Solid-liquid Flow Research Articles

Numerical Simulation of the Mixing and Hydrodynamics of Asphalt and Rubber in a Stirred Tank

Computational fluid dynamics (CFD) has been used to analyze the mixing process of Asphalt and Rubber (AR) in a stirred tank with a six flat-blade disc turbine (Rushton), a down-pumping 45° pitched-blade turbine (PBTD-6) and a down-pumping propeller (TXL). The two-phase (solid-liquid) flow in the considered stirred tank has been modelled in the framework of an Eulerian-Eulerian approach, a laminar-flow assumption and a multi-reference frame strategy. The following effects have been investigated: The influence of the impeller speed, impeller type, crumb rubber (CR) particle diameter and initial CR particle loading on the quality of the CR particle’s suspension. The outcomes of the numerical simulations have been found to be in good agreement with the experimental results. The most important findings can be summarized as follows. The flow velocity on the lower part of the stirred tank, induced by the Rushton impeller, is the highest for the three considered mixing systems at the same impeller speed. The suspension quality of CR particles increases with the impeller speed. A larger particle diameter and a higher initial CR particle loading lead to an uneven distribution of particles. The degree of homogeneity in the Rushton impeller system is better than that of the PBTD-6 impeller system and the TXL impeller system at the same impeller speed, while the suspension uniformity of the TXL impeller system is the best possible one for the same power consumption.

Dynamic Response Analysis of Retaining Dam under the Impact of Solid-Liquid Two-Phase Debris Flow Based on the Coupled SPH-DEM-FEM Method

Based on the coupled SPH-DEM-FEM numerical method, this paper analyzes the dynamic interaction of solid debris flow particle-liquid debris flow slurry-retaining dam in order to explore the dynamic response of retaining dam under the impact of the solid-liquid two-phase debris flow and delves into the process of the debris flow impact on the dam, the impact force of debris flow, and the elastic-plastic time-history characteristics of the dam under different slopes of trapezoidal grooves. The calculation results show that the coupled SPH-DEM-FEM method can vividly simulate the impact behavior of the solid-liquid two-phase debris flow on the dam, reproduce the impact, climbing, and siltation in the process of the debris flow impact; the dynamic time-history curve of the retaining dam is consistent with the law of the literature, and the result of the debris flow impact force obtained is close to that of the empirical formula. Moreover, this paper studies the impact force distribution of the debris flow impact process. The results have a certain reference value for the study of the dynamic response of the retaining dam under the impact of the solid-liquid two-phase debris flow and the engineering design of the debris flow-retaining dam.

CFD SIMULATION OF EROSION BY PARTICLE COLLISION IN U-BEND AND HELICAL TYPE PIPES

Erosion caused by solid particles in curve pipes is one of the major concerns in the oil and gas industries. Small solid particles flow with a carrier liquid fluid and impact the inner wall of the piping, valves, and other equipment. These components face a high risk of solid particle erosion due to the constant collision, which may result in equipment malfunctioning and even failure. In this study, the two-way coupled Eulerian-Lagrangian method with the Oka erosion and Grant and Tabakoff particle-wall rebound models approach is employed to simulate the liquid-solid flow in U-bend and helical pipes using computational fluid dynamics. The effects of operating parameters (inlet fluid velocity and temperature, particle density and diameter, and mass flow rate) and design parameters (mean curvature radius/pipe diameter ratio) are investigated on the erosion of these tubes walls. It is obtained that increasing the fluid velocity and temperature, particle mass flow and particle density increase the penetration rate, particle diameter affects the rate of penetration, and increasing mean curvature radius/pipe diameter ratio decreases the rate of penetration.

Numerical investigations of phase change material (PCM) based thermal control module (TCM) under the influence of low gravity environment

The present work aims to address the effect of gravity on the melting and solidification of phase change materials (PCM) in an optimized thermal control module (TCM) having pin fins as heat transfer enhancers. The enthalpy-porosity technique is used to model the solid-liquid phase change process and flow evaluation inside TCM. The melting and solidification processes are simulated for three-phase change materials (hexadecane, acetic acid, and glycerol) at different values of gravitational accelerations (i.e., melting at g, g/2, g/10, g/20, g/40, g/80 and solidification at g, g/80). The governing equations are non-dimensionalized, and results are reported in the form of dimensionless numbers. It is evident from the study that the gravity environment significantly influences the melting and solidification of PCM. The research shows that the value of PCM average liquid fraction gradually decreases by 18% as the value of gravitational acceleration reduces from g to g/80. The effect of the natural convection is noticeable on the melting of hexadecane and acetic acid. However, the minimal effect of natural convection was observed on the melting of glycerol due to highly viscous nature and faster heat propagation through the material. The effect of gravity on the solidification is small compared to the melting because the conduction heat transfer primarily dominates the solidification process. The present study provides information on the effect of gravity on performance parameters of the PCMs, which helps determine the size of the heat sinks operating under terrestrial and space environments.

Experimental and CFD simulation of slurry flow in the annular flow path using two-fluid model

The current study is allocated to experimental evaluation of the multiphase flow of fine solid particles (FSPs) as well as comprehensive numerical study in an annular space under static, laminar, and turbulent flow conditions with consideration of the inner pipe eccentricity and rotation. The experimental investigation was carried out using an annular pipe flow loop. The numerical modeling and simulation of the multiphase flow in the annular space have been performed using the Euler-Euler approach. The unsteady-state multiphase model based on the kinetic theory of granular flow (KTGF) is developed to investigate the particulate flow characteristics in the annular space. Moreover, Standard and Realizable k-ε turbulence models used to predict turbulence in this study. The Realizable Per-Phase turbulence model with new corrected coefficients (C2=4.2,C3=1.3,CT=0.0131,σk=1,σε=1.2) is calibrated to predict the pressure drop along the annular pipe for solid-liquid multiphase flow. Comparison between numerical and experimental analyses showed that under both flowing and static conditions, the simulation results are in good agreement with experimental data. Based on the error estimation model, the CFD model's accuracy for pressure drop and FSPs concentration prediction is 99% and 95%, respectively. The trends of the variation in particle concentration along the annular pipe were investigated for different flow velocities (0.05–2.5 m/s) and different inner pipe rotations of 500, 1000, and 1500 rpm. The results also showed that the higher particle settling occurred at the critical inclination angles of 45–60°.

Computational study of solid-liquid supercritical flow of 4th-grade fluid through magnetized surface

This paper offers a comparative investigation of the multiphase flow of Newtonian and non-Newtonian dispersions passing through an inclined channel. Couette and Generalized Couette flow models are taken into account. A fourth-grade fluid is taken as non-Newtonian fluid, as well as base fluid. The stress tensor of fourth-grade fluid is used to formulate the problem. The relative motion between fluid and the upper plate is considered, while the relative motion between fluid and lower plate is mistreated. Crystal and Hafnium nano-sized particles are utilized to prepare dispersions. An external magnetic field is applied to the multiphase flows of dispersions in the channel and at the same time, the impact of gravitational force is also examined which has great mastery on flows. The governing equations for two-phase flows problem are determined by using Naiver-Stokes equations of continuity and momentum. Partial differential equations are reduced into ordinary differential equations by using appropriate transformations. The perturbation method is used to find out analytical solutions to these ordinary differential equations. Exact and approximation solutions are obtained by using MATHEMATICA Software. The impacts of salient parameters on each type of flow for velocity profile are discussed graphically. Furthermore, the comparison of velocity profiles of multiphase flows of dispersions is also presented in tabular forms. The variation in the magnitude of the fourth-grade non-Newtonian dimensionless parameter has great importance in non-Newtonian dispersions. The outcomes dispose of that the two-phase flows of Newtonian fluids suspended with crystal and hafnium particles are better one than the bi-phase flows of fourth-grade dispersions. Moreover, the Newtonian fluids suspended with hafnium particles are more consequential than the Newtonian fluids suspended with crystal particles. Similarly, the same behavior is observed in fourth-grade non-Newtonian dispersions. Then it is concluded that hafnium particles are a better option than crystal particles. These amalgams are very useful in every field of life, especially medicine as nanofluid drug delivery. In addition to this, no comparative analysis between Newtonian and fourth-grade non-Newtonian bi-phase flows has so far been reported in the existing literature.

Direct numerical simulation of turbulent liquid–solid flow in a small-scale stirred tank

Particle-resolved direct numerical simulation of a 4-baffled cylindrical stirred tank with a 6-pitched blade-turbine-downflow (PBTD) impeller was carried out for the first time to understand the hydrodynamic characteristics of its turbulent solid–liquid flow. The fluid-particle and fluid-wall interactions are numerically described by the immersed boundary method (IBM) with smeared and sharp interfaces jointly on a staggered Cartesian grid. The particle diameter is 1 mm, and the impeller rotation speed changes between 23.88 and 15.88 rev/s, resulting in the impeller Reynolds number at 7031 and 4676, respectively, belonging to medium turbulent regime. The average solid volume fraction ranged from 0 to 0.1. The effect of particle inertia was also investigated by changing the particle–fluid density ratio from 1.5 to 3.0. Analysis of the simulation results indicates turbulence suppression in the bulk region and particle-induced strengthening of the axial liquid circulation. The quasi-steady and unsteady drag is correlated to the relative turbulence intensity and the turbulence dissipation rate obtained from the simulation data, respectively.

Analytical Methods and Verification of Impeller Outlet Velocity Slip of Solid–Liquid Disc Pump with Multi-Type Blades

The intensive exploration to improve the accuracy of the calculation model of velocity slip and theoretical head has always been a major issue in pump research. Discontinuous blade of disc pump is different from the continuous blade of traditional pump. Disc pump realizes energy transfer by the effect of boundary layer. In order to fill in the theoretical blank of current research on the velocity slip and theoretical head of blade disc pump, the velocity slip is calculated by the systematic analysis under solid–liquid flow. In this study, the current misconception of velocity slip was corrected. Based on the different normal velocity components between particle and liquid on the blade surface, a new method is proposed to further verify the difference of solid–liquid flow velocity in impeller passage. Through the proposed method of calculating average circumferential velocity, the calculation model of the velocity slip coefficient and theoretical head of disc pump with linear and curved blade are given and verified. The accuracy of calculation model is increased by 39.4%. This model has good application value in theoretical head calculation, which lays a foundation for further research on energy conversion, energy efficiency prediction and reverse optimization design of disc pump with different blade shapes.

CFD-DEM simulations of solid-liquid flow in stirred tanks using a non-inertial frame of reference

Mixing applications operating in the laminar regime are used in numerous industrial processes in the pharmaceutical, chemical, and food industries. The aim of this paper is to introduce a numerical model adapted to solid-liquid mixing situations in stirred tanks. The method presented herein is based on a Euler-Lagrange approach using the CFD-DEM method. This method couples computational fluid dynamics (CFD) for the fluid with the discrete element method (DEM) for the solid particles. We introduce a rotating frame of reference approach, which is the first of its kind for CFD-DEM. In this paper we discuss the main issues related to the modeling of complex rotating impeller geometries, we explain the various issues involved in conducting a CFD-DEM simulation in a non-inertial frame, we compare our model with experimental results obtained with a pitched blade turbine and, lastly, we use our model to study solid-liquid mixing with a double helical ribbon.

CFD-DEM Simulation for the Distribution and Motion Feature of Solid Particles in Single-Channel Pump

Since various foreign bodies can cause clogging and wear in single-channel pumps, considerable attention has been focused on the numerical study of solid-liquid flows in the single-channel pump. However, conventional numerical simulation cannot responsibly assess the significant effect of the particle material properties, inter-particle collision, and size on the pump. In consideration of the particle features and behaviors, the Computational Fluid Dynamics (CFD)-Discrete Element Method (DEM) coupling method was applied for the first time to simulate the solid-liquid flows in a single-channel pump. The results showed that the smaller particles possessed a wider velocity distribution range and velocity peak, while the larger particles exerted a greater contact force. Additionally, the pie-shaped particles had the most severe collisions, and spherical particles had the least in total. Furthermore, the hub and shroud wall suffered a minor contact force, but the blade and volute wall both sustained a considerable contact force. This paper could present some supply data for future research on the optimization of a single-channel pump.

Complete liquid-solid momentum coupling for unresolved CFD-DEM simulations

Liquid-solid systems are frequently encountered in industrial processes and it is broadly recognised that numerical simulations are a useful tool for gaining insight in these processes. In this study, the unresolved CFD-DEM approach is extended with a complete momentum coupling for liquid-solid flows. Established correlations are used for the drag and lift forces, while new implementations are introduced for the unsteady interaction forces. A virtual mass force model based on the work of Felderhof (Felderhof 1991) is introduced, which accounts for the local particle volume fraction and the liquid-solid density ratio. The Basset history force, which is usually neglected due to computational difficulties related to its implementation, is evaluated according to the approach proposed by Parmar et al. A liquid fluidised bed is used as a demonstration case for the extended model. In this work, it is shown that with appropriate stabilisation measures, the Basset history force is approximated accurately (within 5%), while computational efficiency is maintained ( < 30% increase in computational time). Furthermore, the relevance of the complete momentum coupling is demonstrated by analysis of the solids mixing in the liquid fluidised bed. It is shown that when accounting for the complete interaction force, solids mixing is up to 20% slower compared to simulations with the drag-only approach.

Study of soft abrasive flow field measurement based on particle image velocimetry

Soft abrasive flow (SAF) is a kind of solid-liquid flow used to grind complicated and tiny structures on moulds. In this study, soft abrasive flow field is simulated and then measured via the particle image velocimetry (PIV) to obtain its characteristics. Taking the structural surface of automobile mould as the research object, realizable k-e double-equation turbulent model is used to describe the soft abrasive flow field. The distributions of dynamic pressure, the velocity of the solid particles and the turbulent dissipation rate of the SAF field are obtained in simulation. The particle image velocimetry (PIV) measurement platform is established, and distributions of particle motion, velocity vector and vorticity of the flow field were obtained by PIV measurement platform. The measurement result of PIV is corresponding to that of the simulation, which shows that the soft abrasive flow field is turbulent. By using SAF, the roughness of the machined surface can be up to 27 μm.

Numerical Simulation of Coexisting Solid-liquid Slag Trickle Flow in a Coke Bed by the SPH Method with a Non-Newtonian Fluid Model

Numerical Simulation of Coexisting Solid-liquid Slag Trickle Flow in a Coke Bed by the SPH Method with a Non-Newtonian Fluid Model

Dissociation equilibrium height and friction coefficient in pipeline transportation of gas hydrate-bearing sediment particles

Compared with traditional fossil fuels, gas hydrates have vast reserves, cause little pollution, and are an essential strategic energy resource. Pipeline transportation is critical to realize the development and utilization of natural gas hydrate resources. The Eulerian multiphase flow model within the computational fluid dynamics software FLUENT was employed to calculate gas–liquid–solid flow, taking into account phase interactions, heat transfer, and collision among particles. Pipeline transportation of gas hydrate-bearing sediment (GHBS) particles was studied based on dimensional analysis and numerical simulation. First, the essential dimensionless numbers controlling multiphase flow and hydrate dissociation were deduced. Further, the obtained simulation results clearly indicate that when the system was in a stable state, there was a dissociation equilibrium height above which hydrate dissociated completely. The influences of the dimensionless numbers on the dissociation equilibrium height and friction coefficient in the pipe were determined, and power-law correlations for the dissociation equilibrium height and friction coefficient were obtained from the numerical data. Finally, an analytical expression of dissociation equilibrium height was derived by decoupling the solid–liquid flow and gas hydrate dissociation, and the validity of the power-law correlation for the dissociation equilibrium height was verified by the analytical expression.

Simulation and Experimental Study on Fishing Performance of Vacuum Suction Wellbore Cleaning Tool

During the completion of shale gas wells, bridge plug debris and debris particles are often left at the bottom of the well, which are difficult to clean up, pose a serious risk to wellbore operations, and reduce productivity. In order to solve the difficulty of cleaning the debris at the bottom of the well, a kind of wellbore cleaning tool is proposed based on the principle of negative jet pressure and liquid-solid two-phase flow theory. The finite element analysis method and laboratory test were used to verify the function of cleaning tools: the finite element method can effectively reflect the principle and process of dredging bottom debris with cleaning tools. In order to improve the applicability and fishing ability of wellbore cleaning tools, factors influencing the performance of cleaning tools were analyzed as follows: choosing high-density and low-viscosity working fluid is beneficial to improve the negative pressure effect of cleaning tools. Under the conditions of wellbore safety and economy, increasing pump pressure and displacement and reducing annular pressure can effectively increase the fishing performance of cleaning tools.

Systematic sensitivity analysis of cuttings transport in drilling operation using computational fluid dynamics approach

Hole cleaning and cuttings transport play a vital role in the drilling operation. Various drilling problems such as a reduction in penetration rate, an increase in the torque and drag, and an increase in the potential of differential sticking are often related to poor cuttings transport from a wellbore. Multiple parameters, including the fluid rheology, mud velocity, cuttings size, and drill pipe inclination generally influence the cuttings transport performance. Although several experimental and modelling research works have been conducted in this area, the interactions among the parameters during cuttings transport have not been adequately investigated. This study focuses on interactions between the drilling parameters. Cuttings transport in the wellbore represents a solid-liquid multiphase flow phenomenon. In this research work, Computational Fluid Dynamics (CFD) model was employed to simulate the cuttings transport behaviours in a horizontal wellbore. The Eulerian-Eulerian multiphase flow model was adopted to describe the flow characteristics in the wellbore annular section. Design of Experiment (DoE) was used to systematically study the sensitivity and interactions among the operating parameters. It was observed that the mud viscosity, mud velocity, and drill pipe rotation have a positive impact, whereas an increase in cuttings size and eccentricity in annular clearance show a significant adverse effect on cuttings transport performance. According to the results, the cuttings between 1 mm to 2 mm are difficult to clean, compared to larger cuttings. The study also revealed important interaction effects between the parameters. Although both drilling mud viscosity and velocity show a positive effect, the interaction among them exhibits a negative influence on cuttings transport.

Turbulent coarse-particle suspension flow: Measurement and modelling

Solid-liquid suspension flows are widely encountered in industrial applications. In many of these flows, the carrier fluid exhibits shear-thinning behaviour and the solids have a broad size distribution. Shear-thinning suspensions can occur in laminar or weakly turbulent regimes due to their high viscosity. This paper presents a DNS-DEM model for weakly turbulent coarse-particle suspension flows. Although our interest is in shear-thinning suspensions, we aim firstly to develop a liquid-solid model in a Newtonian fluid to remove the uncertainty in particle-fluid interaction in non-Newtonian suspensions. Matching experiments were conducted for validation. The predicted mixture velocity and concentration profiles are in good agreement with experiments, and discrepancies are mostly less than 10%. The mean velocity profiles are significantly damped by coarse particles and particle phase generally exhibits a higher fluctuation. This DNS-DEM modelling approach is viable for simulating these flows and will form the basis of future work on shear-thinning suspension flow.

Current Situation and Prospect of Erosion Wear

The material loss and equipment failure caused by erosion wear is a serious problem in solid-liquid mixture flow in the mechanical, metallurgy, energy, building materials, transportation, aviation, aerospace, military and other industrial departments. Therefore, understanding the erosion wear mechanism, the influencing factors, and how to set up mathematical model are very important. Since the 1950s, the research on the erosion wear made great development. The purpose of this paper is to give a comprehensive review about previous research work of erosion wear. Firstly, the mechanism and influencing factors of erosion wear are introduced. Secondly, the forces of particle caused by fluid are analysed and several erosion models which tested by experimental with good results are introduced. Thirdly, the method of erosion numerical simulation combining computer software and CFD theory is introduced. Finally, based on the conclusion, some useful conclusions are drawn and the future research direction is prospected.

Modeling of solid-liquid flow inside conical diverging sections using computational fluid dynamics approach

In a slurry pipeline, the diverging sections are an important pipe fitting and also a cause of major pressure loss and sometimes flow separation. To address this potential issue, the complex solid-liquid flow of coal water slurry through conical diverging sections is simulated using the computational fluid dynamics approach. Nine different geometries of the diverging sections are analyzed in the present study. The length of the diverging section is the key variable in the geometric variations and ranges from 0.05 m to 0.6 m. The influx velocity at the entrance of all the diverging sections is varied in the range of 0.5 m/s to 5 m/s. The mass concentration of the solids dispersed inside the liquid phase is varied from 10 to 60%. The results generated by the computational fluid dynamics tool are in good agreement with the experimental data. The design of the diverging section is evaluated based on results obtained for three characterization parameters viz. pressure recovery coefficient, head-loss across the diverging section and volumetric efficiency. The 0.3 m long diverging section is found to be the optimum design for best pressure recovery, maximum volumetric efficiency and lowest head-loss.

Hydrodynamics and phenol adsorption studies in continuous counter current liquid-solid settling column

Adsorption is a cost-efficient and a well-established method to treat a large volume of wastewater. Most of the adsorption studies have been carried out in batch and continuous (packed and fluidized bed column) reactors. In most of the continuous operations, a solid adsorbent is held in batch mode and the liquid phase is continuous. In a counter-current liquid-solid adsorber, both the liquid and solid phase will be continuous. In this study, synthetic wastewater containing phenol of 200 ppm is treated in a counter-current liquid-solid adsorber using activated carbon as the adsorbent. The adsorption kinetics and the effect of size and mass of adsorbent were studied in batch operation. Thermodynamic properties including Gibbs' free energy, standard enthalpy and entropy change were calculated and the feasibility of the process is confirmed. In the continuous counter-current liquid-solid settling column, the effects of liquid flow rate, particle size and solid flow rate on hydrodynamics and mass transfer have been studied. From the range of flow rates studied in this work, liquid flowrate of 10 lph and solids (of diameter 0.5 mm) flow rate of 24 g/s gave the maximum phenol removal. An empirical equation has been proposed to predict the mass transfer coefficient for the range of continuous process.