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Plotting the pressure graph.

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Old   July 2, 2021, 12:02
Default Plotting the pressure graph.
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Herren Thomas D'Souza
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Greeting CFD'ians

I was running laminar, transient pressure-based CFD simulations on a rocket combustion chamber to capture the pressure oscillations due to Obstacle Vortex Shedding using a segregated PISO algorithm in Fluent.

I am recording the vertex average of the static pressure from a virtual sensor and I am able to capture the resonating frequencies when I do the FFT in the fluent itself with PSD.

However, when I look at my reference research paper, they consider something which I cannot comprehend (maybe I'm not thinking). They consider Prms/Pmean as the y-axis. (I've attached the image of the graph)

I wanted to know, how is Prms calculated and how to obtain the values to plot the graph like the one which I've attached. I don't know if Fluent can capture the Prms.

pressure_graph.png

It'd be a great if anyone help me understand these,

"The study of the frequency response of the pressure oscillation data is based on a spectral analysis conducted by means of the FFT"

The amplitude of the pressure oscillations is usually evaluated by means of:
Prms(f_k) = \frac{Prms(f_k)}{\sqrt2}

where the discretized frequency f_k is an integer f_k=k\Delta{f}.
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