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-   -   wall roughness in OpenFOAM (https://www.cfd-online.com/Forums/openfoam-programming-development/157431-wall-roughness-openfoam.html)

harsha_kulkarni July 29, 2015 06:56
wall roughness in OpenFOAM
 
I want to give roughness for wall in OpenFOAM
how should I give this????

what is the difference between

nutURoughWallFunction
and
nutkRoughWallFunction


and when I'm using following t

type nutURoughWallFunction::Ks;
value uniform 0.001;
type nutURoughWallFunction::Cs;
value uniform 0.5;

it produces following error

Unknown patchField type nutURoughWallFunction::Cs for patch type wall

donQi November 15, 2016 20:43
- nutkRoughWallFunction
http://www.openfoam.com/documentatio...0.html#details
This boundary condition provides a turbulent kinematic viscosity condition when using wall functions for rough walls, based on turbulence kinetic energy. The condition manipulates the E parameter to account for roughness effects.
Parameter ranges:
roughness height = sand-grain roughness (0 for smooth walls)
roughness constant = 0.5-1.0
Example of the boundary condition specification:

Code:
myPatch
    {
        type            nutkRoughWallFunction;
        Ks              uniform 0;
        Cs              uniform 0.5;
    }
where
Ks sand-grain roughness height
Cs roughness constant
--------------------------------------
- nutURoughWallFunction
[http://www.openfoam.com/documentatio....html#details]
This boundary condition provides a turbulent kinematic viscosity condition when using wall functions for rough walls, based on velocity.
Example of the boundary condition specification:
Code:
myPatch
    {
        type            nutURoughWallFunction;
        roughnessHeight 1e-5;
        roughnessConstant 0.5;
        roughnessFactor 1;
    }
where:
roughnessHeight roughness height
roughnessConstant roughness constant
roughnessFactor scaling factor

xinsui178 October 31, 2017 22:40
function
 
Do you know the exact equation for turbulent kinematic viscosity based on the two wall functions?


Quote:
Originally Posted by donQi (Post 625490)
- nutkRoughWallFunction
http://www.openfoam.com/documentatio...0.html#details
This boundary condition provides a turbulent kinematic viscosity condition when using wall functions for rough walls, based on turbulence kinetic energy. The condition manipulates the E parameter to account for roughness effects.
Parameter ranges:
roughness height = sand-grain roughness (0 for smooth walls)
roughness constant = 0.5-1.0
Example of the boundary condition specification:

Code:
myPatch
    {
        type            nutkRoughWallFunction;
        Ks              uniform 0;
        Cs              uniform 0.5;
    }
where
Ks sand-grain roughness height
Cs roughness constant
--------------------------------------
- nutURoughWallFunction
[http://www.openfoam.com/documentatio....html#details]
This boundary condition provides a turbulent kinematic viscosity condition when using wall functions for rough walls, based on velocity.
Example of the boundary condition specification:
Code:
myPatch
    {
        type            nutURoughWallFunction;
        roughnessHeight 1e-5;
        roughnessConstant 0.5;
        roughnessFactor 1;
    }
where:
roughnessHeight roughness height
roughnessConstant roughness constant
roughnessFactor scaling factor


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