UNSTEADY FLOW CHARACTERISTICS OF PARTICLE SYSTEM CONSIDERING SLENDERNESS RATIO

Under high-speed flow,sand,and other typical particle systems exhibit significant unpredictability in their shear velocity distribution and velocity fluctuation characteristics. However,it is currently unclear how the mesoscopic properties of granular systems affect their macro flow parameters,and there has been no thorough investigation into the stochastic characteristic parameters of particle flow. In this study,the discrete element ring shear element experiment is employed to capture both the macro and micro properties of the high-speed shear flow of particle systems with various forms. The findings demonstrate that:(1)Particle shape has a significant effect on the macroscopic shear stress of the system. The shear residual stress is larger in the particle system with a complex particle shape. (2)The spatial distribution of velocity fluctuation of the particle system is affected by both shear velocity and boundary effect. The greater the shear rate,the greater the velocity fluctuation. The boundary has a certain constraint effect on particle velocity fluctuation. (3)Particle shape has a significant effect on the velocity fluctuation of the system. For particles with more complex shapes,the system microscopic velocity fluctuation is small. (4)The shape characteristics have a significant influence on the meso-contact characteristics of the particle system. The longer the particle is,the larger the average coordination number is,and the smaller the probability of large intergranular contact force is.