The Coefficient of Restitution of Spheroid Particles Impacting on a Wall—Part I: Experiments

Coefficients of restitution (CoR) is used to scale the kinetic energy dissipation, which is a necessary parameter for discrete element modeling simulations of granular flow. Differences from the collision of spherical particles, CoRs of spheroid particle are affected not only by materials, particle size, and impacting velocity, but also by the contact inclination angle of the particle. This article presents our experimental investigation to measure the velocities of translation and rotation using high-speed camera and calculate the CoR in normal direction of prolate spheroid particles impacting flat targets. The results show that this CoR of a prolate spheroid particle is composed of two parts, translation and rotation. The effect from the contact inclination angle is not obvious for a given velocity. When the contact point is close to a pole, the first part plays a major role. On the contrary, the second part dominates the CoR, when the contact point is close to the equator. A dimensionless number, e*, is defined to scale the proportion of velocity due to rotation in the total rebound velocity at the contact point. The relationship between the contact inclination angle, ϕ, and e* for 25 deg < ϕ < 90 deg is given in this article.

The Angle Distribution of the Spheroid Particle upon Optical Surface

The angle distribution of the spheroid particle upon optical surface is discussed in this paper. Taking the advantage of the Bobbert-Vlieger (BV) theorem, the scattering model between optical surface and spheroid particles is established. The scattering process is analyzed and the scattering coefficients are derived by using of the vector spherical harmonic function. The differential scattering cross section (DSCS) of a spheroid particle upon the optical surface is calculated which is compared with the Discrete Sources Method (DSM) proved the validity of the method and the influences of the incident angle and scattering angle on the DSCS are analyzed numerically in details. The results show that the influence of the incident angle on the scattering intensity is less at the smaller scattering angle, which can be concluded that the influence of the incident angle is more serious to the back scattering .The polarization effect and back scattering effect become weaker and weaker with the increase of the incident angle, which provide strong theoretical foundation to the nondestructive detector engineer.

Inversion of spheroid particle size distribution in wider size range and aspect ratio range

The non-spherical particle sizing is very important in the aerosol science, and it can be determined by the light extinction measurement. This paper studies the effect of relationship of the size range and aspect ratio range on the inversion of spheroid particle size distribution by the dependent mode algorithm. The T matrix method and the geometric optics approximation method are used to calculate the extinction efficiency of the spheroids with different size range and aspect ratio range, and the inversion of spheroid particle size distribution in these different ranges is conducted. Numerical simulation indicates that a fairly reasonable representation of the spheroid particle size distribution can be obtained when the size range and aspect ratio range are suitably chosen.