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-   -   pressure plot over surface (http://www.cfd-online.com/Forums/star-ccm/106408-pressure-plot-over-surface.html)

gmoehl August 28, 2012 08:31

pressure plot over surface
 
Hi,

I've got a complete 3D simulation of an airflow around a turbine vane.
Now I'd like to make a plot of the pressure over the vanes surface.
But when I create an x-y-Plot I can only choose a direction under "X-Type".
When I choose this I only get two points in my dot. I guess that the problem is that I only choose a direction and not the vane surface.

Thank you for your help in advance

GM_XIII August 28, 2012 12:23

Correct if I'm wrong, you'd like to plot a pressure map over the surface?
If so, you have to right click on scene > new scalar scene and select in scalar field pressure and select the parts you'd like to represent

gmoehl August 29, 2012 02:30

Thank you for your answer.

But no, that's not what I would like to do.

I'd like to make a x-y-Plot. The x-Axis should be the length of the surface and the y-Axis should be the Pressure. It would be enogh to get out the Pressure at Some points along the surface so I can create my own plot in Excel.

sebastianh August 29, 2012 04:58

You can create a Line-Probe under Derived Parts on your surface and plot the results over the line length. You can change the resolution for the line if you want more or less points.

gmoehl August 30, 2012 03:33

I've tried this but I wasn't able to attach the line probe to the surface because it is not a plane area.

abdul099 August 30, 2012 18:53

There's at least a painful way. You can extract a table with pressure values and coordinates for every surface on your airfoil boundary and export it in csv format. Then you can delete all the lines you don't need (cells not on the line you want to evaluate) and put it together in Excel.
But be warned, it could be painful since the table can be pretty big, depending on your mesh resolution.

NickFSI September 5, 2012 13:32

Hi gmoehl,
I don't know if I'm too late to be of help, but the way I do it (if I understand you correctly) is as follows.
Create a section plane as a derived part, and when you apply it to a part in you region, apply it to the surface of the vane that you want the plot from. This then effectively gives you a line along the surface of the vane (as long as you plane section is oriented correctly). This derived part section plane can then be used to make an xy plot, using whichever variable you like.
I hope that's clear!

gmoehl September 9, 2012 03:14

First of all thank you for your help Nick.

But it still won't work.
I create a new plane section, give it the right orientation and choose the vane surface as the input part.
Then I create a new x-Y-Plot and choose the new plane section under "Parts".
Under "Y-Type " I choose the pressure as the scalar function.
But under "X-Type " I can still only choose between "position" and "scalar".
The plot that is created doesn't show anything.
I think the problem is that I havn't chosen the plane section as reference for the x-Axis of my plot.

gmoehl September 9, 2012 03:37

I think I have to change the "X-Type".
So I choose "scalar".
That leads to the wide range of possible Field Functions to choose from.
But no matter which one I choose (e.g. Position), nothing changes.
I've still got the x-y-Plot with an x-Axis that ranges from 0 to 102.
The only thing that changes is the title under the x-Axis.

Could it be a problem that the surface is closed? Due to this the created line has no defined end or start.

It works when I choose centroid x as the Field Function for the x-Axis and take the interface between the air and the vane in the part air as the Part for the plane section.
Until now I chose the surface of the air to the vane as the part for the plane section.

Again, thank you very much for your help Nick

eRzBeNgEl September 11, 2012 14:20

Is your model a periodic model? Than it is possible to create a line over suction and pressure side of the airfoil with Data Blocked Mappers, Isosurfaces and (i hope i remember right) with treshold which gives you a line.

If your model is a full (non periodic) model i do not know a way to create these plots with star-ccm.

NickFSI October 2, 2012 09:10

Hi gmoehl,

I don't know if I'm a bit late to provide any help, but this works perfectly for me, so I'm surprised it won't work for you.
My x-axis is position, which corresponds to the location of the point being plotted. In my case, this is along the x-axis, and my plane runs in the direction of leading to trailing edge. The set-up sounds similar to mine. I have pressure on the Y-axis, which is the chosen scalar function under the Y Types section in the tree. Just below this is the label of the derived part which I want to plot along.
Have you definitely picked the aerofoil part when you created your section plane? Is the orientation of the plane definitely correct?
I haven't tried it on a closed surface, as I'm simulating flow around a ram-air parachute, which has a ram-air inlet. I would've thought that it would just give you one line but it would plot both the suction side and pressure side values, but I don't know for sure.

Let us know how you get on,
Nick

rwryne October 2, 2012 13:45

This is the same way others have mentioned but ill write out each step.

1. Under derived parts, create new section plane and set up your origin and normal. Change your Input parts to JUST the surfaec you want.

2. Make a plot (X-Y)

3. Click your Plot entry (default XY Plot 1) and click the ... button next to parts, select your cutplane

4. Go to XY Plot 1->X Type->Position and define the vector that is parallel to your interest (chord line?)

5. Go to XY Plot 1-> Y Types->Y Type 1-> and select your function (Pressure)

6. Open the plot, it should be populated


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