Plotting the pressure graph.
 

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.

Attachment 85212

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:


where the discretized frequency is an integer .