Numerical simulation of the interaction forces between turbine meter and particles in a standpipe

A numerical study of the dynamic behaviour of a turbine meter measuring solid flowrate was carried out by use of the discrete element method. The simulation was conducted with a cylindrical standpipe of 30d in diameter and 40d high, filled with 30000 mono-sized spheres of diameter d, and with a turbine fixed at the centre of the standpipe at a height of 20d. The variations of the torque and rotational speed of the turbine and the porosity of particles around the turbine with time were first investigated. It was observed that these variables fluctuate significantly at the initial stage and gradually reach a macroscopically steady stage. The dependence of the resultant rotational speed on solid flowrate was then measured and shown to be qualitatively comparable to the experimental observation. The force structure of particles around the turbine and the statistical distributions of the forces and torques acting on the turbine originated from its interaction with neighbouring particles were finally analysed. The results indicate that the torque originated from the particle-blade interactions on the blade top surface acts as a driving torque to make the turbine rotate, while the torques due to the particle-blade interactions on the blade bottom and side surfaces balance this driving torque, leading to a macroscopically constant rotational speed.KeywordsDiscrete element simulation, granular dynamics, flow measurement, turbine meter