Investigation of the effect of the shape of grains on flows inside hoppers

Abstract

Non-spherical granular flow is strongly affected by the shape of grains. In this project, a numerical analysis is performed for two non-spherical grains such as rice and lentil by applying a kinematic continuum model as the governing equation in rectangular hoppers with two different opening sizes. The kinematic continuum model is based on the velocity field and shape of grains, where the velocity field is provided by experiment and the shape of the grains is characterized by two geometrical dimensions. Results include the orientation field of grains compared to experimental measurements to investigate the performance of the model. It was observed that the orientation of grains is horizontal at the highest layer of the hopper and it changes to vertical as the grains flow closer to the opening. It was observed that the grains were less aligned in the center in comparison to the grains near the walls. Moreover, the grains orient with the streamline, as they flow down. This orientation with the streamline happens at farther upstream for the smaller opening in comparison to the larger opening. However, rice was orienting with the streamline at farther upstream in comparison to lentils in the smaller opening. This can be rooted in having a more ellipsoidal shape for rice compared to lentils. Furthermore, two parameters in the model which are a function of the shape of grains are determined to have a better agreement in terms of the orientation field of grains compared to the experimental measurements.