S.S. Motsa and P. Sibanda
A detailed investigation of the effects of surface flexibility on the inviscid instability of boundary‐layer flow over a horizontal flat plate with heat transfer when the fluid…
Abstract
Purpose
A detailed investigation of the effects of surface flexibility on the inviscid instability of boundary‐layer flow over a horizontal flat plate with heat transfer when the fluid buoyancy is large is undertaken. The aim of this study is to determine whether the inviscid disturbances that arise at this limit are stabilized or destabilized by surface compliancy.
Design/methodology/approach
For large positive buoyancy numbers, the motion of the disturbances is governed by the Taylor‐Goldstein (TG) equation. Using the Chebyshev collocation spectral method, the eigen‐solutions of the TG equation are obtained and compared with known results from boundary‐layer flow over rigid flat plates.
Findings
The numerical results show that the effects of surface compliancy are important for small wave numbers and that for the inviscid modes, increasing surface parameters has the effect of destabilizing the flow. For large compliancy parameters the flow structure is indistinguishable from that which obtains in boundary layer flow over rigid surfaces.
Research limitations/implications
The multiplicity of the compliant wall parameters makes a full parametric study that should show the effect of varying the compliance of the boundary surface on the stability of the flow mathematically intractable. In this study only a brief parametric study, for selected parameters is presented.
Originality/value
It is believed that this paper would be of immense value to applied mathematicians and engineers working in the areas of boundary layer stability and natural convection flows. In the last four decades there has been overwhelming interest shown by researchers in convective boundary‐layer flow. This has largely stemmed from the numerous applications of such flows in geophysics and engineering problems. Many of these applications, for example, polymer and food processing involve the flow of a fluid over a flexible surface. This research aims to bring the dynamics of the surface as a possible mechanism to stabilize convective boundary layer flows and prevent separation.
Details
Keywords
Hammed Abiodun Ogunseye, Sulyman Olakunle Salawu, Yusuf Olatunji Tijani, Mustapha Riliwan and Precious Sibanda
The purpose of this paper is to investigate the dynamical behavior of heat and mass transfer of non-Newtonian nanofluid flow through parallel horizontal sheet with heat-dependent…
Abstract
Purpose
The purpose of this paper is to investigate the dynamical behavior of heat and mass transfer of non-Newtonian nanofluid flow through parallel horizontal sheet with heat-dependent thermal conductivity and magnetic field. The effects of thermophoresis and Brownian motion on the Eyring‒Powell nanofluid heat and concentration are also considered. The flow fluid is propelled by squeezing force and constant pressure gradient. The hydromagnetic fluid is induced by periodic time variations.
Design/methodology/approach
The dimensionless momentum, energy and species balance equations are solved by the spectral local linearization method that is employed to numerically integrate the coupled non-linear differential equations.
Findings
The response of the fluid flow, temperature and concentration to variational increase in the values of the parameters is graphically presented and discussed accordingly.
Originality/value
The validity of the method used was checked by comparing it with previous related article.
Details
Keywords
Precious Sibanda, Sandile Motsa and Zodwa Makukula
The purpose of this paper is to study the steady laminar flow of a pressure driven third‐grade fluid with heat transfer in a horizontal channel. The study serves two purposes: to…
Abstract
Purpose
The purpose of this paper is to study the steady laminar flow of a pressure driven third‐grade fluid with heat transfer in a horizontal channel. The study serves two purposes: to correct the inaccurate results presented in Siddiqui et al., where the homotopy perturbation method was used, and to demonstrate the computational efficiency and accuracy of the spectral‐homotopy analysis methods (SHAM and MSHAM) in solving problems that arise in fluid mechanics.
Design/methodology/approach
Exact and approximate analytical series solutions of the non‐linear equations that govern the flow of a steady laminar flow of a third grade fluid through a horizontal channel are constructed using the homotopy analysis method and two new modifications of this method. These solutions are compared to the full numerical results. A new method for calculating the optimum value of the embedded auxiliary parameter ∼ is proposed.
Findings
The “standard” HAM and the two modifications of the HAM (the SHAM and the MSHAM) lead to faster convergence when compared to the homotopy perturbation method. The paper shows that when the same initial approximation is used, the HAM and the SHAM give identical results. Nonetheless, the advantage of the SHAM is that it eliminates the restriction of searching for solutions to the nonlinear equations in terms of prescribed solution forms that conform to the rule of solution expression and the rule of coefficient ergodicity. In addition, an alternative and more efficient implementation of the SHAM (referred to as the MSHAM) converges much faster, and for all parameter values.
Research limitations/implications
The spectral modification of the homotopy analysis method is a new procedure that has been shown to work efficiently for fluid flow problems in bounded domains. It however remains to be generalized and verified for more complicated nonlinear problems.
Originality/value
The spectral‐HAM has already been proposed and implemented by the authors in a recent paper. This paper serves the purpose of verifying and demonstrating the utility of the new spectral modification of the HAM in solving problems that arise in fluid mechanics. The MSHAM is a further modification of the SHAM to speed up converge and to allow for convergence for a much wider range of system parameter values. The utility of these methods has not been tested and verified for systems of nonlinear equations. For this reason as much emphasis has been placed on proving the reliability and validity of the solution techniques as on the physics of the problem.
Details
Keywords
Mehmet Yavuz Çetinkaya, Yurdanur Yumuk and Halyna Kushniruk
Diaspora tourism primarily refers to various population groups, including migrants, foreign workers, political refugees, ethnic and religious minorities and overseas communities…
Abstract
Diaspora tourism primarily refers to various population groups, including migrants, foreign workers, political refugees, ethnic and religious minorities and overseas communities living away from their ancestral homeland for various reasons. Throughout history, people have been forced to leave their original homeland due to various factors ranging from economic crises to natural and human-made tragedies, including war. The 24 February 2022 unjustified and unproved Russia's war of aggression against Ukraine, which started on the heels of the two-year COVID-19 pandemic, has resulted in massive and terrible consequences for many domains of political, economic and social life. The Russian invasion of Ukraine has generated the largest historical migration flows at a scale unforeseen in Europe since World War II. Since Russia invaded Ukraine, at least 12 million people have been displaced from their homes, according to the United Nations. The unprecedented influx of the Ukrainian people raises concerns about future developments, issues and challenges associated with Ukrainians' presence in other countries, particularly neighbouring ones. Therefore, this chapter analyses the possibility of diaspora tourism for Ukrainians shortly by utilising a critical approach when the situation stabilises in Ukraine. To begin with, this chapter first explains diaspora tourism with its definition and characteristics. Furthermore, it reviews the literature on the Russia–Ukraine war and its impact on Ukrainian tourism. In conclusion, it discusses the new Ukrainian diaspora wave soon.
Details
Keywords
Mangwiro Magodora, Hiranmoy Mondal and Precious Sibanda
The purpose of this paper is to focus on the application of Chebyshev spectral collocation methodology with Gauss Lobatto grid points to micropolar fluid over a stretching or…
Abstract
Purpose
The purpose of this paper is to focus on the application of Chebyshev spectral collocation methodology with Gauss Lobatto grid points to micropolar fluid over a stretching or shrinking surface. Radiation, thermophoresis and nanoparticle Brownian motion are considered. The results have attainable scientific and technological applications in systems involving stretchable materials.
Design/methodology/approach
The model equations governing the flow are transformed into non-linear ordinary differential equations which are then reworked into linear form using the Newton-based quasilinearization method (SQLM). Spectral collocation is then used to solve the resulting linearised system of equations.
Findings
The validity of the model is established using error analysis. The velocity, temperature, micro-rotation, skin friction and couple stress parameters are conferred diagrammatically and analysed in detail.
Originality/value
The study obtains numerical explanations for rapidly convergent solutions using the spectral quasilinearization method. Convergence of the numerical solutions was monitored using the residual error analysis. The influence of radiation, heat and mass parameters on the flow are depicted graphically and analysed. The study is an extension on the work by Zheng et al. (2012) and therefore the novelty is that the authors tend to take into account nanoparticles, Brownian motion and thermophoresis in the flow of a micropolar fluid.
Details
Keywords
RamReddy Chetteti, Sweta and Pranitha Janapatla
This study aims to enhance heat transfer efficiency while minimizing friction factor and entropy generation in the flow of Nickel zinc ferrite (NiZnFe2O4) nanoparticles suspended…
Abstract
Purpose
This study aims to enhance heat transfer efficiency while minimizing friction factor and entropy generation in the flow of Nickel zinc ferrite (NiZnFe2O4) nanoparticles suspended in multigrade 20W-40 motor oil (as specified by the Society of Automotive Engineers). The investigation focuses on the effects of the melting process, nonspherical particle shapes, thermal dispersion and viscous dissipation on the nanofluid flow.
Design/methodology/approach
The fundamental governing equations are transformed into a set of similarity equations using Lie group transformations. The resulting set of equations is numerically solved using the spectral local linearization method. Additionally, sensitivity analysis using response surface methodology (RSM) is conducted to evaluate the influence of key parameters on response function.
Findings
Higher dispersion reduces entropy production. Needle-shaped particles significantly enhance heat transfer by 27.65% with melting and reduce entropy generation by 45.32%. Increasing the Darcy number results in a reduction of friction by 16.06%, lower entropy by 31.72% and an increase in heat transfer by 17.26%. The Nusselt number is highly sensitive to thermal dispersion across melting and varying volume fraction parameters.
Originality/value
This study addresses a significant research gap by exploring the combined effects of melting, particle shapes and thermal dispersion on nanofluid flow, which has not been thoroughly investigated before. The focus on practical applications such as fuel cells, material processing, biomedicine and various cooling systems underscores its relevance to sectors such as nuclear reactors, tumor treatments and manufacturing. The incorporation of RSM for friction factor analysis introduces a unique dimension to the research, offering novel insights into optimizing nanofluid performance under diverse conditions.
Details
Keywords
P.K. Kameswaran, Z.G. Makukula, P. Sibanda, S.S. Motsa and P.V.S.N. Murthy
The purpose of this paper is to study heat and mass transfer in copper-water and silver-water nanofluid flow over stretching sheet placed in saturated porous medium with internal…
Abstract
Purpose
The purpose of this paper is to study heat and mass transfer in copper-water and silver-water nanofluid flow over stretching sheet placed in saturated porous medium with internal heat generation or absorption. The authors further introduce a new algorithm for solving heat transfer problems in fluid mechanics. The model used for the nanofluid incorporates the nanoparticle volume fraction parameter and a consideration of the chemical reaction effects among other features.
Design/methodology/approach
The partial differential equations for heat and mass transfer in copper-water and silver-water nanofluid flow over stretching sheet were transformed into a system of nonlinear ordinary differential equations. Exact solutions for the boundary layer equations were obtained in terms of a confluent hypergeometric series. A novel spectral relaxation method (SRM) is used to obtain numerical approximations of the governing differential equations. The exact solutions are used to test the convergence and accuracy of the SRM.
Findings
Results were obtained for the fluid properties as well as the skin friction, and the heat and mass transfer rates. The results are compared with limiting cases from previous studies and they show that the proposed technique is an efficient numerical algorithm with assured convergence that serves as an alternative to numerical methods for solving nonlinear boundary value problems.
Originality/value
A new algorithm is used for the first time in this paper. In addition, new exact solutions for the energy and mass transport equations have been obtained in terms of a confluent hypergeometric series.
Details
Keywords
The purpose of this study is to investigate the effects of entropy generation of some embedded thermophysical properties on heat and mass transfer of pulsatile flow of…
Abstract
Purpose
The purpose of this study is to investigate the effects of entropy generation of some embedded thermophysical properties on heat and mass transfer of pulsatile flow of non-Newtonian nanofluid flows between two porous parallel plates in the presence of Lorentz force are taken into account in this research.
Design/methodology/approach
The governing partial differential equations (PDEs) were nondimensionalized using suitable nondimensional quantities to transform the PDEs into a system of coupled nonlinear PDEs. The resulting equations are solved using the spectral relaxation method due to the effectiveness and accuracy of the method. The obtained velocity and temperature profiles are used to compute the entropy generation rate and Bejan number. The influence of various flow parameters on the velocity, temperature, entropy generation rate and Bejan number are discussed graphically.
Findings
The results indicate that the energy losses can be minimized in the system by choosing appropriate values for pertinent parameters; when thermal conductivity is increasing, this leads to the depreciation of entropy generation, and while this increment in thermal conductivity appreciates the Bejan number, the Eckert number on entropy generation and Bejan number, the graph shows that each time of increase in Eckert will lead to rising of entropy generation while this increase shows a reduction in Bejan number. To shed more light, these results were further demonstrated graphically. The current research was very well supported by prior literature works.
Originality/value
All results are presented graphically, and the results in this article are anticipated to be helpful in the area of engineering.
Details
Keywords
Moses Sunday Dada and Cletus Onwubuoya
The purpose of this paper is to consider heat and mass transfer on magnetohydrodynamics (MHD) Williamson fluid flow over a slendering stretching sheet with variable thickness in…
Abstract
Purpose
The purpose of this paper is to consider heat and mass transfer on magnetohydrodynamics (MHD) Williamson fluid flow over a slendering stretching sheet with variable thickness in the presence of radiation and chemical reaction. All pertinent flow parameters are discussed and their influence on the hydrodynamics, thermal and concentration boundary layer are presented with the aid of the diagram.
Design/methodology/approach
The governing partial differential equations are reduced into a system of ordinary differential equations with the help of suitable similarity variables. A discrete version of the homotopy analysis method (HAM) called the spectral homotopy analysis method (SHAM) was used to solve the transformed equations. SHAM is efficient, and it converges faster than the HAM. The SHAM provides flexibility when solving linear ordinary differential equations with the use of the Chebyshev spectral collocation method.
Findings
The findings revealed that an increase in the variable thermal conductivity hike the temperature and the thermal boundary layer thickness, whereas the reverse is the case for velocity close to the wall.
Originality/value
The uniqueness of this paper is the exploration of combined effects of heat and mass transfer on MHD Williamson fluid flow over a slendering stretching sheet. The Williamson fluid term in the momentum equation is expressed as a linear function and the viscosity and thermal conductivity are considered to vary in the boundary layer.
Details
Keywords
R. Sivaraj, I.L. Animasaun, A.S. Olabiyi, S. Saleem and N. Sandeep
The purpose of this paper is to provide an insight into the influence of gyrotactic microorganisms and Hall effect on the boundary layer flow of 29 nm CuO-water mixture on the…
Abstract
Purpose
The purpose of this paper is to provide an insight into the influence of gyrotactic microorganisms and Hall effect on the boundary layer flow of 29 nm CuO-water mixture on the upper pointed surface of a rocket, over the bonnet of a car and upper pointed surface of an aircraft. This is true since all these objects are examples of an object with variable thickness.
Design/methodology/approach
The simplification of Rosseland approximation (Taylor series expansion of T4 about T∞) is avoided; thus, two different parameters relating to the study of nonlinear thermal radiation are obtained. The governing equation is non-dimensionalized, parameterized and solved numerically.
Findings
Maximum vertical and horizontal velocities of the 29 nm CuO-water nanofluid flow is guaranteed at a small value of Peclet number and large value of buoyancy parameter depending on the temperature difference. When the magnitude of thickness parameter χ is small, cross-flow velocity decreases with the velocity index and the opposite effect is observed when the magnitude of χ is large.
Originality/value
Directly or indirectly, the importance of the fluid flow which contains 29 nm CuO nanoparticle, water, and gyrotactic microorganisms in the presence of Hall current has been pointed out as an open question in the literature due to its relevance in imaging, ophthalmological and translational medicine informatics.