Gamma ReTheta Transition Model Reference

Properties

Convection

Controls the convection scheme.

• 1st-order: Selects the first-order upwind convection scheme.
• 2nd-order: Selects the second-order upwind convection scheme.

Cross-Flow term

Controls whether to apply a correlation for stationary cross-flow instabilities. The correlation accounts for transition that is triggered by surface roughnesses whose height is in the order of micrometers.

When On, Simcenter STAR-CCM+ includes the cross-flow term of Eqn. (1517) in the equation for the transported transition momentum thickness Reynolds number $\overline{{Re}_{\theta t}}$ . The default setting is Off.

Cross-flow parameters

Child node that provides the model constant C_scf, that is $C_{SCF}$ in Eqn. (1517), and the cross-flow inducing roughness height in meters h(m), that is $h$ in Eqn. (1520).

Activating this option introduces a Reynolds number dependency to the Gamma ReTheta model.

Sigma_f

The coefficient ${\sigma }_f$, see Eqn. (1500).

ca2

The coefficient $C_{a2}$, see Eqn. (1506).

ce2

The coefficient $C_{e2}$, see Eqn. (1506).

Intermittency Minimum

The minimum value that the transported variable $\gamma$ is permitted to have. An appropriate value is a small number that is greater than the floating point minimum of the computer.

Secondary Gradients

Neglect or include the boundary secondary gradients for diffusion and/or the interior secondary gradients at mesh faces.

• On: Include both secondary gradients.
• Off: Exclude both secondary gradients.
• Interior Only: Include the interior secondary gradients only.
• Boundaries Only: Include the boundary secondary gradients only.

Correlation Method

Choose how the correlations for ${\mathrm{Re}}_{\theta c}$ and $F_{length}$ are to be specified.

• Suluksna-Juntasaro: Use the internally-specified correlations (see Eqn. (1530), Eqn. (1548) and Eqn. (1549)).
• User Field Function: Use correlations defined by user specified field function.

  Transition onset Re Correlation

  Child node that controls the correlation used for ${\mathrm{Re}}_{\theta t}$.

  • Modified: Selects the ${\mathrm{Re}}_{\theta t}$ correlation of Eqn. (1530).
  • Modified NZPG: Selects the ${\mathrm{Re}}_{\theta t}$ correlation of Eqn. (1545).
  • Original: Selects the ${\mathrm{Re}}_{\theta t}$ correlation of Eqn. (1529).
  • Original NZPG: Selects the ${\mathrm{Re}}_{\theta t}$ correlation of Eqn. (1540).
  • Abu-Ghannam & Shaw: Selects the ${\mathrm{Re}}_{\theta t}$ correlation of Eqn. (1528).
  • Abu-Ghannam & Shaw NZPG: Selects the ${\mathrm{Re}}_{\theta t}$ correlation of Eqn. (1537).
  • User Field Function: Allows specification of ${\mathrm{Re}}_{\theta t}$ through a user field function. Activates the Re_theta_t correlation child node.

  F-length correlation

  Child node that defines the field function for the $F_{length}$ correlation.

  Re_crit correlation

  Child node that defines the field function for the ${\mathrm{Re}}_{\theta c}$ correlation.

  Re_theta_t correlation

  Child node that defines the field function for the ${\mathrm{Re}}_{\theta t}$ correlation.

Sigma_ReTheta

The coefficient ${\sigma }_{\theta t}$, see Eqn. (1511).

ca1

The coefficient $C_{a1}$, see Eqn. (1501).

ce1

The coefficient $C_{e1}$, see Eqn. (1501).

cTheta_t

The coefficient $C_{\theta t}$, see Eqn. (1512).

s1

The coefficient $s_1$, see Eqn. (1508).

Conset1

The coefficient $C_{\mathrm{onset}1}$, see Eqn. (1505).

ReThetaTMinimum

The minimum value that the transported variable $\overline{{\mathrm{Re}}_{\theta t}}$ is permitted to have. The default value is 20.

Initial Conditions

Intermittency

Scalar profile value to specify the transported variable $\gamma$.

Gamma ReTheta Transition Solver

This solver controls the solution of the Gamma ReTheta transition model in all the continua for which the model is activated.

For each transported variable, $\gamma$ and $\overline{{\mathrm{Re}}_{\theta t}}$, the basic steps that are involved in the solution update are as follows:

• Update boundary conditions.
• Compute the reconstruction gradients and cell gradients.
• Create the linear system of equations using the discretization methods that are described in the K-Omega model formulation.
• Compute the residual sum for monitoring convergence:
  $$R={\sum }_{\text{cells}}^{}\left|r\right|$$
• Solve the linear system.
• Update the transported variable field.

Under-Relaxation Factor

At each iteration, governs the extent to which the old solution is supplanted by the newly computed solution. The default value is 0.8. For the theoretical background, see Eqn. (920) in Finite Volume Discretization.

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.

Field Functions

Effective Intermittency

The transported variable ${\gamma }_{eff}$ , see Eqn. (1510).

Flength Correlation

The specified correlation for $F_{length}$ , see Eqn. (1549).

Intermittency

The transported variable $\gamma$ , see Eqn. (1500).

ReThetaCrit Correlation

The specified correlation for ${\mathrm{Re}}_{\theta c}$ , see Eqn. (1548).

Specific Dissipation Rate Reynolds Number

The specific dissipation rate Reynolds number, ${\mathrm{Re}}_{\omega }$ , see Eqn. (1516).

Transition Momentum Thickness Reynolds Number

The transported variable $\overline{{\mathrm{Re}}_{\theta t}}$ , see Eqn. (1511).

Turbulence Intensity

The turbulence intensity, defined as $I=\sqrt{2/3k}/U$