The physics and thermodynamics of in-flight icing involve strong heat convection in fluids, heat conduction through solids, droplet impingement, surface water film flow, water evaporation, change of phase and ice formation. Realistic simulations of these phenomena are too complex to treat within a single computational domain. A computationally-efficient alternative consists in applying a divide-and-conquer strategy by computing the solutions of the various domains separately and exchanging the interface boundary conditions in an iterative manner. Convergence is achieved when the heat fluxes and temperatures are equalized across the interfaces. This strategy also has the benefit of simplifying the mesh generation process.

CHT3D is the module that solves Conjugate Heat Transfer (CHT) problems in either dry- or wet-air regimes for anti-icing or de-icing simulations. CHT3D in anti-icing mode can handle up to two independent airflow domains separated by one solid domain, usually a metallic material, however multi-layer synthetic materials are also supported. For bleed-air applications, for example, the simulation involves cold external two-phase flow where wall-bound turbulence, transition, strong convection, evaporation and phase-change dominate and a hot internal single-phase flow with strong turbulence and recirculation, convection, and heat conduction through the thin metallic solid skin that separates the two fluid domains. For electro-thermal unsteady de-icing problems, a single external two-phase flow domain is typically required, but the solid is usually a multi-layered composite of synthetic materials, each with its own material properties.

CHT3D fully supports non-conformal domain interfaces, which can be constructed with any type of linear elements and can take advantage of the most appropriate grid type in each domain. Several airflow solution methods are supported, from the most complex full RANS with surface roughness, to the simplest constant Heat Transfer Coefficient (HTC), where the flow solution is frozen and only the solid surface temperature and heat fluxes are updated.