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-   -   Introducing normalized velocity (http://www.cfd-online.com/Forums/cfx/113057-introducing-normalized-velocity.html)

 kmgraju February 11, 2013 09:56

Introducing normalized velocity

Dear friends
I would like to introduce normalized velocity profile as an input. The velocity changes with respect to time under different condition. So I did normalized the data (0 to 1).
Now the output data has no unit ( assume I am correct). How to introduce this normalized data to the input boundary condition in the velocity field?

Thank you for your kind attention

Regards

Govind

 ghorrocks February 11, 2013 18:15

Velocity boundaries need an input in units of length/time, so you just need to un-normalise it.

Alternately you can trick CFX into using non-dimensional inputs providing you work the unit change through all units in the simulation and end up with a consistent set of units (which are actually unitless :) ). Using this you can do non-dimensional simulations in CFX.

 kmgraju February 11, 2013 23:53

Quote:
 Originally Posted by ghorrocks (Post 407253) Velocity boundaries need an input in units of length/time, so you just need to un-normalise it. Alternately you can trick CFX into using non-dimensional inputs providing you work the unit change through all units in the simulation and end up with a consistent set of units (which are actually unitless :) ). Using this you can do non-dimensional simulations in CFX.
Dear Mr. Glenn

That means I have to choose simply all the dimensionless number to velocity unit. Am I correct?

If this is the case, the maximum velocity becomes 1 m/s and minimum velocity becomes 0 m/s.

in my data at t=0, the normalized value is 0.7070 . this value corresponds to
0.2375 m/s ( un normalized value).

In a global initialization, what is the initial value at t= 0 s? . Is it 0.7070 or 0.2375?
( I put at t=0, velocity 0.7070 m/s).

If I use normalized value , one simulation is sufficient. Am I correct?

If I want to change the input parameter for the next result, what is the procedure?

( Note: If I use normalized method other set of readings also traces the same value )

Thank you

Regards

Govind

 ghorrocks February 12, 2013 07:08

No matter what you do the unit system you use has to be consistent.

It can either be a non-dimensional scheme or a quasi-dimensional scheme (simply un-normalising your velocities). What is the best approach will depend on what information you know and what you are trying to achieve.

 kmgraju February 12, 2013 07:26

Quote:
 Originally Posted by ghorrocks (Post 407364) No matter what you do the unit system you use has to be consistent. It can either be a non-dimensional scheme or a quasi-dimensional scheme (simply un-normalising your velocities). What is the best approach will depend on what information you know and what you are trying to achieve.
Thank you Mr Glenn
I will try my best

Regards

Govind

 shaswat February 19, 2013 00:18

Quote:
 Originally Posted by ghorrocks (Post 407253) Velocity boundaries need an input in units of length/time, so you just need to un-normalise it. Alternately you can trick CFX into using non-dimensional inputs providing you work the unit change through all units in the simulation and end up with a consistent set of units (which are actually unitless :) ). Using this you can do non-dimensional simulations in CFX.

Dear friends

I have an CEL expression for velocity U(t)= U(max)[1+sin (4*pi*f*t- (pi/2))]

for my simulation I want to change U(max ) everytime.

If I convert into normalized, I got a same curve for all the U(max) values.

Now, is there any way to proceed with single simulation and get multiple results for different U(max) values?

Regards

Shashwat

 ghorrocks February 19, 2013 04:58

Do you want to see the result for a series of U(max) values in a steady state simulation? The best way to do this is to either script up a series of steady state runs, possibly using other runs as intial conditions to speed sonvergence; OR use a multiple configuration def file to do multiple setups OR use workbench to do a parametric sweep.

There's three ways of doing it, you choose the one you like the best.

 shaswat February 19, 2013 22:02

Quote:
 Originally Posted by ghorrocks (Post 408633) Do you want to see the result for a series of U(max) values in a steady state simulation? The best way to do this is to either script up a series of steady state runs, possibly using other runs as intial conditions to speed sonvergence; OR use a multiple configuration def file to do multiple setups OR use workbench to do a parametric sweep. There's three ways of doing it, you choose the one you like the best.
dear friend
No my simulations are transient simulation.