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How to monitor torque or force in CFX?

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Old   April 13, 2016, 23:18
Default How to monitor torque or force in CFX?
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HI,

I am simulating a turbine.

I want to know that how do i monitor torque or force in CFX, in fact i want judge to convergence by using monitored torque or force.

Thanks.

Last edited by aja1345; April 22, 2016 at 08:47.
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Old   April 13, 2016, 23:34
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How do i compute flow rate(m^3/s) in CFX?

Is there such an option in CFD-post?
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Old   April 14, 2016, 00:02
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All these values are easily calculated with CEL expressions. For instance force(), torque(), areaInt(), and many others are available. Have a look in the CFX documentation - the reference guide for the full list. And the tutorial examples in the documentation shows some examples of how to use these functions.

In CFD-Post it is easier still - just go to the function calculator and you can evaluate these functions directly. Or put them onto a table spreadsheet. Or define a variable and chart it. You have lots of options.
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Old   April 14, 2016, 01:27
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Hi

flow rate=surface area*velocity
So you can integrate velocity on a surface like this:

areaint(velocity)@location => [m^3 s^-1] is the default unit

location is area where you want to measure flow rate and be sure to pick out velocity in proper direction or just velocity.

And I think that result should be the same for:
areaavg(velocity)@location * area@location => flow rate

For torque use:
torque_y@location this is for torque in [y] direction you can use x or z instead

And if you want to monitor convergence you can set those expresions as monitor points in CFXpre under; Output->monitor
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Last edited by urosgrivc; April 14, 2016 at 03:40.
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Old   April 14, 2016, 05:25
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Quote:
Originally Posted by urosgrivc View Post
Hi

flow rate=surface area*velocity
So you can integrate velocity on a surface like this:

areaint(velocity)@location => [m^3 s^-1] is the default unit

location is area where you want to measure flow rate and be sure to pick out velocity in proper direction or just velocity.

And I think that result should be the same for:
areaavg(velocity)@location * area@location => flow rate

For torque use:
torque_y@location this is for torque in [y] direction you can use x or z instead

And if you want to monitor convergence you can set those expresions as monitor points in CFXpre under; Output->monitor
Thanks for your answer.

About monitor convergence, I don't see any parameter as force or torque in the following picture:

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Old   April 14, 2016, 05:42
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No do not set monitor points directly threw output->monitor

Make a seperate expression that you will later just cal in the output->monitor

example:

under Expressions -> insert a new expression
-Expression; torque_y@rotor ; let say that rotor is the fluid side of surface you want to measure torque on in y direction
- ok expression is set, now...

- go to output control->monitor->monitor Points and Expressions
- Insert new monitor point
- Under options ->change to Expression
- under Expression Value -> call in your expresion

And your first monitor point is set, you can make as meny as you want.
Just it is a lot easier to call in an expreession that has already been writen
unless you want data in a sertain point in space like pressure or temperature or whatewer you like.
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Old   April 14, 2016, 06:04
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Quote:
Originally Posted by urosgrivc View Post
No do not set monitor points directly threw output->monitor

Make a seperate expression that you will later just cal in the output->monitor

example:

under Expressions -> insert a new expression
-Expression; torque_y@rotor ; let say that rotor is the fluid side of surface you want to measure torque on in y direction
- ok expression is set, now...

- go to output control->monitor->monitor Points and Expressions
- Insert new monitor point
- Under options ->change to Expression
- under Expression Value -> call in your expresion

And your first monitor point is set, you can make as meny as you want.
Just it is a lot easier to call in an expreession that has already been writen
unless you want data in a sertain point in space like pressure or temperature or whatewer you like.
Thanks.

According to your statement, Is not possible that torque monitors in solution panel when i am running? In fluent, I did this work. in fact, in Fluent, when i was running, torque plot was seen.
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Old   April 14, 2016, 06:38
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Define a monitor point as a CEL expression. Then use an expression force_X()@somewhere and you can monitor force during the run.
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Old   April 14, 2016, 06:40
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Of course you can monitor whatever you like while solving.
I have writen a guide to how you do it in the previous post.

Monitor points are stuf you can see while solving the problem.

And there was no torque or force in the picture you have posted because you can not measure force or torque in (one point in space)
for that you need a surface wich you define with an expression.
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Old   April 14, 2016, 07:37
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How do I set "value" under Evaluate in expressions pannel? this Value is necessary for Monitor panel.
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Old   April 14, 2016, 18:51
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Have you done the CFX tutorials provided with CFX? It shows how to do the basic stuff like this.
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Old   April 15, 2016, 03:58
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Hi

You should read this:

http://www.docfoc.com/chapter-11-cfx...n-language-cel
and
http://www.padtinc.com/blog/the-focu...essions-part-5
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