wallShearStress

Description

The wallShearStress function object computes the wall-shear stress at selected wall patches.

$$\vec \tau = \vec R \cdot \vec n$$

where:

$\vec \tau$ : Wall shear stress vector [m2/s2]

$\vec R$ : Shear-stress symmetric tensor (retrieved from turbulence model)

$\vec n$ : Patch normal vector (into the domain)

Operands

Operand	Type	Location
input	-	-
output file	dat	$FOAM_CASE/postProcessing/<FO>/<time>/<field>
output field	volVectorField (only boundaryField)	$FOAM_CASE/<time>/<outField>

Usage

Example of the wallShearStress function object by using functions sub-dictionary in system/controlDict file:

wallShearStress1
{
    // Mandatory entries (unmodifiable)
    type            wallShearStress;
    libs            (fieldFunctionObjects);

    // Optional entries (runtime modifiable)
    patches         (<patch1> ... <patchN>); // (wall1 "(wall2|wall3)");

    // Optional (inherited) entries
    writePrecision  8;
    writeToFile     true;
    useUserTime     true;
    region          region0;
    enabled         true;
    log             true;
    timeStart       0;
    timeEnd         1000;
    executeControl  timeStep;
    executeInterval 1;
    writeControl    timeStep;
    writeInterval   1;

}

where the entries mean:

Property	Description	Type	Required	Default
type	Type name: wallShearStress	word	yes	-
libs	Library name: fieldFunctionObjects	word	yes	-
patches	Names of operand patches	wordList	no	all wall patches

The inherited entries are elaborated in:

• functionObject
• writeFile

Example by using the postProcess utility:

<solver> -postProcess -func wallShearStress

Further information

Tutorial:

• cavity

Source code:

• wallShearStress

API:

• Foam::functionObjects::wallShearStress

History: Introduced in version v1606+