direction as the positive direction of the edge to which the load is applied. To visualize edge orientations, select Show edge direction arrows in the appropriate View node.
The Drag force per unit length drop-down list can also contain drag force variables announced by the Pipe Flow interface.
Select a method for entering the Centrifugal force per unit length, Fc. The choice User defined is always available, in which case you enter values or expressions in the text fields. In the User defined case, the input is similar to using an Edge Load.
The Centrifugal force per unit length drop-down list can also contain drag force variables announced by the Pipe Flow interface.
See also
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Effects of Internal Pressure and Fluid Flow Forces in the Theory for the Pipe Mechanics Interface section
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Using Common Model Input
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Default Model Inputs and Model Input in the COMSOL Multiphysics Reference Manual.
You can assign this load to a load group. See Load Cases in the Structural Mechanics Modeling chapter.
Location in User Interface
Context Menus
Pipe Mechanics>Line and Volume Loads>Edge Load
Ribbon
Physics tab with Pipe Mechanics selected:
Edges>Line and Volume Loads>Fluid Load (3D)
Boundaries>Line and Volume Loads>Fluid Load (2D)