incorrect temperature in pressure based solution

September 19, 2007, 00:21

Hello,

I am comparing solutions of pressure based and density based solutions for the transient case below: Inviscid flow of air (perfect gas) in a 1-meter long tube (2-D). There is no flow initially, but using tables, the mass flux and temperature uniformly increase at the inlet B.C.

Two simulations, density based and pressure based are performed using the same time step (2.0E-05) and implicit formulation. The mesh size is 500x20. Obviously there is no need to have 20 grids in the direction normal to the flow, as we are basically modelling a one-dimensional flow.

After some time (2.5 milliseconds), the profiles of pressure, density, velocity, and temperature are compared between the density based and pressure based solutions.

All match quite well, except for temperature, which has a different and incorrect trend at the pressure based solution.

Any comments? The plots are available at:

http://www.time-step.org/cfd/index.html

Thank you,

Kian

Giuki · July 6, 2009, 06:59

Dear Dian,

I have the same problem, with a different case but still. I'm having a pressure inlet, using the pressure-based solver, and would like to have a temperature of 800K. But my guess is due to the pressure inlet and the temperature dependence of Cp. I get temperatures of more than 1200K at my inlet.

Have you found a solution for your problem?

Regards,

Giuki

September 19, 2007, 00:21	incorrect temperature in pressure based solution	#1
Kian Guest Posts: n/a	Hello, I am comparing solutions of pressure based and density based solutions for the transient case below: Inviscid flow of air (perfect gas) in a 1-meter long tube (2-D). There is no flow initially, but using tables, the mass flux and temperature uniformly increase at the inlet B.C. Two simulations, density based and pressure based are performed using the same time step (2.0E-05) and implicit formulation. The mesh size is 500x20. Obviously there is no need to have 20 grids in the direction normal to the flow, as we are basically modelling a one-dimensional flow. After some time (2.5 milliseconds), the profiles of pressure, density, velocity, and temperature are compared between the density based and pressure based solutions. All match quite well, except for temperature, which has a different and incorrect trend at the pressure based solution. Any comments? The plots are available at: http://www.time-step.org/cfd/index.html Thank you, Kian

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July 6, 2009, 06:59		#2
Giuki New Member Giuki Cael Join Date: May 2009 Location: Belgium/The Netherlands Posts: 13 Rep Power: 17	Dear Dian, I have the same problem, with a different case but still. I'm having a pressure inlet, using the pressure-based solver, and would like to have a temperature of 800K. But my guess is due to the pressure inlet and the temperature dependence of Cp. I get temperatures of more than 1200K at my inlet. Have you found a solution for your problem? Regards, Giuki