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Old   March 5, 2003, 08:39
Default TASCFlow2.12-CFX5.5.1
  #1
vlado
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I am runing the same problem with the same mesh in tascflow and CFX 5.5. I am getting differen results. The problem i am workin on is axial turbine with stator rotor with frozen rotor interface. Do anybody knows the solution of the problem?
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Old   March 5, 2003, 10:45
Default Re: TASCFlow2.12-CFX5.5.1
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KG
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Interesting,

Please describe such diference in solution.

Did you check your grid. I mean mm...cm..m.

Regards, KG
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Old   March 5, 2003, 18:16
Default Re: TASCFlow2.12-CFX5.5.1
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Robin
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Hi Vlado,

What advection scheme are you using in each code? Also, why are you not using 5.5.1?

Robin
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Old   March 6, 2003, 02:00
Default TASCFlow2.12-CFX5.5.1
  #4
vlado
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I am using CFXTascflow 2.12 and CFX 5.5.1. In both softwares i used the same structured mesh which i generated in ICEM CFD hexa. The advection cheme in tascflow is iskew 3 and lpac is set on t. In cfx i set the blend factor on 0.75 The torque results are different and consequently the power utput is different. I am convinced that tascflow is giving me good results because t have more experience with tascflow and i just started to use CFX. Is it possible that the torque function in cfx calculator isnt working right?
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Old   March 6, 2003, 14:15
Default Re: TASCFlow2.12-CFX5.5.1
  #5
Robin
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How are you calculating torque in TASCFlow?

Robin
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Old   March 6, 2003, 15:02
Default Re: TASCFlow2.12-CFX5.5.1
  #6
vlado
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I wrote a macro to calculate a torque!

macro for torque

torque_all = p*(area_wall_x*y-area_wall_y*x) torque_pressure = sum(torque_all@pressure)

this is only a star of the macro you also have to calculate torque on suction side and edge of teh blade and then you have to sum all thre parts. Drag forces are also included which decrease the total torque. With all the experience i have on the turbines i can say that the result from tascflow is ok!

I think that i made a mistake in CFX build where i dont have a lot of experience.

What do you thik is it ok to have (in CFX5.5.1) two parallel planes which are on the rotating rotor and are conected with two equal planes on stator (stator is on both sides of the turbine) with frozen rotor interface under one interface (boundary condition).
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Old   March 10, 2003, 18:56
Default Re: TASCFlow2.12-CFX5.5.1
  #7
Neale
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OK, make sure to include viscous forces as well though, otherwise you will not get the proper result.

How are you calculating this in CFX-5, the solver output file, or by setting "output eq flows" in Build and then using the torque function in CFX-post.

Neale
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Old   March 11, 2003, 05:15
Default Re: TASCFlow2.12-CFX5.5.1
  #8
vlado
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Are viscous forces included in torque function in CFX 5.5.1?
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Old   March 14, 2003, 19:02
Default Re: TASCFlow2.12-CFX5.5.1
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Neale
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Hi,

Yew, CFX-Post uses the boundary momentum flows written by the CFX-5-Solver to compute force and torque. This includes both viscous + pressure forces. There isn't an easy way of separating the torques in CFX-Post in 5.5.1 either. You can separate the forces though. Get the pressure force by separately computing the areaInt of pressure the x, y andy z direction.

Neale.
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