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-   -   francis turbin difference between experiment values and CFD (http://www.cfd-online.com/Forums/cfx/71301-francis-turbin-difference-between-experiment-values-cfd.html)

snoopy December 23, 2009 23:02

francis turbin difference between experiment values and CFD
 
Hello.
I have something to solve urgently. Please please help me.
I have flow rate 1.37 m^3/s at outlet from an experiment.
I imposed initial conditions as 4.16ATM pressure at inlet but after CFX 11 runned I got a result 2 m^3/s at outlet.
As I told you, I have to have result as 1.37 m^3/s at outlet.
What should I do?
I already checked modeling, scale and fluid properties and so on.
Thank you in advance.
Have a nice day.

Abou ali December 25, 2009 03:20

Hi,
It may be that you have a problem with boundary conditions, you should take a look on this section from the CFX Help: ANSYS CFX Reference Guide | ANSYS CFX Best Practices Guide for Turbomachinery | Liquid Pumps and Turbines | and if the problem persists you should give us more details about the boundary conditions.

snoopy December 28, 2009 00:21

Hi Ali
 
Hi Mr. Ali. Thank you for your kind response.
I read turbomachinery boundary condition and set boundary conditions as it is said.
I set inlet BC as 547.76 ATM of total pressure and outlet BC as 1370 kg/s of flow rate.
But I can't find any difference between pressure of inlet and outlet.
How can I fix it?
Thank you in advance.

sans December 28, 2009 00:43

Hi, Simple question, has your simulation fully converged? because there is no point in discussing results of an unconverged simulation.
Also where is this mass flow being measured? Is it at the outlet of the domain?

snoopy December 28, 2009 01:38

Re
 
Hi. My result are fully converged.
And I got results of inlet condition and outlet conditon from the experiment. I measured mass flow rate at outlet.
Do you have any idea?

sans December 28, 2009 02:07

Can you post an .out file here?

snoopy December 28, 2009 02:14

hi
 
Hi

Do you know how to send file to you here?
or please give me your e-mail address?

snoopy December 28, 2009 03:05

hi
 
Hi
I attached out file. please read it and give me a great idea.
have a nice day

Abou ali December 28, 2009 03:12

Hello all,
The used BC at inlet is unrealistic, a total pressure of 547.76 ATM is very high and you can't find a correct solution.
It's a good idea to attach your output file here.
Go to the bottom of the Reply to Thread page, in the Additional Options you can find Attach Files .


snoopy December 28, 2009 03:12

hi
 
1 Attachment(s)
Hi
I attached out file. please read it and give me a great idea.
have a nice day

PS : inlet condition is 45m of head at inlet.
and according to my calculation, the total pressure is 4.5 ATM + 0.5 * density * velocity^2 is 547.76 ATM
am I wrong?

Abou ali December 28, 2009 03:58

Hi,
After reading your output file, I find this tow mistacs:

1- MASS AND MOMENTUM:
Option = Total Pressure
Relative Pressure = 547.76 [atm]
END

As I sad previously the total pressure is not correct????!!!!!

2- BOUNDARY: SH02
Boundary Type = WALL
Frame Type = Rotating
Location = SHROUD1 2
BOUNDARY CONDITIONS:
WALL INFLUENCE ON FLOW:
Option = No Slip
END
END
END

This Boundary is defined as rotating Boundary, but in reality it isn't. To define it as stationary, go to the Boundary Details and activate Wall Velocity then select Counter Rotating Wall in the option Box.
You have to do that for all stationary boundaries in the rotating domain.


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