Numerical simulation of slurry flows in heterogeneous and saltation regimes in horizontal pipelines

In this work, the simulation of a two-phase liquid-particles flow is performed using an Eulerian- Eulerian model to predict the complex flow behavior where both particle concentration and particle velocity profile are shown and compared with experimental data. One of the main concerns during implementation of pipeline transportation of multiphase mixtures the is assurance of the flow, where the formation of particle fixed beds should be strongly avoided due to its disadvantageous and damaging effects on the flow, which mostly occur at the bottom sides of the pipeline walls

Numerical simulation of slurry flows in heterogeneous and saltation regimes in horizontal pipelines

In this work, the simulation of a two-phase liquid-particles flow is performed using an Eulerian- Eulerian model to predict the complex flow behavior where both particle concentration and particle velocity profile are shown and compared with experimental data. One of the main concerns during implementation of pipeline transportation of multiphase mixtures the is assurance of the flow, where the formation of particle fixed beds should be strongly avoided due to its disadvantageous and damaging effects on the flow, which mostly occur at the bottom sides of the pipeline walls

CFD software applications for transcritical free surface flow

Flows in rivers, floodplains and coastal zones are very complex due to uneven bottom topography and irregular boundaries of the flow domain. In particular, when the flow shows strong gradients in water depth and velocity it is very difficult to predict, with accuracy, flow characteristics such as water profiles in all points of the domain. Traditional approaches solve shallow-water flow equations, known as Saint-Venant equations, when one or two dimension solutions can be adequate for obtaining most of the important flow characteristics. However, complex situations can require solving Navier-Stokes equations. In these cases, a two-phase flow problem must be solved and, as water profiles are not known in advance, only a numerical approach can be used to obtain approximate solutions. In addition, flow can be subcritical, supercritical or in a mixed-flow regime. These flow characteristics and complex geometries can make the use of in-house developed software difficult. The arrival of high performance computers and commercial software packages offers new possibilities in the field of numerical hydraulics. However, commercial software packages should be tested on some specific cases; so that these can be used with confidence. In this paper we solve, several cases of free surface flow that consider subcritical, supercritical, critical, oscillatory depth profiles and hydraulic jumps using a commercial package, CFX™. Most of these cases were proposed as benchmark solutions by MacDonald et al. (1997) for non-prismatic cross section, non-uniform bed slope and transition between subcritical and supercritical flow. Hydraulic jump cases consist of experimental data of hydraulics jumps obtained by Gharangik & Chaudhry (1991) for incident flow with Froude numbers of 2.3 and 4.23. In all simulated cases flow was described using a homogeneous model for each phase of the flow. Turbulence was modeled by using the well-known k-ε model. In addition, sensitivity to turbulence level in the entrance of flow domain was done to assure independence of results with this variable. Experimental facilities were properly represented in order to assure exact correspondence between boundary conditions of the model and the actual facility. Results obtained with CFX™ show excellent agreement with analytical solutions, for subcritical, supercritical, transitional and hydraulic jump cases. Special care with grid selection and entrance boundary condition is crucial to simulate with accuracy these types of flows. In particular, when a proper structured mesh is used, quality results are highly improved. Finally, results show to be insensitive to entrance turbulence condition

Numerical modelling of compound channel flow

Most natural rivers have compound cross-section. Compound channel flow is characterized by complicated three-dimensional flow structures. These structures are called secondary flows and have been classified into two categories by Prandtl (1952). He distinguished the secondary flows of the first kind and of the second kind. The secondary flows of the the second type are typically about 2-3% of the maximum streamwise velocity (Nezu and Rodi, 1985), however, they have a major impact on the mean flow and turbulence structures