Coupling Systems

This tutorial assumes XCOMPUTE-CLIENT is connected to a live XCOMPUTE-SERVER session with one or more numerical systems containing two or more regions.

Theory

Boundary conditions provide closure to numerical systems but are limited to asserting values known a priori. As systems grow in complexity, static boundary conditions become insufficient for capturing global interactions.

Coupling interpolates data across regions to provide dynamic closure, replacing traditional boundary conditions. This approach enables teams to analyze complex multi-physics and multi-domain interactions.

Interpolation Methods

Coupling Regions

Coupling is always defined between two regions (typically surfaces). Pairs can be:

• Intra-system: Two regions within the same system, owned by that system.

• Inter-system: Two regions in different systems, owned by the parent system.

Sampling Modes

Different physical scenarios require different interpolation strategies. Supported modes include:

Mode	Description	Use Case
1:1	Direct nodal mapping	Abstract systems with matching topology
nearest	Sparse mapping to closest node	Coarse-to-fine transfers
distance	Dense mapping based on 1/r²	Proximity-based diffusion
view_factor	Dense mapping using integrated steradian values	Radiative heat transfer
contact	Sparse mapping based on overlapping nodes/elements	Mechanical contact & friction

Coupled Properties

While most shared properties can be interpolated, only specific variables should be coupled to maintain stability:

• Thermal-Fluid: Typically Temperature

• Fluid-Structure: Typically Displacement and Pressure

• Multi-Physics: Define custom PropertyKey pairs as needed

Tip

Coupling stability depends heavily on mesh quality at the interface. Ensure matching or smoothly transitioning element sizes across coupled regions.