Coupling to Other Physics Interfaces

Often, you may be simulating applications that couple fluid-flow to another type of phenomenon described in another physics interface. Although this is not often another type of flow, it can still involve physics interfaces supported in the CFD Module and COMSOL Multiphysics base package. This is especially the case for applications that include chemical reactions and mass transport, as described in Chemical Species Transport Branch section.

More extensive descriptions of heat transfer, such as involving radiation and thin, solid layers, can be found in the Heat Transfer Module, while a more vigorous tool for modeling chemical reactions and mass transport is found in the Chemical Reaction Engineering Module.

The interfaces in the Non-Isothermal Flow branch are important to simulate the cooling of equipment and components. Outside of the process industry, this application is also highly relevant to electromagnetic phenomena, such as heat created through induction and microwave heating. These phenomena are simulated in the AC/DC and RF Modules, respectively, and often require that their material properties be coupled to temperature that is, of course, affected by the non-isothermal fluid-flow.

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The next sections list all the physics interfaces and the features associated with them under the Non-Isothermal Fluid Flow branch. The descriptions follow a structured order as defined by the order in the branch. Because many of the interfaces are integrated with each other, some features described also cross reference to other interfaces. At the end of this section is a summary of the theory that goes towards deriving the physics interfaces under the Non-Isothermal Fluid Flow branch.

There are several variations of the same predefined multiphysics interface (all with the

Interface Identifier nitf), that combine the heat equation with either a laminar or a turbulent flow. The advantage of using the multiphysics interfaces—compared to adding the individual interfaces separately—is that predefined couplings are available in both directions. In particular, interfaces use the same definition of the density, which can therefore be a function of both pressure and temperature. Solving this coupled system of equation usually requires numerical stabilization, which the predefined multiphysics interface also sets up.

These interfaces in the Fluid Flow>Non-Isothermal Flow () and Heat Transfer>Conjugate Heat Transfer () branches vary only by one or two default settings (see Table 12-1), which are selected during Model Wizard selection, or from a check box or drop-down list in the Physical Model section on the Settings window.

TABLE 12-1: THE NON-ISOTHERMAL FLOW PHYSICAL MODEL DEFAULT SETTINGS*

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TABLE 12-1: THE NON-ISOTHERMAL FLOW PHYSICAL MODEL DEFAULT SETTINGS*

*For all the interfaces, the Neglect Initial Term (Stokes Flow) check box is not selected by default.

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