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-   -   Pressure/Density Gradient (http://www.cfd-online.com/Forums/fluent/124503-pressure-density-gradient.html)

hicabiye October 6, 2013 22:44

Pressure/Density Gradient
 
Is there a way to plot either pressure or density gradients in Fluent (Fluid)? Or obtain values for for pressure and density derivatives in respect to x, y and z directions, such as dp-dx, dp-dy and dp-dz?

gfoam October 8, 2013 11:36

yes, go to Plots under Results, then under Y Axis Function choose derivatives and the tipe of Derivative you want. Also yo have to select the lines over wich you want to calculate the gradients. Hope this helps you. Regards. Gonzalo

hicabiye October 9, 2013 10:43

Dear gfoam,

I do not see the "derivative" options under the "Y Axis Function." Do you think that I might be missing particular inputs?

gfoam October 9, 2013 13:42

1 Attachment(s)
I don't know why you can't see that, but here you can see an image of it:
Attachment 25938

hicabiye October 13, 2013 20:13

Dear gfoam,

Derivatives is still missing from that section. I do not see it as one of my options. Do you think that I might be missing something in the setup stage?

Since it is not working, is it valid to say that density in respect to the x direction is drho-dx since it is discretized?

gfoam October 15, 2013 06:47

Hi, I'm confused. If you solved your problem (I mean, if you press Calculate and let the software run) you must see the Results/Plots task page. There you can find the derivatives of velocity and pressure, but there isn't a derivative of density. To plot the derivatives of density you can use CFDPost, but I don't how you can do this in that software. Another option you can use is, export the density along the line you want to, and numerically find the derivatives in a spreadsheet. i hope this helps you. Regards. Gonzalo

hicabiye December 5, 2013 22:17

1 Attachment(s)
Dear gfoam,

I went ahead and exported the pressure and density data to discretize them as dp/dx and drho/dx; however, I have no idea why derivatives do not show up (see figure). Do you happen to know why?


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