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[javat33489]

Hello colleagues.

I am researching pressure pulsation in Fluent.

DES turbulence model.

I need to identify the amplitudes of pressure fluctuations, so that I can then decompose these data using the Fourier method and use them in harmonic analysis.

By choosing different substep time sizes, I have different oscillation amplitudes.

In this regard, I have several questions.

1. Can I track the pressure amplitudes at the outlet of the product using the AreaAve(TotalPressure) graph? Or maybe look at the AbsolutePressure graphs or the StaticPressure on the outlet?
2. I have selected a measurement point, but the graph does not work:
3. I did some research with different time substeps, how do I choose the right one to take amplitudes from there for further solution? Here are the screenshots:Number steps 2000, time step 5e-5

 

see the rest in the next post>>>

[javat33489]

Number steps 2000, time step 0.005

 

 

Number steps 2000, time step 0.1

[javat33489]

Number steps 2000, time step 0.5

 

Number steps 2000, time step 1

 

Number steps 200, time step 0.2

[Federico]

Hi, 

I would recommend using Static pressure to track pressure oscillations. Depending on your application and what you are looking for, you can do this at the outlet (using a area-arveraged value) or by defining point receivers in your domain. I suspect your point-graph does not work because you specified area-average for a point (which has no dimensions).

Regarding your time step, it depends on your frequencies of interest for your Fourier analysis. All frequencies of interest must be spatially and temporally resolved from the source to the receiver location. The source zone will require sufficient mesh and temporal resolution to capture scale-resolving turbulent flow, while the region of propagation (transmission zone) needs to be resolved with at least 15-20 grid points per wavelength for the highest frequency of interest. Under-resolved waves will numerically dissipate through the transmission zone. Then, depending on your smallest grid size dx and the speed of sound c0 of your fluid, you should select a time step dt to achieve CFL of approximately 1 (CFL=c0*dt/dx).

[javat33489]

Thanks!