The High Mach Number Flow, Laminar (hmnf) interface (), found under the Fluid Flow>High Mach Number Flow branch () when adding a physics interface, is used to model gas flows at low and moderate Reynolds number where the velocity magnitude is comparable to the speed of sound, that is, laminar flows in the transonic and supersonic range. This state is often connected to very low pressures.

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 Reference temperature Tref is used to define the reference enthalpy Href which is set to 0 J/kg at pref (1 atm) and Tref.

By definition, no turbulence model is needed when studying laminar flows. The default is None. See The High Mach Number Flow, k-ε Interface or The High Mach Number Flow, Spalart-Allmaras Interface for the settings if RANS is chosen as the Turbulence model type.

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). The names can be changed but the names of fields and dependent variables must be unique within a component.

To display this section, click the Show More Options button () and select Advanced Physics Options in the Show More Options dialog box. Normally these settings do not need to be changed.

Select the Use pseudo time stepping for stationary equation form check box to add pseudo time derivatives to the equation when the Stationary equation form is used. When selected, also choose a CFL number expression — Automatic (the default) or Manual. Automatic calculates the local CFL number (from the Courant–Friedrichs–Lewy condition) from a built-in expression. For Manual enter a Local CFL number CFLloc.

By default the Enable conversions between material and spatial frames check box is selected.