Wavy-walled Cavity Research Articles

Magnetic field impact on free convection of a nanofluid in a cavity with corrugated walls and having V-shaped baffles

In this study, an investigation of heat transfer by free convection in a wavy-walled cavity loaded with Al2O3–water nanofluid and subjected to a magnetic field was developed. In lower wall of this cavity baffles are installed. The different conservation equations were solved via Ansys-Fluent software by applying the finite volume technique and the buoyancy forces were expressed by Boussinesq approximation. This investigation gives explanations on the impact of the different factors on heat exchange and nanofluid movement in the chosen geometry, namely, Rayleigh and Hartmann numbers, volume fraction, and presence of baffles which is considered the novelty of this work. Results found illustrate that heat exchange is enhanced by intensification of Rayleigh number and addition of nanoparticles, due to development of a significant temperature gradient and the improved characteristics of nanofluids while the growth of Hartmann number reduces heat exchange owing to the magnetic field action on free convection. Depending on the configuration studied, the installation of the baffles can sometimes localizes the flow in an area of the enclosure and reduces heat transmission which is the case of this study. Finally, correlations were proposed for Nusselt number to get an idea on heat exchange rate and which are rarely given in this type of studies. These results can help in the design of certain energy systems.

Convective heat transport in a porous wavy enclosure: Nonuniform multi-frequency heating with hybrid nanofluid and magnetic field

This work investigates the dynamics of the hybrid nanofluidic convective heat transfer in a permeable thermal system under the influence of multifrequency heating and a magnetic field. The geometry comprises a wavy-walled cavity filled with a water-based hybrid nanoliquid (Al2O3–Cu–H2O) in a saturated porous medium. The finite volume approach is applied to scrutinize the hydro-thermal characteristics resulting from bottom heating and side cooling, considering various flow-controlling parameters. The analysis reveals that nonuniform multi-frequency heating can be a highly effective strategy for enhancing heat transfer in complex geometries involving porous systems, nanofluid flow, and magnetic fields. Significant heat transfer improvement is observed at higher frequencies, with an increase of approximately 261.49 % when offset temperatures are introduced. Additionally, an increase in the undulation height of the wavy sidewalls contributes to a partial heat transfer improvement of 13.41 % compared to the case without undulations. The influence of the Darcy number, Hartmann number, porosity index, and nanoparticle concentration on heat transfer performance is also investigated. Higher Darcy and Hartmann numbers result in reduced thermal convection, while increased porosity enhances thermal convection. Elevated nanoparticle concentrations weaken the flow strength due to higher viscosity. System engineers can optimize heat transfer systems in their respective applications by comprehending the interactions between these flow-controlling parameters. This work contributes to a deeper understanding of the hydro-thermal phenomena in a multiphysics problem and provides a foundation for the development of more efficient heat transfer systems.

Magnetotactic bacteria and Fe3O4–water in a wavy walled cavity

PurposeThe purpose of this study is to investigate the interaction between magnetotactic bacteria and Fe3O4–water nanofluid (NF) in a wavy enclosure in the presence of 2D natural convection flow.Design/methodology/approachUniform magnetic field (MF), Brownian and thermophoresis effects are also contemplated. The dimensionless, time-dependent equations are governed by stream function, vorticity, energy, nanoparticle concentration and number of bacteria. Radial basis function-based finite difference method for the space derivatives and the second-order backward differentiation formula for the time derivatives are performed. Numerical outputs in view of isolines as well as average Nusselt number, average Sherwood number and flux density of microorganisms are presented.FindingsConvective mass transfer rises if any of Lewis number, Peclet number, Rayleigh number, bioconvection Rayleigh number and Brownian motion parameter increases, and the flux density of microorganisms is an increasing function of Rayleigh number, bioconvection Rayleigh number, Peclet number, Brownian and thermophoresis parameters. The rise in buoyancy ratio parameter between 0.1 and 1 and the rise in Hartmann number between 0 and 50 reduce all outputs average Nusselt, average Sherwood numbers and flux density of microorganisms.Research limitations/implicationsThis study implies the importance of the presence of magnetotactic bacteria and magnetite nanoparticles inside a host fluid in view of heat transfer and fluid flow. The limitation is to check the efficiency on numerical aspect. Experimental observations would be more effective.Practical implicationsIn practical point of view, in a heat transfer and fluid flow system involving magnetite nanoparticles, the inclusion of magnetotactic bacteria and MF effect provide control over fluid flow and heat transfer.Social implicationsThis is a scientific study. However, this idea may be extended to sustainable energy or biofuel studies, too. This means that a better world may create better social environment between people.Originality/valueThe presence of magnetotactic bacteria inside a Fe3O4–water NF under the effect of a MF is a good controller on fluid flow and heat transfer. Since the magnetotactic bacteria is fed by nanoparticles Fe3O4 which has strong magnetic property, varying nanoparticle concentration and Brownian and thermophoresis effects are first considered.

Assessment of thermal behavior of nanofluid flow in a wavy walled cavity in presence of sliding motion and magnetic field

In this study, magnetohydrodynamic mixed convective heat transport phenomena of CuO-water nanofluid in a double lid-driven cavity having a heated wavy bottom wall is investigated numerically. The cavity in consideration has moving vertical walls, assumed adiabatic. The wavy bottom wall is kept at a high temperature and the top wall is exposed with ambient temperature, respectively. The dimensionless governing equations are discretized and solved using the finite element approach. The impacts of various governing parameters such as the Rayleigh number (Ra = 103–106), Hartmann number (Ha = 0–70), Reynolds number (Re = 10–500), and nanoparticle concentration (φ = 0–3%) are examined and visualized by illustrations of local distributions of streamlines and isotherms. A correlation representing the relationship of the average Nusselt number, Nu in terms of all the examined parameters has been presented. The numerical simulations reveal that the convective heat transfer rate within the wavy enclosure is maximum for higher values of Reynold’s number and nanoparticle concentration and lower values of Hartmann number. Comparisons with other similar published numerical investigations show good agreement with the current outcomes.

Hydromagnetic natural convection in a wavy-walled enclosure equipped with hybrid nanofluid and heat generating cylinder

Flow and heat transfer components of buoyancy driven convection in a hybrid nanofluid filled wavy-walled cavity are numerically investigated in this study. A cylindrical heat generating blockage is placed at the center of the cavity. The cavity is partially heated from its bottom wall and cooled from wavy-walls while the remaining walls are adiabatic. The cavity is permeated by a transverse magnetic field. Thermal conductivity model of hybrid nanofluid is developed comprising Brownian motions of different nanoparticles. The non dimensional governing equations are solved by implementing finite element method. Obtained results demonstrate the intensification of fluid flow circulation for increasing Rayleigh number and heater length. The heat transfer rate is expeditiously augmented for increase in Rayleigh number and hybrid nanoparticles volume fraction but reverse trend is observed for higher Hartmann number. The flow circulation and temperature distribution are influenced with the presence of heat generating cylinder and roughness of the cavity walls. In addition, strength of fluid motion becomes higher for wavy cavity containing heat generating obstacle compared to smooth cavity without blockage. Maximum heat transfer is ensured at lower heater length and radius of the heat generating cylinder. Heat transfer rate also increases with the roughness of the cavity.

Latent Heat Phase Change Heat Transfer of a Nanoliquid with Nano–Encapsulated Phase Change Materials in a Wavy-Wall Enclosure with an Active Rotating Cylinder

A Nano-Encapsulated Phase-Change Material (NEPCM) suspension is made of nanoparticles containing a Phase Change Material in their core and dispersed in a fluid. These particles can contribute to thermal energy storage and heat transfer by their latent heat of phase change as moving with the host fluid. Thus, such novel nanoliquids are promising for applications in waste heat recovery and thermal energy storage systems. In the present research, the mixed convection of NEPCM suspensions was addressed in a wavy wall cavity containing a rotating solid cylinder. As the nanoparticles move with the liquid, they undergo a phase change and transfer the latent heat. The phase change of nanoparticles was considered as temperature-dependent heat capacity. The governing equations of mass, momentum, and energy conservation were presented as partial differential equations. Then, the governing equations were converted to a non-dimensional form to generalize the solution, and solved by the finite element method. The influence of control parameters such as volume concentration of nanoparticles, fusion temperature of nanoparticles, Stefan number, wall undulations number, and as well as the cylinder size, angular rotation, and thermal conductivities was addressed on the heat transfer in the enclosure. The wall undulation number induces a remarkable change in the Nusselt number. There are optimum fusion temperatures for nanoparticles, which could maximize the heat transfer rate. The increase of the latent heat of nanoparticles (a decline of Stefan number) boosts the heat transfer advantage of employing the phase change particles.

Impact of heat source on combined convection flow inside wavy-walled cavity filled with nanofluids via heatline concept

The appearance of a heat source at the bottom of a cavity against the cold part at the top wavy surface is examined in this work. The heat transportation, velocity of the fluid, and the temperature behaviour toward the mixed convection of nanofluids are obtained from the simulation of the Galerkin finite element technique and the Navier-Stokes equations. The other surfaces are considered adiabatic as well as both sides of the lid-driven cavity. It should be noted that the Grashof number, the volume fraction of alumina-nanoparticles, and the differentially-moving vertical walls are fixed at 105,0.02, the upward (right) and downward (left), respectively. To verify the computational code of derivation, the experimental and theoretical data from other researchers are compared. The results of the non-primitive variables, including the Richardson number, Reynolds number, number of undulations, dimensionless length, and the location of the heat source are compared. The numerical results indicate that larger values of the Richardson number and the Reynolds number enhance the rate of heat transfer. Not only two waves appear at the upper surface, but the heat source located at the centre with optimum height causes the entire cavity to have maximum heat transfer performance. The current problem is solved to benefit the installation of microelectronic cooling of a water-to-air heat exchanger or a pin-fin MHS heat transfer media.

Numerical simulation of MHD double diffusive natural convection and entropy generation in a wavy enclosure filled with nanofluid with discrete heating

A numerical investigation of entropy generation, heat and mass transfer is performed on steady double diffusive natural convection of water-based Al2O3 nanofluid within a wavy-walled cavity with a center heater under the influence of an uniform vertical magnetic field. The top horizontal wavy wall, left and right vertical walls of the enclosure are kept at low temperature and concentration of Tc and cc whereas central part of the bottom horizontal wall is maintained at high temperature and concentration of Th and ch and the remaining part is kept adiabatic where temperature and concentration gradient are taken as zero. The Bi-CGStab method and Tri-diagonal algorithm are used to solve the governing equations. The study has been performed for several relevant parameters such as Rayleigh number (103≤Ra≤105), Hartmann number (0≤Ha≤60), buoyancy ratio number (−2≤N≤2), volume fraction of nanoparticles (0.0≤ϕ≤0.2) and different undulation number of the upper wavy wall (n). The Prandtl number and Lewis number are kept fixed at Pr=6.2 and Le=2. The effect of these parameters are revealed in terms of streamlines, isotherms, isoconcentrations, entropy generation, average Nusselt number and Sherwood number. Results indicate that heat and mass transfer rate augment as Rayleigh number and volume fraction of nanoparticles increase and are found to drop with the increase in Hartmann number and buoyancy ratio.

Entropy generation and natural convection in a wavy-wall cavity filled with a nanofluid and containing an inner solid cylinder

This work investigates the problem of entropy generation and natural convection in a wavy-wall cavity filled with a nanofluid and containing solid inner cylinder using the Galerkin finite-element method. An isothermal heat source fixed at the left vertical wall of the cavity and the horizontal walls have taken adiabatic, while the right wavy wall cooled isothermally. An Al2O3-water nanofluid fills the space between the wavy-wall cavity and the solid cylinder. To study this problem, the influence of three variables have taken into account. These variables are Rayleigh number (103 ≤ Ra ≤ 106), nanoparticle volume fraction (0 ≤ φ ≤ 0.04), and the number of undulations (1≤ N ≤ 4). The numerical results can be in the forms of streamlines, isotherms and local entropy generation as well as the average Nusselt number. The obtained results indicate that the effect of the nanoparticles addition on the heat transfer rate is essential for low Rayleigh number and number of undulations.

Free Convection in a Wavy Walled Cavity With a Magnetic Source Using Radial Basis Functions

In this study, free convection in a cavity with differentially heated wavy walls is numerically investigated in the presence of a magnetic source. Polyharmonic spline radial basis function (RBF) is utilized to discretize the governing dimensionless equations formulated by stream function-vorticity. The effects of dimensionless Hartmann number, Rayleigh number, the number of undulations, amplitude of wave, and the location of magnetic source are visualized in streamlines and isotherms as well as calculating average Nusselt number through the heated wall. Results show that primary vortex in streamlines is altered with the impact of magnetic source. The augmentation of undulations and amplitude causes convective heat transfer to decrease if Ra = 105. The impact of location of magnetic source is noted close to the top wall.

Natural convection of an alumina-water nanofluid inside an inclined wavy-walled cavity with a non-uniform heating using Tiwari and Das’ nanofluid model

The present study is devoted to numerical analysis of natural convective heat transfer and fluid flow of alumina-water nanofluid in an inclined wavy-walled cavity under the effect of non-uniform heating. A single-phase nanofluid model with experimental correlations for the nanofluid viscosity and thermal conductivity has been included in the mathematical model. The considered governing equations formulated in dimensionless stream function, vorticity, and temperature have been solved by the finite difference method. The cavity inclination angle and irregular walls (wavy and undulation numbers) are very good control parameters for the heat transfer and fluid flow. Nowadays, optimal parameters are necessary for the heat transfer enhancement in different practical applications. The effects of the involved parameters on the streamlines and isotherms as well as on the average Nusselt number and nanofluid flow rate have been analyzed. It has been found that the heat transfer rate and fluid flow rate are non-monotonic functions of the cavity inclination angle and undulation number.

Numerical Investigation of Mixed Convection and Entropy Generation in a Wavy-Walled Cavity Filled with Nanofluid and Involving a Rotating Cylinder.

This numerical study considers the mixed convection and the inherent entropy generated in AlO–water nanofluid filling a cavity containing a rotating conductive cylinder. The vertical walls of the cavity are wavy and are cooled isothermally. The horizontal walls are thermally insulated, except for a heat source segment located at the bottom wall. The dimensionless governing equations subject to the selected boundary conditions are solved numerically using the Galerkin finite-element method. The study is accomplished by inspecting different ranges of the physical and geometrical parameters, namely, the Rayleigh number (), angular rotational velocity (), number of undulations (), volume fraction of AlO nanoparticles (), and the length of the heat source . The results show that the rotation of the cylinder boosts the rate of heat exchange when the Rayleigh number is less than . The number of undulations affects the average Nusselt number for a still cylinder. The rate of heat exchange increases with the volume fraction of the AlO nanoparticles and the length of the heater segment.

Heat transfer and entropy generation of mixed convection flow in Cu-water nanofluid-filled lid-driven cavity with wavy surface

A numerical investigation is performed into the heat transfer effect and associated entropy generation of mixed convection flow in a lid-driven wavy-wall cavity filled with Cu-water nanofluid. In modeling the cavity, it is assumed that the left wall has a flat surface and a constant high temperature, while the right wall has a wavy surface and a constant low temperature. In addition, the left wall moves in the vertical direction, while the right wall remains stationary. Finally, the upper and lower walls are both flat and insulated. The simulations focus on the effects of the flow parameters and wavy-wall geometry conditions on the Nusselt number, entropy generation rate and Bejan number. In addition, the energy flux vectors are used in order to clarify the heat energy transport process. The results show that the mean Nusselt number and total entropy generation increase as the Richardson number, nanoparticle volume fraction and Reynolds number increase. The Bejan number reduces as the irreversibility distribution ratio increases, but increases as the Reynolds number increases. The mean Nusselt number and total entropy generation both increase as the amplitude of the wavy surface increases. Finally, an optimal heat transfer effect is obtained given an appropriate wavelength of the wavy surface depending on the Richardson numbers.

Natural convection and entropy generation of Al2O3–water nanofluid in an inclined wavy-wall cavity

A numerical investigation is performed into the natural convection heat transfer performance and entropy generation of Al2O3–water nanofluid in an inclined wavy-wall cavity. The simulations focus specifically on the effects of the cavity inclination angle, nanoparticle volume fraction, Rayleigh number and wave amplitude of the wavy surface on the flow streamlines, isotherm distribution, Nusselt number and entropy generation within the cavity. The range of the studied parameters is as follows: cavity inclination angle from 0° to 360°, nanoparticle volume fraction from 0% to 4%, Rayleigh number from 102 to 106, wavy-surface amplitude from 0.0 to 0.5. The results show that the inclination angle has a strong effect on the flow streamlines, isotherms, local entropy generation and heat transfer performance; particularly at higher Rayleigh numbers. In addition, it is shown that for a given Rayleigh number and cavity inclination angle, the mean Nusselt number increases and the total entropy generation decreases as the volume fraction of Al2O3 nanoparticles increases. Finally, it is shown that for a constant Rayleigh number and inclination angle, the Nusselt number in a wavy-surface cavity is higher than that in a regular cavity, while the total energy generation is lower.

Magnetic field effect on the unsteady natural convection in a wavy-walled cavity filled with a nanofluid: Buongiorno's mathematical model

A numerical investigation is performed on the unsteady natural convection of water based nanofluid within a wavy-walled cavity under the influence of a uniform inclined magnetic field using the mathematical nanofluid model proposed by Buongiorno. The left vertical wavy and right vertical flat walls of the cavity are kept at constant but different temperatures whereas the top and bottom horizontal walls are adiabatic. All boundaries are assumed to be impermeable to the base fluid and nanoparticles. The mathematical model formulated in dimensionless stream function, vorticity and temperature variables is solved using implicit finite difference schemes of the second order. The governing parameters are the Hartmann number, undulation number, wavy contraction ratio, inclination angle of the magnetic field relative to the gravity vector and dimensionless time. The effects of these parameters on the average Nusselt number along the hot wavy wall, as well as on the streamlines, isotherms and isoconcentrations are analyzed.

Effect of surface radiation on transient natural convection in a wavy-walled cavity

ABSTRACTTransient natural convection in a differentially heated square cavity that has one vertical wavy wall has been studied numerically. The domain of interest is bounded by vertical isothermal walls and horizontal adiabatic walls. The governing equations formulated in dimensionless stream function, vorticity, and temperature, within the Boussinesq approximation with corresponding initial and boundary conditions, have been solved using an iterative implicit finite-difference method. The main objective is to investigate the effect of the dimensionless time 0 ≤ τ ≤ 0.4, Rayleigh number 104 ≤Ra ≤ 106, surface emissivity 0 ≤ ε < 1, undulations number 1 ≤ κ ≤ 6, and shape parameter 0.6 ≤ a ≤ 1.4 on fluid flow and heat transfer. Results are presented in the form of streamlines, isotherms, and distribution of average total Nusselt number at the wavy wall.

Effect of thermal dispersion on transient natural convection in a wavy-walled porous cavity filled with a nanofluid: Tiwari and Das’ nanofluid model

Transient natural convection in a porous wavy-walled cavity filled with a nanofluid has been studied numerically. The domain of interest is bounded by vertical flat and horizontal wavy walls having constant temperatures. The unsteady governing equations formulated in dimensionless stream function and temperature, within the Darcy–Boussinesq approximation and the mathematical nanofluid model proposed by Tiwari and Das in the presence of thermal dispersion with corresponding initial and boundary conditions have been solved numerically using an iterative implicit finite-difference method. The main objective is to investigate the effect of the dimensionless time, thermal dispersion parameter and solid volume fraction parameter of nanoparticles on the fluid flow and heat transfer characteristics. Results are presented in the form of streamlines, isotherms and distributions of the average Nusselt number at the bottom wavy wall.

Numerical Analysis of Al2O3/Water Nanofluids Natural Convection in a Wavy Walled Cavity

In the present work, heat transfer enhancement of Al2O3-water nanofluids in natural convection applied to differentially heated wavy cavities is investigated numerically. The governing equations are written in stream function-vorticity form and solved by using the finite volume technique. The effective thermal conductivity and viscosity of the nanofluid are approximated by the Maxwell–Garnetts and Brinkman models, respectively. The solutions are presented by streamlines, isotherms, local and mean Nusselt numbers, and velocity profiles for different Rayleigh numbers (103 ≤ Ra ≤ 105), amplitude of wavy wall (0.85 ≤ a ≤ 1.1), and different volume fraction of nanofluids (ϕ = 0.05 and 0.1). It is observed that the addition of a nanoparticle of Al2O3 into the base fluid increases the mean Nusselt number. It is also more effective on flow field than that of temperature distribution. The geometry parameter or surface waviness can be decided to heat transfer regime even for the same Rayleigh number.

MLPG Application of Nanofluid Flow Mixed Convection Heat Transfer in a Wavy Wall Cavity

MLPG Application of Nanofluid Flow Mixed Convection Heat Transfer in a Wavy Wall Cavity