Multi-Region Meshing

Multi-region meshing creates separate mesh zones for different physical domains within the same simulation. Each region is independently meshed and coupled at shared interfaces.

When to Use Multi-Region

Scenario	Regions	Example
Conjugate heat transfer	Fluid + Solid	Air flowing over an aluminum heat sink
Rotating machinery	Rotating + Stationary	Fan impeller inside a duct
Multi-material thermal	Solid + Solid	PCB with copper traces in FR4 substrate
Porous media	Fluid + Porous	Flow through a filter or catalyst

How It Works

When you set up a multi-region mesh, the mesher:

1. Meshes each region independently using its own cell size and near-wall AMR settings

2. Tags every cell with its region — so the solver knows which cells belong to which region

3. Detects or constructs interfaces between touching regions

4. Assigns appropriate physics to each region for simulation

Creating Regions

From the Regions Tab

1. Navigate to the Regions tab

2. Click Add Region

3. Configure each region:

Field	Description	Example
Name	Unique label for this region	fluid, heatsink, rotor
Type	Physics type for this zone	Fluid, Solid, Porous, Rotating
CAD geometry	The solid body or volume that defines this region	Select from uploaded bodies
Cell size	Target mesh cell size for this region	2 mm
Boundary layers	Enable/configure BL for this region	Enabled for fluid, disabled for solid

Region Types

Type	Description	Typical Use
Fluid	Standard incompressible flow	Air, water, coolant
Solid	Solid material, thermal conduction only	Aluminum heat sink, PCB, housing
Porous	Fluid with added flow resistance	Filter, packed bed, heat exchanger
Rotating	Fluid in a rotating reference frame (MRF)	Fan impeller, pump rotor, turbine

From Multi-Body CAD

When you upload a multi-body STEP file, each solid body is automatically detected. You can then assign each body to a named region with its type and mesh settings. The bodies are listed in the feature tree — click each one to configure it.

Region Overview

After meshing, the Regions panel shows a summary of each region:

Region Name	Type	Cells
pipe_wall	Solid	8,965
internal_flow	Fluid	3,624

Interfaces

Where two regions share a boundary, an interface couples them. Interfaces are defined by referencing the names of the two regions they connect.

Auto-Detection

Enable Auto-detect interfaces to have Studio automatically identify touching faces between regions. This works well for clean, imported multi-body CAD where bodies share exact face geometry.

Manual Interface Setup

1. Navigate to the Interfaces tab

2. Click Add Interface

3. Select the two region names (e.g., pipe_wall ↔ internal_flow)

4. Choose the interface type

Interface Types

Type	Description	Use Case
CHT	Conjugate heat transfer coupling	Fluid-solid thermal problems
CHT with contact resistance	Adds thermal resistance at the boundary	Imperfect contact, thermal paste
CHT thin wall	Models a thin solid layer at the interface	Sheet metal, PCB copper layer
Frozen rotor	Steady-state rotating-stationary coupling	Fans, pumps (steady RANS)
Mixing plane	Circumferentially averaged interface	Turbomachinery stage coupling
Sliding mesh	Transient rotating interface	Time-accurate turbomachinery
Periodic	Repeating pattern coupling	Sector models, cyclic symmetry

Conformal vs. Non-Conformal

• Conformal — Faces on both sides of the interface match exactly (1:1 node correspondence). Best accuracy, requires geometry to be matched in CAD.

• Non-conformal — Faces don’t match exactly. More flexible but requires interpolation at the interface. Used when mesh sizes differ significantly between regions.

Per-Region Mesh Settings

Each region has independent mesh control:

Setting	Fluid Region	Solid Region
Cell size	Smaller (resolve flow)	Larger (save cells)
Near-wall AMR	Enabled	Disabled
Min cell size	Flow-dependent	Less critical

Tip

For CHT problems, the solid region typically needs a coarser mesh than the fluid region. Set the solid cell size 2–4× larger than the fluid cell size to save cells without sacrificing thermal accuracy.

Multi-Region Example: Pipe CHT

A conjugate heat transfer pipe — fluid flowing inside a solid pipe wall:

Regions:

Name	Type	Cell Size	Near-Wall AMR
pipe_wall	Solid	1.5 mm	Disabled
internal_flow	Fluid	2.0 mm	Enabled (medium)

Interface:

Name	Region A	Region B	Type
cht_interface	pipe_wall	internal_flow	CHT

Resulting regions in the mesh:

• pipe_wall → Solid zone

• internal_flow → Fluid zone