Standard Spalart-Allmaras Solvers Reference

Spalart-Allmaras Turbulence

This solver controls the solution of the turbulence transport equations in all the continua for which a Spalart-Allmaras model is activated.

For the transported variable $\tilde{\nu }$ the basic steps that are involved in the solution update are as follows:

1. Update boundary conditions.
2. Compute the reconstruction gradients and cell gradients.
3. Create the linear system of equations using discretization methods.
4. Compute the residual sum $R={\displaystyle \sum _{cells}^{}}\left|r\right|$ for monitoring convergence.
5. Solve the linear system.
6. Update the transported variable field.

Properties

Under-Relaxation Factor

At each iteration, governs the extent to which the newly computed solution supplants the old solution. The default value is 0.7. For the theoretical background, see Eqn. (920).

Boundary Layer Initialization

When On, computes initial values for the modified diffusivity automatically, taking account of the proximity of walls and of free-stream values. Boundary layer initialization speeds convergence in most cases. See Boundary Layer Initialization. The property is Off by default.

Reconstruction Frozen

When On, Simcenter STAR-CCM+ does not update reconstruction gradients with each iteration, but rather uses gradients from the last iteration in which they were updated. Activate Temporary Storage Retained in conjunction with this property. This property is Off by default.

Reconstruction Zeroed

When On, the solver sets reconstruction gradients to zero at the next iteration. This action means that face values used for upwinding (Eqn. (905)) and for computing cell gradients (Eqn. (917) and Eqn. (918)) become first-order estimates. This property is Off by default. If you turn this property Off after having it On, the solver recomputes the gradients on the next iteration.

Solver Frozen

When On, the solver does not update any quantity during an iteration. It is Off by default. This is a debugging option that can result in non-recoverable errors and wrong solutions due to missing storage. See Finite Volume Solvers Reference for details.

Temporary Storage Retained

When On, Simcenter STAR-CCM+ retains additional field data that the solver generates during an iteration. The particular data retained depends on the solver, and becomes available as field functions during subsequent iterations. Off by default.

Under-Relaxation Factor Ramp

The Spalart-Allmaras Turbulence > Under-Relaxation Factor Ramp node allows you to set and control a linear ramp for under-relaxation. For details, see Under-Relaxation Factor Ramp Reference.

AMG Linear Solver

The Spalart-Allmaras Turbulence > AMG Linear Solver node allows you to set the algebraic multigrid parameters for the turbulence solver. For details, see Algebraic Multigrid and AMG Linear Solver Properties.

Spalart-Allmaras Turbulent Viscosity

This solver controls the update of the turbulent viscosity.

Let ${\mu }_t^n$ be the value of the previous iteration, and ${\mu }_t^{\text{new}}$ be the value that is computed during the current iteration. The update is controlled as follows:

${\mu }_t^{n+1}={\omega }_{\mu }{\mu }_t^{\text{new}}+\left(1-{\omega }_{\mu }\right){\mu }_t^n$

Properties