Simulation Of Flow Behavior Research Articles

Flow Behavior Simulation with Computational Fluid Dynamics in Spray Tower Scrubber

Flow Behavior Simulation with Computational Fluid Dynamics in Spray Tower Scrubber

A Study on Jobaru River Basin Management by Numerical Simulations of Flooding and Sediment Deposition with Field Survey

River basin management in Japan in the early modern period can be considered as providing a prototype of possible countermeasures for present-day flood exceeding the design level. The river basin management in the Saga region of Japan was established by Naritomi Hyogo in the early Edo era. This study evaluates characteristics of river basin management in Jobaru River Basin located in the eastern Saga Plain using numerical simulations and geotechnical surveys. A flood flow of Jobaru River was calculated using a 1-D flow numerical simulation. Overflow discharges from Nokoshi, open levee and no-levee intervals are estimated and these discharges are specified as boundary conditions for quasi 3-D inundation flow simulations. 2-D sediment transport by water flow is also simulated. A Geoslicer is used for field surveys that uncover clues of how the sediment has been deposited in the past. The ages of the sampled stratums was measured by using radiocarbon dating methods. The classified sediments columns and estimated ages of the stratum by the radiocarbon dating correspond to the simulated flood flow behavior in the retarding basin after overflow from the Nokoshi and open levee. Moreover, No.1 open levee reproduced by the geotechnical survey's result is used for the flow simulation successfully.

Simulations of flow behavior of oscillatory opposed dilute gas–solid jets

Flow behavior of gas and particles by means of oscillatory opposed dilute gas–solid mixture jets is presented in this work. Two opposed jets with high velocities of gas-particles mixture are made to oscillate with the same frequency but with a phase shift of π/2. The two opposed jet dilute gas–solid streams are idealization of an array of oscillating opposed jets. Numerical simulations are performed in 3D chamber. The pressure and viscosity of particles and the drag force between gas phase and solid phase are predicted using a commercial FLUENT code. The realizable k–ε model is used to predict turbulence viscosity of gas phase. Flow behavior of gas and particles is investigated with respect to the oscillation frequency of opposed jets. The computational results show that there is an impingement region in the oscillatory flow jets. The solid volume fraction and turbulence kinetic energy of gas phase are high and a stagnation point occurs in the impingement zone. It is shown that the periodic velocities of gas and particles of the opposed jet lead to the horizontal reciprocating movement of impingement zone. The stagnation point with two times frequency of opposed jets oscillates along horizontal reciprocating movement. Further, the analysis shows the large velocities of gas and particles and solid volume fraction in the impingement zone decreases with the increase of frequency of opposed jets. The study shows that low frequency is effective to improve momentum transfer between two opposed jets.

Investigation of hydraulic parameters and cavitation in Kheir Abad flood release structure

The simulation of flow behaviors before the construction of spillways using physical model and simulating packages is a crucial task. This paper investigates the flow behaviors in Kheir Abad flood release structure on Ab Shirin River, Iran by using Flow3D software and the results were compared with those of the physical model. First, by setting up a virtual model of spillway, the software performance was verified and calibrated. Then, by entering different flow discharge values, the two-dimensional flow hydraulics through the spillway was simulated by the software and flow depths, velocities and pressure were obtained for different flow discharges along the spillway. The cavitation was calculated based on the hydraulic parameters. The results show that Flow3D software is capable of simulating two-dimensional hydraulic flow over spillways. The results also indicate that the Kheir Abad flood release structure performs well during flood events considering cavitation.

Molecular dynamics simulation on flow behaviors of nanofluids confined in nanochannel

Nanofluids are new heat transfer liquids with remarkable heat transfer capability prepared by suspending nanoparticles in traditional heat transfer liquids (water, ethylene glycol and engine oil). The key reason for the enhanced heat transfer properties of nanofluids is not only their increased thermal conductivity but also the changed rheological behavior of base fluid due to the adding of nanoparticles. However, currently the investigation into influence of shear velocity on flow behaviors of nanofluids is still inadequate. In this paper molecular dynamics simulations are used to simulate flow behaviors of nanofluids confined in nanochannel under different shear velocities. Rotation and translation of nanoparticles and nonlinear velocity profiles of nanofluids are observed. The degree of nonlinearity, as well as the rotation and translation of nanoparticles, are enhanced with the shear velocity increasing. The existence of “solid-like” absorbed layers near the plates and around the nanoparticles is also demonstrated.

Modelado y simulación del flujo de intercambiadores de calor de tubos y aletas con cambio de fase en el refrigerante

This paper presents the development of a computational tool for the simulation of flow behavior in the fin-and-tube heat exchangers with phase change in the coolant side, for which the finite volume method was used for exchanger modeling and representation of the connection of the tubes was made using graph theory. Because the hydrodynamic phenomena and the 2 phase flow is not well developed, the model supports various empirical correlations for calculating the pressure drop and heat transfer coefficient. As a result a computational tool for simulating of fin-and-tube heat exchangers that allows the modeling of the refrigerant flow in single phase or two-phase state was obtained. With the model of the exchanger was possible to predict the flow behavior of an evaporator under conditions of dry and wet fins give error values below 6% with respect to the experimental data.

Cluster structure-dependent drag model for liquid–solid circulating fluidized bed

The formation of clusters in liquid–solid circulating fluidized beds effects on momentum transfer between phases. In this article, a cluster structure-dependent drag model is proposed to take the effect of clusters on momentum transfer between dispersed phase and clusters into account by means of an Eulerian–Eulerian two-fluid model. The momentum and energy balances that characterize the clusters in the dense phase as well as dispersed particles in the dilute phase are described by the multi-scale resolution approach. The proposed model of cluster structure-dependent (CSD) drag coefficient is on the basis of the minimization of energy dissipation by heterogeneous drag (MEDHD) as a function of Reynolds number. The CSD drag coefficient model is incorporated into the two-fluid model to simulate flow behavior of liquid and particles in a liquid–solid riser. Predicted volume fraction and particle velocity distributions are in good agreement with experimental data published in the literature.

Numerical investigation of flow and heat transfer in a novel configuration multi-tubular fixed bed reactor for propylene to acrolein process

In the present contribution, a numerical study of fluid flow and heat transfer performance in a pilot-scale multi-tubular fixed bed reactor for propylene to acrolein oxidation reaction is presented using computational fluid dynamics (CFD) method. Firstly, a two-dimensional CFD model is developed to simulate flow behaviors, catalytic oxidation reaction, heat and mass transfer adopting porous medium model on tube side to achieve the temperature distribution and investigate the effect of operation parameters on hot spot temperature. Secondly, based on the conclusions of tube-side, a novel configuration multi-tubular fixed-bed reactor comprising 790 tubes design with disk-and-doughnut baffles is proposed by comparing with segmental baffles reactor and their performance of fluid flow and heat transfer is analyzed to ensure the uniformity condition using molten salt as heat carrier medium on shell-side by three-dimensional CFD method. The results reveal that comprehensive performance of the reactor with disk-and-doughnut baffles is better than that of with segmental baffles. Finally, the effects of operating conditions to control the hot spots are investigated. The results show that the flow velocity range about 0.65 m/s is applicable and the co-current cooling system flow direction is better than counter-current flow to control the hottest temperature.

A model of two-phase resin and void flow during composites processing

The reduction of porosity during composites manufacturing remains a critical design goal for successful processing. High porosity composite parts exhibit reduced mechanical properties and increased design risk. A primary source of porosity is the formation and transport of trapped air bubbles during polymer resin flow through fibrous porous media reinforcement. A model experiment has been developed in which a flow cell comprised of two transparent parallel plates is injected with a simulated resin and air bubbles to investigate two-phase flow. The flow cell is designed to simulate flow behavior exhibited during Resin Transfer Molding (RTM) or Out-of-Autoclave (OOA) prepreg composites processing. A flow visualization setup captures the two-phase resin flow and void migration through the flow cell. A computational model is formulated to describe the two phase flow and validated with experimental results. The model material and process parameters can be optimized to maximize the relative void velocity with respect to the resin, thus achieving effective void migration and overall porosity reduction during processing. A parametric scaling analysis is conducted to identify and quantify the sensitivity of material and process parameters on two phase resin and void transport in composites processing.

Numerical simulation of flow behavior of particles in an inverse liquid–solid fluidized bed

Flow behavior of particles is simulated by means of two-fluid model combining with kinetic theory of granular flow in an inverse liquid–solid fluidized bed. The Huilin–Gidaspow drag model is used to obtain the interphase interaction of liquid and solid phases. The virtual mass force is considered in simulations. A detailed description of the model equations used has been presented. Predictions are compared with experimental data measured by Renganathan (2005) in an inverse liquid–solid fluidized bed. This comparison shows that the present model can capture flow behavior of liquid and solids phases in an inverse fluidized bed. The distributions of velocity and volume fraction are predicted at the different superficial liquid velocities. Simulations indicate that axial velocities of particles and the bed expansion height are increased with an increase of liquid velocity. The granular temperature as a function of solids concentrations is computed from simulations. Roughly, the granular temperatures increase, reach maximum, and then decrease with the increase of solids volume fraction. The effects of liquid viscosity and temperature on flow behavior of particles are generally scarce using CFD. Present simulations show the temperature is not main effect on flow of particles in an inverse liquid–solid fluidized bed. The bed height and velocity increase with the increase of fluid viscosity which effects on flow behavior of particles in the bed.

Experimental and Theoretical Study of Minimum Fluidization Velocity and Void Fraction of a Limestone Based CO2 Sorbent

Abstract Calcium looping is a promising technology for CO2 capture as it may reduce considerably the energy penalty represented by the capture system. The CO2 capture efficiency will strongly depend on the reactor configuration, solids residence time and thermal operation. As these parameters are also interdependent, the impact on the process can be better understood by process modelling and flow modelling. Use of model results can be very valuable in the design of the process. Properties such as minimum fluidization velocity and void fraction related to limestone particles are important parameters for process simulations as well as for simulations of flow behaviour in the reactor. Limestone (calcite) with a high content of CaCO3 can be a good sorbent material as it is readily available at low cost. Limestone from a local cement plant was used in this study. The material which had been pre-crushed in a mill at the plant was classified into four different size classes: 120-150 μm, 150-180 μm, 180-300 μm and 300-500 μm. A lab-scale fluidized bed made in plexi-glass, with a diameter of 146 mm and a uniform air distribution, was used to determine the properties of the sorbent. Four separate experiments were run for each group of particles. The minimum fluidization velocity and the related void fraction were then determined. Multiphase flow simulations were then carried out, using the computational fluid dynamics (CFD) software BARRACUDA®. The simulation results compared reasonably well with the experimental results.

Numerical Simulation of Flow Behavior within a Venturi Scrubber

The present work details the three-dimensional numerical simulation of single-phase and two-phase flow (air-water) in a venturi scrubber with an inlet and throat diameters of 250 and 122.5 mm, respectively. The dimensions and operating parameters correspond to industrial applications. The mass flow rate conditions were 0.483 kg/s, 0.736 kg/s, 0.861 kg/s, and 0.987 kg/s for the gas only simulation; the mass flow rate for the liquid was 0.013 kg/s and 0.038 kg/s. The gas flow was simulated in five geometries with different converging and diverging angles while the two-phase flow was only simulated for one geometry. The results obtained were validated with experimental data obtained by other researchers. The results show that the pressure drop depends significantly on the gas flow rate and that water flow rate does not have significant effects neither on the pressure drop nor on the fluid maximum velocity within the scrubber.

Simulation and experiment study on adhesive ejection behavior in jetting dispenser

In this paper, fundamental equations for jetting dispenser are presented to express the influence of adhesive pressure, nozzle diameter, and needle movement law, and the equations are then verified by flow behavior simulation. Subsequently, a novel jetting dispenser system is built to finish experiments about the mentioned influence parameters, and simulation results verify the regularities from experiment are correct. Flow velocity in the central nozzle will be faster and radius of the droplet will be bigger if the pressure in the chamber became higher, flow velocity in the central nozzle will be constant and the radius of the droplet will be bigger if the dead time became longer, and bigger nozzle diameter can lead to faster flow velocity in the central nozzle and bigger droplet. Besides, these mentioned works prove that our designed jetting dispenser is practical and useful for adhesive jetting.

Enhancement of flow behavior of polypropylene composite via LMW and HMW flow promoters

This paper discusses how melt flow indices and flow behavior data can be used to predict polymer flow in real industrial processes. The ability to simulate flow behavior can help us establish a robust process that has a large processing window and which accommodates a natural variation. The effect of shear rate on viscosity is of far greater significance. It is therefore important to find the Newtonian region of the curve and set the process parameters in this region for a specified mould thickness. This paper also aims at modifying the flow behavior of polypropylene blends using various lubricants and flow promoters both low molecular weight and polymeric flow promoters.

CFD simulation of gas–solid flow with a cluster structure-dependent drag coefficient model in circulating fluidized beds

To model the effect of clusters on hydrodynamics of gas and particles phases in risers, the interfacial drag coefficient is taken into account in computational fluid dynamic simulations by means of a two-fluid model. The momentum and energy balances that characterize the clusters in the dense phase and dispersed particles in the dilute phase are described by the multi-scale resolution approach. The model of cluster structure-dependent (CSD) drag coefficient is proposed on the basis of the minimization of energy dissipation by heterogeneous drag (MEDHD) in the full range of Reynolds number. The model of CSD drag coefficient is then incorporated into the two-fluid model to simulate flow behavior of gas and particles in a riser. The distributions of volume fraction and velocity of particles are predicted. Simulated results are in agreement with experimental data published in the literature.

Numerical simulation of flow behavior of liquid and particles in liquid–solid risers with multi scale interfacial drag method

Formation of particle clusters in liquid–solid circulating fluidized beds significantly affects macroscopic hydrodynamic behavior of the system. A multi scale interfacial drag coefficient (MSD) is proposed to determine effects of particle clusters on the mesoscale structure, by taking momentum and energy balance of dense phase, dilute phase and interphase into account. Based on the transportation and suspension energy-minimization method, the multi scale interfacial drag coefficient model used in this work is combined with the Euler–Euler two fluid model to simulate the heterogeneous behaviors of liquid–solid circulating fluidized bed. It was found that the reduction in drag coefficient is at least an important factor for the simulation of clusters formation, and the core-annulus flow is observed in the riser. The liquid–solid flow regime was significantly affected by the down-flow of particles in the form of clusters near the walls of the riser. The calculated concentration of particles inside the riser compared reasonably well with the available experimental data obtained by Razzak et al.

Simulation of Gas-Solid Two-Phase Flow Using LES-SOM Model

Flow behavior of gas and particles is predicted by the large eddy simulation of gas-second order moment of solid model (LES-SOM model) in the simulation of flow behavior in CFB. This study shows that the simulated solid volume fractions and velocity along height using a two-dimensional model are in agreement with experiments. The second-order moments of particles are computed.

Simulation of flow behavior of particles in liquid–solid fluidized bed with uniform magnetic field

Abstract Flow behavior of solid phases is simulated by means of DEM–CFD in a liquid–solid fluidized bed with magnetization of preliminarily fluidized bed (LAST) mode along an axial uniform magnetic field. By changing the magnetic field strength, the distribution of particles is studied within the bed. The distributions of velocity and concentration of ferromagnetic particles are analyzed at the different magnetic field intensities. When the magnetic field strength is increased to a value at which the fluidization of strings starts, the particles are found to form straight-chain aggregates along the direction of the magnetic field. At very high magnetic field strengths, the defluidization is observed at which particles are fixed in the bed. Simulations indicate that the granular temperature of particles increases, reaches a maximum, and then decreases with the increase of magnetic-flux density. The moderate strength magnetic field gives a high fluctuation of particles. The predicted solid pressure increases with the increase of concentration of particles.

Resin Flow Behavior Simulation of Grooved Foam Sandwich Composites with the Vacuum Assisted Resin Infusion (VARI) Molding Process

The resin flow behavior in the vacuum assisted resin infusion molding process (VARI) of foam sandwich composites was studied by both visualization flow experiments and computer simulation. Both experimental and simulation results show that: the distribution medium (DM) leads to a shorter molding filling time in grooved foam sandwich composites via the VARI process, and the mold filling time is linearly reduced with the increase of the ratio of DM/Preform. Patterns of the resin sources have a significant influence on the resin filling time. The filling time of center source is shorter than that of edge pattern. Point pattern results in longer filling time than of linear source. Short edge/center patterns need a longer time to fill the mould compared with Long edge/center sources.

Simulation of flow behavior of particles by cluster structure-dependent drag coefficient model for chemical looping combustion process: Air reactor modeling

A computational fluid dynamic (CFD) model for the air reactor of chemical looping combustion (CLC) technology has been developed, with special focus on flow of clusters. To model effects of clusters on flow behavior of gas and particles in a riser of air reactor, the model of cluster structure-dependent (CSD) drag coefficient is proposed on the basis of the minimization of energy dissipation by heterogeneous drag (MEDHD). The momentum balances that characterize the clusters in the dense phase and dispersed particles in the dilute phase are proposed. The CSD drag coefficient model is incorporated into the two-fluid model. The distributions of concentration and velocity of particles are predicted in a riser of air reactor. The Ergun/Wen and Yu drag model underestimates the distribution of concentration of particles in the riser. Dynamic evolution of clusters is reproduced and the profile of concentration and solid fluxes is analyzed. Predictions using the CSD drag coefficient model are in agreement with experimental data published in the literature. The distributions of O2 concentration and temperatures of gas phase and particles are predicted with CuO as oxygen carrier in the AR.