Gamma Transition Models 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, modifies the transition trigger function $F_{onset}$ (see Eqn. (1562)), which activates the production term in the equation for the transported intermittency $\gamma$. The default setting is Off.

Cross-flow parameters

Child node that provides the model constant C_scf, that is $C_{SCF}$ in Eqn. (1564), and the cross-flow inducing roughness height in meters h(m), that is $h$ in Eqn. (1574). Increasing the default values accelerates the cross-flow induced transition.

Freestream Turb. Intensity (only for the SA Gamma Transition model)

The coefficient $T_{U_L}$ , see Eqn. (1558).

Sigma_f

The coefficient ${\sigma }_f$, see Eqn. (1550).

ca2

The coefficient $C_{a2}$, see Eqn. (1556).

ce2

The coefficient $C_{e2}$, see Eqn. (1556).

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.

CTU1

The coefficient $C_{\mathrm{TU}1}$, see Eqn. (1558).

CTU2

The coefficient $C_{\mathrm{TU}2}$, see Eqn. (1558).

CTU3

The coefficient $C_{\mathrm{TU}3}$, see Eqn. (1558).

Conset1

The coefficient $C_{\mathrm{onset}1}$, see Eqn. (1555).

Initial Conditions

Intermittency

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

Gamma Transition Solver

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

For the transported variable $\gamma$ 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.

冻结重构

开启时，Simcenter STAR-CCM+ 不会在每次迭代时更新重构梯度，而是使用上一次迭代更新的梯度。激活保留临时储存与此属性结合使用。默认情况下，此属性处于关闭状态。

归零重构

开启时，求解器在下一次迭代时会将重构梯度设为零。此操作意味着，用于迎风的面值 (Eqn. (905)) 以及用于计算网格单元梯度的面值（Eqn. (917) 和 Eqn. (918)）将变为一阶估计值。默认情况下，此属性处于关闭状态。如果开启此属性之后关闭它，则求解器将在下一次迭代时重新计算梯度。

冻结求解器

开启时，求解器在迭代过程中不更新任何物理量。该选项默认情况下关闭。这是一个调试选项，由于缺少储存，它可能导致不可恢复的错误和错误的求解。有关详细信息，请参见有限体积求解器参考。

保留临时储存

开启时，Simcenter STAR-CCM+ 将保留求解器在迭代期间生成的额外场数据。保留的特定数据取决于求解器，且在后续迭代期间可用作场函数。默认情况下关闭。

Field Functions

Intermittency

The transported variable $\gamma$ , see Eqn. (1550).

Specific Dissipation Rate Reynolds Number

The specific dissipation rate Reynolds number defined as ${\mathrm{Re}}_{\omega }=\frac{\omega d^2}{\nu }$.

Turbulence Intensity

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