The High Mach Number Reacting Turbulent Flow, Spalart-Allmaras, Diluted Species multiphysics interface () is used to simulate the transport of dilute solutes in turbulent gas flows where the velocity magnitude is comparable to the speed of sound in the gas, that is, flows in the transonic and supersonic range.

It combines the High Mach Number Flow, Spalart-Allmaras and the Transport of Diluted Species physics interfaces. The High Mach Number Reacting Flow, Diluted Species, which is added automatically, couples the velocity field, adds turbulent mixing contributions to the mass transport equations and introduces mass transport turbulence modeling. The mass transfer solves for the development of one or several solutes dissolved in the gas flow in the transonic and supersonic range.

The equations solved by the High Mach Number Flow, Spalart-Allmaras interface are the Navier-Stokes equations for conservation of momentum, the continuity equation for conservation of mass and the equation for the conservation of energy. Turbulence effects are modeled using the Spalart-Allmaras one-equation model. The Spalart-Allmaras model is a so-called low-Reynolds number model, which means that it can resolve the flow 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. A Fluid Properties feature is active by default on the entire interface selection.

The Transport of Diluted Species interface solves for an arbitrary number of concentrations. The species equations include transport by convection, diffusion and, optionally, migration in an electric field.