混合弹性颗粒体系声衰减数值模拟

采用概率统计方法——蒙特卡罗方法,建立一种预测液固两相体系中混合弹性球形颗粒声衰减的理论模型。在单颗粒声散射和吸收的基础上,将连续超声波抽象离散化为大量独立的声子,追踪声散射过程,通过统计接收器探测声子数最终确定声衰减系数。采用数值方法对单一球形颗粒的液固两相体系中声衰减进行预测和比较,确定了该方法的可行性后将该方法推广到混合颗粒体系中,对玻璃微珠/铁粉构成的混合颗粒及多分散混合颗粒体系进行数值研究。结果表明:在体积浓度低于10%时,蒙特卡罗法预测得玻璃微珠或铁粉颗粒声衰减和ECAH,Lloyd和Berry,Waterman等建立的模型结果吻合。对于混合颗粒构成的两相体系,算例中,随着体积浓度增大到10%,声衰减系数随混合颗粒数目比的变化呈现出了非线性的变化,同时颗粒物性也会影响不同组分颗粒对声衰减的贡献,算例中铁粉颗粒比玻璃微珠对声衰减的影响更大。

Simulation of ultrasonic attenuation in the elastic mixing particle system

For the study of establishing a theoretical model which aims at predicting ultrasonic attenuation of elastic, spherical mixing particles in the liquid-solid two-phase system, the Monte Carlo Method (MCM) is introduced, serving as a probability and statistics technique. On the basis of ultrasonic scattering and aborption, the continuous ultrasonic waves are represented as discrete and independent phonons. By tracing the movement and scattering events as well as calculating the number of phonons which finally reach the receiving transducer, the ultrasonic attenuatioil coefficient is finally obtained. Numerical investigations have been carried out to predict and compare the ultrasonic attenuation for a solid-liquid two-phase system with a single type particle. Apply such method into mixing particle system after ensuring its feasibility. Then, the mixing iron and glass bead particles with various ratios are set as examples for the purpose of predicting ultrasonic attenuation for the monodisperse and polydisperse mixing particle systems. Tile results of MCM, the ECAH model, the Lloyd&Berry model and the Waterman model match well when the particle volume concentration is lower than 10%, corresponding to iron and glass bead respectively. In the case of two-phase system with mixing particles, it is shown that as the particle volume concentration increases to 10%, the variation of the ultrasonic attenuation coefficient with mixing ratio yields a nonlinear tendency. The nature of particles can also influence ultrasonic attenuation significantly.