Simulation Of Natural Convection Research Articles

Assessment of Thermal Boundary Models for Large Eddy Simulations of Natural Convection

Assessment of Thermal Boundary Models for Large Eddy Simulations of Natural Convection

Assessing Turbulence Model Performance in OpenFOAM for Natural Convection Simulations

Abstract Natural convection processes are pivotal in various engineering applications, necessitating accurate and reliable computational fluid dynamics (CFD) models for their simulation. This study evaluates the efficacy of different turbulence models implemented in OpenFOAM for a natural convection scenario, aiming to identify the most suitable model for capturing complex thermal and fluid dynamic behaviors. We compared several turbulence models, including the k − ε, k − ω, and k − ω SST, using a benchmark thermal convection case. Our methodology involved setting up the simulations to reflect realistic thermal gradients and boundary conditions, followed by a rigorous analysis of temperature distribution, vertical velocity profiles, and computational efficiency. The results indicate that the k − ω SST achieved the lowest averaged root mean square error (RMSE) values for temperature (0.076) and vertical velocity (0.03) while also requiring the fewest convergence iterations (314) compared to k − ε (411) and k − ω (1474). These findings demonstrate that the k − ω SST model is a suitable compromise between accuracy and computational cost for engineering applications. This study underscores the importance of selecting an appropriate turbulence model in OpenFOAM to enhance the accuracy of natural convection simulations, which can significantly influence design and safety considerations in engineering systems.

Simulation of nanofluid natural convection based on single-particle hydrodynamics in energy-conserving dissipative particle dynamics (eDPD)

Simulation of nanofluid natural convection based on single-particle hydrodynamics in energy-conserving dissipative particle dynamics (eDPD)

Numerical simulation of natural convection in a differentially heated cubical cavity with solid fins

PurposeThe performance of solid fins inside a differentially heated cubical cavity is numerically studied in this paper. The main purpose of the study is to make an optimization to reach the maximum heat transfer in the enclosure having the solid fins with studied parameters.Design/methodology/approachThe considered domain of interest is a differentially heated cube having heat-conducting solid fins placed on the heated wall while an opposite wall is a cooled one. Other walls are adiabatic. Governing equations describing natural convection in the fluid filled cube and heat conduction in solid fins have been written using non-dimensional variables such velocity and vorticity taking into account the Boussinesq approximation for the buoyancy force and ideal solid/fluid interfaces between solid fins and fluid. The formulated equations with appropriate initial and boundary conditions have been solved by the finite difference method of the second of accuracy. The developed in-house computational code has been validated using the mesh sensitivity analysis and numerical data of other authors. Analysis has been performed in a wide range of key parameters such as Rayleigh number (Ra = 104–106), non-dimensional fins length (l = 0.2–0.8), non-dimensional location of fins (d = 0.2–0.6) and number of fins (n = 1–3).FindingsFrom numerical methods point of view the used non-primitive variables allows to perform numerical simulation of convective heat transfer in three-dimensional (3D) regions with two advantages, namely, excluding difficulties that can be found using vector potential functions and reducing the computational time compared to primitive variables and SIMPLE-like algorithms. From a physical point of view, it has been shown that using solid fins can intensify the heat transfer performance compared to cavities without any fins. Fins located close to the bottom wall of the cavity have a better heat transfer rate than those placed close to the upper cavity surface. At high Rayleigh numbers, increasing the fins length beyond 0.6 leads to a reduction of the average Nusselt number, and one solid fin can be used to intensify the heat transfer.Originality/valueThe present numerical study is based on hybrid approach for numerical analysis of convective heat transfer using velocity and vorticity that has some mentioned advantages. Obtained results allow intensifying the heat transfer using solid fins in 3D chambers with appropriate location and length.

Segment-based wall treatment model for heat transfer rate in smoothed particle hydrodynamics

We propose a new smoothed particle hydrodynamics (SPH) model that applies a segment-based wall boundary treatment method (SBWM) for heat transfer applications. We begin by focusing on natural convection simulations, where accurately modeling heat-transferring wall boundaries is crucial as they are the energy source driving the flow. A conventional SPH approach that handles such tasks is the boundary particle (BP) method, which constructs wall boundaries by placing multiple layers of particles on and behind the walls. Despite its capability of imposing accurate boundary conditions, the BP approach becomes a non-trivial task when the fluid domain involves complex boundaries. Moreover, computational costs may significantly increase because of the increased number of SPH particles necessary for modeling walls. Therefore, we utilize the recent development of SBWM to efficiently model energy-transferring wall boundaries. Specifically, SBWM is applied to the energy conservation equation for the wall heat transfer model, using the boundary truncation terms derived in this work. The SBWM-SPH method is verified in various numerical examples, comparing the results with BP-SPH and finite volume method as well as experimental data in the literature. Our study finally extends to investigating a heat exchanger with an optimized shape, demonstrating how SBWM-SPH effectively handles practical issues associated with the BP method while providing accurate heat transfer calculations for the wall.

Numerical simulation of magnetohydrodynamics double-diffusive natural convection in a cavity with non-uniform heated walls

The fluid flow in a closed domain with heat and mass transfer has enormous applications in thermal engineering. Specifically, the natural convection with fin has applications in cooling electronic devices, automobile engines, solar collectors, etc. So, this research aims to explore the simultaneous aspects of the natural convection flow of heat and mass transfer, as well as the entropy generation in a square cavity with four fins attached diagonally at each corner and a circular object in the center. The enclosure is filled with non-Newtonian fluid and an inclined magnetic field is applied. The left and right walls are heated by non-uniform linear increasing temperature (Th) having higher concentration (CL). The governing equations are first transformed to dimensionless form and then the finite element method is utilized to resolve it. The parameters and inclusion of fins are deeply analyzed to flow particularities. It is inspected that flow is more consistent in the absence of fins giving rise to more heat and mass transport. The maximum entropy is found in the vicinity of fins corners and solid surfaces. Due to non-uniform heating, negative gradients can also be achieved on the heated walls. Parameters impacts revealed that increasing the Hartmann number (Ha) decreases the kinetic energy, heat and mass transfer rate, and entropy generation. Almost three times lesser kinetic energy (K.Eavg) is obtained in the considered range of Ha. The velocity, temperature and entropy generation lead to amplification as Casson parameter (β) is enhanced. The inclusion of fins produces more resistance to fluid motion resulting in lower Nusselt (Nuavg) and Sherwood number (Shavg). The Higher Rayleigh number (Ra) can motivate the velocity and result in smaller Bejan number.

Numerical Simulation of Natural Convection in a Rhombic Enclosure with Heated Sidewall Coated with Metal Foam

Numerical Simulation of Natural Convection in a Rhombic Enclosure with Heated Sidewall Coated with Metal Foam

Finite difference simulation of natural convection of two-phase hybrid nanofluid along a vertical heated wavy surface

This study employs finite difference modelling to investigate the natural convection of a two-phase hybrid nanofluid consisting of Al 2 O 3 and Cu nanoparticles dispersed in water along a vertically heated wavy surface. The hybrid nanofluid has unique features that influence convective heat transfer. Numerical solutions analyze fluid flow patterns and temperature distributions, providing insights into heat exchange and thermal management. The research highlights the importance of hybrid nanofluids, notably those containing Al 2 O 3 and Cu in a water base, in improving overall heat transfer efficiency. The mathematical model accounts for laminar and incompressible fluid flow with a Prandtl number of Pr = 6.2, Lewis number Le = 10, and maximum 10 % concentration of hybrid nanoparticles. After transforming the governing equations into a non-dimensional form, the implicit finite difference method is used to solve them. The solution employs the in-house FORTRAN 90 code and compares its outcomes with the benchmark results. Various parameters, such as the Schmidt number (Sc = 1 to 10), volume fraction of nanoparticles ( ϕ = 0.0 to 0.1), wavy amplitude (A = 0.0 to 0.3), and N BT = (0.05 to 0.2), are investigated regarding temperature, velocity, local skin friction coefficient ( C f ) , local Nusselt number (Nu), streamlines, and isotherms. Elevated volume fraction generally decreases skin friction, increases temperature, and may reduce velocity. Meanwhile, higher skin friction, temperature, velocity, and local Nusselt numbers often correlate with elevated Schmidt numbers. Changes in amplitude and N BT affect skin friction, temperature, velocity, and local Nusselt numbers, providing information on the dynamics of fluid systems. For example, when the volume fraction (ϕ) increases from 0 to 0.1 at Y = 2, the temperature rises by 75 % , while the velocity gradually decreases by 11.11 % . This is in contrast to findings according to when the N BT rises from 0.05 to 0.2 at Y = 1. In this case, the temperature drops by 18.75 % , followed by a 9.68 % fall in fluid velocity. Understanding these interactions enhances comprehension of heat transfer and fluid dynamics. By investigating these interactions, we not only improve our understanding of heat transfer and fluid dynamics, but also open the door to new strategies for improving thermal systems and manufacturing procedures.

Numerical simulation of natural convection in a rectangular enclosure filled with porous medium saturated with magnetic nanofluid using Buongiorno's two‐component model

AbstractMotivated by studying emerging nanofluid‐based magnetic fuel cells and hybrid direct absorber solar collectors, a numerical study is presented for buoyancy‐driven flow in a vertical enclosure containing a porous medium saturated with magnetized nanofluid flow under a transverse static magnetic field. The enclosure features adiabatic side walls and vertical heat slits, ensuring consistent cold temperatures on the lower and upper bounded walls. The side walls of the regime are insulated, and the hot slits are centrally located on these walls. The finite difference method (FDM) is applied to employ the transformed dimensionless vorticity–stream function (VSF) formulation of the transport equations. The impact of pertinent parameters on isotherm, streamline, iso‐concentration, and average Nusselt and Sherwood numbers are visualized with contour plots and graphs. Increasing Darcy number values tend to amplify the isotherm magnitudes. Higher Hartmann (magnetic) number values, on the other hand, lead to a reduction in local Nusselt number profiles but do not significantly modify the local Sherwood number. The porous medium permeability, as simulated via the Darcy number, has a strong impact on streamlines, thermal contours, and iso‐concentrations. A reduction in Darcy's number suppresses local Nusselt and Sherwood numbers, whereas an elevation in Rayleigh's number enhances them. Increasing the Buongiorno nanoscale Brownian motion parameter enhances local Nusselt and Sherwood numbers at both cold walls of the enclosure. The simulations provide a deeper insight into enclosure flows involving electrically conducting nanofluids in advanced processing systems for nanomaterials and hybrid fuel cells utilizing electromagnetic and liquid fuel technologies.

Expression of Concern: MRT-LB Simulation and Response Surface Analysis of Natural Convection of Non-Newtonian Ferrofluid in an Enclosure with Non-uniformly Heated Radiator through GPU Computing

Expression of Concern: MRT-LB Simulation and Response Surface Analysis of Natural Convection of Non-Newtonian Ferrofluid in an Enclosure with Non-uniformly Heated Radiator through GPU Computing

Expression of Concern: Lattice-Boltzmann numerical simulation of double-diffusive natural convection and entropy generation in an n-shaped partially heated storage tank

Expression of Concern: Lattice-Boltzmann numerical simulation of double-diffusive natural convection and entropy generation in an n-shaped partially heated storage tank

Simulation of Natural Convection with Sinusoidal Temperature Distribution of Heat Source at the Bottom of an Enclosed Square Cavity.

The lattice Boltzmann method is employed in the current study to simulate the heat transfer characteristics of sinusoidal-temperature-distributed heat sources at the bottom of a square cavity under various conditions, including different amplitudes, phase angles, initial positions, and angular velocities. Additionally, a machine learning-based model is developed to accurately predict the Nusselt number in such a sinusoidal temperature distribution of heat source at the bottom of a square cavity. The results indicate that (1) in the phase angle range from 0 to π, Nu basically shows a decreasing trend with an increase in phase angle. The decline in Nu at an accelerated rate is consistently observed when the phase angle reaches 4π/16. The corresponding Nu decreases as the amplitude increases at the same phase angle. (2) The initial position of the sinusoidal-temperature-distributed heat source Lc significantly impacts the convective heat transfer in the cavity. Moreover, the decline in Nu was further exacerbated when Lc reached 7/16. (3) The optimal overall heat transfer effect was achieved when the angular velocity of the non-uniform heat source reached π. As the angular velocity increases, the local Nu in the square cavity exhibits a gradual and oscillatory decline. Notably, it is observed that Nu at odd multiples of π surpasses that at even multiples of π. Furthermore, the current work integrates LBM with machine learning, enabling the development of a precise and efficient prediction model for simulating Nu under specific operational conditions. This research provides valuable insights into the application of machine learning in the field of heat transfer.

Simulation of natural convection of nanofluid inside a square cavity using experimental data by lattice Boltzmann method

The Lattice Boltzmann Method (LBM) is one of the suggested numerical approaches that has been shown to accurately estimate the increase in heat transfer caused by nanofluids. Several approaches to the prediction of the characteristics of nanofluids are investigated, and it is shown to what degree the classical models are accurate representations of the experimental data. The first thing that was done in this study was to explain the thermophysical parameters of the Ethylene Glycol (EG)-iron nanofluid that was employed. The effect of the Rayleigh number, the volume fraction of nanoparticles (φ), and the cavity angle (θ) on the isotherms and the average Nusselt number (Nuavg) are investigated. Finally, the effect of the adiabatic fin on the flow is investigated, and it is demonstrated in which scenario the adiabatic vane will be the most effective. The findings demonstrate that raising the Rayleigh number to 105 and 106 causes the heat to be transferred under the adiabatic fin. This finding suggests that the buoyancy force has a stronger influence on the heat transfer process when it is carried out close to the source of the cold. In general, if the Rayleigh number is increased, the rate of heat transfer in the fluid will rise as well. The Nu avg is increased by 44 % when the Ra number is increased from 103 to 105, and it is increased by 118 % when the Ra number is increased from 105 to 106. The chances of heat entering the cold source are reduced when the adiabatic fin is longer and situated lower. There is a wider cold zone within the hollow when Lf = 80 and Hf = 20, indicating that less heat is entering the cold source.

An efficient discrete unified gas-kinetic scheme for compressible thermal flows

In this paper, an efficient discrete unified gas-kinetic scheme (DUGKS) is developed for compressible thermal flows based on the total energy kinetic model for natural convection with a large relative temperature difference. A double distribution function model is designed with the second distribution representing the total energy. This efficient DUGKS enables the simulation of compressible thermal flows, governed by the compressible Navier–Stokes–Fourier system, using only a seventh-order, off-lattice Gauss–Hermite quadrature (GHQ) D3V27A7 combined with a fifth-order GHQ D3V13A5. The external force is included by truncated Hermite expansions. Based on the Chapman–Enskog approximation and Hermite projection, we propose a systematic approach to derive the discrete kinetic boundary conditions for the density and total energy distribution functions. The discrete kinetic boundary treatments are provided for the no-slip boundary condition, Dirichlet boundary condition and Neumann boundary condition. To validate our scheme, we perform simulations of steady natural convection (Ra=103−106) in two- and three-dimensional cavities with differentially heated sidewalls and a large temperature difference (ε=0.6), where the Oberbeck–Boussinesq approximation is invalid. The results demonstrate that the current efficient DUGKS is robust and accurate for thermal compressible flow simulations. With the D3V27A7 and D3V13A5 off-lattice discrete particle velocity model, the computational efficiency of the DUGKS is improved by a factor of 3.09 when compared to the previous partial energy kinetic model requiring the ninth-order Gauss–Hermite quadrature.

A numerical simulation of natural convection in a porous enclosure with nanofluid

In day-to-day life, heat transfer has several applications and hence we have many research areas of interest to learn new things. Nanoparticles improve the characteristics of heat transfer due to the random motion of particles. In this study, a computational approach is used to study natural convection in a porous enclosure with nanofluid. The convective term is solved by the QUICK scheme, and the finite difference method is used to solve the stream function with a 60 × 60 mesh size. CuO-water nanofluid is used in this work since nanoparticles are widely used in almost all engineering fields. In this study, we considered a two-dimensional complex cavity which is solved mathematically by using the Boussinesq approximation method. For validation of the software code, the obtained results are compared with the existing results in the literature and are found to be in good agreement. We see distortion of isotherms increases with an increase in the Rayleigh number and the nanoparticle content. That is, heat transfer takes place by natural convection very fast. Nusselt number increases with increasing nanofluid particles and the Rayleigh number. Also, it can be concluded that the heat transfer is a strong function of the Darcy number and The Rayleigh number.

Numerical Simulation of Magnetohydrodynamic Natural Convection in an Enclosure Filled with Nanofluid

Numerical Simulation of Magnetohydrodynamic Natural Convection in an Enclosure Filled with Nanofluid

Numerical simulation of thermosolutal natural convection of power-law non-Newtonian fluids in a parallelogram with sensitivity analysis by response surface methodology

Thermosolutal natural convection originates in a fluid when the density changes due to the presence of two distinct components with varying rates of diffusion. This convection is driven by buoyancy resulting from concurrent temperature and concentration gradients. This study focuses on the thermosolutal free convection flow within a parallelogrammic enclosure. The functioning fluid under consideration is non-Newtonian and formulated by the viscosity model (power-law). The top and bottom walls of the chamber are adiabatic and are assumed to be impermeable. The temperature and concentration on the left side are maintained at a high level, while the conditions on the right side are cold and low. The controlling parameters for the present case include Rayleigh number Lewis number (Le = 5, 10), Prandtl number (Pr = 6.2), buoyancy ratio (N = 0.8, −0.8) along with power-law index (n = 0.6, 1, 1.4). The results obtained from this numerical study are validated with existing results and indicate the correctness of the code. The output of the study is shown in terms of velocity and temperature profiles, streamlines, isotherms, and iso-concentrations, the average rate of heat and mass transmission in terms of the average Nusselt number () and the average Sherwood number (). The correlation equation derived from the RSM approach demonstrates the relationship between the output responses and the input parameters. It concludes that n negatively affects both heat and mass transfer, while Ra affects positively. The findings of this study could be helpful for understanding of thermosolutal natural convection behavior of non-Newtonian (power-law) fluid in an enclosure and therefore accelerate the industrial application of such fluid in the relevant field, such as HVAC (heating, ventilation, and air conditioning) system.

Mesoscopic CUDA 3D MRT-LBM Simulation of Natural Convection of Power-Law Fluids in a Differentially Heated Cubic Cavity with a Machine Learning Cross-Validation

Mesoscopic CUDA 3D MRT-LBM Simulation of Natural Convection of Power-Law Fluids in a Differentially Heated Cubic Cavity with a Machine Learning Cross-Validation

MRT-lattice Boltzmann simulation of MHD natural convection of Bingham nanofluid in a C-shaped enclosure with response surface analysis

This paper focuses on the natural convection of heat transfer using magnetohydrodynamic (MHD) Bingham nanofluid. Utilizing the multiple-relaxation-time (MRT) lattice Boltzmann method (LBM) within a C-shaped enclosure and the NVIDIA graphics processing unit (GPU)-based compute unified architecture (CUDA) C/C++ platform, the simulation is carried out numerically. Inside the cavity, the base fluid is water and the nanofluid is Al2O3. Boundary conditions are presented in accordance with the heated, cold, and adiabatic conditions present in the cavity's various walls. Several parameters including Bingham number (Bn=0,0.5,1,1.5,2), Rayleigh number (Ra=104,105,106), Hartmann number (Ha=0,10,20,30), and nanoparticle volume fraction (ϕ=0,0.01,0.02,0.03,0.04). The results of the numerical simulation are shown using streamlines and isotherms, velocity-temperature, Local Nusselt number, and average Nusselt number. From the obtained results it is found that for the variation of Bn, Ha, and ϕ with different Ra the rate of heat transfer decreases along the bottom wall and increases for the left and top walls. The average Nusselt number decreases while Bn, Ha rises. On the other contrary, the average Nu increases as ϕ increases. Response surface methodology (RSM) is added here to have better understanding of the effects of parameter used. RSM includes statistical table for the combination of data set and their graphs to understand the accuracy. Moreover, regression analysis shows how average Nu increases or decreases with the variation of different parameters. The C-shaped geometry provides an excellent option in heat exchanging or electronic cooling equipment the chip designing technology. This study is only for two-dimensional laminar flow.

Simulation of Turbulent Natural Convection in Photovoltaic Solar Panels Based on the Spalart–Allmares (SA) Turbulence Model

Simulation of Turbulent Natural Convection in Photovoltaic Solar Panels Based on the Spalart–Allmares (SA) Turbulence Model