Periodic Boundary Condition

Use a Periodic Boundary Condition simulation object to set identical flow and scalar fields at the periodic boundaries. This results in a spatially cyclic solution.

You can:

• Reduce model size and solution time in certain applications. For example, to model a series of identical joined sections, you only need to construct one section with periodic boundary conditions.

• Model both translational periodicity, such as a series of identical baffles, and rotational periodicity, such as flow in a cylinder.

• Create the periodicities for the fluid domain with calculated fluid, thermal, scalar and turbulence quantities.

Periodic Boundary Condition requirements

• The entire model can be broken down into identical, periodic sections.

• Each periodic section has a pair of matching and opposed periodic faces with identical fluid/thermal conditions on the face.

• The two periodic faces that represent the common boundaries of the periodic flow must have identical meshes. You can force these meshes to be identical by defining a 2D Dependent Mesh, a Mapped Mesh or a 3D Swept Mesh, depending on your model.

• The two periodic faces must have matching boundary conditions.

• The periodic face consists of free faces meshed with 3D fluid elements. You select the polygon faces to define the periodicity.

Types of periodic boundary conditions

• Rotational Periodicity lets you simulate a portion (an arc) of a cylindrical fluid domain.Note: The parallel flow solver supports the rotational periodic boundary condition only in the Fully Coupled Pressure-Velocity scheme. You specify this scheme from the Parallel Flow Solver Scheme list in the Solution dialog box.

• Translational Periodicity lets you specify a pressure drop from the master boundary region to the slave boundary region, which greatly reduces the fluid domain and the computational time.

Periodic Boundary Condition example

In the example below, a Periodic Boundary Condition simulation object simulates a flow from Boundary A to Boundary B (or vice versa) under identical conditions (such as velocity, temperature, and scalar values). The periodic boundary conditions act as if the solution domain was rolled up so that boundaries A and B were adjacent. Only the segment between Boundary A and Boundary B requires modeling. The other segments produce identical results.

Translational Periodicity	Rotational periodicity

	Periodic Boundary A
	Periodic Boundary B

Where do I find it?

Application	Pre/Post
Prerequisite	An active solution with the appropriate solver, analysis type, and solution type
Command Finder	Periodic Boundary Condition
Simulation Navigator	Right-click Simulation Object→New Simulation Object→Periodic Boundary Condition

How do I

Create a Rotational Periodic Boundary Condition

Create a Translational Periodic Boundary Condition

Learn more

Inputs to expressions

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Auto-generated expressions

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Simcenter 3D Thermal/Flow, Electronic Systems Cooling, and Space Systems Thermal boundary conditions

Thermal/Flow, Electronic Systems Cooling, and Space Systems Thermal

Command reference

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Periodic Boundary Condition, Simcenter 3D 2021.1 Series

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