Implementing FFT in Field Function
 

Hello everybody,

I am new to this forum and a doctoral student.
I am currently using Star CCM+ to simulate fluids flowing down a wire. This works very well. :D

I use a field function on the inlet to set the speed of the fluid, which then flows down the wire.
Using another field function, I now generate a forced disturbance (frequency) in the flow (sinus function). Using post-processing (FFT) I also find the frequency of the disturbance at the inlet.

Now to my question: I have seen in different publications that also a white noise was simulated. For this I must add to my above mentioned field function for the velocity an another field function, instead of the forced interference frequency (see picture). For this I must add to my above mentioned field function for the velocity another, instead of the forced interference frequency (see attached Thumbnails). How should I implement the lower equation as a field function :confused::confused: ?

I would be super grateful if someone could help me ;) .

best regards

CFD2DXY

Table/Fieldfunktion Problem
 

Hello everybody,

I have now solved the problem with the help of a matlab code. I was able to generate random values with a function. Now I am confronted with the problem that I want to add a random value to my function for the velocity at the inlet (radial profile) at every time step.

I have written the following field function:
${velocity u} + interpolateTable(@Table("file"), "column1", LINEAR, "column0",${TimeStep})

where column1: timestep from 0 to 8 seconds
and column0: Random value, which should be added to the field function at each time step.

I have started the simulation but still have a constant inlet-speed.
Does anyone have an idea what my error could be?

Greetings

I solved my problem...

${velocity u} + interpolateTable(@Table("file"), "column1", LINEAR, "column0",${Time})

greetz