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-   -   pressure gradient plots (http://www.cfd-online.com/Forums/cfx/106137-pressure-gradient-plots.html)

shaswat August 20, 2012 10:16

pressure gradient plots
 
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

Felggv August 20, 2012 10:34

Hello there,

Try plotting "Pressure vs. Lenght (the same axis of the artery)".

Good luck

shaswat August 20, 2012 13:10

Quote:

Originally Posted by Felggv (Post 377808)
Hello there,

Try plotting "Pressure vs. Lenght (the same axis of the artery)".

Good luck

Dear friend

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

Felggv August 20, 2012 17:43

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 :D

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!

ghorrocks August 20, 2012 19:13

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?

shaswat August 20, 2012 21:01

Pressure gradient
 
Quote:

Originally Posted by ghorrocks (Post 377867)
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?

shaswat August 20, 2012 23:23

pressure gradient
 
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

ghorrocks August 21, 2012 19:33

Put some monitor points along the line and redo the simulation. Export the data to matlab/excel/whatever and calculate your averages and gradients.

shaswat August 23, 2012 04:45

Quote:

Originally Posted by ghorrocks (Post 378065)
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

bratzinger August 23, 2012 05:31

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 ;)

ghorrocks August 23, 2012 08:03

You can export monitor point data in the solver manager.

shaswat August 23, 2012 10:53

Quote:

Originally Posted by bratzinger (Post 378292)
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
can you explain further please. creating additional variable in cfx post?

thanks

shaswat August 23, 2012 10:55

Quote:

Originally Posted by ghorrocks (Post 378315)
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

shaswat August 23, 2012 13:55

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

shaswat August 24, 2012 00:33

pressure gradient
 
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

bratzinger August 24, 2012 04:12

Quote:

Originally Posted by shaswat (Post 378356)
Dear friend
can you explain further please. creating additional variable in cfx post?

thanks

Hi

creating the additional variable: cfx-pre
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 ... ;)

ghorrocks August 24, 2012 07:41

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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