Drag Coefficients of Irregularly Shaped Particles in Newtonian Fluids

Abstract

An accurate prediction of the settling velocities of drill cuttings is essential in effectively designing, running, and optimizing drilling operations. If there is no reliable process for modelling the drag coefficient, the settling velocity cannot be obtained. In most current literature, particles are assumed to be spherical, which can be easily modelled. However, this assumption may lead to inaccurate results for other irregular particle shapes. This paper studies the transport behavior of irregular particles by modelling these shapes as variants of a bow shape, with a numerical simulation approach for their drag coefficients. The drilling fluid around the particle is water (Newtonian). The drag coefficients of the non-spherical particle (grouped into three sub-shapes) were modelled. In addition, the inlet velocity of the fluid is varied to show the effects on the shape drag coefficients. The results of the simulations were compared to experimental results carried out by other researchers. It was observed that as the particles became less streamlined, their drag coefficient increased. A sensitivity analysis was carried out to investigate the effects of fluid properties on the drag coefficient. The results were consistent and logical. The results showed that Computational Fluid Dynamics analysis provided a reliable estimation of the drag coefficient, which can help optimize the transport of drill cuttings during drilling operations.