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 interface combining k-ε turbulence model for compressible flow with a heat transfer model. 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-EVM, the default Turbulence model is k-ε. The Heat transport turbulence model is implicitly set to Turbulent Prandtl number. The default Turbulent Prandtl number model is Kays–Crawford, which can be changed to Extended Kays–Crawford or User-defined turbulent Prandtl number. For Extended Kays–Crawford, enter a Reynolds number at infinity Re∞. For User-defined turbulent Prandtl number, enter a Turbulent Prandtl number PrT.

The values or expressions required are entered in the Model Inputs section of the Fluid feature node. For the description of theory of turbulent heat transport see Turbulent Conductivity.

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.