Flow Surface

You can use a Flow Surface to model:

• Convection to the surrounding fluid from a surface with or without small meshes that obstruct the flow.

• Drag of objects that obstruct the flow.

• Drag due to a specific wall friction on the surface.

• An embedded object modeled only with a 2D mesh that constrains or directs the fluid flow. Examples of such embedded objects include, a PC board, a baffle, a duct, or a chamber wall.

• A displacing or rotating wall seen from an inertial frame of reference. An example would be the casing walls of a fan in a moving frame of reference simulation.

• A semi-permeable membrane such as a GORE-TEX® textile.

For the selected faces, a flow surface overrides the Friction and Convection Parameters options in the 3D Flow node of the Solution dialog box.

Flow Surface types

You can use one of the following Flow Surface types:

• Embedded Flow Surface and Embedded Flow Surface With Obstructions let you model thin surfaces that have fluid on both sides. You must define convection, roughness, and/or velocity properties for both sides.

• Boundary Flow Surface and Boundary Flow Surface With Obstructions let you model thin surfaces that have fluid on only one side. You must define convection, roughness, and/or velocity properties for only the side facing the fluid.

Wall velocity

The Flow Surface simulation object lets you model moving walls when you select the Rotating/Translating Surface in Shear check box. The movement of these surfaces can be defined in terms of rotation or translation.

• You must define the axis and the rotation rate for a rotating surface.

• You must define the movement direction and the velocity of the surface for a translating surface.

Translating surface	Rotating surface

	Flow field
	Translating surface velocity vector
	Rotating surface angular velocity

Use this option to model scenarios where the walls around your fluid domain are moving, or to constraint the walls of a moving fluid domain in a rotating frame of reference.

Note:

Do not specify a movement normal to the flow. The selected faces must be in pure shear with respect to the flow.

Particle tracking simulation

When you do a particle tracking simulation, you can specify whether the particles stick to the flow surface or rebound. You can also request a particle impact report. When you request the report, the flow solver generates the ParticleAndImpactTrackingSummary.dat file which contains two tables:

• The Particle Tracking Summary table lists the number of injected and ejected particles in total for your model and per boundary condition.

• The Particle Surface Impact and Screen Pass-Through Tracking Report table lists the number of particles that impact walls in your model per injection boundary condition and the number of particles that pass through screens per injection boundary condition.

The file is generated in the simulation’s run directory.

Where do I find it?

Application	Pre/Post
Command Finder	Flow Surface
Simulation Navigator	Right-click the Simulation Objects node→New Simulation Object→Flow Surface

How do I

Create a flow surface

Learn more

Understanding flow surfaces

Modeling flow surface obstructions

Meshing for flow surfaces

Modeling semi-permeable surfaces

Convection Properties

Inputs to expressions

Look up more details

Auto-generated expressions

Quick links

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

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

Command reference

Pre/Post video examples

Bulk Entry Descriptions

Simcenter 3D tutorials

Browse Simcenter 3D help by product area

Flow Surface, Simcenter 3D 2021.1 Series

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