Ultrasonic attenuation model of mixed particle three-phase system based on Monte Carlo method

From the perspective of calculating ultrasonic absorption and scattering properties of individual solidparticle and droplet, the ultrasonic wave is treated as discrete phonons. And by tracking their motion processand event statistics, a new prediction model of ultrasonic attenuation of spherical mixed particles in gaseousmedium is established with Monte Carlo method. Considering the difference in physical properties between solidparticles and liquid particles, the ultrasonic absorption characteristics of the two kinds of particles are obviouslydifferent, and when dimensionless particle size kR <= 1, the backscattering of particles is uniform and dominant,then the ultrasonic scattering pressures gradually transit from the dominant position of backscattering to thetrend of forward enhancement with the increase of dimensionless particle size. The numerical simulation resultsfor the system with a single particle type are compared with those from various standard models such asclassical ECAH model and McC model, showing that they are in good agreement. Similarly, the results are thencompared with experimental results, which accord with each other in general. After calculating and verifyingthe ultrasonic attenuation of aluminum particles and submicron droplets respectively in air, the method isextended to the three-phase monodisperse and polydisperse mixed particle system composed of aluminumparticles and liquid droplets. In the three-phase system of gas-liquid-solid mixed particles, the particle type hasa significant influence on ultrasonic attenuation, and the attenuation contribution of different particles againstmixing ratio does not follow the linear gradient with the increase of volume concentration. For a polydispersesystem, the ultrasonic attenuation spectrum is greatly affected by the average particle size, but it is insensitiveto the width of particle size distribution. The numerical results also show that both the particle type andparticle distribution size should be carefully take into account in the polydisperse system. Moreover, the MCMmodel can be further extended to non-spherical particles and combined with mathematical inversion to form thetheoretical basis for the measurement of mixed particle system.