The representation and numerical solution of interactions between models that describe different physical phenomena (for example, thermal, mechanical, chemical, electromagnetic) within a single analysis so that the mutual influence of those phenomena is captured.

Principle

Enforce compatibility of shared fields and conservation laws across physics, provide consistent constitutive couplings and boundary/interface conditions, and iterate or solve simultaneously as required by the strength of the cross‑physics interactions.

Demonstration

A thermoelastic simulation couples heat conduction and solid mechanics: temperature fields alter material stiffness and generate thermal strains, while deformation changes conduction paths; the coupled solver applies temperature–strain constitutive relations and enforces energy and momentum balance at each step.

Misapplication

Treating coupled physics as independent one‑way problems (e.g., computing temperature first and then mechanics without feedback) when feedback is significant leads to quantitatively wrong predictions and may miss critical failure modes.

Consequence

Captures emergent behaviors arising from physical interactions, improves predictive fidelity for multiphysical systems, and often increases model complexity, computational cost, and the need for validated inter‑physics transfer laws.

Reversal

Single‑physics simulation that neglects interactions with other phenomena, which may be adequate when couplings are provably negligible but will fail where cross‑effects matter.

Boundary

Concerns coupling between distinct physical descriptions within the same spatial/temporal domain; it excludes pure parameter passing between unrelated models and does not necessarily imply multi‑scale algorithms.

Semantic Tension

Tension with multiscale coupling arises because multiphysics emphasizes distinct phenomena coexisting at the same or overlapping scales, while multiscale emphasizes scale separation; nearby terms like multiphase or multicomponent coupling can be conflated but have different physical meanings.

Synthesis

Multiphysics coupling integrates multiple physical descriptions into a single computational treatment, enforcing shared conservation and constitutive relations so that mutual influences among phenomena are represented and resolved.