scholarly journals Two-phase modelling for sediment water mixtures above the limit deposit velocity in horizontal pipelines

2021 ◽  
Vol 69 (3) ◽  
pp. 263-274
Author(s):  
Thijs Schouten ◽  
Cees van Rhee ◽  
Geert Keetels
Keyword(s):  
Pressure Gradient ◽  
Land Reclamation ◽  
Particle Diameter ◽  
Mesh Size ◽  
Fluid Phase ◽  
Two Phase ◽  
Algebraic Form ◽  
Continuity Equations ◽  
Wide Range ◽  
Euler Solver

Abstract In dredging applications, deep sea mining and land reclamation projects typically large amounts of sediments are transported through pipes in the form of hyper concentrated (40% sediment or more) sediment-water mixtures or slurries. In this paper it is investigated how well a generic Euler-Euler CFD-model is capable to model velocity, concentration profiles and the pressure gradient of sediment above deposition limit velocity in a pipeline. This Euler-Euler solver treats both phases as a continuum with its own momentum and continuity equations. The full kinetic theory for granular flows is accounted for (no algebraic form is used) and is combined with a buoyant k-ε turbulence model for the fluid phase. The influence of the mesh size has been checked and grid convergence is achieved. All numerical schemes used are of second-order accuracy in space. The pressure gradient was calibrated by adjusting the specularity coefficient in one calibration case and kept constant afterwards. Simulations were carried out in a wide range of slurry flow parameters, in situ volume concentration (9–42%), pipe diameter (0.05–0.90 m), particle diameter (90–440 μm) and flow velocity of (3–7 m/s). The model shows satisfactory agreement to experimental data from existing literature.

scholarly journals On the transition between turbulence regimes in particle-laden channel flows

2018 ◽  
Vol 845 ◽  
pp. 499-519 ◽  
Author(s):  
Jesse Capecelatro ◽  
Olivier Desjardins ◽  
Rodney O. Fox
Keyword(s):  
Reynolds Number ◽  
Fluid Phase ◽  
Stokes Number ◽  
Channel Flows ◽  
High Mass ◽  
Inertial Particles ◽  
Mass Loading ◽  
Two Phase ◽  
Phase Dynamics ◽  
Wide Range

Turbulent wall-bounded flows exhibit a wide range of regimes with significant interaction between scales. The fluid dynamics associated with single-phase channel flows is predominantly characterized by the Reynolds number. Meanwhile, vastly different behaviour exists in particle-laden channel flows, even at a fixed Reynolds number. Vertical turbulent channel flows seeded with a low concentration of inertial particles are known to exhibit segregation in the particle distribution without significant modification to the underlying turbulent kinetic energy (TKE). At moderate (but still low) concentrations, enhancement or attenuation of fluid-phase TKE results from increased dissipation and wakes past individual particles. Recent studies have shown that denser suspensions significantly alter the two-phase dynamics, where the majority of TKE is generated by interphase coupling (i.e.  drag) between the carrier gas and clusters of particles that fall near the channel wall. In the present study, a series of simulations of vertical particle-laden channel flows with increasing mass loading is conducted to analyse the transition from the dilute limit where classical mean-shear production is primarily responsible for generating fluid-phase TKE to high-mass-loading suspensions dominated by drag production. Eulerian–Lagrangian simulations are performed for a wide range of particle loadings at two values of the Stokes number, and the corresponding two-phase energy balances are reported to identify the mechanisms responsible for the observed transition.

Bounds on Two-Phase Flow: Part I — Frictional Pressure Gradient in Circular Pipes

2005 ◽  
Author(s):  
M. M. Awad ◽  
Y. S. Muzychka
Keyword(s):  
Turbulent Flow ◽  
Pressure Gradient ◽  
Published Data ◽  
Two Phase ◽  
Working Fluids ◽  
Circular Pipes ◽  
Mass Fluxes ◽  
Wide Range ◽  
Flow Part ◽  
Fanning Friction Factor

Simple rules are developed for obtaining rational bounds for two-phase frictional pressure gradient. Both the lower and upper bounds are based on the separate cylinders formulation. The lower bound is based on turbulent-turbulent flow that uses the Blasius equation to represent the Fanning friction factor. The upper bound is based on an equation that represents well the Lockhart-Martinelli correlation for turbulent-turbulent flow. The model is verified using published experimental data of two-phase frictional pressure gradient versus mass flux at constant mass quality. The published data include different working fluids such as R-12 and R-22 at different mass qualities, different pipe diameters, and different saturation temperatures. It is shown that the published data can be well bounded for a wide range of mass fluxes, mass qualities, pipe diameters and saturation temperatures. The bounds models are also presented in a dimensionless form as two-phase frictional multiplier (φl and φg) versus Lockhart-Martinelli parameter (X) for different working fluids such as R-12, R-22, air-oil and air-water mixtures.

scholarly journals Numerical Investigation of the Pressure Drop Characteristics of Isothermal Ice Slurry Flow under Variable Ice Particle Diameter

2020 ◽  
Vol 2020 ◽  
pp. 1-13
Author(s):  
Shehnaz Akhtar ◽  
Taqi Ahmad Cheema ◽  
Haider Ali ◽  
Moon Kyu Kwak ◽  
Cheol Woo Park
Keyword(s):  
Pressure Drop ◽  
Flow Velocity ◽  
Mass Fraction ◽  
Fluid Dynamic ◽  
Particle Diameter ◽  
Ice Slurry ◽  
Slurry Flow ◽  
Two Phase ◽  
Wide Range ◽  
Volumetric Loading

Ice slurry is an advanced secondary refrigerant that has been attracting considerable attention for the past decade due to the growing concerns regarding energy shortage and environmental protection. To stimulate the potential applications of ice slurry, the corresponding pressure drop of this refrigerant must be comprehensively investigated. The flow of ice slurry is a complex phenomenon that is affected by various parameters, including flow velocity, ice particle size, and ice mass fraction. To predict the pressure drop of ice slurry flow in pipes, a mixture computational fluid dynamic model was adopted to simulate a two-phase flow without considering ice melting. The numerical calculations were performed on a wide range of six ice particle sizes (0.1, 0.3, 0.5, 0.75, 1, and 1.2 mm) and ice mass fraction ranging within 5%–20% in the laminar range of ice slurry flow. The numerical model was validated using experimental data. Results showed that the ice volumetric loading and flow velocity have a direct effect on pressure drop; it increases with the increase in volumetric concentration and flow velocity. The findings also confirmed that for constant ice mass fraction and flow velocity, the pressure drop is directly and inversely related to the particle and pipe diameters, respectively. Moreover, the rise in pressure drop is more significant for large ice particle diameter in comparison to smaller size ice particles at high values of ice concentration and flow velocity.

scholarly journals Sediment dynamics. Part 1. Bed-load transport by laminar shearing flows

2009 ◽  
Vol 636 ◽  
pp. 295-319 ◽  
Author(s):  
MALIKA OURIEMI ◽  
PASCALE AUSSILLOUS ◽  
ÉLISABETH GUAZZELLI
Keyword(s):  
Fluid Velocity ◽  
Particle Diameter ◽  
Fluid Phase ◽  
Momentum Equation ◽  
Brinkman Equation ◽  
Bed Load ◽  
Two Phase ◽  
Parabolic Profile ◽  
Load Transport ◽  
Bed Load Transport

We propose a two-phase model having a Newtonian rheology for the fluid phase and friction for the particle phase to describe bed-load transport in the laminar viscous regime. We have applied this continuum model to sediment transport by viscous shearing flows. The equations are shown to reduce to the momentum equation for the mixture and the Brinkman equation for the fluid velocity. This modelling is able to provide a description of the flow of the mobile granular layer. At some distance from threshold of particle motion, where the continuum approach is more realistic as the mobile layer is larger than one particle diameter, there is very little slip between the two phases and the velocities inside the mobile bed have approximately a parabolic profile. When the Poiseuille (or Couette) flow is not significantly perturbed, simple analytical results of the particle flux varying cubically with the Shields number and of the bed-load thickness varying linearly with it can then be obtained. These predictions compare favourably with experimental observations of bed-load transport in pipe flows.

Performance Analysis of Cavitating Flow in Centrifugal Pumps Using Multiphase CFD

2002 ◽  
Vol 124 (2) ◽  
pp. 377-383 ◽  
Author(s):  
Richard B. Medvitz ◽  
Robert F. Kunz ◽  
David A. Boger ◽  
Jules W. Lindau ◽  
Adam M. Yocum ◽  
...  
Keyword(s):  
Stokes Equations ◽  
Volume Fraction ◽  
Design Flow ◽  
Centrifugal Pumps ◽  
Two Phase ◽  
Local Flow ◽  
Differential Model ◽  
Sheet Cavitation ◽  
Continuity Equations ◽  
Wide Range

A multi-phase CFD method is used to analyze centrifugal pump performance under developed cavitating conditions. The differential model employed is the homogeneous two-phase Reynolds-Averaged-Navier-Stokes equations, wherein mixture momentum and volume continuity equations are solved along with vapor volume fraction continuity. Mass transfer modeling is provided for the phase change associated with sheet cavitation. Using quasi-3D (Q3D) analysis, steady and time-dependent analyses were performed across a wide range of flow coefficients and cavitation numbers. Characteristic performance trends associated with off-design flow and blade cavitation are observed. The rapid drop in head coefficient at low cavitation numbers (breakdown) is captured for all flow coefficients. Local flow field solution plots elucidate the principal physical mechanisms associated with the onset of breakdown.

Brief history and ways of further development of the department of hydraulic engineering and hydraulics FSBI «VNIIGiM named after A.N. Kostyakov»

2020 ◽  
pp. 18-23
Author(s):  
Alexey Shcherbakov ◽  
Valentin Zhezmer
Keyword(s):  
Land Reclamation ◽  
Water Source ◽  
Water Sources ◽  
Hydraulic Engineering ◽  
Negative Effects ◽  
Extensive Experience ◽  
Safety Level ◽  
Theoretical Substantiation ◽  
Wide Range ◽  
Construction Operation

Department of hydraulic engineering and hydraulics FGBNU «VNIIGiM them. A.N. Kostyakova «has a long history. For many years, the department’s staff has been such scientists and water engineers with extensive experience as M.A. Volynov, V.S. Verbitsky, S.S. Medvedev, N.V. Lebedev, B.C. Panfilov, T.G. Voynich-Syanozhentsky, V.A. Golubkova, G.V. Lyapin and others. The department solved a wide range of tasks, the main areas of research were the following: – theoretical and applied hydrodynamics and hydraulics, with reference to the open channel flows that affect the state and level of safety of the hydraulic structures; – integrated use and protection of water bodies – water sources and water sources of water resources used in land reclamation; – development of measures and technical solutions for the protection of objects from the negative effects of water; – theoretical substantiation of works to improve the safety level of the GTS (declaration); – development and implementation of digitalization methods for solving design, construction, operation and control of landreclamation facilities. Currently, promising areas of research is the development of a decision-making algorithm in the designation of measures to rationalize the provision of resources to water amelioration. The algorithm is developed on the basis of a detailed study, systematization and processing of data both on safety and on the efficiency of systems and structures, ensuring the delivery of irrigation water of the required quality and in sufficient quantity from a water source to the field.

scholarly journals Effect of an oscillating time-dependent pressure gradient on Dean flow: transient solution

2020 ◽  
Vol 9 (1) ◽  
Author(s):  
Basant K. Jha ◽  
Dauda Gambo
Keyword(s):  
Pressure Gradient ◽  
Initial Conditions ◽  
Fluid Velocity ◽  
Outer Cylinder ◽  
Time Dependent ◽  
Navier Stokes ◽  
Dean Flow ◽  
Continuity Equations ◽  
Riemann Sum ◽  
Flow Formation

Abstract Background Navier-Stokes and continuity equations are utilized to simulate fully developed laminar Dean flow with an oscillating time-dependent pressure gradient. These equations are solved analytically with the appropriate boundary and initial conditions in terms of Laplace domain and inverted to time domain using a numerical inversion technique known as Riemann-Sum Approximation (RSA). The flow is assumed to be triggered by the applied circumferential pressure gradient (azimuthal pressure gradient) and the oscillating time-dependent pressure gradient. The influence of the various flow parameters on the flow formation are depicted graphically. Comparisons with previously established result has been made as a limit case when the frequency of the oscillation is taken as 0 (ω = 0). Results It was revealed that maintaining the frequency of oscillation, the velocity and skin frictions can be made increasing functions of time. An increasing frequency of the oscillating time-dependent pressure gradient and relatively a small amount of time is desirable for a decreasing velocity and skin frictions. The fluid vorticity decreases with further distance towards the outer cylinder as time passes. Conclusion Findings confirm that increasing the frequency of oscillation weakens the fluid velocity and the drag on both walls of the cylinders.

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