[FAKHREDDINE]

Dear CFD Community

I would like to obtain the derivative of the speed of sound with respect to density in CFX [ dc/drho ], is there any way to create this expression ?

Thanks in advance for your Help

[ghorrocks]

Is it a single value or a fixed function (and probably therefore a fixed material property) or does it vary over the simulation field?

[FAKHREDDINE]

Thanks for your reply

it is not a single, it is a set of data between the inlet of the domain and the outlet (turbine) so it varies over the simulation field

[ghorrocks]

Can you define a CFD-Post variable of dc/dx * 1/(drho/dx)? You can evaluate the d/dx terms using the CEL gradient functions.

[FAKHREDDINE]

I tried this option but I used the gradient expression :

Speed of Sound.Gradient / Density.Gradient

since I am working on 3D flow simulation

I am not sure if I am right or wrong because I want to get the derivative of the speed of sound with respect to the density not with respect to time dt or distance dx

[ghorrocks]

You will have to define the direction to take the gradient in. You might have to define gradient use variables to access them, but just use the x direction gradients.

I am not sure if I am right or wrong because I want to get the derivative of the speed of sound with respect to the density not with respect to time dt or distance dx

Have a look at the chain rule: https://en.wikipedia.org/wiki/Chain_rule