Boundary Layer Heat Transfer Research Articles

Boundary layer and heat transfer analysis of mixed convective nanofluid flow capturing the aspects of nanoparticles over a needle

Since their significance in commercial and scientific procedures has been recognized, studies regarding boundary layer flow and heat transfer have increased. The goal of this research is to examine the effects of hydromagnetic forces, mixed convection, and joule heating on ethylene glycol-based nanofluids suspended above a thin vertical needle. For thermal conductivity and viscosity, both aggregation and non-aggregation models are used. Here, we employed the similarity transformation to turn partial differential equations (PDEs) into dimensionless ODEs. Skin friction coefficients, Nusselt numbers, velocities, and temperature profiles were computed over a wide range of parameter values. The velocity and temperature profiles generated by the models that account for aggregation are superior to those generated by the homogeneous model. Velocity profile increases with λ and ε and decreases with M and e. Thermal profile increases with ϕ,M,e and Ec and decreases against λ. Skin friction and Nusselt number increases with increasing values of ϕ and λ towards ε. When comparing the findings from the present research to those from the past, it is clear that there is a high level of concordance between the two. Data availability“Data will be available on demand from Bilal.Ali”.

Darcy–Brinkman porous medium for dusty fluid flow with steady boundary layer flow in the presence of slip effect

This study looks at the Darcy–Brinkman flow across a stretched sheet of porous dissipation and frictional heating. The geometry of a steady flow of dust particles fluid through a porous material in the existence of slip effect and porous dissipation is the subject of this study. The equations that govern the system are shown and summarized as boundary layer assumptions, and then modified into framework of first-order DEs using the similarity approach. By using similarity transformation, a two-dimensional nonlinear partial differential equation is decreased to a sequence of nonlinear ordinary differential equations (ODEs). Then, by employing numerical techniques such as Maple packages, the solution of system of nonlinear equations is represented using the RK4 method. The numerical findings are derived under specific unique situations. The Nusselt number and coefficient of skin-friction are also given numerically. The increase in Brinkman number [Formula: see text] raises the temperature profile for both the dusty and the fluid phases. The results also demonstrate that rise in the suction number S falls the temperature distribution within the boundary layer for the dusty phase and fluid phase. For a variety of flow quantities of attention, the variation of parameters is studied, and the outcomes are reported in the shape of graphs and tables. Several industrial processes make advantage of boundary layer flow and heat transfer over such a stretched surface in porous materials.

Nanoparticle shape effects on MHD Cu–water nanofluid flow over a stretching sheet with thermal radiation and heat source/sink

This study provides an insight into the effects of various nanoparticle shape factors on magnetohydrodynamic boundary layer flow and heat transfer over a stretching sheet. Choosing appropriate nanoparticles can control velocity and heat transfer. A magnetic field is part of the momentum equation, and the effects of radiation and heat source/sink are part of the energy equation. Equations governing the problem are converted into nonlinear ODEs by similarity transformation. Afterwards, Runge–Kutta fourth-order scheme combined with shooting technique is employed. A magnetic field and porosity decrease the velocity. Radiation and a heat source/sink both escalate temperature. The Eckert number and porosity also improve the temperature. As nanoparticle volume fraction increases, the Nusselt number decreases and skin friction increases. Among the nanoparticle shapes considered in this study, platelet-shaped nanoparticles have the best flow and heat transfer performance. According to the studies we examined, the results obtained are consistent with those previously published.

Polymer presence in boundary layer flow and heat transfer of dusty fluid over a stretching surface

PurposeTo explore the fusion of dust particles and of polymers in a viscous liquid is the main purpose of this article. Newtonian fluid as a base fluid is considered and the mutual presence of polymers and dusty bodies is investigated. It discusses the steady laminar flow and heat transportation of a polymeric dusty liquid induced by a uniformly heated, penetrable and stretchable surface inside the boundary layer.Design/methodology/approachThe mathematical system incorporates separate equations of energy and momentum for dusty bodies and for fluid. The classical Oldroyd-B model is chosen for exploring polymer presence. For the fluid phase, this model adds another stress to the conservation law of momentum. Appropriate similarity variables are introduced to transform the system of partial differential equations (PDEs) into a system of nonlinear ordinary differential equations (ODEs). The problem is solved by introducing a numerical iterative procedure which turned out to be fastly converging.FindingsExpeditious changes inside the boundary layer cause polymers to deform. No changes outside the boundary layer are noticed on account of polymer stretching. The dependence of heat transfer rate and skin friction on the parameter of polymer concentration and Weissenberg number is analyzed and displayed graphically against interaction parameters for temperature and velocity, dust particles’ mass concentration, Eckert and Prandtl numbers. Combining effects of polymers and dust particles cause skin friction to decrease and heat transfer rate to increase. Increasing values of interaction parameter for velocity, dust particles’ mass concentration and Eckert number reduces the drag coefficient and local Nusselt number. On the other hand, the Prandtl number and interaction parameter of temperature magnify the heat flux at the wall.Research limitations/implicationsThis article studies the infinite extensibility of polymers. FENE and FENE-P models can be used to investigate the polymer presence in dusty fluids in the future.Originality/valueIn this article, the authors’ aim is to study the combined presence of polymers and dusty bodies. Keeping the existing literature in view, this type of fusion is not studied yet. Polymer inclusion in a viscous dusty fluid is studied and the behavior of fluid flow and heat transportation is investigated within the boundary layer over a permeable linearly stretching sheet.

Thermal boundary layer depletion in minichannels by electrohydrodynamic conduction pumping

The article presents a numerical analysis of two-dimensional laminar flow and heat transfer in a minichannel with flat plate electrode pairs periodically flushed to the bottom wall. The two-way coupled governing equations of flow, heat transfer, electric potential and charge conservation are solved using the opensource finite-volume framework of OpenFOAM. Two cases of the minichannel at completely horizontal (case A) and 90° bent (case B) configurations are considered. The inlet laminar flow with Reynolds number varying from 10 to 1000 has been taken into account. The applied electric potential is varied in three steps 0, 0.5 and 1 kV. Electrohydrodynamic (EHD) conduction pumping due to the residual conductivity of the working fluid and the electric-field enhanced dissociation of free charges generate vortices in the proximity of electrodes. The flow and thermal performance of the minichannel in the presence of EHD conduction induced vortices are quantified in terms of pressure drop, Nusselt number and a performance factor (which is a combined function of pressure drop and Nusselt number). The vortices generated by EHD conduction pumping phenomenon deplete the thermal boundary layer, aid mixing and enhance the heat transfer. The mean and local Nusselt numbers are notably increased with only a minimal raise in pressure drop. In both the configurations of the minichannel, the performance factor is greater than 1 for the entire parameter space considered in this study. However, the thermal boundary layer depletion and heat transfer enhancement is prominent at low Reynolds number flows. The maximum drop in performance factor from case A to case B is only 18.5%. Results of this study indicate that EHD conduction pumping is a potential technique to enhance heat transfer in minichannels with minimum additional power consumption.

Dual Solutions of Boundary Layer Flow and Heat Transfer in Hybrid Nanofluid over a Stretching/Shrinking Cylinder

The boundary layer flow over a stretching/shrinking cylinder in hybrid nanofluid with the effects of suction, partial slip and convective boundary condition is studied. Hybrid nanoparticles Al2O3 and TiO2 with water as based fluid are considered in the study. The partial differential equations are transformed to ordinary differential equations by employing the similarity variables. The numerical results are obtained using the bvp4c solver in MATLAB software. The influence of nanoparticles volume fraction (Al2O3-TiO2 in water-based fluid), curvature parameter, suction parameter, partial slip parameter and Biot number on the velocity profile, temperature profile, skin friction coefficient and heat transfer rate are discussed. The numerical results indicate that for shrinking surface case, the dual solutions exist for a certain range of curvature parameter and suction parameter.

MHD flow and heat transfer of micropolar nanofluid on a linearly stretching/shrinking porous surface

In this paper, there is considered incompressible steady two-dimensional laminar MHD boundary layer flow, heat and mass transfer characteristics of micropolar nanofluid across a linearly stretching/shrinking porous surface. The effects of the magnetic, thermal slip, mass slip and heat source sink parameters are also considered. By applyingn appropriate similarity variables, the system of governing partial differential equations associated to micropolar nanofluid flow is transformed into a system of non - linear ordinary differential equations. The resulting equations are numerically solved in the Maple software by using shooting technique. The impact of the different applied parameters on skin friction, couple stress, Nusselt and the Sherwood numbers along the related profiles are determined for both stretching and shrinking cases of the surfaces. It was observed that with an increase in suction and magnetic parameters, the fluid velocity decreased. An increment in the thermal slip, the fluid temperature decreased and nanoparticles concentration decreases as the mass slip parameter is enhanced. An increase in concentration decreases but temperature increases. While, concentration and temperature both increase due to increase in thermophoresis parameter, and concentration also increases by increase in rate of chemical reaction. Thus, suction at the boundary and magnetic parameter acted as flow controlling parameter. It is believed that this type of investigation is very much helpful for the manufacturing of complex fluids and also for cleaning oil from surfaces.

Radiation Effects on Boundary Layer Flow and Heat Transfer of the Power Law Fluid Over a Stretching Cylinder with Convective Boundary Conditions

In this work, a power law fluid model is used to examine the boundary layer flow and heat transfer characteristics over an unsteady horizontal stretching cylinder under the influence of convective boundary conditions. It is presumed that partial slip conditions exist and that the thermal conductivity of the nanofluid is a function of temperature at the boundary. Through similarity transformation, the coupled partial differential equations are converted into ordinary differential equations (ODEs), which are then resolved in MATLAB with BVP4C. By contrasting the computed findings with the published results, the validity of the results is proven. The effects of different parameters on the temperature and velocity profiles are carefully looked at and analysed. As the Eckert number increases, the thermal boundary layer thickens. All of the physical factors that affect the local Nusselt number and skin friction coefficient have been studied carefully and are shown in the tables.

Experimental research on effect of zonal heating airfoil about boundary layer flow and heat transfer

The anti-icing of aircraft and large wind turbines, where the wall temperature is higher than the fluid temperature, can significantly alter the flow evolution characteristics of the boundary layer. Local heating strategies for the manifold state need to be designed based on the changing characteristics of the flow velocity and temperature field in order to precisely control the heat supply and reduce inefficient energy consumption. In order to obtain accurate heat transfer characteristics of the airfoil’s boundary layer flow, it is necessary to refine the measurement of the boundary layer characteristics during flow and heat transfer. In this paper, wind tunnel experiments are carried out on the NACA2412 model with full surface’s zonal electric heating. The wall surface is equipped with a built-in heater and the temperature of the wall surface is obtained through the corresponding temperature sensor. By studying layer characteristics of the four heated regions, namely the laminar flow region near leading edge, the laminar flow destabilisation region, the transition region and the fully turbulent flow region, and comparing them with the boundary layer characteristics of the unheated airfoil, the effects of the presence of heat sources in different regions on the stability of the flow field and the spatial heat transfer pattern are revealed. The results show that heating in the laminar and turbulent zones maintains the stability of the flow field to a greater extent and achieves better heat transfer strength, while heating in the unstable zone brings forward the turbulence and heating in the fully turbulent zone intensifies the flow separation at the trailing edge of the airfoil. This study can be used as a reference for the design of efficient anti-icing systems on full wing surfaces.

Viscoelastic hybrid nanofluid flow over a vertical plate with sinusoidal surface temperature variations

Natural convection of a viscoelastic hybrid nanofluid along a vertically heated plate with sinusoidal surface temperature variations is investigated. The current investigation explores the non-similar boundary layer flow patterns and heat transfer of second-grade viscoelastic flow of hybrid nanofluid. Effects of magnetic field and thermal radiation are considered. The governing dimensional equations are converted into a non-dimensional form taking suitable transformations. Resulting equations are solved with the aid of finite difference method. It is discovered that the momentum boundary layer lessens while the thermal boundary layer grows for higher radiation parameters, surface temperature parameters, Eckert numbers, magnetic field parameters and amount of nanoparticles. For larger Deborah numbers (De1), shear stress (τ) and heat transfer rate (q) accelerate, but momentum and thermal boundary decline near the leading edge of the vertical plate. However, the effects of Deborah number (De2) show opposite results. Increase in magnetic field parameters causes a reduction in shear stress. The higher volume fraction of nanoparticles (φ1, φ2) enhances q as it was expected. Moreover, τ and q were increased with larger surface temperature parameters and decrease with higher Eckert numbers. This is because higher surface temperature boost up the fluid temperature, but higher Eckert numbers admit the fluid to spread over the surface. An increase in the amplitude of surface temperature oscillation enhances the shear stress and heat transfer rate.

Genetically-inspired convective heat transfer enhancement in a turbulent boundary layer

The convective heat transfer in a turbulent boundary layer (TBL) on a flat plate is enhanced using an artificial intelligence approach based on linear genetic algorithms control (LGAC). The actuator is a set of six slot jets in crossflow aligned with the freestream. An open-loop optimal periodic forcing is defined by the carrier frequency, the duty cycle and the phase difference between actuators as control parameters. The control laws are optimised with respect to the unperturbed TBL and to the actuation with a steady jet. The cost function includes the wall convective heat transfer rate and the cost of the actuation. The performance of the controller is assessed by infrared thermography and characterised also with particle image velocimetry measurements. The optimal controller yields a slightly asymmetric flow field. The LGAC algorithm converges to the same frequency and duty cycle for all the actuators. It is noted that such frequency is strikingly equal to the inverse of the characteristic travel time of large-scale turbulent structures advected within the near-wall region. The phase difference between multiple jet actuation has shown to be very relevant and the main driver of flow asymmetry. The results pinpoint the potential of machine learning control in unravelling unexplored controllers within the actuation space. Our study furthermore demonstrates the viability of employing sophisticated measurement techniques together with advanced algorithms in an experimental investigation.

Heat transfer transmission in a Marangoni boundary layer flow along an inclined disk in a porous medium

Effects of thermal radiation and pressure work on Marangoni boundary layer flow and heat transfer over an inclined disk through a porous medium are numerically discussed. The partial differential equations dominant flow phenomenon are switched into ordinary differential equations with the aid of appropriate similarity transformations. The switched ordinary differential equations are solved numerically by Rung-Kutta. The influence of the different parameters on the velocity and temperature of the fluid are discussed and analysed. Nusselt number is computed and investigated for different embedded parameters in the problem statements.

Magnetohydrodynamics effect of Marangoni nano boundary layer flow and heat transfer with CNT and radiation

The investigation focuses on 2-dimensional MHD steady incompressible flow and heat transfer. To improve the thermal efficiency, nanoparticles are added to the water base fluid and a strong transverse magnetic field is applied. After performing the appropriate similarity transformations, the governing equations for the prescribed flow form a system of PDEs, which are then converted to a system of ODEs. After solving the resulting system analytically, the velocity profile and temperature distribution are expressed in terms of exponential and Gamma functions. The existence of physical threats and the flow field are influenced by factors such as magnetic field, viscoelasticity, and suction/injection. However, the temperature field is influenced by factors including thermal radiation, Prandtl number, and others. The result shows that the axial velocity is influenced by the viscoelastic constraint, magnetic field, and suction/injection parameters. Graphical representations of the effects of mass transpiration on velocity profiles and temperature distribution are provided. It was discovered that Marangoni convection improved the rate of heat transfer. In contrast, it decreases as a result of the applied magnetic energy. Additionally, SWCNT nano liquid is hotter than nano liquid. Numerous commercial and scientific applications of the issue under discussion can be found in fields like aviation and medicine. Under the influence of radiation, the effects of MHD and suction/injection on the fluid's flow and heat transfer properties are investigated. The results of each profile's solution and the results of the interface velocity and rate of surface heat transfer are shown in the form of figures.

Local Non-Similar Solution for Non-Isothermal Electroconductive Radiative Stretching Boundary Layer Heat Transfer with Aligned Magnetic Field

Continuous two-dimensional boundary layer heat transfer in an electroconductive Newtonian fluid from a stretching surface that is biased by a magnetic field aligned with thermal radiation is the subject of this study. The effects of magnetic induction are induced because the Reynolds number is not small. The sheet is traveling with a temperature and velocity that are inversely related to how far away from the steady edge it is from the plane in which it is traveling. We also imposed external velocity u=uex=Dxp in the boundary. The necessary major equations are made dimensionless by the local non-similarity transformation and become a system of non-linear ordinary differential equations after being transformed from non-linear partial differential equations. The subsequent numerical solution of the arisen non-dimensional boundary value problem utilizes a sixth-order Runge–Kutta integration scheme and Nachtsheim–Swigert shooting iterative technique. A good correlation is seen when the solutions are compared to previously published results from the literature. Through the use of graphical representation, the physical impacts of the fluid parameters on speed, induced magnetic field, and temperature distribution are carried out. Furthermore, the distributions for skin friction coefficient and local Nusselt number are also studied for different scenarios. The skin friction coefficient and local Nusselt number are observed to increase with greater values of the temperature exponent parameter and velocity exponent parameter. However, as heat radiation increases, the local Nusselt number decreases even though temperatures are noticeably higher. The study finds applications in magnetic polymer fabrication systems.

Impact of porosity on two-dimensional unsteady MHD boundary layer heat and mass transfer stagnation point flow with radiation and viscous dissipation

The purpose of the present research is to examine the effect of porosity in the presence of radiation and viscous dissipation on two-dimensional unsteady MHD mixed convection heat and mass transport at the stagnation point. The governing time-dependent nonlinear PDEs are converted into nonlinear ODEs by utilizing similarity transformations. The mathematical formulation is produced as ordinary differential equations. The achieved coupled system has been analyzed using the Keller–Box technique. Newton’s system dictates that the coefficients must be accurate and refined. To assess the influence of flow-controlling factors on relevant profiles, quantitative, and qualitative analysis are conducted. With the use of graphs and tables, beneficial talks were conducted. Under the restricting conditions, prior findings were compared and determined to be satisfactory. The conclusions of this study are widely accepted by the scientific community.

Assessments of the heat transfer performance of a novel continuous oscillatory baffled crystallizer via two-fluid model

An Eulerian-Eulerian two-fluid model which incorporates the kinetic theory of granular flow, the energy balance equations, was firstly applied to investigate the heat transfer performance of solid–liquid two-phase flow in continuous oscillatory baffled crystallizers (COBC). The results show that the novel COBC (#6) has both excellent heat transfer and particle suspension performance, as compared with other COBCs, indicating that importance of optimizing the chamber connection structure of COBCs. Then, the COBC #6 was further selected to study the effects of operating conditions and particle physical properties on its heat transfer performance. With increase of oscillation Reynolds number (Reo), the radial mixing of fluid gradually reaches the peak, resulting in the increasing rate of Nusselt number (Nu) gradually decreases. Compared with single-phase flow, the existence of solid particles can produce shear stress on the wall surface, reducing the thickness of heat transfer boundary layer and thermal resistance, thereby increasing the heat flux. With increase of particle size or volume fraction, such effect becomes more obvious, which significantly enhances heat transfer. The novel designed COBC can be operated in the optimized Reo to achieve good heat transfer performance and low power consumption.

The novelty of using the AGM and FEM for solutions of partial differential and ordinary equations along a stretchable straight cylinder

Near the suction/injection area, a scientific definition for laminar boundary layer flow and heat transfer of an incompressible viscous flow over a stretching cylinder is given. In the study, differential equations with partial derivatives are converted into dimensionless coupled equations using numerical and analytical methods of Akbari- Ganji and Finite Elements Methods. The goal of this first stage of research and research on this topic is to use simplified forms to simplify equations using derivatives of simplified forms; the analysis of the displacement of the heat flux and the velocity gradient will be done using the changes of the Prandtl number. Based on the results obtained on this issue, it is found that the suction process increments surface firmness and quality, whereas the injection decreases surface skin friction. Also, at the points where the water and oil are attached to the surface of the cylinder, the heat has reached its maximum value, and as the distance increases along the Y axis, the temperature decreases. The highest temperature gradient is observed for water fluid. This shows that the use of water fluid around the cylinder accelerates the process of heat transfer from the surface to the outside of the boundary layer. One of the differences between the use of oil and water fluid around the cylinder according to the 2D contours is the difference in the temperature gradient of the two fluids. So that the highest temperature gradient is observed for water fluid.

Analytic similarity solutions for fully resolved unsteady laminar boundary layer flow and heat transfer in the presence of radiation

In this paper, we have compared a new type of similarity transformation derived systematically by using Lie point symmetries with the existing similarity transformations for unsteady fluid flow and heat transfer in the boundary layer in the presence of radiation. It is observed that the existing transformations map the steady and marginally accelerating flows only, while the Lie similarity transformations provide solutions for all types of accelerating flows and are independent of unsteadiness in the fluid. The previous transformations are valid for a specific time interval which depends on a range of unsteadiness parameter, however the Lie similarity transformations provide valid solutions at any given time. This implies that the Lie similarity transformations yield solutions for previously unexplored ranges of unsteadiness in the fluid. Boundary layer flow physics for both types of transformations is discussed by employing the Homotopy analysis method. We show that for accelerating fluids, in the developing region, the boundary layer thickness first increases and than starts to decrease with increase in unsteadiness for fully developed flow. Detailed comparison of velocity and temperature profiles in the boundary layer is made using the tables and graphs which show that with Lie similarity transformations the region of study of the considered flow extends significantly for the unsteadiness parameter. The effect of the Prandtl number and radiation parameter on temperature distribution is also compared for both types of similarity transformations. The Lie symmetry similarity transformations are shown to explain the unsteady laminar boundary layer flow and heat transfer to an extent where the existing similarity transformations do not work.

Decomposition of the skin-friction coefficient of compressible boundary layers

We derive an integral formula for the skin-friction coefficient of compressible boundary layers by extending the formula of Elnahhas and Johnson [“On the enhancement of boundary layer skin friction by turbulence: An angular momentum approach,” J. Fluid Mech. 940, A36 (2022)] for incompressible boundary layers. The skin-friction coefficient is decomposed into the sum of the contributions of the laminar coefficient, the change of the dynamic viscosity with the temperature, the Favre–Reynolds stresses, and the mean flow. This decomposition is applied to numerical data for laminar and turbulent boundary layers, and the role of each term on the wall-shear stress is quantified. We also show that the threefold integration identity of Gomez et al. [“Contribution of Reynolds stress distribution to the skin friction in compressible turbulent channel flows,” Phys. Rev. E 79(3), 035301 (2009)] and the twofold integration identities of Wenzel et al. [“About the influences of compressibility, heat transfer and pressure gradients in compressible turbulent boundary layers,” J. Fluid Mech. 930, A1 (2022)] and Xu et al. [“Skin-friction and heat-transfer decompositions in hypersonic transitional and turbulent boundary layers,” J. Fluid Mech. 941, A4 (2022)] for turbulent boundary layers all simplify to the compressible von Kármán momentum integral equation when the upper limit of integration is asymptotically large. The dependence of these identities on the upper integration bound is studied. By using asymptotic methods, we prove that the multiple-integration identity of Wenzel et al. [“About the influences of compressibility, heat transfer and pressure gradients in compressible turbulent boundary layers,” J. Fluid Mech. 930, A1 (2022)] degenerates to the definition of the skin-friction coefficient when the number of integrations is asymptotically large.

The Effects of Buoyancy, Magnetic Field and Thermal Radiation on the Flow and Heat Transfer due to an Exponentially Stretching Sheet

The boundary layer flow and heat transfer across an exponentially stretched sheet with buoyancy, magnetic field, and thermal radiation are investigated. The similarity transformation is applied to the governing equations to generate nonlinear ordinary differential equations. They are resolved using a numerical technique referred to the Keller-box method. The impact of determined controlling parameters on flow and heat transfer characteristics are investigated. It has been discovered that the buoyancy parameter increases both the heat transfer rate and fluid flow from the exponentially extending sheet to the fluid.