Convective Flow Research Articles

Comparative analysis on the forced and mixed convection in a hybrid nanofluid flow over a stretching surface: a numerical analysis

Comparative analysis on the forced and mixed convection in a hybrid nanofluid flow over a stretching surface: a numerical analysis

Advances in Mapping Lowermost Mantle Convective Flow With Seismic Anisotropy Observations

Advances in Mapping Lowermost Mantle Convective Flow With Seismic Anisotropy Observations

Numerical analysis of electrothermoconvection of a dielectric nanofluid in a heated cavity

A numerical analysis of electrohydrodynamic (EHD) flow and heat transfer of nanofluid in a heated rectangular cavity is presented. A two-dimensional (2D) rectangular cavity heated from the bottom is considered. An electric potential difference is applied vertically, with the bottom wall acting as a high-voltage electrode, and the top wall is grounded. TiO2-25 # transformer oil nanofluid with nanoparticle volume fraction ranging from 0–5% is considered. The numerical model for EHD flow and heat transfer of nanofluid is implemented in the finite-volume method (FVM) based numerical framework of OpenFOAM. A single-phase approach based on the effective properties is adopted to model the nanofluids. A two-way coupled EHD flow model is employed to consider mutual interactions of flow and electric field variables. The flow and heat transfer behavior of nanofluids in the presence of an electric field is quantified with reference to the key parameters, electric Rayleigh number (T), and the nanoparticle volume fraction ϕ. The addition of nanoparticles increased the viscosity and marginally reduced the natural convective flow and heat transfer. However, EHD flow induced by the electric field aided in overcoming the weak natural convection flow in nanofluids. Results confirm that nanofluids’ net effective heat transfer rates are notably increased in the presence of the electric field. For the parameters under consideration, combining electric fields with nanofluids led to a significant heat transfer enhancement of up to 32.3%. The present study showcases the feasibility of combining passive heat transfer enhancement using nanoparticles and active heat transfer enhancement using EHD flow.

Natural convection and heat transmission of two-phase Bingham Fe3O4-CoFe2O4-water hybrid nanofluid flow in an enclosure with a corrugated heated cylinder

Abstract The Galerkin weighted residual finite element method (GFEM) has been used to numerically investigate the natural convection flow of two-phase Bingham hybrid nanofluid in a square cavity with a corrugated cylinder at the center. The base fluid here is water. The hybrid nanofluid is made of Fe$_3$O$_4$-CoFe$_2$O$_4$ nanoparticles. The flow inside the enclosure is considered laminar, non-Newtonian, and incompressible. The corrugated cylinder is taken heated. The top and bottom walls of the outer square are considered adiabatic, and the left and right walls are considered cold. Several non-dimensional parameters including the Rayleigh number ($Ra=10^4, 10^5, 10^6$), the Bingham number ($Bn=0, 0.5, 1$), the volume fraction ($\phi=0.00, 0.04$), the Brownian parameter ($Nb=0.1, 0.2, 0.3$), thermophoresis parameter ($Nt=0.1, 0.2, 0.3$), buoyancy ratio ($Nr=0.1, 0.2, 0.3$), corrugation ($N= 5, 6, 7$), the Prandtl number ($Pr=6.2$), and the Lewis number ($Le=1000$) have been numerically simulated. 
The results show that an upsurge in $Ra$ increases the extent of the upper two vortices and decreases the extent of the lower two vortices. All four vortices are seen to increase in dimension for an increase in $Bn$. The same observation is found for an increase in $\phi$. The lower vortices are growing, and the top ones are nearly eliminated for base fluid, while those are visible for nanofluid when corrugation is increased. A further expansion completely destroyed the higher ones and increased the size of the bottom ones. 
The average Nusselt number ($\overline{Nu}$) increases when $Ra$ is incremented. $\overline{Nu}$ rises with rise in $\phi$. An increment in $\phi$ to 0.04 results in $4.43\%$ gain in $\overline{Nu}$. An increase in $Bn$ is causing $\overline{Nu}$ to drop by $18.02\%$. For $Ra=10^5$ and $Bn=2$, $\phi=0.02$ has the maximum heat transfer enhancement between $0.00\le\phi\le0.04$

Numerical Investigation of Mixed Convective Flow of Micropolar Casson Fluid with Cattaneo-Christov Heat Flux Model on an Inclined Vertical Stretching Surface

Numerical Investigation of Mixed Convective Flow of Micropolar Casson Fluid with Cattaneo-Christov Heat Flux Model on an Inclined Vertical Stretching Surface

Formation of convective roll patterns over a longitudinal throughflow in an active inhomogeneous porous medium with weak clogging

The convective stability of a plane-parallel longitudinal throughflow in a system consisting of two porous sublayers with distinct permeability is studied taking into account the weak pore clogging effect and given a finite difference in concentration between the upper and lower boundaries of the system. A system of differential equations for convection is derived within the framework of the continuum approach and the nonlinear MIM model. A linear stability analysis of the basic longitudinal flow is carried out. The boundary value problem is solved using the numerical technique for constructing a fundamental system of solutions. The neutral stability curves of the basic flow with respect to the disturbances in the form of rolls with different wavelength are obtained. For the absence of pore clogging, the convective stability maps of the critical solutal Rayleigh-Darcy number versus the permeability ratio for the initial uncontaminated sublayers, as well as the plots of the critical disturbance frequency and wave number versus the permeability ratio for some values of the Peclet number, are constructed. It is shown that these results have symmetry with respect to the solution for equal initial permeability of sublayers. The clogging effect associated with the solute adsorption and desorption in a porous medium is studied in the two-layered systems with the values 0.1 and 10 of the ratio of initial permeabilities of the sublayers; convection localization occurs in distinct sublayers. It was found that clogging increases the stability of the longitudinal basic flow relative to solutal inhomogeneity and breaks the symmetry of solutions with respect to the case when the two-layered system is reduced to a single layer with the same filtration properties of the porous medium throughout its volume. The influence of sorption effects on the critical parameters of oscillatory convection is investigated by plotting the critical solutal Rayleigh-Darcy number, disturbance frequency and wave number against the adsorption coefficient at fixed values of the desorption coefficient. The isolines of the stream function are constructed to analyze convective flow patterns. It was established that there is a weak relationship between the typical size of local convective roll patterns and the clogging parameters. It is shown that the sorption processes, which can lead to clogging, have a significant impact on the velocity of convective rolls moving along the two-layered system at a slight variation in their sizes.

Theoretical investigation of the convective heat transfer mechanism along a cantilever shape

The present study aims to investigate the steady state mixed convection flow for a viscous incompressible fluid along a cantilever shape. The study has analyzed the impact of mixed convection boundary layer flow behavior and heat transfer characteristic of the cantilever shape. The leading equations for the said problem are the Navier-Stokes and energy equations. These leading equations are converted into ordinary differential equations using the stream function formulation, and the numerical solution is obtained using the shooting technique with BVP4C and built in MATLAB program. The impact of dimensionless parameters such as n, Pr, and λ on the velocity and temperature profile within the boundary layer of the cantilever cylinder is presented graphically. The results for velocity slope and temperature gradient under the effects of various emerging parameters are presented in tables. The study has concluded that mixed convection parameter has a significant impact on the velocity and temperature distribution, as well as on the velocity slope and temperature gradient rates along a cantilever shape geometry. The outcomes of the current study can be utilized for the design and optimization of various engineering devices involving cantilever shapes. Further, research regarding the impact of other parameters on the cantilever shape including heat transfer characteristics can be conducted using the approach presented in this study. The novelty of the current work can be claimed by saying that for reduced gravity, other forces involved in the flow model induced the fluid motion and temperature gradient.

An impact of Richardson number on the inclined MHD mixed convective flow with heat and mass transfer

AbstractThe two‐dimensional mixed convective MHD flow with heat and mass transfer is investigated for its behavior with Dufour and Soret mechanisms over the porous sheet. The copper–alumina (Cu–Al2O3) hybrid nanoparticles are used in the base fluid water. The governing system of partial differential equations is converted into a system of ordinary differential equations via similarity transformations, obtaining the solution for velocity, temperature, and concentration fields in exponential form. The problem is demonstrated in the Darcy–Brinkman model, the impact of included parameters such as Richardson number, magnetic field, and Dufour numbers are studied for the obtained solution with the help of graphs. Increasing the magnetic field decreases both transverse and axial velocity profiles. Increasing the magnetic field and Richardson's number decreases the solution (Al2O3–H2O). Increasing the values magnetic field and Richardson's number decreases both transverse and axial velocity profiles. Increasing the values of the Dufour effect increases the axial and transverse velocity boundary layer. The magnetohydrodynamic hybrid nanofluid flow over porous media works efficiently in liquid cooling and, therefore, has significant applications in industrial heating and cooling systems, solar energy, magnetohydrodynamic flow meters and pumps, manufacturing, regenerative heat exchange, thermal energy storage, solar power collectors, geothermal recovery, and chemical catalytic reactors.

Environmentally Friendly Synthesis of Polymer Nanoparticles in a Packed Reactor Using Glass Beads

AbstractPolymeric particles less than 100 nm in size (polymer nanoparticles), which are useful in the fields of medicine and so on, are synthesized through emulsion polymerization, wherein surfactants are essential for maintaining their dispersion stability, contaminating particle surfaces and causing high environmental pollution. The soap‐free emulsion polymerization (SFEP) of styrene in a packed reactor using microglass beads enables the synthesis of polymer nanoparticles without surfactants. Ultraviolet irradiation is used for radical polymerization using an initiator during the SFEP of styrene. The reaction space in the packed reactor is controlled by the size of glass beads to be filled in the reactor. A decrease in the size of the glass beads narrows the reaction space, causing the average polystyrene particle size to reach 27.3 nm and suppress convection flow by the wall of the glass beads, thereby limiting particle motion and preventing particle growth through particle collisions.This article is protected by copyright. All rights reserved

Geometrical investigation of forced convective flows over staggered arrangement of cylinders employing constructal design

The current numerical work conducted a geometrical investigation of forced convective flows over a staggered arrangement of four cylinders applying constructal design. The main objectives are to determine designs maximizing the Nusselt number (NuD) and minimizing the drag coefficient (CD) of the cylinders at three distinct Reynolds numbers (ReD = 10, 40, and 150) considering Pr = 0.71. The problem involves two constraints: cross-sectional area of the cylinders and the occupation area of the arrangement, and three degrees of freedom: ST/D, SL1/D and SL2/D. These represent the ratios between the transversal pitch, the longitudinal pitch between the frontal and intermediate cylinders, and the longitudinal pitch between the intermediate and posterior cylinders over the diameter. The introduction of two longitudinal pitches enabled an exploration of the generation of asymmetrical patterns in the flow direction. Results indicated a strong dependency of the arrangement design on the Reynolds number. Moreover, asymmetrical configurations generally benefited both performance indicators for the present conditions. The most favorable arrangements for the fluid dynamics were achieved with the lowest ST/D, more concentrated longitudinal pitches for ReD = 10, and asymmetrical pitches for ReD = 40 and 150. Concerning the thermal purpose, the highest magnitude of ST/D and asymmetrical longitudinal pitches led to the highest NuD. For ReD = 10, the intermediate cylinders are near the upstream one; for ReD = 40 the length of the arrangement increases with the intermediate cylinders near the downstream one, and for ReD = 150, the arrangement occupied all the length of occupation area with slight asymmetry.

Experimental and numerical investigation on the heat and mass transfer performance of tar rich coal in-situ pyrolysis

On ground experiments are conducted firstly to simulate the multi-physics underground pyrolysis of tar rich coal and find out the kinetic parameters of the reaction. And then multi-physics simulation is performed by coupling heat transfer, fluid flow and chemical reactions. Three pyrolysis models are compared and it’s found that the convective flow of heat carrier in coal seam plays an important role in heat transfer although the flow velocity is low. Then the effects of permeability, inlet mass flow rate on heat and mass transfer are investigated for two geometric models with homogeneous and inhomogeneous permeability. It’s found that increasing the permeability is beneficial for fast production of tar. For the homogeneous permeability model, the pyrolysis reaction can be completed in only 140 days when the permeability is 1000 md while for the non-homogeneous permeability model, increasing the inlet mass flow rate can improve the heat and mass transfer performance only in the early stage when the pyrolysis occurs mainly in the fractured zone with higher permeability. The pyrolysis reaction time when the inlet mass flow rate is 0.174 kg/s is 22 days shorter than that of 0.054 kg/s. But in the later stage the inlet mass flow rate has little effect on the reaction rate and brings about a higher pressure drop. The pyrolysis under different well patterns is also compared and the results indicate that four-well heating and six-well heating modes can improve the uniformity and the reaction conversion rate with the same total inlet mass flow rate during the same time. For the six-well heating mode, the pyrolysis reaction can be completed in about 100 days, which is 60 days shorter than the single-well heating mode.

Approximate closed‐form solution of free convection flow past a vertical cone

AbstractThis paper presents a technique to find the closed‐form solution of the boundary‐value problem representing free convection flow past a vertical cone. Partial differential equations that govern the flow are converted into nonlinear ordinary differential equations with the aid of similarity transformations. First, a numerical solution is obtained with the help of the bvp4c package of MATLAB, and then utilizing the numerical solution, the closed‐form solution is obtained. The accuracy of the closed‐form solution is analyzed by the residual technique. Graphs of the residuals of the governing equations indicate that our approximate closed‐form solution closely matches the exact solution.

Mixed convection flows from a revolving cylindrical cavity

Efforts are made to describe the thermofluidic behavior around a spinning hot cylindrical open cavity with negligible wall thickness suspended in air within the laminar regime. Several important input parameters, such as, Rayleigh number ( 10 2 ≤ Ra ≤ 10 6 ) , aspect ratio ( 0.5 ≤ H / D ≤ 10 ) , and Reynolds number ( 0 ≤ Re D ≤ 300 ) are considered to carry out the ongoing numerical analysis. Firstly, thermal plumes are provided to describe the pattern of flow and heat transfer around the heated surfaces of shell by considering the effect of Ra , H / D , and Re D . It is predicted that the heated plume is thrown radially due to the presence of swirling motion ( Re D ≠ 0 ) of the cylindrical shell unlike the pattern of thermal plume around the stationary vessel. Furthermore, the influence of Re D on behavior of cooling rate from inner ( Q iw ) and outer ( Q ow ) surfaces has also been predicted by considering both stationary and swirling conditions. A substantial growth in Q iw is noticed with the growth of Re D for a constant H / D . This effect is substantially greater at lower H / D compared to higher H / D . Again, attempts are made to elucidate the influence of Re D on Nusselt number for cylindrical inner wall ( Nu cyl − iw ) , cylindrical outer wall ( Nu cyl − ow ) , base inner wall ( Nu base − iw ) , and base outer wall ( Nu base − ow ) . Fluid flow behavior around the stationary and revolving cylindrical open cavity is also explained by employing velocity vectors. Finally, an appropriate correlation demonstrating a reasonable agreement with numerical data is found for average Nusselt number in terms of Ra , H / D , and Re D .

Enhanced Efficiency of MHD-Driven Double-Diffusive Natural Convection in Ternary Hybrid Nanofluid-Filled Quadrantal Enclosure: A Numerical Study

The study investigates the performance of fluid flow, thermal, and mass transport within a cavity, highlighting its application in various engineering sectors like nuclear reactors and solar collectors. Currently, the focus is on enhancing heat and mass transfer through the use of ternary hybrid nanofluid. Motivated by this, our research delves into the efficiency of double-diffusive natural convective (DDNC) flow, heat, and mass transfer of a ternary hybrid nanosuspension (a mixture of Cu-CuO-Al2O3 in water) in a quadrantal enclosure. The enclosure’s lower wall is set to high temperatures and concentrations (Th and Ch), while the vertical wall is kept at lower levels (Tc and Cc). The curved wall is thermally insulated, with no temperature or concentration gradients. We utilize the finite element method, a distinguished numerical approach, to solve the dimensionless partial differential equations governing the system. Our analysis examines the effects of nanoparticle volume fraction, Rayleigh number, Hartmann number, and Lewis number on flow and thermal patterns, assessed through Nusselt and Sherwood numbers using streamlines, isotherms, isoconcentration, and other appropriate representations. The results show that ternary hybrid nanofluid outperforms both nanofluid and hybrid nanofluid, exhibiting a more substantial enhancement in heat transfer efficiency with increasing volume concentration of nanoparticles.

Analytical solution to boundary layer flow and convective heat transfer for low Prandtl number fluids under the magnetic field effect over a flat plate

AbstractThe present study aims to quantify the flow field, flow velocity, and heat transfer features over a horizontal flat plate under the influence of an applied magnetic field, with a particular emphasis on low Prandtl number fluids. Nonlinear partial differential expressions can be incorporated into the ordinary differential framework with the use of appropriate transformations. This research utilizes the variational iteration method (VIM) to approximate solutions for the system of nonlinear differential equations that define the problem. The objective is to demonstrate superior flexibility and broader application of the VIM in addressing heat transfer issues, compared to alternative approaches. The results obtained from the VIM are compared with numerical solutions, revealing a significant level of accuracy in the approximation. The numerical findings strongly suggest that the VIM is effective in providing precise numerical solutions for nonlinear differential equations. The analysis includes an examination of the flow field, velocity, and temperature distribution across various parameters. The study found that improving temperature patterns, velocity distribution, and flow dynamics were all positively impacted by increasing the Prandtl numbers. As a result, this leads to the thickness of the boundary layer to decrease and improves heat transfer at the moving surface. Thus, the convection process becomes more efficient. When the strength of the magnetic field is increased, the velocity of the fluid decreases. This observation aligns with expectations since the magnetic field hampers the natural flow of convection. Notably, the convection process can be precisely controlled by carefully applying magnetic force.

Fractal Numerical Investigation of Mixed Convective Prandtl-Eyring Nanofluid Flow with Space and Temperature-Dependent Heat Source

Fractal Numerical Investigation of Mixed Convective Prandtl-Eyring Nanofluid Flow with Space and Temperature-Dependent Heat Source

Significance of chemical reaction and viscous dissipation on magnetized-Marangoni convective flow of dusty Casson hybrid (AA7072+AA7075/sodium alginate) nanofluid with Soret and Dufour effects

ABSTRACT In the current study, mass and heat transfer flow of radiated Casson hybrid nanofluid with nanoparticles and dust deferment over sheet are explored. The Soret and Dufour effects, activation energy and microorganisms in the hybrid nanofluid model are described. Marangoni convection, a prominent occurrence in microgravity caused by surface tension gradients. It can be used for many different things, such as the creation of molten crystals, thin-film diffusion, the generation of vapour bubbles during nucleation, and semiconductor manufacturing. In sodium alginate, we wondered about the aluminium alloys AA7072 and AA7075. The aluminium alloys included in this study are specially made materials with improved heat transmission characteristics. aluminium and zinc are combined in AA7072 alloy in the ratios of 98 & 1, respectively, with the addition of silicon, ferrous metals, and copper. Similarly, AA7075 is a blend of aluminium, magnesium, zinc, and copper in the proportions of ~ 90, ~3, ~6, and ~ 1, respectively, with silicon ferrous and magnesium as additional metals. The controlling PDEs are transformed into nonlinear ODEs with the aid of a new set of similarity variables. These ODEs are then numerically solved using the RKF-45th method. The findings show that when the Marangoni convection parameter increases, the concentration, temperature, and microbiological characteristics drop while the velocity profile increases for both the dust and fluid phases.

Simulation of enhancement techniques impact on fluid dynamics and thermal mixing of laminar forced convection flow

Simulation of enhancement techniques impact on fluid dynamics and thermal mixing of laminar forced convection flow

Mathematical Solutions of Free Convection Flow of Casson Fluid in Channel with Accelerated Plate

Mathematical Solutions of Free Convection Flow of Casson Fluid in Channel with Accelerated Plate

Mixed Convection Flow of a Casson Fluid Past a Thin Needle

Mixed Convection Flow of a Casson Fluid Past a Thin Needle