COMSOL 6.2 - Pipe Cross Section

Pipe Cross Section

In the node, you specify the geometric properties of the pipe’s cross section. In addition, some stress evaluation properties can be defined.

For 3D models, a default Section Orientation subnode is added, in which you specify the orientation of the principal axes of the section. You can add any number of subnodes if the same section appears with different spatial orientations in the structure.


	This is required input data.

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Cross Sections

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Beam Cross Section

Pipe Shape

The default is . Select , , , or . Then go to the relevant section below to continue defining the section

For go to Wall Cross Section Properties and Stress Evaluation Properties to continue defining the cross section.

For equations and a figure see:

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Enter values or expressions for the following.

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Piping standards may require stresses to be evaluated using a reduced thickness to account for possible corrosion or erosion effects on the pipe’s wall. The thickness changes can occur on both the inner and the outer side of the wall. In the section Thickness reduction for stress evaluation enter values or expressions for the thickness reduction on the inner or outer sides:

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Δto

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Δti

For both sides the default value is 0[%]*pipem.t_nom, where the variable pipem.t_nom is the nominal wall thickness given by do and di. The reduced inner and outer diameters are then defined as

Note that the reduced wall thickness only has an effect on the stress evaluation. That is, the flexibility of the piping system is still computed using nominal thicknesses. Internally, COMSOL Multiphysics creates separate variables for stiffness properties such as the cross-section area or the 2nd moment of inertia. All stress measures that can be evaluated in postprocessing are computed using the reduced wall diameters.

Square

Enter values or expressions for the following:

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Rectangular

Enter values or expressions for the following:

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Wall Cross Section Properties


	This section is only available if User defined is selected as the Cross-Section Definition.

The following table lists the basic section properties (some apply in 3D only). Enter values for these properties in the associated fields. The default values correspond to a circular cross section with a diameter of 0.1 m:


Comment	Description	Parameter	SI Unit
2D and 3D	Area of cross section	A	m2
2D and 3D	Moment of inertia about local z-axis	Izz	m4
2D and 3D, Timoshenko beam	Shear correction factor along local y-axis	κy	1
3D only	Distance to shear center in local z direction	ez	m
3D only	Moment of inertia about local y-axis	Iyy	m4
3D only	Distance to shear center in local y direction	ey	m
3D only	Torsional constant	J	m4
3D only, Timoshenko beam	Shear correction factor along local z-axis	κz	1


	For 3D models, the orientation of the cross section is given in Section Orientation. If the beam’s cross section is a square or circle (solid or tube), the area moments of inertia are the same independent of direction, so the beam is totally symmetric and the orientation of the principal axes of the cross section is not a problem unless you are interested in looking at results defined using the local coordinate system. Such results are bending moments, shear forces, local displacements and rotations.

Fluid Cross Section Properties

Enter the , Af. This is the same as the internal cross section of the pipe.

Stress Evaluation Properties


	This section is only available if User defined is selected as the Cross-Section Definition.

Select the — (the default) or .

Stress evaluation using only section heights is meaningful only when the cross section is symmetric.

The max shear stress factor determines the ratio between the peak and the average shear stress over the cross section as described by Equation 12-1 and Equation 12-2.

From Section Heights

For enter values in each field for the following parameters as needed for the space dimension:


Comment	Description	Parameter	SI Unit
2D and 3D	Section height in local y direction	hy	m
2D and 3D	Max shear stress factor in local y direction	μy	1
3D only	Section height in local z direction	hz	m
3D only	Torsional section modulus	Wt	m3
3D only	Max shear stress factor in local z direction	μz	1
2D and 3D	Pressure membrane stress factor	γm	1
2D and 3D	Pressure bending stress factor	γb	1

From Specified Points

For enter values in the table as needed for the space dimension. Then enter the following parameters in the applicable fields.


Comment	Description	Parameter	SI Unit
2D and 3D	Max shear stress factor in local y direction	μy	1
3D only	Torsional section modulus	Wt	m3
3D only	Max shear stress factor in local z direction	μz	1
2D and 3D	Pressure membrane stress factor	γm	1
2D and 3D	Pressure bending stress factor	γb	1

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