Search results
1 – 10 of over 3000Iskandar Waini, Anuar Ishak and Ioan Pop
This paper aims to examine the effect of Dufour and Soret diffusions on Al2O3-water nanofluid flow over a moving thin needle by using the Tiwari and Das model.
Abstract
Purpose
This paper aims to examine the effect of Dufour and Soret diffusions on Al2O3-water nanofluid flow over a moving thin needle by using the Tiwari and Das model.
Design/methodology/approach
The governing equations are reduced to the similarity equations using similarity transformations. The resulting equations are programmed in Matlab software through the bvp4c solver to obtain their solutions. The features of the skin friction, heat transfer and mass transfer coefficients, as well as the velocity, temperature and concentration profiles for different values of the physical parameters, are analysed and discussed.
Findings
The non-uniqueness of the solutions is observed for a certain range of the physical parameters. The authors also notice that the bifurcation of the solutions occurs in which the needle moves toward the origin (λ < 0). It is discovered that the first branch solutions of the skin friction coefficient and the heat transfer coefficients increase, but the mass transfer coefficient decreases in the presence of nanoparticle. Additionally, the simultaneous effect of Dufour and Soret diffusions tends to enhance the heat transfer coefficient; however, dual behaviours are observed for the mass transfer coefficient. Further analysis shows that between the two solutions, only one of them is stable and thus physically reliable in the long run.
Originality/value
The problem of Al2O3-water nanofluid flow over a moving thin needle with Dufour and Soret effects are the important originality of the present study. Besides, the temporal stability of the dual solutions is examined for time.
Details
Keywords
Rajiv Tiwari and Rahul Chandran
In optimum designs of deep-groove ball bearings (DDGBs), an extended service life is one of the vital criteria. The life of a bearing depends on several factors. The purpose of…
Abstract
Purpose
In optimum designs of deep-groove ball bearings (DDGBs), an extended service life is one of the vital criteria. The life of a bearing depends on several factors. The purpose of this paper is to sequentially optimize three prime objectives for DDGB, i.e. the dynamic capacity (Cd), the maximum bearing temperature (Tmax) and the elasto-hydrodynamic minimum film thickness (Hmin).
Design/methodology/approach
For solving constrained non-linear optimization formulations with multitude of objectives, an optimal design methodology has been put forth with the help of artificial bee colony algorithms. A study on the constraint violation has been carried out. By the Monte Carlo simulation method, a sensitivity investigation of diverse design variables has been done to examine variations in three objective functions and violation of constraints.
Findings
Excellent improvement in the dynamic capacity (Cd), the maximum bearing temperature (Tmax) and the elasto-hydrodynamic minimum film thickness (Hmin) have been found in optimized bearing designs.
Originality/value
Ball bearing design has been done based on multi-discipline objectives that are based on strength, tribology and thermal consideration. This type of design is essential in practical scenario where these physical phenomena will be present simultaneously.
Details
Keywords
The fatigue, thermal and wear-based bearing lives are the most important factors in the design of spherical roller bearings (SRBs). The main novelty of the present work is…
Abstract
Purpose
The fatigue, thermal and wear-based bearing lives are the most important factors in the design of spherical roller bearings (SRBs). The main novelty of the present work is consideration of thermal effects as an additional objective function. The dynamic capacity (Cd), the elasto-hydrodynamic minimum film thickness (hmin) and the maximum bearing temperature (Tmax) are related directly with overall lives of the bearing, and these constitute the multiple tasking operating requirements for the design of bearings.
Design/methodology/approach
These tasks depend upon various bearing design variables and associated constraints to help in formulating the realistic design optimization problem and in the present work these have been used to get optimal designs of SRBs in the form of Pareto-optimum fronts by using genetic algorithms.
Findings
The optimized lives show higher values as compared to the standard lives and better design choices as compared to that are available in the literature. The robustness of obtained designs are shown by conducting the sensitivity analysis of optimized operating requirements by perturbing optimum bearing variables.
Research limitations/implications
The robustness of the design could be improved by optimizing tolerances of design variables based on desired variation in multiple tasking operating requirements.
Practical implications
For the aerospace and space applications such critical design of bearings are required based on multiple tasking operating requirements. For example for higher temperature application in gearboxes, turbines and drilling equipment.
Originality/value
In critical applications, multiple tasking operating requirements are essential and often bearings put limit to the life of satellites and aircraft, and bearing design methodology proposed and implemented in the present paper addresses these issues, especially addition of thermal issue in bearing design.
Details
Keywords
Abhishek Kumar, Alpana Srivastava, R.P. Jeevan Kumar and Rajesh K. Tiwari
This SWOT (strengths, weaknesses, opportunities and threats) analysis was conducted to have a portrait of the competitiveness of Council of Scientific and Industrial Research…
Abstract
Purpose
This SWOT (strengths, weaknesses, opportunities and threats) analysis was conducted to have a portrait of the competitiveness of Council of Scientific and Industrial Research (CSIR) on the global map. Being a 75-year-old scientific organization, CSIR has raised each and every laboratory with a specific mandate and competency. It is definite that the organization would get some assistance from these points, which are briefly stated, as the institutional data reside with the laboratory only. To some extent, they can be considered on their discretion; however, the organization has raised its position to international standards, but still it can consider few areas/suggestions from this analysis. These points are suggestive and flexible in nature, which are identified and defined to elevate this organization on the globe. Scientific publications do make a difference, but on the ground, if the technologies are not viable and received by public, it makes no difference. Today, India is fortunate to have a Prime Minister like Mr Modi, who always re-evaluates the issues and solutions so that the country moves from developing to a fast-pace developed nation. It is a fact that if these research organizations reorganize themselves and prioritize the research problems, they are capable enough to become a pioneer among the world R&D industry. This paper aims to analyze the organization and suggest few points with significant findings which can assist in scaling toward excellence on a global scale.
Design/methodology/approach
On the basis of random sampling, laboratories were identified where their achievements and contribution toward industry and society were evaluated. On the basis of their setup, the organization and laboratories were evaluated to frame-out a SWOT analysis.
Findings
SWOT analysis is a deliberate technique carried out to analyze the current situation of the system and to analyze the internal and external environment, which provides and edge to the organization to sustain. The major factors assessed were manpower, machines, money and funding, and achievements and deliverables were studied.
Originality/value
The research, i.e. SWOT, is unique in nature, as it was not carried out earlier on such a scale. To some extent, the points suggested in SWOT and conclusion can be considered on their discretion; however, the organization has raised its position to international standards, but still it can consider few areas/suggestions from this analysis. These points are suggestive and flexible in nature, which are identified and defined to elevate this organization on the globe. Scientific publications do make a difference, but on the ground; if the technologies are not viable and received by public, it makes no difference. Today, India is fortunate to have a Prime Minister like Mr Modi, who always re-evaluates the issues and solutions so that the country moves from developing to a fast-pace developed nation. It is a fact that if these research organizations reorganize themselves and prioritize the research problems, they are capable enough to become a pioneer among the world R&D industry.
Details
Keywords
The purpose of this paper is to address various works on mixed convection and proposes 10 unified models (Models 1–10) based on various thermal and kinematic conditions of the…
Abstract
Purpose
The purpose of this paper is to address various works on mixed convection and proposes 10 unified models (Models 1–10) based on various thermal and kinematic conditions of the boundary walls, thermal conditions and/ or kinematics of objects embedded in the cavities and kinematics of external flow field through the ventilation ports. Experimental works on mixed convection have also been addressed.
Design/methodology/approach
This review is based on 10 unified models on mixed convection within cavities. Models 1–5 involve mixed convection based on the movement of single or double walls subjected to various temperature boundary conditions. Model 6 elucidates mixed convection due to the movement of single or double walls of cavities containing discrete heaters at the stationary wall(s). Model 7A focuses mixed convection based on the movement of wall(s) for cavities containing stationary solid obstacles (hot or cold or adiabatic) whereas Model 7B elucidates mixed convection based on the rotation of solid cylinders (hot or conductive or adiabatic) within the cavities enclosed by stationary or moving wall(s). Model 8 is based on mixed convection due to the flow of air through ventilation ports of cavities (with or without adiabatic baffles) subjected to hot and adiabatic walls. Models 9 and 10 elucidate mixed convection due to flow of air through ventilation ports of cavities involving discrete heaters and/or solid obstacles (conductive or hot) at various locations within cavities.
Findings
Mixed convection plays an important role for various processes based on convection pattern and heat transfer rate. An important dimensionless number, Richardson number (Ri) identifies various convection regimes (forced, mixed and natural convection). Generalized models also depict the role of “aiding” and “opposing” flow and combination of both on mixed convection processes. Aiding flow (interaction of buoyancy and inertial forces in the same direction) may result in the augmentation of the heat transfer rate whereas opposing flow (interaction of buoyancy and inertial forces in the opposite directions) may result in decrease of the heat transfer rate. Works involving fluid media, porous media and nanofluids (with magnetohydrodynamics) have been highlighted. Various numerical and experimental works on mixed convection have been elucidated. Flow and thermal maps associated with the heat transfer rate for a few representative cases of unified models [Models 1–10] have been elucidated involving specific dimensionless numbers.
Originality/value
This review paper will provide guidelines for optimal design/operation involving mixed convection processing applications.
Details
Keywords
S. Manjunatha, B. Ammani Kuttan, G.K. Ramesh, B.J. Gireesha and Emad H. Aly
The purpose of this paper is to discuss the 3D micropolar hybrid (Ag-CuO/H2O) nanofluid past rapid moving surface, where porous medium has been considered.
Abstract
Purpose
The purpose of this paper is to discuss the 3D micropolar hybrid (Ag-CuO/H2O) nanofluid past rapid moving surface, where porous medium has been considered.
Design/methodology/approach
The model of problem was represented by highly partial differential equations which were deduced by using suitable approximations (boundary layer). Then, the governing model was converted into five combined ordinary differential equations applying proper similarity transformations. Therefore, the eminent iterative Runge–Kutta–Fehlberg method (RKF45) has been applied to solve the resulting equations.
Findings
Higher values of vortex viscosity, spin gradient viscosity and micro-inertia density parameters are reduced in horizontal direction, whereas opposite behaviour is noticed for vertical direction.
Originality/value
The work has not been done in the area of hybrid micropolar nanofluid. Hence, this article culminates to probe how to improve the thermal conduction and fluid flow in 3D boundary layer flow of micropolar mixture of nanoparticles driven by rapidly moving plate with convective boundary condition.
Details
Keywords
Rashmi Agrawal and Pradeep Kaswan
This paper aims to examine the squeezing flow of hybrid nanofluid within the two parallel disks. The 50:50% water–ethylene glycol mixture is used as a base fluid to prepare…
Abstract
Purpose
This paper aims to examine the squeezing flow of hybrid nanofluid within the two parallel disks. The 50:50% water–ethylene glycol mixture is used as a base fluid to prepare Ag–Fe_3O_4 hybrid nanofluid. Entropy generation analysis is examined by using the second law of thermodynamics, and Darcy’s modal involves estimating the behavior of a porous medium. The influences of Viscous dissipation, Joule heating and thermal radiation in modeling are further exerted into concern.
Design/methodology/approach
For converting partial differential systems to ordinary systems, a transformation technique is used. For the validation part, the numerical solution is computed by embracing a fourth-order exactness program (bvp4c) and compared with the analytical solution added by the homotopy analysis method (HAM). Graphical decisions expose the values of miscellaneous-arising parameters on the velocity, temperature and local-Nusselt numbers.
Findings
Hybrid nanofluid gives significant enhancement in the rate of heat transfer compared with nanofluid. The outcomes indicate that the average Nusselt number and entropy generation are increasing functions of the magnetic field, porosity and Brinkman number. When the thermal radiation rises, the average Nusselt number diminishes and the entropy generation advances. Furthermore, combining silver and magnetite nanoparticles into the water–ethylene glycol base fluid significantly enhances entropy generation performance.
Originality/value
Entropy generation analysis of the magneto-hydrodynamics (MHD) fluid squeezed between two parallel disks by considering Joule heating, viscous dissipation and thermal radiation for different nanoparticles is addressed. Furthermore, an appropriate agreement is obtained in comparing the numerical results with previously published and analytical results.
Details
Keywords
V. Rajesh, A.J. Chamkha, Ch. Sridevi and A.F. Al-Mudhaf
The purpose of this paper is to study numerically the influence of a magnetic field on the transient free convective boundary layer flow of a nanofluid over a moving semi-infinite…
Abstract
Purpose
The purpose of this paper is to study numerically the influence of a magnetic field on the transient free convective boundary layer flow of a nanofluid over a moving semi-infinite vertical cylinder with heat transfer
Design/methodology/approach
The problem is governed by the coupled non-linear partial differential equations with appropriate boundary conditions. The fluid is a water-based nanofluid containing nanoparticles of copper. The Brinkman model for dynamic viscosity and Maxwell–Garnett model for thermal conductivity are used. The governing boundary layer equations are written according to The Tiwari–Das nanofluid model. A robust, well-tested, implicit finite difference method of Crank–Nicolson type, which is unconditionally stable and convergent, is used to find the numerical solutions of the problem. The velocity and temperature profiles are studied for significant physical parameters such as the magnetic parameter, nanoparticles volume fraction and the thermal Grashof number Gr. The local skin-friction coefficient and the Nusselt number are also analysed and presented graphically.
Findings
The present computations have shown that an increase in the values of either magnetic parameter M or nanoparticle volume fraction decreases the local skin-friction coefficient, whereas the opposite effect is observed for thermal Grashof number Gr. The local Nusselt number increases with a rise in Gr and ϕ values. But an increase in M reduces the local Nusselt number.
Originality/value
This paper is relatively original and presents numerical investigation of transient two-dimensional laminar boundary layer free convective flow of a nanofluid over a moving semi-infinite vertical cylinder in the presence of an applied magnetic field. The present study is of immediate application to all those processes which are highly affected by heat enhancement concept and a magnetic field. Further the present study is relevant to nanofluid materials processing, chemical engineering coating operations exploiting nanomaterials and others.
Details
Keywords
Natalia C. Roşca, Alin V. Roşca and Ioan Pop
The purpose of this paper is to theoretically investigate the unsteady separated stagnation-point flow and heat transfer past an impermeable stretching/shrinking sheet in a copper…
Abstract
Purpose
The purpose of this paper is to theoretically investigate the unsteady separated stagnation-point flow and heat transfer past an impermeable stretching/shrinking sheet in a copper (Cu)-water nanofluid using the mathematical nanofluid model proposed by Tiwari and Das.
Design/methodology/approach
A similarity transformation is used to reduce the governing partial differential equations to a set of nonlinear ordinary (similarity) differential equations which are then solved numerically using the function bvp4c from Matlab for different values of the governing parameters.
Findings
It is found that the solution is unique for stretching case; however, multiple (dual) solutions exist for the shrinking case.
Originality/value
The authors believe that all numerical results are new and original, and have not been published elsewhere.
Details
Keywords
Amin Jafarimoghaddam and Ioan Pop
The purpose of this study is to present a simple analytic solution to wall jet flow of nanofluids. The concept of exponentially decaying wall jet flows proposed by Glauert (1956)…
Abstract
Purpose
The purpose of this study is to present a simple analytic solution to wall jet flow of nanofluids. The concept of exponentially decaying wall jet flows proposed by Glauert (1956) is considered.
Design/methodology/approach
A proper similarity variables are used to transform the system of partial differential equations into a system of ordinary (similarity) differential equations. This system is then solved analytically.
Findings
Dual solutions are found and a stability analysis has been done. These solutions show that the first solution is physically realizable, whereas the second solution is not practicable.
Originality/value
The present results are original and new for the study of fluid flow and heat transfer over a static permeable wall, as they successfully extend the problem considered by Glauert (1956) to the case of nanofluids.
Details