The extraordinary enhancement in heat transfer efficiency of nanofluids at extremely low volume fractions has attracted a lot of attention in identifying the governing mechanisms. The nanoscale ...effects, Brownian motion (random motion of particles inside the base fluid) and thermophoresis (diffusion of particles due to temperature gradient) are found to be important slip mechanisms in nanofluids. Based on these findings, a set of partial differential equations for conservation laws for nanofluids was formed. Since then, a large number of mathematical studies on convective heat transfer in nanofluids became feasible. The present paper summarizes the studies pertaining to instability of a horizontal nanofluid layer under the impact of various parameters such as rotation, magnetic field, Hall currents and LTNE effects in both porous and non-porous medium. Initially, investigations were made using the model considering fixed initial and boundary conditions on the layer, gradually the model was revised in the light of more practical boundary conditions and recently it has been modified to get new and more interesting results. The exhaustive analysis of instability problems is presented in the paper and prospects for future research are also identified.
This article is a maiden and naive attempt to formulate, analyse and investigate the Rayleigh–Taylor (RT) instability of two superimposed horizontal layers of nanofluids having different densities. ...Conservation equations are formulated and linearised by keeping in mind that density of the base fluids as well as nanoparticles is not constant. Linearised perturbed equations are sorted out by using the technique of normal modes and a dispersion relation incorporating the effects of surface tension, Atwood number and volume fraction of nanoparticles is obtained. Stable and unstable modes of RT instability are scrutinised using Routh–Hurtwitz criterion in the presence/absence of nanoparticles and presented graphically. Numerical calculations have been performed to explore the effect of surface tension, Atwood number and volume fraction of the nanoparticles. It is observed that in the presence/absence of nanoparticles, surface tension has a significant impact on stabilising the unstable mode of RT instability whereas Atwood number and volume fraction of nanoparticles hasten this instability. The graphical representations of these numerical investigations confirm the very explanation of RT instability under the effect of different parameters that have significant impact on the intensity of growth rate.
The current study introduces the Rayleigh–Taylor instability of two overlaying nanofluids (horizontally) possessing different densities with the magnetic field in the porous media. A set of ...conservation equations including the parameters like volume concentration of nanofluids, surface tension, magnetic field, porosity, and permeability has been formed and further set to infinitesimal perturbation incorporating density, velocity, pressure, and potency of nanoparticles. A related dispersion relation has been derived using the normal mode method, which is further investigated with stable and unstable modes of the system. As an individual varying parameter, magnetic field and surface tension draw the stability in configuration while porosity, the potency of nanoparticles, and permeability accelerate the instability. Here, significant impact is observed while keeping the volume fraction of nanoparticles and magnetic force with the rest of varying parameters in increasing or decreasing order simultaneously. The stronger influences of these combined variations have been depicted by taking suitable numerical values of these parameters. The role of the volume fraction of nanoparticles seems to be more intensified when it is taken as a varying parameter along with varying values of other parameters. A comprehensive presentation has been made, incorporating all the insightful facts through tables and graphs. It is observed that some parameters have a stabilizing impact on the unstable mode of RTI individually. However, their various combinations draw a powerful impact on destabilizing or stabilizing the configuration as critical values of growth rate meet an excellent rise or reduction.
The UK Government has announced its plans to bring forward the deadline for phasing out all petrol and diesel vehicles from 2040 to 2030, 10 years earlier than planned. This is a radical acceleration ...in the transition to electric mobility. The need to draw up coherent and robust UK regulatory structures for managing the end-of-life consequences of this transition is now more urgent than ever. This article explores the potential role of extended producer responsibility (EPR) in facilitating the safe and sustainable management of electric vehicle (EV) batteries at their end of life. It outlines the current EV battery problem from the perspective of end-of-life management, before exploring the utility of EPR in achieving a circular economy approach and reviewing the current EPR frameworks that would apply to this waste stream once a battery is no longer powerful enough to drive an EV. We conclude that current EPR frameworks for battery management are neither sufficiently clear nor suitably robust to ensure safe and sustainable electric lithium ion battery management and suggest how these could be remodelled to achieve better outcomes in this area.
This article examines the judicial approach to emotional harm claims from a medical perspective. Legal rules in this area are already recognised as being illogical and incoherent. Psychological and ...psychiatric research illustrate that they also conflict with empirical findings. By basing claims on erroneous criteria, courts may deny liability in meritorious cases, and impose liability in possibly less deserving claims. This not only brings the law into disrepute, but also reinforces the stigma that surrounds mental illness, and does disservice to an already misunderstood and vulnerable section of people in society. The article examines the evidence for the threshold requirement that distress must qualify for a psychiatric diagnosis to be actionable, and for the Alcock secondary victim criteria. It contends that these legal rules are based in misconceptions about mental illness and trauma, and suggests an alternative approach that is more principled, yet also addresses policy concerns about excessive liability.
In this article, Rayleigh-Bénard convection for nanofluids for more realistic boundary conditions (rigid-free and rigid-rigid) under the influence of the magnetic field is investigated. Presence of ...nanoparticles in base fluid has introduced one additional conservation equation of nanoparticles that incorporates the effect of thermophoretic forces and Brownian motion and the inclusion of magnetic field has introduced Lorentz’s force term in the momentum equation along with Maxwell’s equations. The solution of the Eigen value problem is found in terms of Rayleigh number by implementing the technique of normal modes and weighted residual Galerkin approximation. It is found that the stationary as well as oscillatory motions come into existence and heat transfer takes place through oscillatory motions. The critical Rayleigh number for alumina water nanofluid has an appreciable increase in its value with the rise in Chandrasekhar number and it increases moderately as we move from rigid-free to both rigid boundaries. The effect of different nanofluid parameters on the onset of thermal convection for two types of boundaries is investigated.
Net zero targets have resulted in a drive to decarbonise the transport sector worldwide through electrification. This has, in turn, led to an exponentially growing battery market and, conversely, ...increasing attention on how we can reduce the environmental impact of batteries and promote a more efficient circular economy to achieve real net zero. As these batteries reach the end of their first life, challenges arise as to how to collect and process them, in order to maximise their economical use before finally being recycled. Despite the growing body of work around this topic, the decision-making process on which pathways batteries could take is not yet well understood, and clear policies and standards to support implementation of processes and infrastructure are still lacking. Requirements and challenges behind recycling and second life applications are complex and continue being defined in industry and academia. Both pathways rely on cell collection, selection and processing, and are confronted with the complexities of pack disassembly, as well as a diversity of cell chemistries, state-of-health, size, and form factor. There are several opportunities to address these barriers, such as standardisation of battery design and reviewing the criteria for a battery's end-of-life. These revisions could potentially improve the overall sustainability of batteries, but may require policies to drive such transformation across the industry. The influence of policies in triggering a pattern of behaviour that favours one pathway over another are examined and suggestions are made for policy amendments that could support a second life pipeline, while encouraging the development of an efficient recycling industry. This review explains the different pathways that end-of-life EV batteries could follow, either immediate recycling or service in one of a variety of second life applications, before eventual recycling. The challenges and barriers to each pathway are discussed, taking into account their relative environmental and economic feasibility and competing advantages and disadvantages of each. The review identifies key areas where processes need to be simplified and decision criteria clearly defined, so that optimal pathways can be rapidly determined for each end-of-life battery.
The well-known classifier support vector machine has many parameters associated with its various kernel functions. The radial basis function kernel, being the most preferred kernel, has two ...parameters (namely, regularization parameter
and
) to be optimized. The problem of optimizing these parameter values is called model selection in the literature, and its results strongly influence the performance of the classifier. Another factor that affects the classification performance of a classifier is the feature subset. Both these factors are interdependent and must be dealt with simultaneously. Following the multiobjective definition of feature selection, we have applied a multiobjective genetic algorithm (MOGA), NSGA II, to optimize the feature subset and model parameters simultaneously. Comparison of the proposed approach with the grid algorithm and GA-based method suggests that the MOGA-based approach performs better than the grid algorithm and is as good as the GA-based approach. Moreover, it provides multiple solutions instead of a single solution. The users can prefer one feature subset over the other as per their requirement and available resources.
Linear thermal instability of a horizontal nanofluid layer considering thermally non-equilibrium effect by applying magnetic field is investigated. Analysis is done with more practical boundary ...conditions on volume fraction of nanoparticles i.e. zero nanoparticle flux is considered across free-free boundaries. A two-temperature model has been introduced in order to consider the influence of thermally non-equilibrium phases (fluid and particle). Local thermal non-equilibrium (LTNE) means that there is a difference in temperature between the two phases that cannot be neglected. LTNE model has acquainted three parameters modified thermal diffusivity ratio, modified thermal capacity ratio and Nield number in addition to the Chandrasekhar number which was introduced due to magnetic field. Results are interpreted analytically as well as graphically. It is found that system stability enhances by enhancing the values of Chandrasekhar number, modified thermal diffusivity ratio, modified thermal capacity ratio and falls with the rise in Nield number, Lewis number, concentration Rayleigh number and modified diffusivity ratio. Critical wave number tends to its local thermal equilibrium (LTE) when there is no interaction among the particle and fluid phases and also when both the phases act as a single phase due to having identical temperatures. Further, critical values of two different nanomaterials (alumina and copper) immersed in base fluid water is compared. It is found that with in thermally non-equilibrium conditions among the phases along with revised boundary conditions copper–water nanofluid is having higher critical values (critical wave number as well as critical Rayleigh number) than alumina-water nanofluid in the presence of magnetic field. Thus, stability of copper nanomaterials is more pronounced as compared to alumina nanomaterials under the above said conditions.
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