The Turbulent Flow, Low Reynolds Number k-ε version of the Rotating Machinery, High Mach Number Flow (hmnf) interface (), found under the High Mach Number Flow > Rotating Machinery, High Mach Number Flow > Turbulent Flow branch (), is used to simulate gas flows in geometries with one or more rotating parts and gas 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 is available for 3D and 2D components and it combines the High Mach Number Flow, Low Reynolds Number k-ε interface (), with a Rotating Domain under Definitions > Moving Mesh.

There are two study types available for this physics interface. Using the Time Dependent study type, rotation is achieved through moving mesh functionality, also known as sliding mesh. Using the Frozen Rotor study type, the rotating parts are kept frozen in position, and rotation is accounted for by the inclusion of centrifugal and Coriolis forces. In both types, the physics interface solves for conservation of energy, mass, and momentum. Turbulence effects are modeled using the AKN two-equation k-ε model with realizability constraints. The AKN model is a so-called low-Reynolds number model, which means that it can resolve the velocity, pressure, and temperature fields all the way down to the wall. The AKN 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. However, only fluid domains adjacent to pair boundaries are supported.

When this multiphysics interface is added, the following default nodes are also added in the Model Builder under High Mach Number Flow, Low Reynolds Number k-ε — Fluid, Initial Values, Wall, and Thermal Insulation. When a pair boundary is created, the Continuity node is automatically added. 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. See Moving Mesh for more details of the Rotating Domain node added automatically in the Model Builder under Definitions > Moving Mesh.

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. When the Include kinetic energy checkbox is selected, the conservative total-energy equation is solved.

The default Turbulence model type is RANS-EVM, the default Turbulence model is Low Reynolds Number 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 low Reynolds number 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, Turbulent kinetic energy k (SI unit: m2/s2), Turbulent dissipation rate ep (SI unit: m2/s3) and Reciprocal wall distance G (SI unit: 1/m) variables are also available.