francis turbin difference between experiment values and CFD

snoopy · December 23, 2009, 23:02

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 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

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

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
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
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.

December 23, 2009, 23:02	francis turbin difference between experiment values and CFD	#1
snoopy New Member snoopy Join Date: Dec 2009 Posts: 8 Rep Power: 16	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.

December 28, 2009, 00:21	Hi Ali	#3
snoopy New Member snoopy Join Date: Dec 2009 Posts: 8 Rep Power: 16	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.

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
ATTENTION! Reliability problems in CFX 5.7	Joseph	CFX	14	April 20, 2010 16:45
validation of CFD and windtunnel experiment	M.Arun prasad	FLUENT	4	March 13, 2008 03:12
CFD VALUES AT EXPERIMENTAL POINT	J	FLUENT	1	September 25, 2005 17:55

December 25, 2009, 03:20		#2
Abou ali Member Join Date: Nov 2009 Posts: 49 Rep Power: 17	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.

December 28, 2009, 00:43		#4
sans Member SanS Join Date: Mar 2009 Posts: 41 Rep Power: 17	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?

December 28, 2009, 01:38	Re	#5
snoopy New Member snoopy Join Date: Dec 2009 Posts: 8 Rep Power: 16	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?

December 28, 2009, 02:07		#6
sans Member SanS Join Date: Mar 2009 Posts: 41 Rep Power: 17	Can you post an .out file here?

December 28, 2009, 02:14	hi	#7
snoopy New Member snoopy Join Date: Dec 2009 Posts: 8 Rep Power: 16	Hi Do you know how to send file to you here? or please give me your e-mail address?

December 28, 2009, 03:05	hi	#8
snoopy New Member snoopy Join Date: Dec 2009 Posts: 8 Rep Power: 16	Hi I attached out file. please read it and give me a great idea. have a nice day

December 28, 2009, 03:12		#9
Abou ali Member Join Date: Nov 2009 Posts: 49 Rep Power: 17	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 .

December 28, 2009, 03:58		#11
Abou ali Member Join Date: Nov 2009 Posts: 49 Rep Power: 17	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.