Influence of vibration on granular flowability and its mechanism of aided flow

Abstract

Regarding flowing granular media as weak transverse isotropic media, the phase velocity expressions of wave P, wave SH and wave SV were deduced, the propagation characteristics of waves in flowing granular media were analyzed. The experiments show that vibration has great influence on granular fluidity. The wavefront of wave P is elliptic or closely elliptic, the wavefront of wave SH is elliptic, and the wavefront of wave SV is not elliptic. Wave propagation in the granular flowing field attenuates layer after layer. The theory and experiment both substantiate that the density difference is the key factor which leads to the attenuation of vibrating energy. In terms of characteristics of wave propagation one can deduce that vibrating waves have less influence on flowability of granules when the amplitude and frequency are small. However, when the amplitude and frequency increase gradually, the eccentricity of ellipsoid, the viscosity resistance and inner friction among granules, and shear intensity of granules decrease, and the loosening coefficient of granules increases, which shows the granules have better flowability.

Keywords

granular media / vibrating aided flow / body wave / mechanism

References

[1] WuAi-xiangStudy on the character of granular ores and the theory of dynamics in vibrating field (in Chinese) [D], 1991, Changsha, Central South University of Technology

[2] WuAi-xiang, GuDe-sheng. Study on propagation of vibration wave and energy dissipation in broken ores[J]. J Cent South Inst Min Metall, 1992, 23(3): 267-272(in Chinese)

[3] DaiXing-guoStudy on the theory of ore pressure and flowing mechanism in store field of ore (in Chinese)[D], 1990, Changsha, Central South University of Technology

[4] DaiXing-guo, WuXian-zhen. Probing into mechanism of granular loose and impaction by vibration[J]. Mining and Metallurgical Engineering, 2000, 20(1): 12-14(in Chinese)

[5] WangChang-hanTheory of ore-drawing (in Chinese)[M], 1988, Beijing, Metallurgical Industry Press

[6] WuShi-mingWave propagation in soils (in Chinese)[M], 1997, Beijing, Science Press

[7] LervinF K. Seismic velocities in transversely isotropic media [J]. Geophysics, 1979, 44(5): 818-936

[8] LervinF K. Seismic velocities in transversely media[J]. Geophysics, 1980, 45(1): 3-17

[9] ByunandB S, ChengS W. Apparent axial properties of transversely isotropic media[J]. Geophysics, 1986, 51(4): 1012-1013

[10] RommelB E. Approximate stacking velocities in a weakly transversely isotropic layer[J]. Can J Expl Geophys, 1993, 29(1): 98-108

[11] ThomsenL. Weak elastic anisotropy[J]. Geophysics, 1986, 51(10): 1954-1966

[12] RommelB E. Approximate polarization of plane waves in a medium having weak transverse isotropy[J]. Geophysics, 1994, 59(10): 1605-1612