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What does the "pressure" value mean in the acoustics(frequency domain)?
Posted Dec 29, 2021, 6:47 a.m. EST Acoustics & Vibrations 1 Reply
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Dear Sirs/Madams,
I am a beginner to comsol(acoustics). I have some enquires regarding the acoustic. I am simulating rectangular open end tube, with pressure input(8699Pa) from one end. Matlab is used for data process.
References: 1. The pressure vs distance(z-axis) figure 2. Opentube pressure txt file
Specifications: 1. Rectangular tube length: [2m] 2. Rectangular cross section: [0.008m x 0.02m]
Conditions: 1. [1D Plane wave radiation] 2. [Frequency domain] 3. [Pressure in: 8699Pa in amplitude] 4. [Frequency: 2000Hz] 5. [Speed of sound = 340m/s] 6. [Wavenumber = 36.95 m^-1]
Using general pressure equation, p(x,t)= A exp(jwt-jkx) In freqeuncy domain, temporal term is gone, ony spatial term remains (exp(-jkx)).
From the references(1.) , the pressure(RED) is in a cyclic pattern, my question is what does it represent, mathematically and in physical sense? The pressure keeps fluctuating across the z-axis which I dont understand.
Your input is very much appreciated. Thank you
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In a frequency-dependent calculation, all quantities are phasors.
Physical quantities (pressure, velocity, etc.) cannot be imaginary. To convert phasors to time-dependent quanities, write
v(t)=real(V*e^jwt)
where V is the complex phasor.
Important note: when Comsol is asked to plot a complex quantity, the default is for it to plot the real part of that complex quantity.