Wall Treatment Models Reference

Models Overview

Turbulence Models Lookup

			High y+	Low y+	All y+	2L All y+
Detached Eddy Simulation	EB K-Epsilon Detached Eddy
	SST (Menter) K-Omega Detached Eddy
	Spalart-Allmaras Detached Eddy
Large Eddy Simulation	Dynamic Smagorinsky Subgrid Scale
	Smagorinsky Subgrid Scale
	WALE Subgrid Scale
Reynolds-Averaged Navier-Stokes	K-Epsilon Turbulence	EB K-Epsilon
		Lag EB K-Epsilon
		Realizable K-Epsilon
		Realizable K-Epsilon Two-Layer
		Standard K-Epsilon
		Standard K-Epsilon Low-Re
		Standard K-Epsilon Two-Layer
	K-Omega Turbulence	SST (Menter) K-Omega
		Standard (Wilcox) K-Omega
	Reynolds Stress Turbulence	Elliptic Blending
		Linear Pressure Strain
		Linear Pressure Strain Two-Layer
		Quadratic Pressure Strain
	Spalart-Allmaras Turbulence	Standard Spalart-Allmaras

Properties Lookup

									High y+	Low y+	All y+	2L All y+
Iterative Ustar When On, this property allows iterative computation of the reference velocity $u^{*}$ from the wall law. When this property is Off, the reference velocity $u^{*}$ is computed according to the specific turbulence model.

Boundary Settings

Domain Boundaries

The following boundary conditions and values are equal to all boundaries of type:

• Wall
• Baffle Boundary
• Porous Baffle Boundary
• Contact Interface Boundary
• Mapped Contact Boundary

Blended Wall Function (All y+, 2L All y+)

Added to the Values node on no-slip walls when the all-$y^{+}$ or the two-layer all-$y^{+}$ wall treatment is selected. You need to specify two scalar values:

• E: The log law offset.
• Kappa: The von Karman constant.

Standard Wall Function (High y+)

Added to the Values node on no-slip walls when the high-$y^{+}$ wall treatment is selected. The values you need to specify are equal to the Blended Wall Function.

Wall Surface Specification

Controls whether the boundary is smooth or rough.

Method	Corresponding Value Nodes
Smooth Regular wall treatment without modification for wall roughness.	None.
Rough Modification of wall treatment to incorporate roughness using data correlation. Calculates a roughness function $f$ , which modifies the log law offset $E$ using Eqn. (1604). $f$ is calculated from the specified equivalent sand-grain roughness height $r$ and wall roughness parameters using Eqn. (1639) and Eqn. (1640). Note This method limits the roughness height by the wall distance of the wall-adjacent cell. Simcenter STAR-CCM+ returns the number of faces on which the roughness height is limited in the Output window.	Roughness Height Scalar profile value to specify $r$. You obtain the roughness height that is appropriate for your model either from the literature or empirically. To determine $r$ from an experiment: Measure the friction factor for the Reynolds number of your case in the experiment. Plot your measurements on a Moody diagram. Deduce the equivalent sand-grain roughness height from the Moody diagram curve. Roughness Model Parameters Scalar values to specify: B: Coefficient $B$ in roughness function. C: Coefficient $C$ in roughness function. RplusSmooth: Roughness parameter $R_{smooth}^{+}$ in roughness function corresponding to a fully smooth surface. RplusRough: Roughness parameter $R_{rough}^{+}$ in roughness function corresponding to a fully rough surface.
Rough Displaced Origin Modification of wall treatment to incorporate roughness using displacement of origin. Applies modified wall functions for velocity $u^{+}$ , Temperature $T^{+}$ , turbulent dissipation rate ${\epsilon }^{+}$ , and specific dissipation rate ${\omega }^{+}$ using Eqn. (1642), Eqn. (1645), Eqn. (1648), Eqn. (1650), Eqn. (1652), and Eqn. (1653), respectively. This method does not limit the roughness height by the wall distance of the wall-adjacent cell and is therefore less sensitive to the mesh resolution. You are advised to use this method over the Rough method in case both are available.	Roughness Height As for Rough. Roughness Model Parameters Scalar values to specify: RplusSmooth: As for Rough. RplusRough: As for Rough.

The methods Rough (R) and Rough Displaced Origin (RDO) are available depending on the selected turbulence and wall treatment models as follows:

			High y+	Low y+	All y+	2L All y+
Large Eddy Simulation	Dynamic Smagorinsky Subgrid Scale		-	-	RDO	-
	Smagorinsky Subgrid Scale		-	-	RDO	-
	WALE Subgrid Scale		-	-	RDO	-
Reynolds-Averaged Navier-Stokes	K-Epsilon Turbulence	EB K-Epsilon	R, RDO	-	R, RDO	-
		Lag EB K-Epsilon	-	-	R, RDO	-
		Realizable K-Epsilon	R, RDO	-	-	-
		Realizable K-Epsilon Two-Layer	-	-	-	R
		Standard K-Epsilon	R, RDO	-	-	-
		Standard K-Epsilon Low-Re	-	-	R, RDO	-
		Standard K-Epsilon Two-Layer	-	-	-	R
	K-Omega Turbulence	SST (Menter) K-Omega	R, RDO	RDO	R, RDO	-
		Standard (Wilcox) K-Omega	R, RDO	RDO	R, RDO	-
	Reynolds Stress Turbulence	Elliptic Blending	-	-	R, RDO	-
		Linear Pressure Strain	R, RDO	-	-	-
		Linear Pressure Strain Two-Layer	-	-	-	R
		Quadratic Pressure Strain	R, RDO	-	-	-
	Spalart-Allmaras Turbulence	Standard Spalart-Allmaras	-	-	R, RDO	-

Region Settings

Field Functions

Ustar

Scalar field that represents the reference velocity $u^{*}$, computed according to the selected wall treatment.

Virtual Local Heat Transfer Coefficient

Scalar field that represents an approximation to the true Local Heat Transfer Coefficient. It does not require an energy model to be activated and is defined as $h=\rho C_p{u}^{*}/T^{\text{+}}$ where $T^{\text{+}}$ is computed according to the selected wall treatment. Since thermal material properties are not available, the specific heat $C_p$ and the molecular and turbulent Prandtl numbers are specified as reference values. The fluid density $\rho$ is obtained locally from the simulation.

Wall Roughness R+ (for walls with Wall Surface Specification set to Rough or Rough Displaced Origin)

Scalar field that represents the roughness parameter $R^{+}$ , as defined in Eqn. (1639).

Wall Y+

Scalar field that represents the non-dimensional wall distance. It is defined as $y^{+}=u^{*}y/\nu$ where $u^{*}$ is the reference velocity, $y$ is the normal distance from the centroid to the wall in wall-adjacent cells and $\nu$ is the kinematic viscosity.