hi folks, i want to create a user defined function to give density gradients so that i can compare simulation results with schlieren images. i know this is possible using a fortran udf but will be grateful if someone with experience out there could give me useful tips on how to do this. thanks in advance ben

The solver does not provide density gradients AFAIK i.e. density.Gradient is not supported by USER_GERVAR. You also can't create arbitrary variable gradients within CFX Post AFAIK.

So you will probably have to export the density data from Post to a flat file (x,y,z,density) and post-process it yourself e.g. with matlab.

When I created a particle fortran routine it was not possible to pass temperature.gradient from cfx-pre to the routine but I got the hint from ANSYS-Support to specify temperature.gradient in the ccl. Now it is working when you ignore the error messages from cfx-pre. Maybe you can specify the density.gradient in the ccl to pass it to your routine? Let us know if this works

No need for user fortran.

For compressible flows the solver writes density gradients to the results file.

With some creativity you can recreate "Schlieren" like plots in CFX Post. Start with the inverse logarithmic grayscale colormap. You may need to post process it.