Application of dynamic mode decomposition to acoustic-modes identification and damping in a 3-dimensional chamber with baffled injectors

The dynamic mode decomposition (DMD) is applied to a 3-dimensional chamber in order to identify acoustic resonant modes and quantify their damping. The DMD is one of post-processing methods, which can be applicable with acoustic field information in a full or a partial domain from numerical and experimental data. For application of the DMD method, the 3-dimensional chamber with baffled injectors is selected, in which gaps in baffled injectors enhanced acoustic damping and it has been shown that there exists an optimum gap for maximum damping in the previous works. Damping coefficients are evaluated in order to investigate whether the DMD method is able to predict the influence of gaps in baffled injectors on the damping of the first tangential (1T) mode or not. In addition to the 1T mode, the first longitudinal (1L) mode, the 1T1L mode, and higher modes are extracted and damping coefficients for them are estimated using the DMD method on 2-dimensional planes and they reveal that the baffle gap affects significantly only specific modes and show a good agreement with the damping factors from the previous work in predicting the optimum gap for maximum acoustic damping.