
[Sponsors] 
February 11, 2013, 09:56 
Introducing normalized velocity

#1 
Senior Member
Govindaraju
Join Date: Apr 2010
Posts: 206
Rep Power: 9 
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 

February 11, 2013, 18:15 

#2 
Super Moderator
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 12,559
Rep Power: 97 
Velocity boundaries need an input in units of length/time, so you just need to unnormalise it.
Alternately you can trick CFX into using nondimensional 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 nondimensional simulations in CFX. 

February 11, 2013, 23:53 

#3  
Senior Member
Govindaraju
Join Date: Apr 2010
Posts: 206
Rep Power: 9 
Quote:
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 

February 12, 2013, 07:08 

#4 
Super Moderator
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 12,559
Rep Power: 97 
No matter what you do the unit system you use has to be consistent.
It can either be a nondimensional scheme or a quasidimensional scheme (simply unnormalising your velocities). What is the best approach will depend on what information you know and what you are trying to achieve. 

February 12, 2013, 07:26 

#5  
Senior Member
Govindaraju
Join Date: Apr 2010
Posts: 206
Rep Power: 9 
Quote:
I will try my best Regards Govind 

February 19, 2013, 00:18 

#6  
Senior Member
Shashwat
Join Date: Nov 2011
Posts: 107
Rep Power: 6 
Quote:
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 

February 19, 2013, 04:58 

#7 
Super Moderator
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 12,559
Rep Power: 97 
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. 

February 19, 2013, 22:02 

#8  
Senior Member
Shashwat
Join Date: Nov 2011
Posts: 107
Rep Power: 6 
Quote:
No my simulations are transient simulation. can you please explain bit. I thought in the following way,please correct me if I am wrong. the normalized velocity curve is simillar for the series of U(max).so find the normalized factor . DO one simulation unnormalized velocity as an input and find the result in cfx post. If I want to do series of u (max) , can I simply multiply with normalized factor?.simillary ,can I multiply the normalized factor with result in cfx post?. is the way correct ? Thank you Regards 

Thread Tools  
Display Modes  


Similar Threads  
Thread  Thread Starter  Forum  Replies  Last Post 
Plotting Radial Velocity and Tangential Velocity in CFD Post  ashtonJ  CFX  5  July 13, 2015 02:49 
Steady pipe flow mean velocity higher than inlet velocity  anita  OpenFOAM Running, Solving & CFD  7  September 25, 2012 05:35 
Velocity in Porous medium : HELP! HELP! HELP!  Kali Sanjay  Phoenics  0  November 6, 2006 07:10 
Neumann pressure BC and velocity field  Antech  Main CFD Forum  0  April 25, 2006 02:15 
what the result is negatif pressure at inlet  chong chee nan  FLUENT  0  December 29, 2001 06:13 