Optimization and analysis of the acoustic and resistance performance of the plenum chamber via sample entropy and large eddy simulation

Abstract

The noise of the plenum chamber plays an important role in the acoustic performance evaluation of ventilation and air condition (VAC) systems. The large eddy simulation (LES) model and Ffowcs Williams & Hawkings (FW–H) equation were used to obtain the transient flow and aerodynamic noise, respectively, and a continuous and uniform impedance boundary condition was introduced to calculate the transmission loss (TL) of the perforated board plenum chamber. The aerodynamic noise, TL, resistance and velocity uniformity distribution characteristics of the plenum chamber were predicted by numerical simulation. A full-scale test bed was built to verify the flow field prediction results, and the acoustic prediction results were verified by analog experiments. In addition, based on the sample entropy theory, the pressure fluctuation on the inner surface of the plenum chamber was evaluated. The results show that the perforated board changes the vortex structure in the plenum chamber and reduces the local resistance and the pressure fluctuation on the inner surface wall, and the local resistance coefficient can be reduced by up to 34%. However, the coefficient of velocity uniformity in the plenum chamber decreases by 4%. Furthermore, the perforated board can significantly reduce the TL and peak sound pressure level (SPL) of the plenum chamber. At the receiving point, the overall SPL can be reduced by up to 2.5 dB.