Heat generation due to viscosity/wall friction

Altosmos · March 25, 2023, 08:52

Hey everyone,

I doing a sensitivity analysis in turbomachinery by changing the wall roughness. I also have static wall temperatures defined as boundary conditions. I would like to calculate the heat generation (in Watts) generated due to friction and compare it to the heat flux through conduction in CFX-Post.

How can I build the relation for the heat generation due to viscosity?

Thanks in advance and have a nice day

(Any literature would also be highly appreciated)

Gert-Jan · March 25, 2023, 10:04

Shouldn't you just select the item "Viscous work' in CFX-Pre?

Altosmos · March 26, 2023, 10:19

Hi,

I do enable the viscous work option but that only makes the software account for it. I also want to qualitatively calculate the heat generated by friction. Herefore, I probably need the right equation to convert the shear stress force to power or dissipation.

ghorrocks · March 26, 2023, 17:58

It might be easier to do one simulation with viscous work option activated and another simulation with it turned off. Then you can compare the results. And in CFD-Post there is a difference option which gives you the difference between two simulations which might be useful.

Altosmos · March 26, 2023, 18:31

Thank you for your answer but that might not be a reliable way for my case since I also have conduction heating and the lack of viscous work may increase the heat flux through conduction and degenerate the results.

ghorrocks · March 26, 2023, 20:03

It depends on exactly what you are trying to do. If you want to know what difference the viscous work makes then my suggestion works well. If you want to know how much heating power is coming from viscous heating then you need a different approach.

The viscous work term is discussed in the CFX Theory Manual, in equation 1-86. Note that it is not a "shear stress force" effect as your last post suggested but a stress tensor and velocity vector effect.

Altosmos · March 27, 2023, 05:22

Yeah, I am trying to calculate how much heating power is coming from viscous heating and looking for a way.

Thanks, I will check the Theory Manual and see if I can find a way.

Opaque · March 27, 2023, 11:41

http://www.owlnet.rice.edu/~ceng501/Chap6.pdf

March 25, 2023, 08:52	Heat generation due to viscosity/wall friction	#1
Altosmos New Member Altay Join Date: Nov 2019 Posts: 6 Rep Power: 5	Hey everyone, I doing a sensitivity analysis in turbomachinery by changing the wall roughness. I also have static wall temperatures defined as boundary conditions. I would like to calculate the heat generation (in Watts) generated due to friction and compare it to the heat flux through conduction in CFX-Post. How can I build the relation for the heat generation due to viscosity? Thanks in advance and have a nice day (Any literature would also be highly appreciated)

March 26, 2023, 17:58		#4
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,365 Rep Power: 139	It might be easier to do one simulation with viscous work option activated and another simulation with it turned off. Then you can compare the results. And in CFD-Post there is a difference option which gives you the difference between two simulations which might be useful. __________________ Note: I do not answer CFD questions by PM. CFD questions should be posted on the forum.

March 26, 2023, 20:03		#6
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,365 Rep Power: 139	It depends on exactly what you are trying to do. If you want to know what difference the viscous work makes then my suggestion works well. If you want to know how much heating power is coming from viscous heating then you need a different approach. The viscous work term is discussed in the CFX Theory Manual, in equation 1-86. Note that it is not a "shear stress force" effect as your last post suggested but a stress tensor and velocity vector effect. __________________ Note: I do not answer CFD questions by PM. CFD questions should be posted on the forum.

March 27, 2023, 11:41		#8
Opaque Senior Member Join Date: Jun 2009 Posts: 1,688 Rep Power: 29	http://www.owlnet.rice.edu/~ceng501/Chap6.pdf __________________ Note: I do not answer CFD questions by PM. CFD questions should be posted on the forum.

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search
Display Modes
Linear Mode Switch to Hybrid Mode Switch to Threaded Mode

March 25, 2023, 10:04		#2
Gert-Jan Senior Member Gert-Jan Join Date: Oct 2012 Location: Europe Posts: 1,741 Rep Power: 25	Shouldn't you just select the item "Viscous work' in CFX-Pre?

March 26, 2023, 10:19		#3
Altosmos New Member Altay Join Date: Nov 2019 Posts: 6 Rep Power: 5	Hi, I do enable the viscous work option but that only makes the software account for it. I also want to qualitatively calculate the heat generated by friction. Herefore, I probably need the right equation to convert the shear stress force to power or dissipation.

March 26, 2023, 18:31		#5
Altosmos New Member Altay Join Date: Nov 2019 Posts: 6 Rep Power: 5	Thank you for your answer but that might not be a reliable way for my case since I also have conduction heating and the lack of viscous work may increase the heat flux through conduction and degenerate the results.

March 27, 2023, 05:22		#7
Altosmos New Member Altay Join Date: Nov 2019 Posts: 6 Rep Power: 5	Yeah, I am trying to calculate how much heating power is coming from viscous heating and looking for a way. Thanks, I will check the Theory Manual and see if I can find a way.

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
Custom Thermophysical Properties	wsmith02	OpenFOAM	4	June 1, 2023 14:30
Using PengRobinsonGas EoS with sprayFoam	Jabo	OpenFOAM Running, Solving & CFD	35	April 29, 2022 15:35
Fluent Heat exchanger model	gimson	FLUENT	0	May 10, 2021 04:30
[OpenFOAM.org] Error creating ParaView-4.1.0 OpenFOAM 2.3.0	tlcoons	OpenFOAM Installation	13	April 20, 2016 17:34
Heat Generation rate in W/m³	ashghan	OpenFOAM Programming & Development	0	June 27, 2014 05:42