Three-dimensional Flow Analysis Research Articles

Numerical analysis of three-dimensional MHD natural convection flow in a short horizontal cylindrical annulus

A numerical study of three-dimensional (3D) MHD laminar flow in a short horizontal cylindrical annulus has been performed to characterize the impacts of a uniform axial magnetic field on both hydrodynamic and thermal behaviors. This configuration corresponds to a horizontal annular mold containing molten iron or low carbon steel in electromagnetic casting (EMC). Complex nonlinear governing equations are solved numerically by means of the finite volume method based on artificial compressibility algorithm. The induced electric potential caused by the magnetic field is considered. Results show that a typical 3D steady spiral flow arises and the symmetry breaking occurs under a weak magnetic field of Ha < 10. As the Hartmann number increases, the spiral flow is distinctly suppressed, and then it changes to a helical flow with two transverse cells adjacent to each of the end walls. Correspondingly, the flow patterns and isotherms of fluid become symmetric with respect to the mid-axial plane of the annulus. Further increasing the Hartmann number, the fluid particle trajectories essentially lie in the cross-section of the annulus, as for two-dimensional solutions, with an extremely small axial dependency. In addition, both the values of local Nusselt number at the isothermal walls and its axial dependency, mainly in the upper region (−38π≤φ≤38π), are significantly affected by the magnetic field. The results of the present work can be useful in producing high-quality products by magnetic control.

Analysis of Three-Dimensional Dam Break Flow Using CFD

Analysis of Three-Dimensional Dam Break Flow Using CFD

A numerical study on hemodynamics in the left coronary bifurcation with normal and hypertension conditions.

In this study, a three-dimensional analysis of the non-Newtonian blood flow was carried out in the left coronary bifurcation. The Casson model and hyperelastic and rigid models were used as the constitutive equation for blood flow and vessel wall model, respectively. Physiological conditions were considered first normal and then compliant with hypertension disease with the aim of evaluating hemodynamic parameters and a better understanding of the onset and progression of atherosclerosis plaques in the coronary artery bifurcation. Two-way fluid-structure interaction method applying a fully implicit second-order backward Euler differencing scheme has been used which is performed in the commercial code ANSYS and ANSYS CFX (version 15.0). When artery deformations and blood pressure are associated, arbitrary Lagrangian-Eulerian formulation is employed to calculate the artery domain response using the temporal blood response. As a result of bifurcation, noticeable velocity reduction and backflow formation decrease shear stress and made it oscillatory at the starting point of the LCx branch which caused the shear stress to be less than 1 and 2Pa in the LCx and the LAD branches, respectively. Oscillatory shear index (OSI) as a hemodynamic parameter represents the increase in residence time and oscillatory wall shear stress. Because of using the ideal 3D geometry and realistic physiological conditions, the values obtained for shear stress are more accurate than the previous studies. Comparing the results of this study with previous clinical investigations shows that the regions with low wall shear stress less than 1.20Pa and with high OSI value more than 0.3 are in more potential risk to the atherosclerosis plaque development, especially in the posterior after the bifurcation.

Three-dimensional transient simulation of water filling and draining of gravity flow based on Lattice Boltzmann Method

The traditional one-dimensional method of characteristics is available to analyze the transient flow of system level in full pipe flow. As for water filling of empty pipeline and water draining of water-filled pipeline, it is difficult to analyze with this method as the boundary conditions are changing along with the location and time. Meshless Lattice Boltzmann Method was used in this investigation to simulate these two circumstances in the gravity flow water-delivery system respectively. We visually obtained, by this method, the changing process of liquid level, total time of the filling and draining process, flow state around the butterfly valves in the pipe inlet and outlet respectively. Meanwhile, time history data of water flow rate and submersed fraction on the cross section behind the valves were extracted as well. CFD method used in analysis of three-dimensional pipeline flow in system level is an innovation of this research that it not only makes the result more accurate, but also details and visualizes the local transient flow state in pipeline system of gravity flow.

Performance of Efficiency Indexes for Contact Tanks

Hydraulic and mixing efficiencies of contact tanks are evaluated using several indexes that are used in the literature. These indexes emphasize different aspects of flow and mixing processes in the mixing tank at different scales. Uniformity of the evaluations obtained from these indexes is necessary for unified characterization of the overall performance of contact tanks, which is very difficult to achieve. In this study, several contact tanks with different baffling configurations were studied using computational fluid dynamics (CFD) analysis in which three-dimensional hydrodynamic analysis of flow and transport of a conservative tracer within the flow field were studied. The performance data developed were extended by including the outcome of some of the earlier studies that are reported in the literature. The most common indexes that are used in the literature were used to evaluate the performance of these cases. The results indicate that the performance evaluation obtained for these cases was not consistent for all indexes. An analysis was performed to identify the suitability of the performance indexes for a specific performance parameter. Performance of the newly introduced AD index, which yields more consistent evaluations for both short-circuiting and dispersion evaluation in the contact tank, was compared with the performance of the Morrill index. A dimensionless energy-efficiency index was also proposed for the evaluation of the efficiency of the flow-through system in the tank.

Investigation for squeezing flow of ethylene glycol (C2H6O2) carbon nanotubes (CNTs) in rotating stretching channel with nonlinear thermal radiation

In this paper, an analysis of three-dimensional squeezing flow of carbon nanotubes (CNTs) based nanofluids in a rotating channel with a permeable fixed bottom wall by taking into account the effect of thermal radiation has been presented. The partial differential equations (PDEs) governing the problem were converted to ODEs and then solved using numerical method. The effects of changes in the values of various parameters on linear and angular velocity, temperature, skin friction coefficient, and local Nusselt number profiles have been investigated and for various nanofluids composed of SWCNT and MWCNT as nanoparticles and ethylene glycol as the base fluid. The most important results obtained from these figures are the oscillating behavior of the horizontal linear velocity profile due to the changes in the rotation parameter, the reverse flow in the central areas of the channel, the reduction of the temperature profile caused by increasing the radiation parameter, the direct relationship between the Eckert number and the heat transfer rate in the upper channel wall, and their reverse relationship in the lower wall of the channel.

Spatial-temporal patterns of three-dimensional subsonic turbulent cavity flow

Three-dimensional, high Reynolds number cavity flow is investigated. The cavity was exposed to a free-stream Mach number of 0.40 and a Reynolds number (based on cavity depth) of 1.6 × 106, with a thick incoming turbulent boundary-layer. Dominant modes and structures were studied by conducting unsteady numerical flow simulations (CFD), and applying Proper-Orthogonal-Decomposition (POD) in both two and three-dimensions. Fully three-dimensional POD analysis of cavity flow has been rarely conducted in other studies, and it is demonstrated that two-dimensional POD analysis is valid in order to emphasize patterns which are limited in space, but could be misleading without the comparison with the three-dimensional POD analysis. The analysis sheds new light on three-dimensional cavity flow by disclosing novel non-intuitive dominant structures and modes. Stretched streamwise vortices were found to be dominant, at least as the spanwise structures that originate from the classical two-dimensional shear-layer instability. Furthermore, the effect of symmetry plane assumption, which is usually disregarded, was studied rigorously for the first time. POD decomposition of symmetric and anti-symmetric flow modes revealed that anti-symmetric modes contain a significant portion of the total energy; however, they only interact weakly with the symmetric modes.

Numerical Solution and Analysis of Three-Dimensional Transient Darcy Flow

This paper presents a detailed analysis of a numerical solution of three-dimensional transient Darcy flow. The numerical solution of the governing parabolic partial differential equations is obtained by using stabilized mixed Galerkin method and backward Euler method for the discretization of space and time, respectively. The resulting well-posed system of algebraic equations is subsequently solved using conjugate gradient method. The proposed model is validated against Mongan’s analytical model for underground water flow using a set of hexahedral and tetrahedral meshes. The model is used to analyze the transient behavior by simulating the Darcy flow through homogeneous and heterogeneous as well as isotropic and anisotropic media. For large meshes, a parallel algorithm of the transient Darcy flow is also developed for shared memory architecture using OpenMP library. For structured meshes, a speedup of over 22 is obtained on dual AMD Opteron processors. The proposed numerical method for transient Darcy flow offers stability, ease of implementation in higher dimensions and parallel solution for large and complex geometry using standard finite element spaces.

Three-dimensional Analysis of Air Flow in a Flat Plate Solar Collector

This paper presents the study of fluid flow and heat transfer in solar flat plate collector by using Computational Fluid Dynamics (CFD) which reduces time and cost. In the present paper the computational fluid dynamics (CFD) tool has been used to simulate the solar collector for better understanding the heat transfer capability. 3D model of the collector involving air inlet, the collector is modeled by ANSYS Workbench and the grid was created in ANSYS ICEM. The results were obtained by using ANSYS FLUENT and ANSYS CFX. The objective of this work is to compare theoretically and experimentally work done with the work done by using computational fluid dynamics (CFD) tool with respect to flow and temperature distribution inside the solar collector. The outlet temperature of air is compared with experimental results and there is a good agreement in between them.

An analysis of dynamic stability for a flexible rotor filled with liquid

The investigation of dynamic stability for a flexible rotor completely filled with liquid is carried out. The perturbation differential equations of infinitesimal fluid are established on the basis of three-dimensional flow analysis in the rotor cavity. The analytical expression of the hydrodynamic force exerted on the rotor inner wall is obtained by using the Fourier series expansion. Assuming that both ends of the rotor are simply supported and the fluid motion is axially symmetric, the nondimensional whirling frequency equation of the system is derived. According to the obtained frequency equation, the system stability is analyzed and the results are compared with a rigid rotor system. Moreover, the effects of the mass ratio and system parameter on the stability of a flexible liquid-filled rotor system are discussed.

A Study on Three-Dimensional Flow Analysis and Noise Source of Sirocco Fan

A Study on Three-Dimensional Flow Analysis and Noise Source of Sirocco Fan

Three-dimensional numerical analysis of magnetohydrodynamic flow bounded by conducting walls under alternating-current magnetic fields

Three-dimensional numerical analysis of magnetohydrodynamic flow bounded by conducting walls under alternating-current magnetic fields

Three-dimensional and two-phase nanofluid flow and heat transfer analysis over a stretching infinite solar plate

In this work, 3-D and two-phase nanofluid flow and heat transfer is modeled over a stretching infinite solar plate. The governing equations are presented based on previous studies. The infinite boundary condition and shortcoming of traditional analytical collocation method have been overcome in our study by changing the problem into a finite boundary problem with a new analytical method called optimal collocation method. The accuracy of results is examined by fourth order Runge-Kutta numerical method. Effect of some parameters, Prandtl number, Schmidt number, Brownian motion parameter, thermophoresis parameter, ?=b/a (ratio of the stretching rate along y- to x-directions), and power-law index on the velocities, temperature, and nanoparticles concentration functions are discussed. As an important outcome of our 3-D model analysis, it is found that increase in thermophoretic forces can enhance the thickness of both thermal and nanoparticle volume fraction boundary-layers.

Computational Analysis of Liquid Jet Impingement Micro-channel Cooling

This study evaluated a micro-jet impingement heat sink for the cooling of electronic field at micro level devices. In the present study, a three-dimensional fluid flow and heat transfer analysis was carried out numerically for different fluids and various heat sink materials. Six different materials as copper, aluminum, steel, silicon, titanium and nickel were analyzed to be used as substrate of the micro-channel heat sink. Water, DIUF water (De-Ionized Ultra-Filtered), Performance fluid-5052, and HF-7100 were used as working fluids. For the micro channel heat sink investigated and obtained that the temperature distribution along the flow direction in the solid and fluid regions have linear behavior. Heat transfer coefficient and temperature distribution was obtained for various cases and the results have been interpreted. It was observed that copper based material has the highest value of heat transfer coefficient as compared to remaining five materials analyzed. Copper and working fluid DIUF water together have the highest heat transfer coefficient

Analysis of Heat and Smoke Flow according to Platform Screen Door and Fan Conditions on Fire in Underground Platform

In this study, a three‐dimensional flow analysis of underground subway station was conducted by applying ventilation mode in operation and platform screen door (PSD) opening and closing conditions on fire in underground platform. In order to analyze optimal smoke control and heat removal conditions, the whole underground subway station was set as a model, and a total of eight cases were analyzed by changing the operating conditions of fans for each area under the opening and closing conditions of the PSDs. The analysis results confirmed that the operation mode of supply fan in platform E and I areas located at the third floor underground is more effective than that of exhaust fan in the event of a fire in underground subway station when the PSD is closed. The amount of CO entering a waiting room increased, and the overall CO distribution in the underground subway station was also increased when the PSD is opened. In addition, the CO distributions due to the opening and closing of the PSD were similar to one another when a fire occurred on the platform, which suggests that the operating conditions of the fan affects the formation of CO distribution in the underground subway station rather than the discharge of CO.

최소자승법과 Level-set 방법을 적용한 3차원 슬로싱 유동의 수치해석

최소자승법과 Level-set 방법을 적용한 3차원 슬로싱 유동의 수치해석

Aerodynamic design and numerical study for centrifugal turbine with different shapes of volutes

Centrifugal turbine presents good aerodynamic and geometric compatibility. The straight blade can be directly used without significant effect on three dimensional flow field, and therefore the optimum values of the speed ratio and reaction degree can keep constant along the spanwise direction with higher turbine efficiency and simpler manufacturing. Furthermore, the closed impeller which is made by fixing the blade tip using cover band shows larger impeller strength and is suitable for high-speed rotation. In recent years, the centrifugal turbine with many potential advantages is gradually becoming a research hotspot in the field of turbine. In this paper, three kinds of volutes with different cross section shapes were designed for a single-stage centrifugal turbine unit. Based on the CFD simulation in the whole flow passage, the analysis of three-dimensional steady flow for the designed centrifugal turbine was carried out under both of design and off-design conditions, and the following results were obtained: the aerodynamic performance of centrifugal turbines with three kinds of volutes are almost the same under both of design and off-design conditions. Besides, the pear shaped volute shows slightly higher total efficiency, and its overall efficiency, stage internal efficiency and power are 87.36%, 85.79% and 484.88 kW, respectively.

Combined effects of nanofluid and transverse twisted-baffles on the flow structures, heat transfer and irreversibilities inside a square duct – A numerical study

This paper presents a three-dimensional, numerical thermo-hydrodynamic and second low analysis of nanofluid flow inside a square duct equipped with transverse twisted-baffles. A finite volume method is employed to simulate forced convection of heat in the system with the inclusion of Brownian motion of the nanoparticles. The ultimate aim is to gain further understanding of the underlying physical processes and also to determine the optimal design and working conditions of the system. The effects of variations in the pitch intensity (γ) from 180° to 540° and volume fraction of nanoparticles (φ) from 0 to 0.05 on the nanofluid flow, heat convection and thermodynamic irreversibilities are investigated. The numerical results show that the baffle with γ = 360° features the maximum value of heat transfer coefficient among all values of γ. Additionally, the baffle with γ = 540° shows the minimum pressure drop for the entire range of γ. Finally, it is shown that the thermal entropy generation decreases by increasing the volume fraction of nanoparticles or inserting baffles inside the duct.

Numerical approach to siphon break phenomena in a research reactor pool using the CUPID code

Pool-type reactors, as research reactors, are equipped with a siphon break line to prevent continuous siphonage flow that can cause core uncovery during a loss of coolant accident (LOCA). In this study, the siphonage flow rate and siphon break phenomena during a LOCA in a pool-type research reactor are assessed using the three-dimensional two-phase transient flow analysis code, CUPID. The calculation indicates that the siphonage LOCA break flow rate relies on the wall friction model for the main drainage pipe, and the initiation of a siphon break is significantly affected by the interfacial drag model. The CUPID simulation of the siphon break confirms that the siphonage LOCA break flow rate and the initiation of siphon break phenomena are accurately predicted using the three-dimensional two-phase flow analysis code with the relevant physical models for wall friction and interfacial drag.

Simulation and Analysis of Three-Dimensional Electromagnetism, Heat Transfer, and Gas Flow for Flow-Levitation System

Magnetic levitation systems are influenced by an intense demand to gain greater feature sizes of metal nanoparticles and to increase the production efficiency for the flow-levitation (FL) method. This paper presents a systematic stability and temperature analysis of the process during the induction heating based on ANSYS. The comprehensive model was a liquid aluminum droplet levitated electromagnetically in an axisymmetric magnetic field induced by different sets of coaxial circular coils. First, we developed an optimized coil with a double helix structure to compare the force applied to the sample, electric field distribution, and temperature distribution in the eddy current field with an initial coil structure. The optimized coil has a more stable and efficient induction heating process for the FL method. We also utilized the optimized coil geometry to predict the maximum parameters of the electromagnetic induction system used to fabricate Al nanoparticles. The results from this approach shows that the turns = 2 + 3, D = 24 mm, I = ∼350 A, d = 1∼2 mm, with an equilibrium coefficient k of 0.30, are the maximum and optimal settings in the frequency of 400 kHz induction heating process.