Numerical comparative study on the performance of open photoacoustic cells

Abstract

An open photoacoustic cell has the merit of not having to frequently disassemble and reassemble to fill up with the gas, compared to the closed counterpart, whereas it has the demerit of causing acoustic radiation losses through the openings. In this paper, we have performed numerical simulations on three different types of open photoacoustic cells, H-type and T-type resonant cells and Helmholtz cell, made by attaching a couple of pipe-shaped extensions to both openings with the intent to lessen the acoustic losses and simultaneously understand the geometrical effect of the opening extensions on their performance. For the numerical study, the perturbed forms of the continuity equation, Navier-Stokes equation, energy equation, and equation of state are solved for the quality factor, acoustic pressure and resonance frequency to evaluate the performance. To predict the acoustic losses through the openings, the computational domain for the measurement of acoustic pressure is extended out of the cells. Results show that the geometrical effect of the opening extensions on the performance varies greatly with the type of open cell. In particular, the H-type open cell is the most desirable choice among the three types because of its high acoustic pressure response and enhanced quality factor. We believe that the results of this study would help us select the right type of open cell required for various practical applications.