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 August 20, 2012, 10:16 pressure gradient plots #1 Senior Member   Shashwat Join Date: Nov 2011 Posts: 107 Rep Power: 8 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: 7 Hello there, Try plotting "Pressure vs. Lenght (the same axis of the artery)". Good luck

August 20, 2012, 13:10
#3
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Shashwat
Join Date: Nov 2011
Posts: 107
Rep Power: 8
Quote:
 Originally Posted by Felggv Hello there, Try plotting "Pressure vs. Lenght (the same axis of the artery)". Good luck
Dear friend

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: 7 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: 14,202 Rep Power: 110 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
#6
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Shashwat
Join Date: Nov 2011
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Quote:
 Originally Posted by ghorrocks 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?
Hai Glenn

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: 8 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: 14,202 Rep Power: 110 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
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Shashwat
Join Date: Nov 2011
Posts: 107
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Quote:
 Originally Posted by ghorrocks Put some monitor points along the line and redo the simulation. Export the data to matlab/excel/whatever and calculate your averages and gradients.
Dear Glen
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: 7 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 fluid-domain as Vector Alg. Eq. with the Values "Pessure.Gradient X" ... and do e.g. a volume rendering plot in cfx-post? 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: 14,202 Rep Power: 110 You can export monitor point data in the solver manager.

August 23, 2012, 10:53
#12
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Shashwat
Join Date: Nov 2011
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Quote:
 Originally Posted by bratzinger 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 fluid-domain as Vector Alg. Eq. with the Values "Pessure.Gradient X" ... and do e.g. a volume rendering plot in cfx-post? ok the volume rendering arent the most useful plots but very nice to look at
Dear friend

thanks

August 23, 2012, 10:55
#13
Senior Member

Shashwat
Join Date: Nov 2011
Posts: 107
Rep Power: 8
Quote:
 Originally Posted by ghorrocks You can export monitor point data in the solver manager.
I need to take sample points 100 or more . how it is possible ?
need to write all 100 points on a line
thanks

 August 23, 2012, 13:55 #14 Senior Member   Shashwat Join Date: Nov 2011 Posts: 107 Rep Power: 8 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: 8 Dear friends I just recall pressure gradient which is equal to (P1-P2)/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 [(p1average-P2average )/l] Is there any way to calculate ? Thanks Shashwat

August 24, 2012, 04:12
#16
New Member

Join Date: Jul 2012
Location: Germany
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Quote:
 Originally Posted by shaswat Dear friend can you explain further please. creating additional variable in cfx post? thanks
Hi

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: 14,202 Rep Power: 110 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 CFX-Pre or the solver. * Use perl in the CCL to generate the monitor points.

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