Unsteady Mixed Convection Flow Research Articles

Unsteady flow of Williamson fluid under the impact of prescribed surface temperature (PST) and prescribed heat flux (PHF) heating conditions over a stretching surface in a porous enclosure

AbstractAn unsteady mixed convection flow of Williamson nanofluid over a stretchable surface embedded in a porous medium is scrutinized numerically. Here the porous medium is characterized by Darcy Forchheimer model under the influence of a magnetic field. Heat transfer analysis with two different conditions namely, prescribed surface temperature (PST) and prescribed heat flux (PHF) are taken into account. The evolved mathematical model is numerically solved by utilizing the Keller box method and bvp4c solver in MATLAB. The significance of diverse non‐dimensional physical parameters on the considered flow problem is thoroughly demonstrated and discussed for velocity, temperature and concentration profiles through graphs and tables. From the outcomes, it is stipulated that the velocity of fluid enhances with mixed convection and buoyancy ratio parameter whereas switch pattern is spotted for temperature and concentration distributions in both including conditions.

Thermal radiation effect on unsteady mixed convection boundary layer flow and heat transfer of nanofluid over permeable stretching surface through porous medium in the presence of heat generation.

Here, we study the effect of mixed convection and thermal radiation on unsteady boundary layer of heat transfer and nanofluid flow over permeable moving surface through a porous medium. The effect of heat generation is also discussed. The equations governing the system are the continuity equation, momentum equation and the heat transfer equation. These governing equations transformed into a system of nondimensional equations contain many physical parameters that describe the study. The transformed equations are solved numerically using an implicit finite difference technique with Newton's linearization method. The thermo-physical parameters describe the study are the mixed convection parameter α, , the Radiation parameter Rd, , porous medium parameter k, , the nanoparticles volume ,, the suction or injection parameter fw, , the unsteadiness parameter At, and the heat source parameter λ = 0.5 .The influence of the thermo-physical parameters is obtained analytically and displayed graphically. Comparisons of some special cases of the present study are performed with previously published studies and a good agreement is obtained.

Unsteady mixed convection flow of magneto-Williamson nanofluid due to stretched cylinder with significant non-uniform heat source/sink features

This analysis reports an unsteady and incompressible flow of Williamson nanoliquid in presence of variable thermal characteristics are persuaded by a permeable stretching cylinder. The flow field investigation is established with the effect of mixed convection and non-uniform heat source/sink on flow and heat transfer. On the cylinder surface, the analysis is inspected with utilization of zero mass flux constraints. By using the appropriate similarity variables, the framed equations for the energy, momentum and mass is converted into non-linear ODEs. The numerical communication of the boundary value problem is successfully implemented using a computer algorithm programmed into the fifth Runge-Kutta scheme. Additionally, the wall shear factor and rate of heat transfer are calculated in two different cases namely, with curvature and without curvature. In addition, the results obtained are confirmed by making comparisons with previously published articles and we found an excellent match that guarantees the indemnity of current communication. A comprehensive change in velocity, temperature and concentration is examined for involved parameters like local Weissenberg number, space dependent heat source constant, magnetic number, curvature constant, thermophoretic parameter, buoyancy parameter, Brownian motion parameter, Prandtl number, Schmidt number, unsteadiness parameter, reaction rate parameter, activation energy parameter and temperature difference parameter. A reduction in velocity is observed for unsteady parameter and buoyancy constant. An enhanced nanofluid temperature is noted for space dependent heat source parameter, time dependent heat source parameter and unsteady parameter. Moreover, the nanofluid concentration is increases for temperature difference parameter while reverse observations are noticed for chemical reaction rate.

Unsteady mixed convection flow of variable viscosity nanofluid in a micro-channel filled with a porous medium

Unsteady mixed convection flow of variable viscosity nanofluid in a micro-channel filled with a porous medium

Unsteady mixed convective flow of nanofluid with arbitrary‐shaped nanoparticles over a shrinking sheet

AbstractThe present study describes the unsteady mixed convection nanofluid flow past a vertical shrinking porous surface in occurrence of slips and heat source/sink. Applying proper transformations, the foremost differential equations which are partial in nature are changed into non‐linear differential equations which are ordinary in nature. With the support of Runge–Kutta method, shooting technique is used to find out the numerical solutions of the system of equations stated above. The effects of diverse leading parameters like unsteady parameter, velocity slip parameter, suction/injection parameter, thermal slip parameter, and heat source/sink parameter are offered and explained physically. Also, the coefficient of skin friction and rates of surface heat and mass transport for a number of parameters are investigated numerically.

Numerical solution for Falkner-Skan flow of hybrid nanofluid with porosity effect

ABSTRACT Hybrid nanofluid is known to improve heat transfer performance, and its advantages have led to relatively reasonable expectations for their applications. This research considered a moving wedge, namely the Falkner-Skan model, which is well-known in the aerodynamic field. Hybrid nanofluid has been chosen where the dispersion of alumina and copper nanoparticles with water as the base fluid is considered in the unsteady mixed convection flow over moving wedge. By using similarity transformations, the governing equations are converted into ordinary differential equations and then numerically solved using MATLAB bvp4c solver. The increasing values of porosity parameter caused the velocity of hybrid nanofluid to increase. The results also indicated that, the effect of porosity parameter improved the values of skin friction coefficient but decrease the value of Nusselt number.

Unsteady Mixed Convection Flow along Symmetric Wedge with Variable Surface Temperature Embedded in a Porous Medium Saturated with a Nanofluid

Laminar two-dimensional unsteady mixed-convection boundary-layer flow of a viscous incompressible fluid past asymmetric wedge with variable surface temperature embedded in a porous medium saturated with a nanofluid has been studied. The employed mathematical model for the nanofluid takes into account the effects of Brownian motion and thermophoresis. The velocity in the potential flow is assumed to vary arbitrary with time. The non-Darcy effects including convective, boundary and inertial effects will be included in the analysis. The unsteadiness is due to the time-dependent free stream velocity. The governing boundary layer equations along with the boundary conditions are converted into dimensionless form by a non-similar transformation, and then resulting system of coupled non-linear partial differential equations are solved by perturbation solutions for small dimensionless time until the second order. Numerical solutions of the governing equations are obtained employing the implicit finite-difference scheme in combination with the quasi-linearization technique. To validating the method used, we compared our results with previous results in earlier papers on special cases of the problem and are found to be in agreement. Effects of various parameters on velocity, temperature and nanoparticle volume fraction profiles are graphically presented.

Unsteady mixed convection flow at a three-dimensional stagnation point

PurposeThis paper aims to probe the problem of an unsteady mixed convection stagnation point flow and heat transfer past a stationary surface in an incompressible viscous fluid numerically.Design/methodology/approachThe governing nonlinear partial differential equations are transformed into a system of ordinary differential equations by a similarity transformation, which is then solved numerically by a Runge – Kutta – Fehlberg method with shooting technique and a collocation method, namely, the bvp4c function.FindingsThe effects of the governing parameters on the fluid flow and heat transfer characteristics are illustrated in tables and figures. It is found that dual (upper and lower branch) solutions exist for both the cases of assisting and opposing flow situations. A stability analysis has also been conducted to determine the physical meaning and stability of the dual solutions.Practical implicationsThis theoretical study is significantly relevant to the applications of the heat exchangers placed in a low-velocity environment and electronic devices cooled by fans.Originality/valueThe case of suction on unsteady mixed convection flow at a three-dimensional stagnation point has not been studied before; hence, all generated numerical results are claimed to be novel.

Analytical and Numerical Study on Cross Diffusion Effects on Magneto-Convection of a Chemically Reacting Fluid with Suction/Injection and Convective Boundary Condition

The purpose of this paper is to investigate the Soret and Dufour effects on unsteady mixed convective boundary layer flow of a viscous fluid over a stretching surface in a porous medium in the presence of magnetic field with heat generation/absorption, chemical reaction, suction/injection and convective boundary condition. The governing time-dependent partial differential equations are transformed into non-linear ordinarydifferential equations using similarity transformations. These equations subject to the appropriate boundary conditions are solved analytically by homotopy analysis method (HAM) and numerically by Runge-Kutta fourth order method and shooting technique.The numerical solution is compared with analytical solution. The influence of the different parameters on velocity, temperature and concentration profiles are discussed in graphical as well as in tabular form. It is observed that the fluid velocity and temperature increase on increasing the buoyancy ratio parameter and heat generation/absorption parameter. Also found that the surface heat and mass transfer rates increase on increasingthe suction/injection and heat generation/absorption parameters.

Radiation and Magnetic Field Impacts on Time-Dependent Mixed Convection Flow and Heat Transmission of Maxwellian Fluid Past A Stretching Sheet

The current study was devoted to explicating the impacts of heat transmission in an unsteady mixed convection flow of an upper convected Maxwell (UCM) fluid passing over a continuously stretching surface under the influence of radiation and magnetic field. Appurtenant similarity transmutations were adopted in order to express the constitutive boundary layer Equations of flow and heat transmission in non-dimensionalized form. The reduced system of partial differential Equations was solved by implementing the implicit finite difference method (IFDM). Our center of attention was to scrutinize the behavior of influential flow parameters on some significant features of flow and heat transmission, which were briefly examined, discussed, and presented in both graphical and tabular formats. Finally, a comparison was established with existing literature in limiting cases to support the present results, and a good agreement was found, corroborating our work. It was predicted that the thermal diffusion rate could be controlled by varying the Prandtl number. Moreover, a rise in radiation and magnetic field parameters reduced the skin friction coefficient and led to enhance the heat transmission rate at the surface. The outcomes of the study might have viable implementations in order to improve the quality of industrial products.

Analysis of the effect of generalized fractional Fourier’s and Fick’s laws on convective flows of non-Newtonian fluid subject to Newtonian heating

The aim of this report is to study an unsteady mixed convection flow of an incompressible differential type fluid occurrence of chemical reaction that is first order, heat source and radiative heat source with fractional mass diffusion and thermal transports over an infinite vertical plate. The fractional derivative Caputo–Fabrizio which is defined recently with non-singular kernel is used in constitutive laws for the mass and thermal flux, respectively. Semi analytical solutions of the dimensionless concentration, temperature, and velocity fields in addition the rates of heat and mass transfer from the plate to the fluid are established by virtue of the Laplace inversion numerical algorithms Stehfest’s and Tzou’s. Some solutions for ordinary case and obvious results from articles are retrieved as limiting cases. Finally, an impact of flow and fractionalize parameters $$\alpha $$ and $$\beta $$ on concentration, temperature and velocity profiles is tabularly and graphically underlined and discussed . We present a valuation between second grade (fractional and ordinary) and viscous (fractional and ordinary) fluids is also interpreted. It is identified that the ordinary fluid has high velocity as comparable to fractional fluids.

Slip role for unsteady MHD mixed convection of nanofluid over stretching sheet with thermal radiation and electric field

This paper mainly focuses on the impacts of slip conditions on the two-dimensional unsteady mixed convection flow of electrical magnetohydrodynamic nanofluid over a stretching sheet in the presence of thermal radiation, viscous dissipation, and chemical reaction. The synchronized impacts of electric and magnetic fields on the momentum and energy fields using Buongiorno nanofluid model were introduced to enhance thermal conductivity and hence create more pathways to heat transfer performance of nanofluid. The highly nonlinear couple systems of partial differential equations were modeled as a set of nonlinear ordinary differential equations by using suitably defined transformations which are then solved by implicit finite difference scheme known as Keller box method. It was established that velocity has a direct opposite relationship with electric and magnetic fields. The velocity, temperature, and concentration profiles caused intense decay to velocity slip, thermal slip, and solutal slip, with permeability condition. Magnetic field enhances the nanofluid temperature intensely with impermeable medium resulting in a decrease in heat transfer rate from the surface. The heat convection current is strengthened by viscous dissipation and radiative heat transfer prevailing impermeability, which leads to a reduction in heat transfer rate. Comparisons with previously published works seen in the literature were made, and the result was found to be in excellent agreement.

Boundary-Layer Separations of Mixed Convection Flow Past an Isothermal Circular Cylinder

This study reveals the boundary-layer separations of unsteady mixed convection flow of incompressible fluid past a circular cylinder which is kept at a constant temperature. The governing equations are made dimensionless using an appropriate transformation. These equations are solved with the use of finite difference method. We also solve the problem using perturbation method for small time and local non-similarity method for long time. Results show that numerical solutions agree well with the series solutions obtained by perturbation method for small time and asymptotic method for long time. For an increase of Richardson number and Prandtl number, the local friction factor and the rate of heat transfer increases. Besides, the streamlines and isotherms reveal that when the Richardson number and the Prandtl number are increased, the point of separation of boundary-layer reduces and the size of vortex decreases. Moreover, the larger values of Richardson number thicken the thermal boundary layer whereas the reverse characteristic is observed for higher Prandtl numbers.

Unsteady Boundary Layer Flow of Sphere Filled with Nanofluid in the Present of Magnetic Fields

The development of boundary layer flow problem which is involve of nanofluid for improve thermal efficiency in many applications is gaining momentum as most of base fluid are not very good thermal conductor. The enhancement of thermal conductivity can be improving when the magnetic fields is presented. Also, by using this material may encountered another problem such as separation flow. This research is study about magnetic fields effect on unsteady mixed convection flow on nanofluid past a sphere with heat flux as its boundary condition. This problem will consider its mathematical model where it can help to predict the solution in experimental method. The mathematical method that being used is Keller-box because of its ability to solve non-linear equation. The nanoparticles that being choose are copper and titanium oxide with water as based fluid. There will have three equation which is mass, momentum, and energy equation. All equations are transform into non-similarity ordinary differential equations by using appropriate variables. The effect of magnetic parameter on velocity and temperature profiles as well as skin friction and Nusselt number are studied. The results show that volume fraction affected the heat-transfer rate, and skin friction coefficient. This study also shows that magnetic parameter affected the separation times which is decelerated the flow.

Mixed Convective MHD Micro-Polar Fluid Flow in a Porous Medium with Radiation Absorption

An unsteady mixed convective flow of micro-polar fluid in a porous medium has been considered in presence of transverse magnetic field, Dufour effects and radiation. Effects of radiation absorption and heat source/sink are taken into account. The Buoyancy force leads to free convection and oscillatory free stream velocity is responsible for forced convection. Partial differential equations governed by conservation principles of mass, momentum and energy are solved analytically using perturbation scheme. Effects of various parameters on the governing fluid motion are shown graphically and numerically in tabular form.

Second law analysis in radiative mixed convective squeezing flow of Casson fluid between parallel disks with Soret and Dufour effects

AbstractThe present communication deals the entropy generation by cause of heat and mass transform in an unsteady mixed convective radiative squeezing flow of a Casson fluid confined between two parallel disks in the presence of diffusion‐thermo and thermal‐diffusion effects and temperature jump. The lower disk is taken to be porous and the upper one is impermeable. The governing PDE is converted as nonlinear ordinary differential equations (ODE) by using well‐established similarity transformations; then, the reduced nonlinear ODE are solved by shooting method with Runge‐Kutta fourth‐order approach. The influence of distinct nondimensional fluid and geometric‐related parameters on the velocity profiles, temperature, concentration, entropy generation number, and Bejan number are studied in detail and represented in the form of graphs. The entropy of the Casson fluid is increased with the Eckert number, whereas the concentration profile is decreased by squeezing Reynolds number. The current results are correlated with existing results for the viscous case and found to be in better agreement.

English

English

Exact Solutions for Unsteady Mixed Convection Flow of Nanoliquid with Exponential Heat Source: Bruggeman and Batchelor Nanofluid Model

Exact Solutions for Unsteady Mixed Convection Flow of Nanoliquid with Exponential Heat Source: Bruggeman and Batchelor Nanofluid Model

Cross Diffusion Effects on Heat and Mass Transfer Micropolar Fluid Flow Past a Stretching Surface

Through this study, we investigated the influence of nonlinear thermal radiation, Soret and Dufour effects on unsteady mixed convection boundary flow of micropolar fluid past a stretching sheet. The governing equations of the flow, heat and mass transfer are transformed into a system of nonlinear ordinary differential equations by using self-similarity transformation and solved numerically using bvp4c Matlab package. The influence of various non-dimensional governing parameters on velocity, microrotation, temperature and concentration profiles are discussed and presented with the help of the graphs. Also computed the friction factor, heat and mass transfer rates and presented through tables. Result indicates by increasing the radiation parameter, an improvement is observed in both friction factor and mass transfer rates. .

Unsteady MHD mixed convection flow in a lid-driven cavity with a heated wavy wall

The unsteady mixed convection flow under the effect of an externally applied uniform magnetic field is investigated numerically in a lid-driven cavity with a sinusoidal wavy wall. The governing equations given in terms of stream function, vorticity and temperature are discretized by using the dual reciprocity boundary element method (DRBEM) in space and a two-level time integration scheme is employed in time discretization. The simulations focus on the effects of several physical parameters, namely Hartmann and Rayleigh numbers, Joule heating parameter, the inclination angle of magnetic field and number of undulation of wavy wall on the flow and temperature distribution. Moreover, the stability analysis of the numerical method is performed in terms of time increment and time relaxation parameters for various combinations of the problem controlling parameters.