Slurry pipe transport has directed the efforts of researchers for decades, not only for the practical impact of this problem, but also for the challenges in understanding and modelling the complex phenomena involved. The increase in computer power and the diffusion of multipurpose codes based on Computational Fluid Dynamics (CFD) have opened up the opportunity to gather information on slurry pipe flows at the local level, in contrast with the traditional approaches of simplified theoretical modelling which are mainly based on a macroscopic description of the flow. This review paper discusses the potential of CFD for simulating slurry pipe flows. A comprehensive description of the modelling methods will be presented, followed by an overview of significant publications on the topic. However, the main focus will be the assessment of the potential and the challenges of the CFD approach, underlying the essential interplay between CFD simulations and experiments, discussing the main sources of uncertainty of CFD models, and evaluating existing models based on their interpretative or predictive capacity. This work aims at providing a solid ground for students, academics, and professional engineers dealing with slurry pipe transport, but it will also provide a methodological approach that goes beyond the specific application.

In industrial environments, having instrumentation able to attain fast, accurate, and autonomous measurements is pivotal to understanding the dynamics of liquid and particles during transport. Ideally, these instruments, consisting of either probes or sensors, should be robust, fast, and unintrusive, i.e., not cause interference on the very flows being monitored, and require minimal maintenance. Beyond monitoring, the process knowledge gained through real time inspection allows teams to make informed technical decisions based on particle behavior, i.e., settling of particles causing pipe wear and clustering or blockages that can damage the unit or cause shutdowns, both of which with economical drawbacks. The purpose of this review is to examine experimental measurement techniques used to characterize physical properties and operational parameters of solid-liquid slurry flows, focusing on non-ionizing radiation methods. With this text the intent is not to provide an exhaustive examination of each individual technique but rather an overview on the most pertinent types of instrumentation, which will be presented, in addition to application examples from the literature, while directing the reader for pertinent seminal and review papers for a more in-depth analysis.

The hydraulic conveying of solid-liquid concentrated suspensions in pipelines corresponds to complex flows where particles with different sizes, concentrations and flow velocities exhibit different flow regimens. Predicting their behavior is fundamental for the adequate design of pumping equipment and flow rigs. In traditional numerical approaches the turbulence production is assumed to be directly dependent on the increase of the particle size; this contradicts data from the literature where small particles cause an augmentation of turbulence and medium size particles attenuate turbulence. Also, in the traditional approach the same drag correlation is assumed to account for particle-fluid interaction in different flow regimes, which, in the case of turbulence augmentation and attenuation can differ considerably. In the present work numerical studies were conducted to simulate highly concentrated flows of settling medium sized particles using a Mixture Model, incorporating a Low Reynolds turbulence closure and a Schiller-Naumann drag correlation to depict the flow of concentrated solid-liquid suspensions. Since not all particle distributions were accurately portrayed, different drag correlations were implemented to provide a more adequate representation of the relative velocity between phases and particle distributions. Amongst the drag correlations implemented the Schiller & Naumann showed the best agreement for the highest particle concentrations at intermediate velocities, whilst the Haider & Levenspiel displayed the best fit with the experimental data for the highest flow velocities and particle concentrations. The Gidaspow-Schiller-Naumann drag correlation was more adequate for low flow velocities and with intermediate particle concentrations. With this work it is shown that using the same drag correlation for the numerical description of experimental data for highly concentrated settling solid-liquid flows does not adequately reproduce the different flow regimes