What Is the Linear Pressure Strain Two-Layer Model?

The advantage of the linear pressure-strain model is that it lends itself to being incorporated into a two-layer formulation which can be used to resolve the viscous sublayer for low-Reynolds number type applications. The node of this model has its own properties.

In this model's approach, suggested by Rodi [37], the computation is divided into two layers. In the layer adjacent to the wall, the turbulent dissipation rate

and the turbulent viscosity

are specified as functions of wall distance. The values of

specified in the near-wall layer are blended smoothly with the values computed from solving the transport equation far from the wall.

Linear Pressure Strain Two-Layer Properties

Two-layer type

Selects a two-layer formulation

Shear Driven (Wolfstein)

The two-layer formulation of Wolfstein [40]. This is appropriate for flows that are not dominated by buoyancy forces. See Eqns. (253) to (256) in the K-Epsilon model formulation.

Buoyancy Driven (Xu)

The two-layer formulation of Xu et al. [41]. This is appropriate for flows that are dominated by buoyancy forces. See Eqns. (257) to (260) in K-Epsilon model formulation.

Convection

For guidance on selecting a convection, see Diffusion Term .

1st-order

The first-order convection.

2nd-order

The second-order convection.

Linear Pressure Strain Two-Layer Expert Properties

Unless you are thoroughly familiar with the theoretical aspects of this model and the discretization techniques used in STAR-CCM+, we recommend that you not make any changes within the Expert category. The values in that category reflect both the model's design and discretization approaches that have been optimized for accuracy and performance. Tampering with them may diminish the effectiveness of the model.

The coefficient , see Eqn. 305.

C1w

The coefficient , see Eqn. 307.

The coefficient , see Eqn. 306.

C2e

The coefficient , see Eqn. 302.

C2w

The coefficient , see Eqn. 310.

The coefficient , see Eqn. (12-139).

Cmu

The coefficient , see Eqn. 298

Two-Layer Delta ReY

The value of used in Eqn. 249 in K-Epsilon model formulation.

FwMax

The coefficient , see Eqn. 308.

Buoyancy Production of Dissipation

Determines how the coefficient in Eqn. 301 is calculated.

None

Neglects the term .

Boundary Layer Orientation

Computes according to Eqn. 196.

Thermal Stratification

Computes according to Eqn. 195.

Two-Layer ReY*

The value of used in Eqn. 248 in K-Epsilon model formulation.

Sarkar

The coefficient , see Eqn. 303.

Secondary Gradients

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

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.

Sigma_e

The coefficient , see Eqn. 302.

Sigma_k

The coefficient , see Eqn. 308.

Tdr Minimum

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

TkeMinimum

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

Use Boussinesq Approximation

Instead of using the divergence of the computed Reynolds-stress tensor, use the Boussinesq approximation given by Eqn. 239.

Ticked

Use Boussinesq approximation.

Cleared

Use computed Reynolds stresses.

Wall Reflection Term

Include or omit the wall-reflection terms and (see Eqn. 304).

Ticked

The terms are included.

Cleared

The terms are omitted.