The High Mach Number Flow, k-ε (hmnf) interface (), found under the High Mach Number Flow>Turbulent Flow 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 standard two-equation k-ε model with realizability constraints. Flow and heat transfer close to walls are modeled using wall functions. The physics interface also supports heat transfer in solids as well as surface-to-surface radiation.

This is a predefined multiphysics coupling consisting of a Turbulent Flow k-ε 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 — k-ε for this physics interface.

When this physics interface is added, the following default nodes are also added in the Model Builder — Fluid, Wall, Thermal Insulation, and Initial Values. Then, from the Physics 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 Label is the default physics interface name.

The Name is used primarily as a scope prefix for variables defined by the physics interface. Refer to such physics interface variables in expressions using the pattern <name>.<variable_name>. In order to distinguish between variables belonging to different physics interfaces, the name string must be unique. Only letters, numbers, and underscores (_) are permitted in the Name field. The first character must be a letter.

The default Name (for the first physics interface in the model) is hmnf.

The default Turbulence model type is RANS, the default Turbulence model is k-ε, and the default Heat transport turbulence model is Kays-Crawford. Alternatively, select User-defined turbulent Prandtl number. 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 Model Inputs section of the Fluid feature node.

Edit the model parameters of the k-ε model as needed. Turbulence model parameters are optimized to fit as many flow types as possible, but for some special cases, better performance can be obtained by tuning the model parameters. For a description of the turbulence model and the included model parameters see Theory for the Turbulent Flow Interfaces.

The dependent variables (field variables) are the Velocity field u (SI unit: m/s), the Pressure p (SI unit: Pa), and the Temperature T (SI unit: K). For turbulence modeling and heat radiation, the Turbulent kinetic energy k (SI unit: m2/s2) and Turbulent dissipation rate ep (SI unit: m2/s3) variables are also available.