
[Sponsors] 
August 20, 2012, 10:16 
pressure gradient plots

#1 
Senior Member
Shashwat
Join Date: Nov 2011
Posts: 107
Rep Power: 5 
Dear friend
I am doing blood flow through stenosed artery. I did transient analysis on this model. I am interested to plot pressure gradient from inlet to outlet. . I have calculated and constructed a time vs pressure plot at various points. But I need to know how to plot pressure gradient along the entire length. Thank you Regards Shashwat 

August 20, 2012, 10:34 

#2 
Member
Felipe Gobbi
Join Date: Apr 2012
Location: Brazil
Posts: 76
Rep Power: 5 
Hello there,
Try plotting "Pressure vs. Lenght (the same axis of the artery)". Good luck 

August 20, 2012, 13:10 

#3  
Senior Member
Shashwat
Join Date: Nov 2011
Posts: 107
Rep Power: 5 
Quote:
Please clarify the following: 1. Is it pressure gradient vs length or pressure Vs length? Note: I tried pressure gradient Vs length 2. Is the pressure gradient equal to average pressure /unit length measured in transient state? As I have already mentioned, I measured transient pressure values at various points on the axis then I calculated pressure gradient as (P1 P2)/l. This values are some what not matched with what you have suggested. Thanks Regards Shashwat 

August 20, 2012, 17:43 

#4 
Member
Felipe Gobbi
Join Date: Apr 2012
Location: Brazil
Posts: 76
Rep Power: 5 
What I suggested is simple, you would see how pressure changes with the lenght, and then I believe you'd have enough information for your case!
But I don't know if it's the same thing that you want I just try to give different solutions for one problem, see if it works, if it doesn't discard it... besides more ppl will answer you soon. Good luck! 

August 20, 2012, 19:13 

#5 
Super Moderator
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 10,830
Rep Power: 85 
Isn't this a simple matter of defining a line object along the centreline of your geometry (or close to it) and plotting pressure along that line?


August 20, 2012, 21:01 
Pressure gradient

#6  
Senior Member
Shashwat
Join Date: Nov 2011
Posts: 107
Rep Power: 5 
Quote:
I could not understand your point. can you please give suggestions to calculate pressure gradient along the entire length? I did like this: I draw a line along the axis of the model then I fix the x axis as axial length and y axis as pressure gradient. Is this correct? 

August 20, 2012, 23:23 
pressure gradient

#7 
Senior Member
Shashwat
Join Date: Nov 2011
Posts: 107
Rep Power: 5 
Dear friend
I would like to take average pressure gradient along the axis . I found that If I simply put the line along the axis and export the pressure is wrong. because that pressure is same as the end of the transient simulations. kindly give any method to get average pressure over the time period vs axial length and pressure gradient(over the time period) vs axial length thanks regards shashwat Last edited by shaswat; August 21, 2012 at 00:10. 

August 21, 2012, 19:33 

#8 
Super Moderator
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 10,830
Rep Power: 85 
Put some monitor points along the line and redo the simulation. Export the data to matlab/excel/whatever and calculate your averages and gradients.


August 23, 2012, 04:45 

#9  
Senior Member
Shashwat
Join Date: Nov 2011
Posts: 107
Rep Power: 5 
Quote:
I have already put some monitor points during simulations. But I need to know how to export the data at the monitor points in cfx post Thank you Regards Shashwat 

August 23, 2012, 05:31 

#10 
New Member
Join Date: Jul 2012
Location: Germany
Posts: 23
Rep Power: 5 
Hi
maybe this could be another solution/help: have u tried creating an additional Variable"PaGrad"(Type unspecified/ Unit e.g. [Pa m^1]/Tensor Type Vector), specify it in your fluiddomain as Vector Alg. Eq. with the Values "Pessure.Gradient X" ... and do e.g. a volume rendering plot in cfxpost? ok the volume rendering arent the most useful plots but very nice to look at 

August 23, 2012, 08:03 

#11 
Super Moderator
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 10,830
Rep Power: 85 
You can export monitor point data in the solver manager.


August 23, 2012, 10:53 

#12  
Senior Member
Shashwat
Join Date: Nov 2011
Posts: 107
Rep Power: 5 
Quote:
can you explain further please. creating additional variable in cfx post? thanks 

August 23, 2012, 10:55 

#13 
Senior Member
Shashwat
Join Date: Nov 2011
Posts: 107
Rep Power: 5 

August 23, 2012, 13:55 

#14 
Senior Member
Shashwat
Join Date: Nov 2011
Posts: 107
Rep Power: 5 
dear friends
I got a transient results from monitor points. but I didn't get my pressure values when t=0 ( Cfx solver manager) When I use CFX post I got the above result when t=0 too Please clarify thanks Govind 

August 24, 2012, 00:33 
pressure gradient

#15 
Senior Member
Shashwat
Join Date: Nov 2011
Posts: 107
Rep Power: 5 
Dear friends
I just recall pressure gradient which is equal to (P1P2)/L = constant I got average pressure by inserting monitor points. I need to calculate pressure gradient [( P1average P2 average)/l] Is it correct? After completing transient analysis, How to calculate pressure gradient between 100 over points along the axis of the flow. It is tedious process to put 100 over monitor points along the axis and find the average pressure at all the points then finding pressure gradient [(p1averageP2average )/l] Is there any way to calculate ? Thanks Shashwat 

August 24, 2012, 04:12 

#16  
New Member
Join Date: Jul 2012
Location: Germany
Posts: 23
Rep Power: 5 
Quote:
creating the additional variable: cfxpre afterwards u can also use this variable for monitor points ... p.s. i missspelled s.th. > "Pressure.Gradient X"  the other values are Pressure.Gradient Y ... 

August 24, 2012, 07:41 

#17 
Super Moderator
Glenn Horrocks
Join Date: Mar 2009
Location: Sydney, Australia
Posts: 10,830
Rep Power: 85 
You can set up lots of monitor points a few ways:
* export your CCL with one monitor point set up. copy/paste the CCL for the monitor point and edit it to include all the points. Import it back into CFXPre or the solver. * Use perl in the CCL to generate the monitor points. 

Thread Tools  
Display Modes  


Similar Threads  
Thread  Thread Starter  Forum  Replies  Last Post 
Pressure Inlet VS velocity Inlet difference  Mohsin  FLUENT  6  January 15, 2015 18:15 
Pressure Outlet Guage pressure  Mohsin  FLUENT  34  January 12, 2012 06:45 
Pressure BC for combustion chamber  Giuki  FLUENT  1  July 19, 2011 11:35 
How to create an inlet with pressure gradient?  val17lr  FLUENT  5  July 13, 2010 15:15 
Hydrostatic pressure in 2phase flow modeling (long)  DS & HB  Main CFD Forum  0  January 8, 2000 16:00 