Amr M. Mahros, Emad H. Aly, John H. Merkin and Ioan M. Pop
This paper aims to study the magnetohydrodynamic (MHD) wall jet of a hybrid nanofluid flow over a moving surface with a thermally convective surface, wall moving with…
Abstract
Purpose
This paper aims to study the magnetohydrodynamic (MHD) wall jet of a hybrid nanofluid flow over a moving surface with a thermally convective surface, wall moving with suction/injection.
Design/methodology/approach
On using appropriate similarity transformations, the governing equations that describe the model are converted into a system of nonlinear ordinary differential equations. These equations are solved both analytically and numerically using standard two-point boundary-value problem solvers and Chebyshev pseudospectral differentiation matrix method, respectively.
Findings
These results show that the HNF is heating/cooling with growth of the positive/negative values of the parameter measuring the velocity of the moving surface. The temperature distributions increase, where the thermal boundary layer gets thicker, as the magnetic field strengthens and with an increase in the absolute value of the Biot number.
Originality/value
The current findings for the HNFs are new and original. They generalize successfully the problems investigated previously by different researchers for the cases of fluids and also nanofluids.
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Emad H. Aly, Waqar Khan Usafzai, John H. Merkin and Ioan M. Pop
The steady laminar wall jet flow over a stretching/shrinking surface in the presence of lateral suction or injection with a convective boundary condition is considered.
Abstract
Purpose
The steady laminar wall jet flow over a stretching/shrinking surface in the presence of lateral suction or injection with a convective boundary condition is considered.
Design/methodology/approach
The partial differential equations for mass, momentum and energy conservation are changed to the system of ordinary differential equations through similarity solution transformations. Solutions, both numerical and asymptotic, to these similarity equations are found in some new ranges of parameters in the governing equations.
Findings
The equations are solved both asymptotically and numerically for a range of the transpiration parameter S and the flow parameter λ given in Mahros et al. (2023), thus greatly extending the range of these previous solutions. Asymptotic solutions for both large and small values of the Prandtl number σ are derived, showing good agreement with additional numerical integrations. It should be noted that in Mahros et al. (2023), only the case when σ=1 was treated. A solution for large λ when S=1 is obtained, showing a different asymptotic form to the case when S>0 in Mahros et al. (2023). Multiple solutions were seen by them for S<0 and the nature of the lower solution branch as S→0 from below is discussed. The question as to whether the lower branch solutions join as λ>0 when S<0 is resolved through obtaining an asymptotic solution λ small.
Originality/value
The accuracy of the solutions has been checked through a detailed comparison between the solutions obtained numerically and analytically, where excellent agreement has been found. This study is important for scientists working in the area of jet flows to become familiar with the flow properties and behaviour of jets.
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John H. Merkin, Yian Yian Lok and Ioan Pop
The purpose of this study is to obtain both the numerical and asymptotic solutions of the unsteady mixed convection flow and heat transfer over an expanding or contracting…
Abstract
Purpose
The purpose of this study is to obtain both the numerical and asymptotic solutions of the unsteady mixed convection flow and heat transfer over an expanding or contracting cylinder which is placed vertically.
Design/methodology/approach
Solutions of the governing ordinary (similarity) differential equations for the fluid flow and temperature field are obtained using the function bvp4c from MATLAB. The problem involves the Prandtl number σ, the mixed convection parameter λ and unsteadiness parameter S that characterize an expanding or contracting cylinder. This solution approach is capable of producing multiple solutions once the necessary assumptions are provided.
Findings
It is found that solutions exist for all negative values of S, expanding cylinder, and only for small positive values of S, contracting cylinder. Further, more than one solution is observed; numerical computation shows that the critical point of S becomes singular as λ approaching zero. For the case of expanding cylinder, the mixed convection parameter has a significant effect on both the flow and heat transfer characteristics. Asymptotic analysis also shows that when σ is large, dual solutions exist for some values of S and λ.
Originality/value
The present results are new and original for the study of the unsteady mixed convection flow and heat transfer over an expanding/contracting cylinder where numerical solutions are obtained for representative values of the involved parameters. Asymptotic solutions for large λ and large σ are derived.
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Najiyah Safwa Khashi'ie, Norihan M. Arifin, John H. Merkin, Rusya Iryanti Yahaya and Ioan Pop
The purpose of this paper is to numerically analyze the stagnation point flow of Cu-Al2O3/water hybrid nanofluid with mixed convection past a flat plate and circular cylinder.
Abstract
Purpose
The purpose of this paper is to numerically analyze the stagnation point flow of Cu-Al2O3/water hybrid nanofluid with mixed convection past a flat plate and circular cylinder.
Design/methodology/approach
The similarity equations that reduced from the boundary layer and energy equations are solved using the bvp4c solver. The duality of solutions is observed within the specific range of the control parameters, namely, mixed convection parameter λ, curvature parameter
Findings
Two solutions exist in opposing and assisting flows up to a critical value
Originality/value
The results are new and original. This study benefits to the other researchers, specifically in the observation of the fluid flow characteristics and heat transfer rate of the hybrid nanofluid. Also, this paper features with the mathematical formulation for the solution with large values of
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Natalia C. Rosca, Alin V. Rosca, John H. Merkin and Ioan Pop
The purpose of this study is to consider the effects that buoyancy arising from the combination of both thermal and concentration gradients can have on the mixed convection…
Abstract
Purpose
The purpose of this study is to consider the effects that buoyancy arising from the combination of both thermal and concentration gradients can have on the mixed convection boundary-layer flow near a forward stagnation point with the effect of Stefan blowing being included. Ad suitable choice for the functional forms of the outer flow and the wall temperature and concentration enables the problem to be reduced to a similarity form involving the dimensionless parameters, λ (mixed convection), κ (Stefan blowing) and N (relative strength of concentration driven buoyancy to that of thermal driven), as well as the Prandtl and Schmidt numbers. Numerical solutions to this similarity system for a range of representative parameter values indicate a finite, non-zero range of κ where there can be four solutions in opposing flow with only one solution in aiding flow. Asymptotic solutions for large values of N and κ are derived, the latter having two different structures in the opposing flow.
Design/methodology/approach
This paper sets up a similarity problem to examine the effects of Stefan blowing on a mixed convection flow with the aims of solving the equations numerically and complementing the results with appropriate asymptotic analysis.
Findings
The findings of the study include multiple solution branches, saddle-node bifurcations and singularities appearing in the solution.
Originality/value
The authors believe that all the results, both numerical and asymptotic, are original and have not been published elsewhere.
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Investigates the differences in protocols between arbitral tribunals and courts, with particular emphasis on US, Greek and English law. Gives examples of each country and its way…
Abstract
Investigates the differences in protocols between arbitral tribunals and courts, with particular emphasis on US, Greek and English law. Gives examples of each country and its way of using the law in specific circumstances, and shows the variations therein. Sums up that arbitration is much the better way to gok as it avoids delays and expenses, plus the vexation/frustration of normal litigation. Concludes that the US and Greek constitutions and common law tradition in England appear to allow involved parties to choose their own judge, who can thus be an arbitrator. Discusses e‐commerce and speculates on this for the future.
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Aidan McKearney, Rea Prouska, Monrudee Tungtakanpoung and John Opute
The purpose of this paper is to examine how employee voice in small and medium enterprises (SMEs) is shaped by national culture. Specifically, the paper explores the relationship…
Abstract
Purpose
The purpose of this paper is to examine how employee voice in small and medium enterprises (SMEs) is shaped by national culture. Specifically, the paper explores the relationship between national culture and organisational norms and signals. Furthermore, it explores the impact of such norms on employee voice behaviours. The paper chooses to address these issues in the SME context, in three countries with divergent cultural dimensions.
Design/methodology/approach
The authors use Kwon and Farndale’s (2020) typology as our “a priori” framework to explore the influence of national cultural values and cultural tightness on SME organisation norms, signals and employee voice behaviours. Our study uses qualitative data gathered through in-depth interviews with SME employees in England, Nigeria and Thailand.
Findings
The results from our interviews are presented thematically. The data illustrates how the cultural dimensions identified by Kwon and Farndale (2020) can have an influence on organisational voice norms. The dimensions are power distance, uncertainty avoidance, in-group collectivism, performance orientation, assertiveness and cultural tightness.
Originality/value
Historically, the impact of national culture as a macro factor on voice has been largely ignored by academic research. Studies in non-western contexts are especially rare. This paper derives its originality by offering unique insights into the culture–voice relationship from both western and non-western perspectives. This provides an international, cross-cultural, comparative dimension to our study. This research includes findings from under-researched settings in Nigeria and Thailand.
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Nirmal K. Manna, Abhinav Saha, Nirmalendu Biswas and Koushik Ghosh
The purpose of this study is to investigate the influence of enclosure shape on magnetohydrodynamic (MHD) nanofluidic flow, heat transfer and irreversibility in square…
Abstract
Purpose
The purpose of this study is to investigate the influence of enclosure shape on magnetohydrodynamic (MHD) nanofluidic flow, heat transfer and irreversibility in square, trapezoidal and triangular thermal systems under fluid volume constraints, with the aim of optimizing thermal behavior in diverse applications.
Design/methodology/approach
The study uses numerical simulations based on a finite element-based technique to analyze the effects of the Rayleigh number (Ra), Hartmann number (Ha), magnetic field orientation (γ) and nanoparticle concentration (ζ) on heat transfer characteristics and thermodynamic entropy production.
Findings
The key findings reveal that the geometrical design significantly influences fluid velocity, heat transfer and irreversibility. Trapezoidal thermal systems outperform square systems, while triangular systems achieve optimal enhancement. Nanoparticle concentration enhances heat transfer and flow strength at higher Rayleigh numbers. The magnetic field intensity has a significant impact on fluid flow and heat transport in natural convection, with higher Hartmann numbers resulting in reduced flow strength and heat transfer. The study also highlights the influence of various parameters on thermodynamic entropy production.
Research limitations/implications
Further research can explore additional geometries, parameters and boundary conditions to expand the understanding of enclosure shape effects on MHD nanofluidic flow and heat transfer. Experimental validation can complement the numerical simulations presented in this study.
Originality/value
This study provides valuable insights into the impact of enclosure shape on heat transfer performance in MHD nanofluid flow systems. The findings contribute to the optimization of thermal behavior in applications such as electronics cooling and energy systems. The comparison of different enclosure shapes and the analysis of thermodynamic entropy production add novelty to the study.