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-   -   Locating the location for a specific value (https://www.cfd-online.com/Forums/cfx/222542-locating-location-specific-value.html)

Xamilia November 28, 2019 06:45

Locating the location for a specific value
 
Hello,

I am simulating a shock tube in fluent and want to postprocess it in CFD Post. To locate the shock in the current time step I want to use the pressure.gradient X. To plot the position against x and t I need to now where the value is max. But I don't find a way to get this information. So can someone help me how to find the x-location of the shock?

Thank you

ghorrocks November 28, 2019 06:48

I can't see a way to do this in CFD-Post. You could try a full featured post processing software like tecplot, fieldview or ensight.

Alternately, when I was doing shock tube work I often used the pressure half way between the before and after shock pressure. You can then put a contour line on it and extract the location of the contour line for a chart.

Xamilia November 28, 2019 07:18

Thank you for your quick answer!

Oh okay.

I just found a way to extract the position with a Point and the Method 'Variable Minimum', in the Chart I selected the Location of this Point. Problem is that the pressure.gradient isn't the greatest at the shock in the beginning, it is in the area of expansion waves. Only after a while it does work for the shock.

Your idea seems to work better for this case, but I am not sure if I understood your way exactly. How do insert the contour line with the specific pressure value? It would be very kind if you could explain it in a little more detailed way, thank you very much!

And if I find another way, I'll let you know if you're interested.

Thanks!

ghorrocks November 28, 2019 17:24

Insert a contour object, and change the levels to be a pressure level you define. Then you can get the XYZ location of the contour line using functions like max, min, ave etc of the contour object.


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