roughness function

sarahtuvia · May 3, 2015, 10:03

Hi
I would like to get the results of the roughness parameters and function during
and at the end of the simulation. In the list of field functions I did not find anything. How can I get it ??

fluid23 · May 4, 2015, 10:59

what roughness parameters are you talking about, specifically?

sarahtuvia · May 4, 2015, 11:27

Rplus, kinematic viscosity and Ustar

fluid23 · May 4, 2015, 11:53

Ok... First I will point out that these are not roughness parameters. Ustar is a turbulence parameter, kinematic viscosity is an intrinsic property of the fluid, and I am unfamiliar with Rplus.

Ustar is a standard field function. Are you sure you don't see it under Tools > Field Functions? Its all the way at the bottom and called Ustar, not friction velocity.

Kinematic Viscosity can be added to the field functions quite easily:
1. Right-Click Tools > Field Functions
2. Select New > Scalar
3. Set Function Name to KinematicViscosity
4. Set Dimensions to Length^2/Time
5. Set Definition to ${DynamicViscosity}/${Density}
7. Rename Field Function to Dynamic Viscosity.
8. Now use it like you would any other field funciton.

As for R+, are you sure you don’t mean y+ (as in wall y+)? Wall y+ is also a standard field function (assuming you have a turbulence model enabled). If r+ is something else, can you please define it?

sarahtuvia · May 4, 2015, 13:36

Thanks
About R+. You can find it in the Help in sub section Roughness Function of sub section Wall Laws Formula of section Using Wall Treatment Models.
But if Ill be able to get the kinematic viscosity then Ill get the R+ too - its a function of Ustar the kinematic viscosity and the roughness height which is an input

May 3, 2015, 10:03	roughness function	#1
sarahtuvia Member tuvia milshtein Join Date: Jun 2014 Location: Israel Posts: 42 Rep Power: 11	Hi I would like to get the results of the roughness parameters and function during and at the end of the simulation. In the list of field functions I did not find anything. How can I get it ??

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May 4, 2015, 10:59		#2
fluid23 Senior Member Matt Join Date: Aug 2014 Posts: 947 Rep Power: 17	what roughness parameters are you talking about, specifically?

May 4, 2015, 11:27		#3
sarahtuvia Member tuvia milshtein Join Date: Jun 2014 Location: Israel Posts: 42 Rep Power: 11	Rplus, kinematic viscosity and Ustar

May 4, 2015, 11:53		#4
fluid23 Senior Member Matt Join Date: Aug 2014 Posts: 947 Rep Power: 17	Ok... First I will point out that these are not roughness parameters. Ustar is a turbulence parameter, kinematic viscosity is an intrinsic property of the fluid, and I am unfamiliar with Rplus. Ustar is a standard field function. Are you sure you don't see it under Tools > Field Functions? Its all the way at the bottom and called Ustar, not friction velocity. Kinematic Viscosity can be added to the field functions quite easily: 1. Right-Click Tools > Field Functions 2. Select New > Scalar 3. Set Function Name to KinematicViscosity 4. Set Dimensions to Length^2/Time 5. Set Definition to ${DynamicViscosity}/${Density} 7. Rename Field Function to Dynamic Viscosity. 8. Now use it like you would any other field funciton. As for R+, are you sure you don’t mean y+ (as in wall y+)? Wall y+ is also a standard field function (assuming you have a turbulence model enabled). If r+ is something else, can you please define it?

May 4, 2015, 13:36		#5
sarahtuvia Member tuvia milshtein Join Date: Jun 2014 Location: Israel Posts: 42 Rep Power: 11	Thanks About R+. You can find it in the Help in sub section Roughness Function of sub section Wall Laws Formula of section Using Wall Treatment Models. But if Ill be able to get the kinematic viscosity then Ill get the R+ too - its a function of Ustar the kinematic viscosity and the roughness height which is an input