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In the present study, the Multi-Relaxation Time Lattice Boltzmann method (MRT-LBM) was employed to solve the airflow inside a scaled room model with dimensions of 0.914x0.457x0.305 m. This room model is considered a representative space with a 1:10 scale to an actual room. The selected room is equipped with a ventilation system. For optimizing the inlet and outlet locations of the airflow, 32 different positions in terms of length, width, and height for the inlet and 4 positions for the outlet were considered. The Taguchi method was utilized for optimizing the inlet and outlet locations, reducing the required number of experiments from 128 to 16. To assess the number of suspended particles, 86400 particles with a size of 1µm were injected into the room. Then, the particle behaviors were examined for a total duration of 60 seconds. The obtained results indicate that the location of the air conditioning system significantly influences the concentration of airborne particles responsible for disease transmission. Utilizing the Taguchi optimization method, optimal positions for the inlet and outlet air were determined to minimize the number of suspended particles in the room (the best position) and maximize it (the worst position). [ABSTRACT FROM AUTHOR]

In the present study, natural convection heat transfer is investigated in a porous cavity filled with Cu/water nanofluid and equipped with horizontal fins. Optimization and sensitivity analysis of the fin's geometry, porous medium and nanofluid properties to maximize heat transfer rate is the aim of this work. To achieve this purpose, a design space is created by input parameters which include length, number of fins, distance between fins, porosity, Darcy number and volumetric fraction of the nanoparticles. Several tools have been used to implement optimization methods including the Taguchi method (TM) for design points generation, sensitivity analysis of design variables by using signal-to-noise ratio (SNR) and analysis of variance (ANOVA), response surface method (RSM) for interpolation and regression by using nonparametric regression, and genetic algorithm (GA) for finding optimum design point. The double multi-relaxation time lattice Boltzmann method (MRT-LBM) is used to analyze and simulate the flow field and heat transfer in each design point. The results show that the optimal configuration leads to an average Nusselt number of 5.56. This optimal configuration is at the length of fins L/2, the number of fins 2, the distance between fins L/12, porosity 0.8, Darcy number 0.1, and the volumetric fraction of the nanoparticles 0.02. By using the SNR results, the Darcy number and the number of fins have the most and the least effect in maximizing the average Nusselt number, respectively. The ANOVA results and global sensitivity analysis (GSA) findings further validated this conclusion. [ABSTRACT FROM AUTHOR]

In this work, the three-dimensional free convection flow in a modeled room was studied for various Grashof numbers (Gr = 2 × 104 and 2 × 105) and Hartmann numbers (Ha = 0 and 100) by the lattice Boltzmann method (LBM), and the effect of magnetic field on the flow and temperature field was investigated. For consideration of the effect of magnetic field on particle behavior in a three-dimensional modeled room, 50,000 particles with sizes of 1 and 10 μm were injected into the room. The number of deposited particles on the different walls of the room was obtained, and it was observed that by increasing the Grashof number, the total number of deposited particles for both particle sizes and both Hartmann numbers enhances. Moreover, for Ha = 100, the number of deposited 10 μm particles on the walls increases. Therefore the number of suspended particles in the modeled room decreases, which is environmentally desirable. However, the number of deposited 1 μm particles on the walls decreases in the presence of the magnetic field. Furthermore, it was found that the gravity force has a significant effect on the particle deposition, as the number of deposited 10 μm particles on the floor is much larger than 1 μm particles. [ABSTRACT FROM AUTHOR]

In this paper Double Multi Relaxation Time Lattice Boltzmann method (DMRT-LBM) is utilized to investigate the particle motion in a modeled room for the first time. The effect of indoor heating system location has been considered on both particle deposition and convective heat transfer so six different positions have been selected for the heating system. Results are shown for two Rayleigh numbers (104 and 105) and different particle sizes (1 μ m and 10 μ m). To study the particle motion, after the flow reaches steady state, 50 000 particles are randomly injected to the room and the number of deposited particles on the walls has been reported for 100 s. Considering the present results, when the heating system is in the middle of the wall, the maximum heat transfer rate is seen for both Rayleigh numbers. Also, the number of deposited 1 μ m particles on the walls for all locations of the heating system is zero for R a = 104, so the number of suspended particles is the maximum. For both Rayleigh numbers and 10 μ m particles, the number of deposited particles is maximum when the heating system is fixed on the top of the wall. It is also concluded that when the heating system is located on the top of the wall, the number of suspended 1 μ m particles for R a = 105 reaches its maximum value. [ABSTRACT FROM AUTHOR]

The present study has been examined the effect of the heating system position in a cubic cavity on the heat transfer rate. Also, the effects of adding the nanoparticles to the based fluid for the various heating system positions have been considered. Double multi-relaxation time lattice Boltzmann method has been used in this study as the numerical method. The position of the heating system has been varied from the bottom to the top of the room with H/4 interval ( z HW = 0 , H 4 , H 2 , H ). Cu/water nanofluid has been used to consider the effects of nanoparticle. Results have been presented for the various parameters such as Rayleigh number (103 < Ra < 105) and volume fraction of nanoparticle (0% < φ < 4%). The results show that the present numerical method is a proper method for simulating the internal heat transfer. In addition, by adding the nanoparticles, heat transfer rate increases and the amount of this augmentation depends on the position of the heating system as the maximum increment has been observed when the heating system is fixed on H 4 < z HW < H 2 . Also, the best position for the heater is H 4 < z HW < H 2 with respect to heat transfer rate. The results of the present study will be beneficial for the designing of the future optimal heating systems with high energy-saving capabilities. [ABSTRACT FROM AUTHOR]

Abstract In this study, a three-dimensional mesoscopic simulation of magneto hydrodynamics (MHD) natural convection in a cubic cavity has been studied by new means of the Lattice Boltzmann method with double Multi-Relaxation-Time (MRT) model. In order to solve the momentum and energy equations, two different populations with various lattices have been used. This paper has been conducted for specific values of the Grashof number (Gr = 2 × 1 0 3 _ 2 × 1 0 5) and Hartmann number (Ha=0–100), while the Prandtl number is fixed at Pr = 0. 73. The results are presented in the form of average and local Nusselt number and contours of temperature and velocity at different planes of the cavity. It was found that the double MRT-LBM method is an appropriate approach to solve the studied case. The present results also show that the increase of the Hartmann number causes the heat transfer to drop considerably. Also, the effect of Hartmann number increases by enhancing the Grashof number, as the reduction of average Nusselt number is 12% for Gr = 2 × 1 0 3 and 71% for Gr = 2 × 1 0 5 when Hartmann number increases from 0 to 100. In contrast with Hartmann number, increasing of Grashof number raises heat transfer rate and the average Nusselt number increases by more than three times by enhancing the Grashof number from 2 × 1 0 3 to 2 × 1 0 5. Highlights • Double MRT LBM method has been developed for three-dimensional MHD flow. • Average Nusselt number drops 71% when the Hartmann number rises from 0 to 100 for Gr = 2 × 1 0 5. • Average Nusselt number enhances 330% when Grashof number alters from 2 × 1 0 3 to 2 × 1 0 5. [ABSTRACT FROM AUTHOR]

In this work numerical simulation of magneto hydrodynamics (MHD) natural convection in a three-dimensional cubic cavity with sinusoidal temperature distribution on one side wall has been considered. New means of the Lattice Boltzmann method with double Multi-Relaxation-Time (MRT) model has been applied utilizing cu/water nanofluid. D3Q19 and D3Q7 models have been used to solve the momentum and energy equations, respectively. Different Rayleigh numbers (Ra = 10 3 _ 10 5 ) and various Hartmann numbers (Ha = 0–100) for volumetric fraction of the nanoparticles (Ø) between Ø = 0 and 12% have been investigated. Also, phase deviation varied from θ = 0 to π with interval π/2. The magnetic field is considered horizontally and the results have been shown at different planes and lines of the 3-D enclosure. Based on the results, the double MRT-LBM method is a proper method for simulating the 3-D flows with complex boundary conditions. The results show that augmentation of the Hartmann number decreases the heat transfer rate whereas the increase of the Rayleigh number and nanoparticles’ volumetric fraction enhance the heat transfer rate. The highest effect of magnetic field is obtained at Ra = 10 4 and the lowest effect is seen at Ra = 10 3 . Also, the greatest effect of Rayleigh number is captured at Ha = 0 for all volumetric fraction of the nanoparticles. [ABSTRACT FROM AUTHOR]

In this study, the lattice Boltzmann method was used to solve the turbulent and laminar natural convection in a square cavity. In this paper a fluid with Pr = 6.2 and different Rayleigh numbers (Ra = 103, 104,105 for laminar flow and Ra = 107, 108,109 for turbulent flow) in the presence of a magnetic field (Ha = 0, 25, 50, and 100) was investigated. (Results show that the magnetic field drops the heat transfer in the laminar flow as the heat transfer behaves erratically toward the presence of a magnetic field in a turbulent flow. Moreover, the effect of the magnetic field is marginal for a turbulent flow in contrast with a laminar flow.The greatest influence of the magnetic field is observed at Ra = 105 from Ha = 0 to 100 as the heat transfer decreases significantly. [ABSTRACT FROM AUTHOR]

In this paper the Lattice Boltzmann method (LBM) in conjunction with the large eddy simulations (LES) and Reynolds Averaged Navier–Stokes (RANS) models was used to study the airflow and particle dispersion and deposition in indoor environments. The turbulent airflow was simulated first using the LES in framework of LBM, in which the sub-grid scale turbulence effects were simulated through a shear-improved Smagorinsky model (SISM). The airflow was also simulated using the k−ε turbulence model within the framework of LBM by the addition of two populations for the turbulence kinetic energy, k, and the dissipation rate, ε. The present simulation results for the airflow showed good agreement with the experimental data and the earlier numerical results. To simulate the particle dispersion and deposition in the room, particles with diameters of 10 nm–10 μm were investigated. For generating the instantaneous turbulence fluctuations for thek−ε model, the discrete random walk (DRW) method was used. Effects of SGS turbulence fluctuation on deposition rate of different size particles were also studied. It was shown that inclusion of the SGS turbulence fluctuations improves the model predictions. The simulated results for particle dispersion and deposition showed that the predictions of the present method are quite similar to the earlier finite volume method and are in good agreement with the experimental data. [ABSTRACT FROM AUTHOR]

In this study, the lattice Boltzmann method is used in order to investigate the natural convection in a cavity with linearly heated wall(s). The bottom wall is heated uniformly and the vertical wall(s) are heated linearly, whereas the top wall is insulated. Investigation has been conducted for Rayleigh numbers of 103 to 105, while Prandtl number is varied from 0.7 to 10. The effects of an increase in Rayleigh number and Prandtl number on streamlines, isotherm counters, local Nusselt number and average Nusselt number are depicted. It has been observed that the average Nusselt number at the bottom wall augments with an increase in Prandtl number. [ABSTRACT FROM AUTHOR]

In this paper, lattice Boltzmann simulation of turbulent natural convection with large-eddy simulations (LES) in a square cavity which is filled by water/copper nanofluid has been investigated. The present results are validated by experimental data at Ra = 1.58×10 9. This study is conducted for high Rayleigh numbers (Ra = 10 7–10 9) and volume fractions of nanoparticles (0 ≤ Φ ≤ 0.06). In this research, the effects of nanoparticles are displayed on streamlines and isotherms counters, local and average Nusselt numbers. The average Nusselt number is enhanced by the augmentation of nanoparticle volume fraction in the base fluid while the manner has an erratic trend toward different Rayleigh numbers. [ABSTRACT FROM AUTHOR]

In this article, Lattice Boltzmann simulation of turbulent natural convection with large-eddy simulations (LES) in a square cavity, which is filled by water/copper nanofluid, has been investigated. The present results are validated by the consequences of an experimental research at Pr = 0.71 and Ra = 1.58 × 109. Calculations are performed for high Rayleigh numbers (Ra = 107–109), low volume fractions of nanoparticles (0 ≤ ϕ ≤ 0.06), and three aspect ratios (A = 0.5, 1, and 2). In this investigation, we present that large-eddy turbulent nanofluid flow is modeled by the Lattice Boltzmann method (LBM) with a clear and simple statement. Effects of nanopartcles are displayed on streamlines, isotherm counters, local Nusselt number, and average Nusselt number. The average Nusselt number enhances with the augmentation of the nanoparticles volume fractions in the base fluid for multifarious aspect ratios and the Rayleigh numbers. Heat transfer declines with the increase in the aspect ratios in the base fluid, but the effects of nanopaticles are dissimilar for various aspect ratios at different Rayleigh numbers. [ABSTRACT FROM PUBLISHER]

Abstract: Solving of MHD flow by the lattice Boltzmann method, utilizing classical equations has been investigated by presenting MHD mixed convection in a lid-driven cavity by a linearly heated wall. The Hartmann number varied from to 100; furthermore, the study has been conducted for Richardson numbers (Ri) from 0.01 to 100, while the directions of the magnetic field were investigated for and 90°. Results show that the augmentation of Richardson number causes heat transfer to increase, as the heat transfer decreases by the increment of Hartmann number for various Richardson numbers and the directions of the magnetic field. The highest decline of heat transfer on the linearly heated wall was found at for Richardson numbers of and . On the other hand, the least effect of the magnetic field is observed at from to 100 for both directions on the linearly heated wall. Moreover, the magnetic field influences heat transfer marginally at against , which changes dramatically. Heat transfer on the heated wall at the bottom of the cavity behaves like the linearly heated wall regarding the effect of the magnetic field. [Copyright &y& Elsevier]

Abstract: In this paper Lattice Boltzmann simulation of natural convection in an open enclosure which subjugated to water/copper nanofluid has been investigated. Calculations were performed for Rayleigh numbers (Ra=104–106), volume fractions of nanoparticles () and open enclosure aspect ratios (). The comparisons show that the average Nusselt number increases with augmentation of Rayleigh number and the volume fraction of nanoparticles for whole ranges of aspect ratios. The average Nusselt number decreases as the aspect ratio increases at various Rayleigh numbers and different the nanoparticle volume fractions. But generally the most effect of nanoparticles on heat transfer enhancement is observed at the aspect ratio of A =2. Also nanoparticles influence the heat transfer less at Ra=105 among studied Rayleigh numbers. [Copyright &y& Elsevier]

Abstract: Natural convection in enclosures using water/SiO2 nanofluid is simulated with Lattice Boltzmann method (LBM). This investigation compared with other numerical methods and found to be in excellent agreement. This study has been carried out for the pertinent parameters in the following ranges: the Rayleigh number of base fluid, Ra =103–105, the volumetric fraction of nanoparticles between 0 and 4% and aspect ratio (A) of the enclosure between 0.5 and 2. The thermal conductivity of nanofluids is obtained on basis of experimental data. The comparisons show that the average Nusselt number increases with volume fraction for the whole range of Rayleigh numbers and aspect ratios. Also the effect of nanoparticles on heat transfer augments as the enclosure aspect ratio increases. [Copyright &y& Elsevier]