Heat source as a function of velocity on a plane

Nicki · May 19, 2009, 12:47

Hi,

I want to use an expression where the heat source in a subdomain is dependant on the velocity at a point. Unfortunately, I have many subdomains, and so using monitor points is not really practical. As an initial estimate, I can run an isothermal case to get the velocities on a plane at z=2m, but how do I now create an expression within the subdomain (at a distance away from the plane), based on the values on the plane. I've exported the values from Post, and initialized the profile data to create a user function in Pre, but this is where I get stuck. I've attached an image which hopefully explains it a little better.

Any advice is appreciated,

Thanks,

Nicki

ghorrocks · May 19, 2009, 22:03

Hi,

Is the temperature field coupled to velocity somehow? If not then you should do it as two sequential simulations, the first to get the velocity field and the second to do the thermal stuff. You can turn the heat and fluid solvers on and off using expert parameters.

If they are coupled (eg by buoyancy) then you will need to run them together in a single simulation. This will be more difficult to converge and more time consuming but if you have to do it then you have no choice.

If you want the heat generation to be linked to velocity at a point then I can't see how the profile stuff helps. Don't you just need a probe CEL expression linked to the heat source function?

Glenn Horrocks

Nicki · May 20, 2009, 04:46

Thanks Glenn. The flux in each domain is based on the velocity just below it, which can vary significantly across the plane z=2m. I have just done some manual calculation sensitivity analysis, and the velocity is not the dominant variable in the flux equation, so for this case, I might just estimate its value.

Just out of interest, can the probe function be used to reference the velocity at (x,y,2) without putting a monitor point at (x,y,2)?

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May 19, 2009, 22:03		#2
ghorrocks Super Moderator Glenn Horrocks Join Date: Mar 2009 Location: Sydney, Australia Posts: 17,703 Rep Power: 143	Hi, Is the temperature field coupled to velocity somehow? If not then you should do it as two sequential simulations, the first to get the velocity field and the second to do the thermal stuff. You can turn the heat and fluid solvers on and off using expert parameters. If they are coupled (eg by buoyancy) then you will need to run them together in a single simulation. This will be more difficult to converge and more time consuming but if you have to do it then you have no choice. If you want the heat generation to be linked to velocity at a point then I can't see how the profile stuff helps. Don't you just need a probe CEL expression linked to the heat source function? Glenn Horrocks

May 20, 2009, 04:46		#3
Nicki New Member Nicki Parker Join Date: Mar 2009 Posts: 4 Rep Power: 17	Thanks Glenn. The flux in each domain is based on the velocity just below it, which can vary significantly across the plane z=2m. I have just done some manual calculation sensitivity analysis, and the velocity is not the dominant variable in the flux equation, so for this case, I might just estimate its value. Just out of interest, can the probe function be used to reference the velocity at (x,y,2) without putting a monitor point at (x,y,2)?