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-   -   why absolute pressure and temperature limited to 1.000000e+00? (http://www.cfd-online.com/Forums/fluent/72177-why-absolute-pressure-temperature-limited-1-000000e-00-a.html)

wildli January 27, 2010 16:51

why absolute pressure and temperature limited to 1.000000e+00?
 
Dear all,
I am running a case of two counter rotating wheel in a chamber(adiabatic) to compress air (ideal gas), I am meeting the problem of absolute pressure and temperature limited to 1.00000e+00 for a lot of cells. Whenever I switched the air into constant density but keep energy equation on, there is no problem for the calculation; I checked the fluid characteristics, it looks like both wheels rotate very well, and give me some good result for constant density gas.
The problem lies in solving energy equation.
Can any one give me some hint how to overcome this difficult? it bothers for quite a while, any hint would be highly appreciated.
thanks!

Reference for the settings:
Geometry description starting from the inlet flow:
1. flow inlet --> front chamber flowing zone --> 1st axial impeller(rotating) --> small gap before 2nd wheel --> 2nd wheel(counter rotating) --> back chamber flowing zone --> outlet
2. all of these flowing zone sections have the same out diameter

ANSYS 12-FLUENT
1. Pressure-based, absolute velocity formulation, steady case
2. viscous model selected as standard k-e
3. material selected as idea gas with specific Cp, viscosity
4. fluid inside of two wheels specified as moving reference frame
5. pressure inlet, pressure outlet with static pressure and backflow temperature specified,
6. two impeller wheel are chosen as moving wall which have 0 relative velocity to the adjacent zones.
7. faces between rotating wheel zone and fluid flowing chamber zone are interface
8. simple scheme with least square cell based gradient, and 1st order wind for other parameters
9. URF are set as default

mas January 28, 2010 02:25

I'm sure you'll find many answers to that question in this forum if you search. Generally, I think you should increase the quality of your mesh.


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