Eulerian multi-phase CFD model for predicting the performance of a centrifugal dredge pump

Abstract

Dredge pumps are a complex engineering topic in comparison to water pumps. Mixtures of seawater with several types of soils do not behave as a homogenous fluid, and numerical simulations of these machines can be very challenging. Typical numerical approaches to simulations of dredge pumps are single-phase equivalent slurry and multi-phase liquid-solid, where the specification of the particle flow field can be Eulerian or Lagrangian. The single-phase slurry approach is not sufficient to describe the effects of particle size and concentration of the solid phase on pump performance; for this reason, this paper examines a multi-phase CFD model applied to a dredge pump. The solid phase is modelled with an Eulerian approach, in order to reduce the computational effort required by a Lagrangian method, mainly used for low solid-phase concentrations. The primary purpose of the presented model, developed using commercial software ANSYS CFX, is to predict head losses in a dredge pump working with several particle sizes, from 0.1 to 5 mm, and different volume concentrations of the solid phase, from 20% to 30%. For numerical solid-phase calibration, the effect of the particle size on pump performance is associated with non-Newtonian rheology of the simulated Eulerian phase. The numerical model is validated via experimental tests on the dredge pump using seawater. The calibration of the particle size effect is obtained from scientific literature data about dredge pump losses in different conditions. The model presented could be a useful tool for the analysis of existing dredge pumps or for the design of new machines.