A Numerical Investigation of Internal and External Two-Phase Flows of a Rotating Disk Atomizer

2012 ◽  
Author(s):  
Cheng-Xian (Charlie) Lin ◽  
Long Phan
Keyword(s):  
Volume Fraction ◽  
Numerical Study ◽  
Rotating Disk ◽  
Multiphase Model ◽  
Two Phase Flows ◽  
Two Phase ◽  
Liquid Distribution ◽  
Liquid Feed ◽  
Flow Rate Range ◽  
Uniform Liquid

In this paper, a numerical study has been carried out to model and simulate the air-water two-phase flows in and around a rotating disk atomizer, which uses multiple nozzles to breakout the water and forms droplets. The physical problem was simulated with an Eulerian multiphase model. The realizable two-equation turbulence model was used for the turbulent flow. The governing equations were solved with a finite volume based numerical method. The rotary frame approach was used to deal with the spinning disk. Numerical simulation was conducted in a disk rotational speed range of 1000 to 10000 rpm, a liquid feed flow rate range of 100 to 150 gpm. Both uniform and non-uniform liquid distribution conditions were considered. Detailed results about flow velocity and volume fraction fields inside and outside of the atomizer are presented and discussed. It was found that when liquid is nonuniformly distributed through the distributors, some of the nozzles could reach flooding conditions at lower rotational disk speed and liquid feed volume flow rates, as compared to uniform distribution cases.

Numerical Study of Two-Phase Flow in a Horizontal Pipeline Using an Unconditionally Hyperbolic Two-Fluid Model

2018 ◽  
Author(s):  
Raphael V. N. de Freitas ◽  
Carina N. Sondermann ◽  
Rodrigo A. C. Patricio ◽  
Aline B. Figueiredo ◽  
Gustavo C. R. Bodstein ◽  
...  
Keyword(s):  
Volume Fraction ◽  
Numerical Study ◽  
Fluid Model ◽  
Momentum Conservation ◽  
Design Stage ◽  
Two Phase Flows ◽  
Two Phase ◽  
Efficient Manner ◽  
Two Fluid Model ◽  
Two Fluid

Numerical simulation is a very useful tool for the prediction of physical quantities in two-phase flows. One important application is the study of oil-gas flows in pipelines, which is necessary for the proper selection of the equipment connected to the line during the pipeline design stage and also during the pipeline operation stage. The understanding of the phenomena present in this type of flow is more crucial under the occurrence of undesired effects in the duct, such as hydrate formation, fluid leakage, PIG passage, and valve shutdown. An efficient manner to model two-phase flows in long pipelines regarding a compromise between numerical accuracy and cost is the use of a one-dimensional two-fluid model, discretized with an appropriate numerical method. A two-fluid model consists of a system of non-linear partial differential equations that represent the mass, momentum and energy conservation principles, written for each phase. Depending on the two-fluid model employed, the system of equations may lose hyperbolicity and render the initial-boundary-value problem illposed. This paper uses an unconditionally hyperbolic two-fluid model for solving two-phase flows in pipelines in order to guarantee that the solution presents physical consistency. The mathematical model here referred to as the 5E2P (five equations and two pressures) comprises two equations of continuity and two momentum conservation equations, one for each phase, and one equation for the transport of the volume fraction. A priori this model considers two distinct pressures, one for each phase, and correlates them through a pressure relaxation procedure. This paper presents simulation cases for stratified two-phase flows in horizontal pipelines solved with the 5E2P coupled with the flux corrected transport method. The objective is to evaluate the numerical model capacity to adequately describe the velocities, pressures and volume fraction distributions along the duct.

scholarly journals Numerical Study on an Interface Compression Method for the Volume of Fluid Approach

Fluids ◽  
2021 ◽  
Vol 6 (2) ◽  
pp. 80
Author(s):  
Yuria Okagaki ◽  
Taisuke Yonomoto ◽  
Masahiro Ishigaki ◽  
Yoshiyasu Hirose
Keyword(s):  
Linear Theory ◽  
Volume Fraction ◽  
Numerical Study ◽  
Volume Of Fluid ◽  
Interfacial Wave ◽  
Validation Process ◽  
Two Phase ◽  
Numerical Diffusion ◽  
Mesh Resolution ◽  
Water Reactors

Many thermohydraulic issues about the safety of light water reactors are related to complicated two-phase flow phenomena. In these phenomena, computational fluid dynamics (CFD) analysis using the volume of fluid (VOF) method causes numerical diffusion generated by the first-order upwind scheme used in the convection term of the volume fraction equation. Thus, in this study, we focused on an interface compression (IC) method for such a VOF approach; this technique prevents numerical diffusion issues and maintains boundedness and conservation with negative diffusion. First, on a sufficiently high mesh resolution and without the IC method, the validation process was considered by comparing the amplitude growth of the interfacial wave between a two-dimensional gas sheet and a quiescent liquid using the linear theory. The disturbance growth rates were consistent with the linear theory, and the validation process was considered appropriate. Then, this validation process confirmed the effects of the IC method on numerical diffusion, and we derived the optimum value of the IC coefficient, which is the parameter that controls the numerical diffusion.

scholarly journals Simulation of the Effect of Oil Volume Fractions in an Oil-Water Flows Along a Circular Pipe: A Finite Element Approach

2018 ◽  
Vol 10 (5) ◽  
pp. 19
Author(s):  
Ferdusee Akter ◽  
Md. Bhuyan ◽  
Ujjwal Deb
Keyword(s):  
Finite Element ◽  
Volume Fraction ◽  
Fluid Velocity ◽  
Galerkin Approximation ◽  
Computational Domain ◽  
Two Phase Flows ◽  
Two Phase ◽  
Volume Fractions ◽  
Oil In Water ◽  
Element Approach

Two phase flows in pipelines are very common in industries for the oil transportations. The aim of our work is to observe the effect of oil volume fraction in the oil in water two phase flows. The study has been accomplished using a computational model which is based on a Finite Element Method (FEM) named Galerkin approximation. The velocity profiles and volume fractions are performed by numerical simulations and we have considered the COMSOL Multiphysics Software version 4.2a for our simulation. The computational domain is 8m in length and 0.05m in radius. The results show that the velocity of the mixture decreases as the oil volume fraction increases. It should be noted that if we gradually increase the volume fractions of oil, the fluid velocity also changes and the saturated level of the volume fraction is 22.3%.

scholarly journals The Influence of Combined Turbulators on the Hydraulic-Thermal Performance and Exergy Efficiency of MWCNT-Cu/Water Nanofluid in a Parabolic Solar Collector: A Numerical Approach

2021 ◽  
Vol 9 ◽  
Author(s):  
Yacine Khetib ◽  
Ammar Melaibari ◽  
Radi Alsulami
Keyword(s):  
Solar Collector ◽  
Volume Fraction ◽  
Numerical Approach ◽  
Exergy Efficiency ◽  
Multiphase Model ◽  
Two Phase ◽  
Simpler Algorithm ◽  
Fluent Software ◽  
Parabolic Geometries ◽  
Volume Method

The present research benefits from the finite volume method in investigating the influence of combined turbulators on the thermal and hydraulic exergy of a parabolic solar collector with two-phase hybrid MWCNT-Cu/water nanofluid. All parabolic geometries are produced using DesignModeler software. Furthermore, FLUENT software, equipped with a SIMPLER algorithm, is applied for analyzing the performance of thermal and hydraulic, and exergy efficiency. The Eulerian–Eulerian multiphase model and k-ε were opted for simulating the two-phase hybrid MWCNT-Cu/water nanofluid and turbulence model in the collector. The research was analyzed in torsion ratios from 1 to 4, Re numbers from 6,000 to 18,000 (turbulent flow), and the nanofluid volume fraction of 3%. The numerical outcomes confirm that the heat transfer and lowest pressure drop are relevant to the Re number of 18,000, nanofluid volume fraction of 3%, and torsion ratio of 4. Furthermore, in all torsion ratios, rising Re numbers and volume fraction lead to more exergy efficiency. The maximum value of 26.32% in the exergy efficiency was obtained at a volume fraction of 3% and a torsion ratio of 3, as the Re number goes from 60,000 to 18,000.

Numerical Simulation of Black Liquor Spray Characteristics

2002 ◽  
Author(s):  
Thomas D. Foust ◽  
Kurt D. Hamman ◽  
Brent A. Detering
Keyword(s):  
Droplet Size ◽  
Volume Fraction ◽  
Numerical Study ◽  
Black Liquor ◽  
Flow Distribution ◽  
Physical Models ◽  
Spray Characteristics ◽  
Two Phase ◽  
Vof Model ◽  
Sheet Breakup

The performance and capacity of Kraft recovery boilers is sensitive to black liquor velocity, droplet size and flow distribution in the furnace. Studies have shown that controlling droplet size and flow distribution improves boiler efficiency while allowing increased flight drying and devolatilization, and decreased carryover. The purpose of this study is to develop a robust two-phase numerical model to predict black liquor splashplate nozzle spray characteristics. A three-dimensional time dependent numerical study of black liquor sheet formation and sheet breakup is described. The volume of fluid (VOF) model is used to simulate flow through the splashplate nozzle up to initial sheet breakup and droplet formation. The VOF model solves the conservation equations of volume fraction and momentum utilizing the finite volume technique. Black liquor velocity, droplet size and flow distribution over a range of operating parameters are simulated using scaled physical models of splashplate nozzles. The VOF model is compared to results from a flow visualization experiment and experimental data found in the literature. The details of the simulation and experimental results are presented.

Numerical study of nanofluid flow and heat transfer over a rotating disk using Buongiorno’s model

2017 ◽  
Vol 27 (1) ◽  
pp. 221-234 ◽  
Author(s):  
Junaid Ahmad Khan ◽  
M. Mustafa ◽  
T. Hayat ◽  
Mustafa Turkyilmazoglu ◽  
A. Alsaedi
Keyword(s):  
Brownian Motion ◽  
Volume Fraction ◽  
Numerical Study ◽  
Mathematical Formulation ◽  
Three Dimensional ◽  
Vertical Direction ◽  
Rotating Disk ◽  
Content Type ◽  
Buongiorno’S Model ◽  
Buongiorno Model

Purpose The purpose of the present study is to explore a three-dimensional rotating flow of water-based nanofluids caused by an infinite rotating disk. Design/methodology/approach Mathematical formulation is performed using the well-known Buongiorno model which accounts for the combined influence of Brownian motion and thermophoresis. The recently suggested condition of passively controlled wall nanoparticle volume fraction has been adopted. Findings The results reveal that temperature decreases with an increase in thermophoresis parameter, whereas it is negligibly affected with a variation in the Brownian motion parameter. Axial velocity is negative because of the downward flow in the vertical direction. Originality/value Two- and three-dimensional streamlines are also sketched and discussed. The computations are found to be in very good agreement with the those of existing studies in the literature for pure fluid.

scholarly journals Wake attenuation in large Reynolds number dispersed two-phase flows

2008 ◽  
Vol 366 (1873) ◽  
pp. 2177-2190 ◽  
Author(s):  
Frédéric Risso ◽  
Véronique Roig ◽  
Zouhir Amoura ◽  
Guillaume Riboux ◽  
Anne-Marie Billet
Keyword(s):  
Reynolds Number ◽  
Volume Fraction ◽  
Bubble Diameter ◽  
Temporal Variations ◽  
The Body ◽  
Experimental Investigations ◽  
Large Reynolds Number ◽  
Two Phase Flows ◽  
Two Phase ◽  
Multi Body

The dynamics of high Reynolds number-dispersed two-phase flow strongly depends on the wakes generated behind the moving bodies that constitute the dispersed phase. The length of these wakes is considerably reduced compared with those developing behind isolated bodies. In this paper, this wake attenuation is studied from several complementary experimental investigations with the aim of determining how it depends on the body Reynolds number and the volume fraction α . It is first shown that the wakes inside a homogeneous swarm of rising bubbles decay exponentially with a characteristic length that scales as the ratio of the bubble diameter d to the drag coefficient C d , and surprisingly does not depend on α for 10 −2 ≤ α ≤10 −1 . The attenuation of the wakes in a fixed array of spheres randomly distributed in space ( α =2×10 −2 ) is observed to be stronger than that of the wake of an isolated sphere in a turbulent incident flow, but similar to that of bubbles within a homogeneous swarm. It thus appears that the wakes in dispersed two-phase flows are controlled by multi-body interactions, which cause a much faster decay than turbulent fluctuations having the same energy and integral length scale. Decomposition of velocity fluctuations into a contribution related to temporal variations and that associated to the random character of the body positions is proposed as a perspective for studying the mechanisms responsible for multi-body interactions.

scholarly journals Numerical Investigation of Oil Gas Separation with the Use of VOF CFD

2021 ◽  
Vol 11 (6) ◽  
pp. 7841-7845
Author(s):  
S. Tomescu ◽  
I. O. Bucur
Keyword(s):  
Porous Media ◽  
Numerical Investigation ◽  
Gas Turbines ◽  
Computer Aided Design ◽  
Volume Fraction ◽  
Numerical Study ◽  
Computational Domain ◽  
Two Phase ◽  
Volume Porosity ◽  
Set Up

In this research paper, a numerical study regarding gas-oil separation is presented. Employing the geometry of a classic separator used by the NRDI for Gas Turbines COMOTI and a Computer-Aided Design (CAD) software, the computational domain was defined. To perform the Computational Fluid Dynamics (CFD) investigation, the mesh was created with the ANSYS Meshing tool, and the ANSYS CFX was employed as a solver. The computational domain was split into 5 subdomains, 3 were fluid and 2 were defined as porous media. The volume porosity, loss model, and permeability were set up. In terms of turbulence flow, the standard k–ε model was adopted. The results of the numerical calculations in terms of oil volume fraction and streamline profiles were used to analyze the separator configuration. The results show that the numerical investigation with the VOF (Volume of Fluid Method) - CFD model is capable of analyzing the performance of a two-phase separator equipped with two demisters-porous media.

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