Simulation Of Three-dimensional Flow Research Articles

Analytical Solution of Saltwater Intrusion in Costal Aquifers Considering Climate Changes and Different Boundary Conditions

Groundwater contamination due to saltwater intrusion (SWI) has an extreme effect on freshwater quality. Analytical and numerical models could be used to investigate SWI. This study aims to develop an analytical solution to investigate SWI into coastal aquifers which was applied to a real case study at the Middle Nile Delta aquifer (MNDA). The study presented a new formula to predict the difference in depth of freshwater to seawater interface due to a change in boundary conditions. A Computer Program for Simulation of Three-Dimensional Variable-Density Ground-Water Flow and Transport (SEAWAT) is used for groundwater flow simulation and SWI and the results compared with the developed analytical solution. Four scenarios are considered in the study, including; the sea-level rise (SLR), reduction in recharge, over abstraction, and combination after 50 years (2070). The analytical solution gave good results compared to the numerical one where Equiline 1 intruded to 103 and 101.66 km respectively at the base case. The results also gave a good agreement between numerical and the analytical solution for SLR due to climate changes by 52.80 cm where the Equiline 1 reached to 105 and 103.45 km. However, the reduction in aquifer recharge by 18.50% resulted in an intrusion for the Equiline-1 to 111 and 108.25 km from the shoreline. Over pumping due to the increase in population by 89% has increased the SWI to reach 121,110.31 km, while it reached 131 and 111.32 km at a combination of the three scenarios, which represents the highest threatening scenario. Also, the difference between the two solutions reached 1.30%, 1.48%, 2.48%, 8.84%, and 15.02%, respectively for the base case and four scenarios. For the current case study, the analytical model gave good results compared to the numerical one, so that the analytical solution is recommended for similar studies, which could save the time and capabilities of computer required for the numerical solutions.

Effects of Mesh Generation on Modelling Aluminium Anode Baking Furnaces

Anode baking is critical in carbon anode production for aluminium extraction. Operational and geometrical parameters have a direct impact on the performance of anode baking furnaces (ABF), and hence on the resulting anode quality. Gas flow patterns, velocity field, pressure drop, shear stress and turbulent dissipation rate are the main operational parameters to be optimised, considering a specific geometry that is discretised as a mesh. Therefore, this paper aims to establish the need to generate an appropriate mesh to perform accurate numerical simulations of three-dimensional turbulent flow in a single section of an ABF. Two geometries are considered for generating three meshes, using COMSOL and cfMesh, with different refinement zones. The three meshes are used for creating nine incompressible isothermal turbulent flow models, with varying operational parameters. Velocity field, convergence and turbulent viscosity ratio in the outlet of fuel inlet pipes are the quantification criteria. Quantification criteria have shown that a better physical representation is obtained by refining in the whole combustion zone. COMSOL Multiphysics’ built-in mesh generator allows quadrilateral, tetrahedron and hexahedron shapes. Adaptive cell sizes and shapes have a place within modelling, since refining a mesh in appropriate zones brings the Peclet number down when the incompressible isothermal turbulent flow is simulated.

Seismic-derived geomechanical properties of potential CO2 storage reservoir and cap rock in Smeaheia area, northern North Sea

Geologic CO2 storage site selection requires reservoir, seal, and overburden investigation to prevent injection- and storage-related risks. Three-dimensional geomechanical modeling and flow simulation are crucial to evaluate these mechanical-failure-related consequences; however, the model input parameters are limited and challenging to estimate. This study focuses on geomechanical properties extracted from seismic-derived elastic property cubes. The studied reservoirs (Middle Jurassic Sognefjord, Fensfjord, and Krossfjord formation sandstones) and cap rocks (Heather and Draupne formation shales) are located in the Smeaheia area, northern North Sea, and are evaluated for a potential CO2 storage site. From the elastic property cubes, i.e., acoustic impedance, P- to S-wave velocity ratio, and bulk density, we obtained geomechanical property cubes of Young's modulus, Poisson's ratio, shear modulus, lambda-rho, and mu-rho. Petrophysical property cubes such as porosity and shale volume were also available and were extracted from the elastic property cubes using deterministic methods. We evaluated the geomechanical properties to observe their relationship with depth, compaction/cementation, and petrophysical properties to characterize the cap and reservoir rocks. We found good coherence between the geomechanical and petrophysical properties and their relationship with compaction as a function of depth. The brittleness analyses using elastic property crossplots reveal that both the cap and reservoir rocks are mainly ductile to less ductile, posing lower fracturing risk during CO2 injection. This also indicates lower risks of associated microseismic and possible CO2 leakage.

Experimental and numerical investigation of three-dimensional open channel with simulated partial ice-covers

This paper presents both experimental measurements and three-dimensional (3D) numerical simulations of turbulent flow in open channels with simulated partial ice-covers. The experiments were conducted with a particle image velocimetry system while the simulations were performed with five eddy-viscosity and second-moment closure turbulence models. Four coverage ratios based on the channel width were examined in each case: a reference fully open channel and 25%, 50% and 75% partially covered channels. The results showed that the influence of the partial ice-covers and secondary currents near the sidewall dramatically altered the distributions of the mean velocity, Reynolds stresses and turbulence production across the channel. Based on the 3D simulations, it was shown that the modifications to the turbulence quantities were largely influenced by strong counter-rotating secondary circulations in the core of the partially covered channels and eight smaller secondary cells at the corners. The core secondary circulations interact with adjacent corner cells to form a dynamic link between the open water and ice-covered sections of the channel.

Unsteady Hemodynamics in Intracranial Aneurysms With Varying Dome Orientations

Abstract Fluid loading within an intracranial aneurysm is difficult to measure but can be related to the shape of the flow passage. The outcome of excessive loading is a fatal hemorrhage, making it necessary for early diagnosis. However, arterial diseases are asymptomatic and clinical assessment is a challenge. A realistic approach to examining the severity of wall loading is from the morphology of the aneurysm itself. Accordingly, this study compares pulsatile flow (Reynolds number Re = 426, Womersley number Wo = 4.7) in three different intracranial aneurysm geometries. Specifically, the spatio-temporal movement of vortices is followed in high aspect ratio aneurysm models whose domes are inclined along with angles of 0, 45, and 90 deg relative to the plane of the parent artery. The study is based on finite volume simulation of unsteady three-dimensional flow while a limited set of particle image velocimetry experiments have been carried out. Within a pulsatile cycle, an increase in inclination (0–90 deg) is seen to shift the point of impingement from the distal end toward the aneurysmal apex. This change in flow pattern strengthens helicity, drifts vortex cores, enhances spatial displacement of the vortex, and generates skewed Dean's vortices on transverse planes. Patches of wall shear stress and wall pressure shift spatially from the distal end in models of low inclination (0–45 deg) and circumscribe the aneurysmal wall for an inclination angle of 90 deg. Accordingly, it is concluded that high angles of inclination increase rupture risks while lower inclinations are comparatively safe.

Shape optimisation of wavy mini-channel heat sink

In this study, the optimum shape for a water-cooled mini-channel heat sink was proposed by incorporating three-dimensional simulations of fluid flow and a multi-objective optimisation algorithm. The configuration of a mini-channel along its length was specified by thirteen coordinate points and the multi-objective genetic algorithm (MOGA) was used to find the optimal solution. The optimum point had the least overall heat transfer resistance as well as pumping power. Later, the optimum choice among the non-inferior points was proposed using linear programming techniques for multidimensional analysis of preference (LINMAP). It was shown that the LINMAP solution reduced thermal resistance to 87% of a straight channel by only a 10% increase in pumping power. The result was also compared with a fully wavy channel. It was shown that although the thermal resistance value in a fully wavy channel was better, it required a really high pumping power to access such thermal resistance.

Adaptation and validation of the ParSWMS numerical code for simulation of water flow and solute transport in soilless greenhouse substrates

Numerical simulation of three-dimensional water flow and solute transport in containerized variably saturated soilless substrates with complex hydraulic properties and boundary conditions necessitates high-resolution discretization of the spatial and temporal domains, which commonly leads to several million nodes requiring numerical evaluation. Even today’s computing prowess of workstations is not adequate to tackle such problems within a reasonable timeframe, especially when numerous realizations are required to optimize the geometry, substrate properties, and irrigation and fertigation management of soilless plant growth modules. Hence, the parallelization of the numerical code and utilization of high performance computing (HPC) are essential. Here, we adapted and applied the ParSWMS parallelized code that is amenable to solving the 3D Richards equation for water flow and the convection-dispersion equation for solute transport subject to linear solute adsorption. The code was modified to allow for nonlinear equilibrium solute adsorption with new boundary conditions and applied to simulate water flow and nitrogen and phosphorus transport in containerized soilless substrates. Multi-solute transport simulations with the modified Linux ParSWMS code were first performed on a workstation and referenced to the Windows-based HYDRUS (2D/3D) numerical code. After confirming the agreement between the modified ParSWMS code and HYDRUS (2D/3D), various preconditioners and iterative solvers were evaluated to find the computationally most efficient combinations. The performance of the modified ParSWMS code and its stability were compared to HYDRUS (2D/3D) simulations for three soilless substrates consisting of horticultural perlite, volcanic tuff, and a volcanic tuff/coconut coir mixture. Considering the solute mass balance error as a stability measure, ParSWMS outperformed HYDRUS (2D/3D). Moreover, simulations with the modified ParSWMS code were about 22% faster than simulations with HYDRUS (2D/3D) on the workstation. Tests of the modified ParSWMS on two HPC clusters with 28 and 94 cores revealed a potential computational speedup of 94% relative to the HYDRUS (2D/3D) simulations performed on the workstation.

Cascaded lattice Boltzmann modeling and simulations of three-dimensional non-Newtonian fluid flows

Non-Newtonian fluid flows, especially in three dimensions (3D), arise in numerous settings of interest to physics. Prior studies using the lattice Boltzmann method (LBM) of such flows have so far been limited mainly to two dimensions and used less robust collision models. In this paper, we develop a new 3D cascaded LBM based on central moments and multiple relaxation times (MRT) on a three-dimensional, nineteen velocity (D3Q19) lattice for simulation of generalized Newtonian (power law) fluid flows. The relaxation times of the second order moments are varied locally based on the local shear rate and parameterized by the consistency coefficient and the power law index of the nonlinear constitutive relation of the power law fluid. Numerical validation study of the 3D cascaded LBM for various benchmark problems, including the complex 3D non-Newtonian flow in a cubic cavity at different Reynolds numbers and power law index magnitudes encompassing shear thinning and shear thickening fluids, are presented. Furthermore, in order to demonstrate the advantages of the proposed 3D cascaded LBM based on central moments, numerical stability comparisons against the LBMs based on a single relaxation time model and a MRT model using raw moments are made. Numerical results demonstrate the accuracy, second order grid convergence and significant improvements in numerical stability of the 3D cascaded LBM for simulation of 3D non-Newtonian flows of power law fluids.

Numerical investigation of interference effects on the critical wind velocity of tall buildings

The main aim of this study is to evaluate the upstream and downstream interference effect of two CAARC (Commonwealth Advisory Aeronautical Research Council) standard tall buildings using Computational Fluid Dynamics (CFD). To that end, the Large Eddy Simulation (LES) turbulence model is employed for the three-dimensional simulations of turbulent wind flow with Reynolds numbers of 1.4×104<Re<8×104. The aerodynamic response of the principal building in different interference cases is investigated using mean and fluctuating coefficients of lift and drag forces, pressure distribution and Strouhal number. To better understand the involved physics, streamlines and vorticity contours are presented and their relationship with the aerodynamic results is interpreted. In addition, an isolated CAARC standard tall building is considered for comparison with interference cases and to validate our results compared to previous experimental and numerical studies. In contrast with the isolated case, in most of the interference cases, the shielding effect of the interfering building results in a lower mean drag coefficient of the principal building. Also, compared to the isolated building and, depending on the location of the interfering building, the fluctuating lift coefficient either increases or decreases. While the mean pressure coefficient at the windward surface is not significantly sensitive to the interference states, it is strongly influenced by the different states of the interference at the lateral and leeward surfaces. Also, the principal building’s Strouhal numbers for different interference states and different Reynolds numbers are calculated using spectral analysis of lift signals. It is then shown that Strouhal numbers are highly dependent on the location of the interfering building and are inversely related to the width of the wake region. Our results, furthermore, demonstrate that the aerodynamic parameters have little sensitivity to Reynolds number variations in the considered range. Finally, the critical wind velocity corresponding to the aeroelastic instabilities is estimated based on Strouhal numbers and it is shown that upstream interference cases, will increase the critical velocity of the wind, thereby reducing the likelihood of occurrence of aeroelastic instabilities.

Modeling Air Aspiration in Steel Continuous Casting Slide-Gate Nozzles

Air aspiration is an important cause of nozzle clogging and inclusions in final products of continuous casting of steel due to the presence of metal oxides (such as alumina) which occur through the reoxidation of molten steel. This problem is most likely to occur when the flow control system (slide-gate or stopper rod) causes the pressure inside the nozzle to drop below atmospheric pressure, drawing gas into the system through possible cracks or gaps in the refractory walls. In this work, a 1-D pressure-energy model of the complete metal delivery system from the tundish to the mold is developed to predict the pressure distribution and throughput under dynamic operating conditions and varying clogging conditions. The energy balance approach includes pressure losses in the slide-gate, wall friction, and nozzle geometry variations, including the effects of multiphase flow due to argon gas injection. The model also predicts air aspiration, oxide inclusion formation, and the time for clogging shutdown. The predicted pressure distribution is verified with a three-dimensional numerical simulation of multiphase turbulent flow, and is validated with plant measurements. Parametric studies with different submerged entry nozzle (SEN) designs revealed that a smaller SEN diameter may lessen negative pressure by redistributing the pressure loss from the slide-gate to the entire nozzle through increased friction losses. Under negative pressure, a submillimeter-thin gap was shown to cause considerable air aspiration. Clogging shutdown times were evaluated for several scenarios under static and dynamic operating conditions.

Numerical Investigation of Single-Strand Slab Casting Tundish Flow with Heat Transfer and Inclusion Transport

In continuous casting process, cleanliness of steel can be improved and maintained by promoting the inclusion separation inside the tundish by various means; tundish flow optimization using arrangement of flow control devices inside the tundish is one among them. Three-dimensional computational fluid dynamics simulation of tundish flow is an efficient way to investigate the arrangement of flow control devices. In the present work, three-dimensional isothermal steady-state flow simulations, residence time distribution analysis and inclusion transport simulations of tundish flow are conducted. All the simulation results are validated with experimental measurements reported in literature. Subsequently, the simulations are extended for a non-isothermal flow of the existing tundish in the plant and an additional flow control device, namely a weir with appropriate dimensions is proposed which indicated better steel flow in the tundish with more inclusion separation efficiency as compared to the existing bare tundish.

Non-Newtonian pulsatile flow through an artery with two stenosis

The purpose of this work is to simulate and analyse the movement of blood passing from stenosis of an artery of a person with atherosclerosis artery disease. We used three-dimensional modelling and simulation of blood flow through two arteries consisting of two stenosis each, one with the same radius for both the cases and the other with different radii for each case. The type of blood flow was considered to be simple pulsatile in order to mimic the rhythmic pulses of the human heart. The carreau yasuda model was used for the hemodynamic modeling viscosity of fluid and sst (shear-stress-transport) was used as the numerical model. This study considered blood flow models which is non-newtonian and solved the 3D laminar and unsteady NS Equations to extracted velocity profiles at 6 different locations in a blood vessel and shear strain rate for both cases.

Lattice Boltzmann simulation of liquid falling on horizontal rectangular pillar arrays

Stator coils of automobiles in operation generate heat and are cooled by a coolant poured from above. Since the behavior characteristic of the coolant poured on the coils is not clarified yet due to its complexity, the three-dimensional two-phase flow simulation is conducted. In this study, as a steppingstone to the simulation of the liquid falling on the actual coils, the coils are modelled with horizontal rectangular pillar arrays whose governing parameters can be easily changed. The two-phase flows are simulated using the lattice Boltzmann method and the phase-field model, and the effects of the governing parameters, such as the physical properties of the cooling liquid, the wettability, and the gap between the pillars, on the wetting area are investigated. The results show that the oil tends to spread across the pillars because of its high viscosity. Moreover, the liquid spreads quickly when the contact angle is small. In the case that the pillars are stacked, the wetting area of the inner pillars is larger than that of the exposed pillars.

Numerical simulation of three-dimensional flow and heat transfer characteristics of liquid lead–bismuth

Liquid lead-bismuth cooled fast reactor is one of the most promising reactor types among the fourth-generation nuclear energy systems. The flow and heat transfer characteristics of lead-bismuth eutectic (LBE) are completely different from ordinary fluids due to its special thermal properties, causing that the traditional Reynolds analogy is no longer recommended and appropriate. More accurate turbulence flow and heat transfer model for the liquid metal lead-bismuth should be developed and applied in CFD simulation.In this paper, a specific CFD solver for simulating the flow and heat transfer of liquid lead-bismuth based on the k - ε - kθ- εθ model was developed based on the open source platform OpenFOAM. Then the advantage of proposed model was demonstrated and validated against a set of experimental data. Finally, the simulation of LBE turbulent flow and heat transfer in a 7-pin wire-wrapped rod bundle with the k - ε - kθ- εθ model was carried out. The influence of wire on the flow and heat transfer characteristics and the three-dimensional distribution of key thermal hydraulic parameters such as temperature, cross-flow velocity and Nusselt number were studied and presented.Compared with the traditional SED model with a constant Prt = 1.5 or 2.0, the k - ε - kθ- εθ model is more accurate on predicting the turbulence flow and heat transfer of liquid lead-bismuth. The average relative error of the k - ε - kθ - εθ model is reduced by 11.1% at most under the simulation conditions in this paper. This work is meaningful for the thermal hydraulic analysis and structure design of fuel assembly in the liquid lead-bismuth cooled fast reactor.

Three-dimensional flip-flopping flow around a pair of dual-stepped circular cylinders in a side-by-side arrangement

Three-dimensional direct numerical simulations of flow around a pair of dual-stepped circular cylinders in a side-by-side arrangement and a proximity interference region are presented. The dual-stepped cylinders consist of two coaxial cylinders with a larger-to-smaller diameter ratio of 2. The Reynolds number and the side-by-side gap ratio, based on the larger (smaller) diameter, are 200 (100) and 1 (3), respectively. Two flip-flopping flow regimes A and B are observed behind the dual-stepped cylinders, exhibiting temporal variations of hydrodynamic drag and lift force coefficients. The flow regime B is featured by the flip-flopping, higher vortex-shedding frequencies and greater flow instability than those in the flow regime A. Half-loop and direct connections of vortices take place frequently in the narrower wake, while the vortex reconnection and multiple connection predominate the wider wake. This suggests that the dual-stepped cylinder with the narrower wake behaves similarly to a single dual-stepped cylinder. The dynamic mode decomposition analysis reveals pitchfork and Hopf bifurcation (in-phase and anti-phase synchronization) modes in the larger cylinder wake, with the interaction of these bifurcations originating from the flip-flopping flow pattern. However, the pitchfork mode is not found in the smaller cylinder wake, suggesting that its flip-flopping flow behavior is not self-originated but triggered by the flip-flopping flow mechanism of the larger cylinder.

Investigation of the effect of the finned coiled wire insert on the heat transfer intensification of circular tube: Energy and exergy analysis

In the current investigation, CFD (computational fluid dynamics) code is applied for the three-dimensional simulation of fluid flow and turbulent transferred thermal energy through circular duct with coiled finned wire inserts. The realizable K-ε model will be used for the obtaining the influence of the turbulence. The validation of the model is performed by comparing the numerical Nusselt number with the experimental one. The impact of the various operating parameters i.e. Prandtl and Reynolds numbers and geometric variables i.e. fin height and thickness, coil pitch and wire diameter on the dimensionless exergy loss, thermal efficiency and the dimensionless working power will be obtained. Furthermore, correlations will be suggested to estimate these objective variables as functions of the geometric and operating variables. A new multi-objective optimization way is introduced and applied to obtain the optimal and critical values or range of the input variables in the studied range. Results also show if the Reynolds number increases by 100 % in the study range, the thermal efficiency, the dimensionless exergy loss and dimensional working power reduces by 15.9 %, 9.4 % and 5.9 %, respectively. Furthermore, with doubling pitch, they reduce 17.2 %, 14.9 % and 48.9 %, respectively.

Numerical modelling of a gas-dust sphere scattering by SPH-IDIC method

The paper is devoted to the first application of the SPH-IDIC method to simulation of three-dimensional dusty gas flow. The expansion of a sphere consisting of gas and monodisperse fine dust into vacuum is considered as a model problem. Computing was carried out using graphic accelerators based on nVidia CUDA technology. The numerical simulations show ability of the method to deal with three-dimensional dynamics. We found that in 3D case the method kept all the advantages previously demonstrated on one-dimensional problems: robustness, efficiency and simplicity in implementation.

Three-dimensional simulations of accretion flow in the progenitor of Tycho’s supernova

ABSTRACT We run 3D numerical simulations for the accretion flow around the white dwarf (WD) in the progenitor system of Tycho’s supernova (SN). The mass of the WD, mass of the companion star, and the orbital period are set to be 1M⊙, 1.6M⊙, and 0.794 d, respectively, based on theoretical and observational researches of Tycho’s SN remnant (SNR). We find that when the magnetic field in the accreted material is negligible, outflowing wind is concentrated near the equatorial plane. When the magnetic field has energy equipartition with internal energy, polar wind is comparable with the equatorial wind. A carefully chosen magnetic field between the above two cases ($B=5.44\times 10^3 \rm {G}$) can roughly reproduce the latitude-dependent wind required to form the peculiar periphery of Tycho’s SNR. Including a reasonable amount of viscosity in the calculation does not change our conclusion.

On three-dimensional boundary layer stability analysis on curved aerodynamic surfaces

Numerical simulation of three-dimensional flow past a prolate spheroid located at an angle of attack of 10° accompanied by the laminar-turbulent transition was performed for subsonic (M∞ = 0.136) and transonic (M∞ = 0.75) velocities. The general-purpose gas-dynamic package ANSYS Fluent in integration with a laminar-turbulent transition module based on software bundle LOTRAN 3 was used. The principles of numerical simulation of the main flow are discussed: requirements for the near-wall region allocation and independence of the results from various methods of presetting the position of forced turbulence. It was shown that two instability mechanisms take place in the boundary layer of the spheroid: the Tollmien-Schlichting instability and the cross-flow instability with a predominance of the last on side surfaces. A comparison of predicted position of the transition for different flow regimes was performed.

Effects of Junction Flow on the Free Convection Heat Transfer of a Heated Vertical Plate

The present study covers results of non-stationary numerical simulation of three-dimensional flow in the junction region of a low aspect ratio circular cylinder entirely immerged in laminar free convection boundary layer developing over a heated vertical plate. To categorize the effects of the cylinder surface temperature on the dynamics behavior of the forming vortical structure, its size and position both upstream and downstream of the cylinder the results, which prove the presence of a complex coherent vortical structure, are analyzed. In particular, the influence of horseshoe vortex system formed upstream of the cylinder on the free convection heat transfer of the heated vertical plate in the junction area is evaluated. Finally, the importance of the forming vortical structure on the heat transfer computation for the junction region is demonstrated.