The High Mach Number Flow, Spalart-Allmaras Interface

The interface (

), found under the branch (

) when adding a physics interface, is used to model gas flows at high Reynolds number where the velocity magnitude is comparable to the speed of sound, that is, turbulent flows in the transonic and supersonic range.

The physics interface solves for conservation of energy, mass, and momentum. Turbulence effects are modeled using the one-equation Spalart-Allmaras turbulence model. The Spalart-Allmaras model is a so-called low-Reynolds number model, which means that it resolves the velocity, pressure, and temperature fields all the way down to the wall. The Spalart-Allmaras model depends on the distance to the closest wall. The physics interface therefore includes a wall distance equation. It also supports heat transfer in solids as well as surface-to-surface radiation.

This is a predefined multiphysics coupling consisting of a Turbulent Flow, Spalart-Allmaras interface, applied to compressible flow, in combination with a Heat Transfer interface. As shown in Table 5-1, the turbulent versions of the physics interfaces differ by where they are selected when adding a physics interface and the default Turbulence model selected—for this physics interface.

When this physics interface is added, the following default nodes are also added in the —, , and . Then, from the toolbar, add other nodes that implement, for example, boundary conditions, volume forces, and heat sources. You can also right-click the node to select physics features from the context menu.

The default is , the default is ., and the default is . Alternatively, select . The turbulent Prandtl number model describes the influence of the turbulent fluctuations on the temperature field. It is always possible to have a user-defined model for the turbulence Prandtl number. Enter the user-defined value or expression for the turbulence Prandtl number in the section of the Fluid feature node.

The dependent variables (field variables) are the u (SI unit: m/s), the p (SI unit: Pa), and the T (SI unit: K). For turbulence modeling and heat radiation, the G (SI unit: 1/m) and nutilde (SI unit: m2/s) variables are also available.