Stagnation Point Heat Research Articles

Off-centered stagnation point flow of an experimental-based hybrid nanofluid impinging to a spinning disk with low to high non-alignments

PurposeThe purpose of this study is to model and solve numerically the three-dimensional off-centered stagnation point flow and heat transfer of magnesium oxide–silver/water hybrid nanofluid impinging to a spinning disk.Design/methodology/approachThe applied effective thermophysical properties of hybrid nanofluid including thermal conductivity and dynamics viscosity are according to the reported experimental relations that would be expanded by a mass-based algorithm. The single phase formulations coupled with experimental-based hybrid nanofluid model is implemented to derive the governing partial differential equations which are then transferred to a set of dimensionless ordinary differential equations (ODEs) with the use of the similarity transformation method. Afterward, the reduced ODEs are solved numerically by bvp4c function from MATLAB that is a trustworthy and efficient code according to three-stage Lobatto IIIa formula.FindingsThe effect of spinning parameter and nanoparticles masses (mMgO, mAg) on the hydrodynamics and thermal boundary layers behavior and also the quantities of engineering interest are presented in tabular and graphical forms. The recent work demonstrates that the analysis of flow and heat transfer becomes more complicated when there is a non-alignment between the impinging flow and the disk axes. From computational results demonstrate that, the radial and azimuthal velocities are, respectively, the increasing and decreasing functions of the disk spinning parameter. Further, for the greater values of the spinning parameter, an overshoot of the radial velocity owing to the centrifugal forces of the spinning disk is observed. Besides, the quantities of engineering interest gently enhance with first and second nanoparticle masses, while comparing their absolute values illustrates the fact that the effect of second nanoparticle mass (mAg) is greater. Further, it is inferred that the second nanoparticle’s mass enhancement results in the amplification of the heat transfer; although, the high skin friction and the relevant shear stress should be controlled.Originality/valueThe combination of experimental thermophysical properties with theoretical modeling of the problem can be the novelty of the present work. It is evident that the experimental relations of effective thermophysical properties can be trustable and flexible in the theoretical/mathematical modeling of hybrid nanofluids flows. Besides, to the best of the authors’ knowledge, no one has ever attempted to study the present problem through a mass-based model for hybrid nanofluid.

Magnetohydrodynamic Flow Past a Nonlinear Stretching or Shrinking Cylinder in Nanofluid with Viscous Dissipation and Heat Generation Effect

The Tiwari-Das model is used to investigate magnetohydrodynamic stagnation point flow and heat transfer past a nonlinear stretching or shrinking cylinder in nanofluid with viscous dissipation and heat generation using. The partial differential equations, also known as governing equations, were reduced to nonlinear ordinary differential equations using similarity transformation. MATLAB with the bvp4c solver is used for numerical computing. The controlling parameter, such as nanoparticle volume fraction, magnetic, curvature, nonlinear, radiation, and heat generation parameters, as well as Eckert and Grashof numbers, influence the skin friction coefficient, heat transfer rate, velocity, and temperature profiles. The results are presented as graphs to show the influence of the variables studied. In some circumstances of stretching and shrinking cases, dual solutions can be obtained.

MHD Stagnation Point on Nanofluid Flow and Heat Transfer of Carbon Nanotube over a Shrinking Surface with Heat Sink Effect.

This study is to investigate the magnetohydrodynamic (MHD) stagnation point flow and heat transfer characteristic nanofluid of carbon nanotube (CNTs) over the shrinking surface with heat sink effects. Similarity equations deduced from momentum and energy equation of partial differential equations are solved numerically. This study looks at the different parameters of the flow and heat transfer using first phase model which is Tiwari-Das. The parameter discussed were volume fraction nanoparticle, magnetic parameter, heat sink/source parameters, and a different type of nanofluid and based fluids. Present results revealed that the rate of nanofluid (SWCNT/kerosene) in terms of flow and heat transfer is better than (MWCNT/kerosene) and (CNT/water) and regular fluid (water). Graphically, the variation results of dual solution exist for shrinking parameter in range for different values of volume fraction nanoparticle, magnetic, heat sink parameters, and a different type of nanofluid. However, a unique solution exists at , and no solutions exist at which is a critical value. In addition, the local Nusselt number decreases with increasing volume fraction nanoparticle when there exists a heat sink effect. The values of the skin friction coefficient and local Nusselt number increase for both solutions with the increase in magnetic parameter. In this study, the investigation on the flow and heat transfer of MHD stagnation point nanofluid through a shrinking surface with heat sink effect shows how important the application to industrial applications.

Impact of the magnetic dipole on stagnation point flow of ferromagnetic Walters‐B liquid: A passive control approach with Buongiorno's model

AbstractThe properties of ferromagnetic fluids make them suitable for a wide range of applications, including loudspeakers, magnetic resonance imaging, computer hard drives, magnetic drug delivery, and magnetic hyperthermia. Owing to all such potential applications, the present research work is established to explain the stagnation point flow, heat, and mass transfer of Walters‐B liquid in the presence of magnetic dipole, Brownian diffusion, and thermophoresis. To control the nanoparticles concentration at the surface, a passive control condition is employed. Using suitable similarity transformations, the governing equations are converted into nonlinear ordinary differential equations. Noticeable behavior of significant parameters on flow fields is studied graphically. The significant outcomes of the present study are that the increased values of viscoelastic parameter decline the velocity but an inverse trend is seen in heat transfer. The increased values of the Brownian motion parameter decline the heat transfer but a contrary trend is seen for augmented values of the thermophoresis parameter. The heat transfer rate is increased for rising values of radiation parameter and Biot number. The upward values of the thermophoresis parameter decline the rate of mass transfer. The escalating values of ferromagnetic interaction and velocity ratio parameters improve the skin friction.

Stagnation point flow and heat transfer over an exponentially stretching/shrinking Riga plate with effects of radiation and heat source/sink

Stagnation point flow and heat transfer over an exponentially stretching/shrinking Riga plate with effects of radiation and heat source/sink

The effect of thermal radiation, velocity slip and viscous dissipation on MHD stagnation-point flow and heat transfer over a shrinking sheet in nanofluids with stability analysis

The effect of thermal radiation, velocity slip and viscous dissipation on MHD stagnation-point flow and heat transfer over a shrinking sheet in nanofluids with stability analysis

Dynamics of thermal Marangoni stagnation point flow in dusty Casson nanofluid

ABSTRACT The current perusal presents a stagnation point (SP) flow and heat transfer analysis of Casson dusty nanofluid over a surface with Marangoni convection. Here, non-Newtonian nanoliquid suspended with as nanoparticle and dust particles in base fluid sodium alginate is utilized to scrutinize the present two-phase boundary layer model. Further, suitable transformations are used to reduce the modelled governing equations to a set of ordinary differential equations. Later, numerical solutions are secured using an efficient and well-known Runge-Kutta-Fehlberg fourth fifth-order (RKF-45) method using the shooting technique. The impacts of the governing parameters on various profiles are illustrated with the help of graphs. The significant findings of the current model are that the escalating values of the Marangoni number deteriorations the velocity gradient of both dusty nanoliquids. The augmentation of dust particle mass concentration declines the thermal gradient of both liquid and particle phases. The boost up values of dust particle mass concentration and thermal dust parameter advances the rate of heat transfer.

Homann Stagnation Point Flow and Heat Transfer of Hybrid Nanofluids Over a Permeable Radially Stretching/Shrinking Sheet

The steady two-dimensional Homan stagnation point flow and heat transfer of water base hybrid nanofluids (Al2O3 & Cu) over a permeable radially stretching/shrinking sheet have been studied. The similarity variables are introduced to transform the partial differential equations of the model into the ordinary differential equations. Numerical findings and dual solutions have been carried out by implementing the bvp4c code through MATLAB software. The most prominent effect is illustrated in the boundary layer thickness where the velocity profile increases upon the increment of the suction intensity but decreases in the temperature profile. Besides, the reduced Nusselt number also decreases as enlarging the value of copper and alumina nanoparticle volume fraction. The analysis of the first and second solutions are presented graphically with critical values as well as the detail discussions on the effects of the other involving parameters.

Numerical duality of MHD stagnation point flow and heat transfer of nanofluid past a shrinking/stretching sheet: Metaheuristic approach

In the present era of Industry 4.0, automation, and nanotechnology, many industrial applications require the simultaneous control of heat and fluid flow for better efficiency of machines. The polymeric excursion process, manufacturing of plastic films, glass, metallic equipment, all need control over friction forces and heat flow rates. Considering the importance of the subject, the present study deals with the stagnation point flow and heat transfer of water-based nanofluid over a stretching/shrinking sheet with a non-aligned axis of symmetry. The permeable sheet is considered in the presence of a uniform magnetic field. The non-linear partial differential equations governing the flow and heat transfer are converted into non-linear coupled ordinary differential equations using similarity transformations. The resultant equations are solved using “Particle Swarm Optimization” and Runge-Kutta method based hybrid shooting technique. Considering the nanoparticle size, concentration and shape-dependence on physical and thermal properties of nanofluid more realistic aggregation based mathematical models are used for both viscosity and thermal conductivity. Numerical results for the velocity profile, non-alignment function, temperature distribution and local skin friction are discussed with respect to the physical parameters like nanoparticle concentration, nanoparticle size, magnetic field, suction, and stretching/shrinking velocity. The existence of dual solutions are observed for the shrinking velocity parameter λ<−1, and the practically realizable and stable solutions are filtered out by computing the eigenvalues for the formulated perturbed Eigen problem. The results for the stable solutions unveiled that, by changing the stretching velocity parameter λ from 0 to 0.5, there is approximately 38% enhancement in heat transfer rate and 42% decrement in skin friction coefficient. Moreover, in the case of shrinking velocity parameter λ=−1.25, with an increase in nanoparticle concentration from 0 to 5%, the skin friction coefficient reduces by 53%, whereas the change in nanoparticle size from 10 nm to 50 nm has a skin friction reduction of only 10%.

Stagnation Point Heat Flow and Mass Transfer in a Casson Nanofluid with Viscous Dissipation and Inclined Magnetic Field

Influence of slip and inclined magnetic field on stagnation-point flow with chemical reaction are studied. Implementation of the similarity transformations, transformed the fluid non-linear ordinary differential equations and numerical computation is performed to solve those equations using Spectral Collocation Method. Various pertinent parameters on fluid flow, temperature and concentration distributions of the Casson nanofluid flow as well as the local skin friction coefficient, local Nusselt number, and Sherwood number are graphically displayed. The results indicate that thermophoresis parameter N_t enhanced the temperature and nanoparticle concentration profiles, because a rise in thermophoresis parameter enhances the thermophoresis force within the flow regime. Values of both local Nusselt and Sherwood numbers are enhanced with an increase in Hartman number (magnetic field parameter). The present results are compared with previously reported ones and are found to be in excellent agreement.

A study on heat flux predictions for re-entry flight analysis

The analysis of the risk from re-entry objects has become an important topic. Concerning the uncertainties and different flow regimes, the object-oriented tools have been developed and used for various re-entry mission scenarios because of the simplified computation process and low calculation burden, which allow a probabilistic analysis. In this study, the heat flux correlations that are used in the object-oriented tools are investigated and compared to better understand the heat flux predictions with respect to re-entry survivability. Often these tools calculate the continuum stagnation-point heat flux using the correlation formulae of Lees and Fay–Riddell, which usually assume local thermo-chemical equilibrium with a fully-catalytic wall condition in the shock layer. Based on this observation, heat flux measurements were conducted in a hypersonic wind tunnel, and validated with the theory of Fay–Riddell considering the equivalent velocity gradient. For the comparison, in total, 11 different heat flux correlations were examined. It is shown that, based on the formula of Fay–Riddell, the differences in the final integrated heat flux were less than 16% which led to a large discrepancy in the survivability estimations for the cases of small spheres made of aluminum. This shows the importance of considering the heat flux correlation as well as the velocity gradient effect for such re-entry analysis.

Thermal Radiation Effects on Unsteady Stagnation Point Nanofluid Flow in View of Convective Boundary Conditions

The present communication particularizes nonlinear convective non-Newtonian stagnation point flow and heat transference effects in stretchable flow of nanofluid. Magnetohydromagnetic steady viscous flow of nanofluid is examined. Heat transfer attributes of nanofluids are addressed via a numerical algorithm. Conductivity and diffusivity characteristics of fluid are depending on temperature and concentration and furthermore, on mass conservation, momentum, energy, and concentration yield partial differential equations (PDEs). The boundary layer flow concept pioneered by Prandtl has been employed to simplify the nonlinear constitutive flow laws which are then changed to ordinary differential equations. A built-in bvp4c algorithm in Mathematica software yields convergent outcomes of nonlinear (ODEs) systems. A comprehensive analysis has been made elucidating the physical significance of various governing parameters effects presented graphically. Additionally, the flow nature was confirmed versus streamlines.

Estimation of Aerodynamic Heating on Scramjet Inlets and Validation With Measurements

Abstract Aerodynamic heating levels on a typical inlet configuration of a scramjet engine are estimated using both standard design correlations and numerical flow simulations. The stagnation point heat flux is estimated using the Fay and Riddell formula. Aerodynamic heating over the inclined ramps is estimated using Van Driest method. Numerical flow simulations are carried out using a Reynolds averaged Navier–Stokes (RANS) solver coupled with energy equations and the Shear Stress Transport (SST) k–ω turbulence model. The aerodynamic heat flux estimates are validated with in-house measurements in a shock tunnel and for a scramjet flight experiment in the Mach number range 1.59 to 7.92. The emergence of a good agreement between them confirms the appropriateness of design correlations for heat flux estimation in scramjet inlets. The choice of simplification and appropriateness of design correlations to complex geometries demand critical assessment. Numerical flow simulations capture flow features and enable the identification of potential augmented heating zones, which will be critical for long-duration scramjet missions.

Correlations for heat transfer characteristics of the onset of nucleate boiling in submerged jet impingement

The submerged jet impingement boiling is one of the most effective heat transfer methods in dissipating both transient and steady concentrated heat loads. However, studies on the submerged jet impingement boiling still lack experimental data, especially for the heat transfer characteristics of the onset of nucleate boiling (ONB). Therefore, an experimental study of a submerged circular jet impinging on a polished copper surface is conducted in the subcooled water. The experiments investigate the steady-state heat transfer characteristics at the stagnation point from single phase convection to partial nucleate boiling. The effects of jet Reynolds number, liquid subcooling, and nozzle diameter on the onset of nucleate boiling are systematically studied. The experimental results show that the single phase convective heat transfer can be enhanced by increasing jet velocity at a fixed nozzle diameter or decreasing nozzle diameter under the same jet Reynolds number. The liquid subcooling seems to have negligible effect on the single phase heat transfer coefficient. For the ONB point, it is found that the ONB wall superheat is not influenced by liquid subcooling or jet parameters. The ONB heat flux, on the other hand, is found to depend on the experimental parameters. Increasing the jet Reynolds number and liquid subcooling, or decreasing the nozzle diameter could broaden the single phase convective regime and delay the onset of nucleate boiling, in terms of heat flux. Empirical correlations are proposed for predicting the stagnation point heat transfer coefficient, heat flux, and wall superheat at the ONB point. The comparison between the predicted values and the experimental data indicates that the empirical correlations are able to predict the heat transfer characteristics of the onset of nucleate boiling within an acceptable accuracy under the applicable range.

New Analytical Solution of Stagnation Point Flow and Heat Transfer in a Porous Medium

A new analytical method called q-homotopy analysis method is applied for solving nonlinear differential equations. In this paper, the mathematical study of stagnation points flow and heat transfer phenomena in a porous medium are discussed. The governing coupled nonlinear partial differential equations are converted into coupled nonlinear ordinary differential equations using similarity transformations and solved analytically for the values of Prandtl number Pr, Porous medium K, Casson fluid parameter β, Ratio parameter c using q-homotopy Analysis Method. The influence of the skin-friction coefficients for different parameters is discussed and presented in tabular form. The obtained q-homotopy analysis method solutions are compared with numerical results and it gives a remarkable accuracy.

MHD Stagnation Point Flow and Heat Transfer Over a Stretching Sheet in a Blood-Based Casson Ferrofluid With Newtonian Heating

The present study investigated the magnetohydrodynamic (MHD) flow and heat transfer on a stagnation point past a stretching sheet in a blood-based Casson ferrofluid with Newtonian heating boundary conditions. The ferrite Fe3O4 and cobalt ferrite CoFe2O4 ferroparticles suspended into Casson fluid represent by human blood to form blood-based Casson ferrofluid are numerically examined. The mathematical model for Casson ferrofluid which is in non-linear partial differential equations are first transformed to a more convenient form by similarity transformation approach then solved numerically by using the Runge-Kutta-Fehlberg (RKF45) method. The characteristics and effects of the stretching parameter, the magnetic parameter, the Casson parameter and the ferroparticle volume fraction for Fe3O4 and CoFe2O4 on the variation of surface temperature and the reduced skin friction coefficient are analyzed and discussed. It is found that the blood-based Casson ferrofluid provided up to 46% higher in temperature surface compared to blood-based fluid with the presence of magnetic effects.

Arrhenius Activation Energy Effect on a Stagnation Point Slippery MHD Casson Nanofluid Flow with Entropy Generation and Melting Heat Transfer

This study features the entropy generation analysis on a steady two-dimensional flow of an incompressible Casson fluid with heat and mass transfer over a heated linearly stretching surface is investigated using a modified Arrhenius activation energy. The appropriate model governing the physical phenomenon is converted into a dimensionless equation with the aid of appropriate transformation and are numerically solved using the spectral collocation method. The present research model is concerned to study the stagnation point slippery flow, heat, and mass transfer analysis of a Casson fluid flow past an elastic surface with the impact of a magnetic field. The study focuses on the influences of Arrhenius activation energy, melting heat transfer, and heat source on heat and mass transfer behavior posed by Casson fluid. The magnitude of skin becomes lesser for larger values of slip parameter while the rate of mass transfer is enhanced via greater values of the destructive chemical reaction. Also, an excellent agreement is shown with previous studies for the limiting case.

Evolution of heat transfer at the stagnation point during the detached bow shock establishment

The diffraction of a shock wave over a stationary body is a problem of interest associated with the starting of shock tubes and expansion tubes which are well suited to studies of hypersonic flows. However, these facilities are characterized by very short test times. The transient parameters during the establishment of the detached bow shock in such impulsive facilities are important for both data processing and experimental design. In the present study, numerical simulations are conducted to investigate the diffraction of a normal shock wave over a sphere and the subsequent transient phenomena in a viscous perfect-gas flow field. The incident shock Mach number ranges from 3 to 5 with a specific heat ratio of 1.4. Based on the theoretical description of the reflected shock position during bow shock formation, approximate solutions for the time histories of the stagnation-point heat flux are also derived. The analytical and numerical results agree well. The results show that the stagnation-point pressure and heat flux approach their steady-state values much more rapidly than the shock detachment distance does.

Unsteady hybrid nanofluid flow over a radially permeable shrinking/stretching surface

The time-dependent stagnation point flow (SPF) and heat transfer of a water-based hybrid nanofluid (Cu − Al2O3/Water) from a radially permeable shrinking or stretching surface is examined. The similarity technique is employed to transform the governing equations of hybrid nanofluid (Cu − Al2O3/Water) into similarity equations. These similarity equations are solved numerically using bvp4c function in MATLAB software. The numerical outcomes are acquired for particular values of the selected parameters. The results notice that dual solutions exist, up to a definite amount of the suction, unsteady strengths, and nanoparticle volume fraction. The critical amount declines due to nanoparticle volume fraction and augments due to suction and unsteady parameters. Also, it is seen that hybrid nanofluid (Cu − Al2O3/Water) augments the rate of heat transfer relative to the regular fluid. The temporal stability analysis is implemented to determine the stability of the dual solutions, and it is found that only one of them is stable and thus physically reliable as time passes.

Solar radiation effects on MHD stagnation point flow and heat transfer of a nanofluid over a stretching sheet

The aim of this study is investigation of solar radiation influences on two-dimensional stagnation-point flow of nanofluid over a stretching sheet. The magnetic field is considered and the nonlinear Rosseland approximation is applied for thermal radiation in current work. The governing equations are transformed into a system of coupled nonlinear ordinary differential equations using similarity transformations which are solved numerically by means of the efficient differential quadrature method (DQM). The numerical results show the superb accuracy, good convergence with little computational efforts and the great potential of this method. Also, it is found that the temperature and thermal boundary layer thickness are increasing functions of Biot number. The findings narrate that increasing values of Brownian motion parameter make greater temperature values on the profile and thicker thermal boundary layer.