Delfim-Soares explicit time marching method for modelling of ultrasonic wave in microalgae pre-treatment

Ultrasonic wave is one of the most popular pre-treatment methods of lipid extraction in microalgae, due to its low energy supply requirement, eco-friendliness and excellent cell disruption capability. Although quite some number of experimental works were reported, the numerical modelling of the ultrasonic wave in understanding the working principle of ultrasonic irradiation is limited so far, as to the knowledge of authors. The modelling is required for a more robust pre-treatment optimisation. Therefore, in current work, the numerical model of ultrasonic wave and its cavitation has been developed using the Delfim-Soares explicit time marching method (DSETM), which is proposed in recent years to solve structural vibration problem. The two dimensional wave equation in ultrasonic scale has been solved with the frequency of 20 kHz, 40 kHz and 60 Hz. Moreover, Rayleigh-Plesset equation is solved using the same method too to predict the growth of the radius of bubble due to different initial radius. It is found that higher wave frequency will not improve the speed of cavitation, but instead it can decrease the wavelength to increase the possibility of cavitation process occurrance in enhancing the pretreatment efficiency.