This corresponds to a pressure, no viscous stress condition in regions with subsonic flow and a no viscous stress condition in regions with supersonic flow. When the static pressure at the outlet is not known beforehand, it is recommended that it is set to the inlet pressure. When a converged solution has been reached, the solution can be analyzed to find the pressure level just outside the sonic point (Ma = 1) along the boundary. You can then apply this pressure level instead.

Supersonic Outlet

When the outlet condition is known to be fully supersonic, the viscous stress is specified in accordance to the equations and hence no physical condition is applied. This is done by prescribing the boundary stress using the full stress vector:

It is often possible to use the supersonic condition at outlets that are not strictly supersonic but mainly supersonic (the main part of the outlet boundary contains supersonic flow).

Pseudo Time Stepping for High Mach Number Flow Models

Pseudo time stepping is per default applied to the all governing equations for stationary problems, for 2D models as well as 3D models. The momentum, continuity,

and turbulence equations, when present, use the same expression for the pseudo time

step symbol ˜ t .

For laminar models the automatic expression for CFLloc is

1 +

if niterCMP 10 1.2min niterCMP – 10 12 0 + if niterCMP 32 9 1.3min niterCMP – 32 9 0 + if niterCMP 60 40 1.3min niterCMP – 60 9 0

while for models with turbulent flow it is

366 | C H A P T E R 1 1 : H I G H M A C H N U M B E R F L O W B R A N C H

1 +

if niterCMP 10 1.2min niterCMP – 10 12 0 + if niterCMP 120 1.3min niterCMP – 120 9 0 + if niterCMP 220 1.3min niterCMP – 220 9 0

References for the High Mach Number Flow Interfaces

1.T. Poinsot and D. Veynante, “Theoretical and Numerical Combustion,” 2nd ed., Edwards, 2005.

2.J. Larsson, Numerical Simulation of Turbulent Flows for Turbine Blade Heat Transfer Applications, Ph.D thesis, Chalmers University of Technology, 1998.

3.J.D. Tannehill, D.A. Anderson, and R.H. Pletcher, “Computational Fluid Mechanics and Heat Transfer,” 2nd ed., Taylor & Francis, 1997.

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N o n - I s o t h e r m a l F l o w B r a n c h

There are several fluid flow interfaces available with the CFD Module. The fluid flow interfaces are grouped by type under the Fluid Flow main branch. This chapter discusses applications involving the Non-Isothermal Flow branch () in the Model Wizard. The Mechanisms for Modeling Non-Isothermal Flow helps you choose the best one to start with.

In this chapter:

•The Non-Isothermal Flow Interfaces

•The Non-Isothermal Flow and Conjugate Heat Transfer, Laminar Flow Interfaces

•The Non-Isothermal Flow and Conjugate Heat Transfer, Turbulent Flow Interfaces

•Shared Interface Features

•Theory for the Non-Isothermal Flow and Conjugate Heat Transfer Interfaces

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