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Purpose This paper aims to investigate the influence of smooth curvature distributions on the self-noise of a low Reynolds number aerofoil and to unveil the flow mechanisms in the phenomenon. Design/methodology/approach In this paper, large Eddy simulation (LES) approach was performed to investigate the unsteady aerodynamic performance of both the original aerofoil E387 and the redesigned aerofoil A7 in a time-dependent study of boundary layer characteristics at Reynolds number 100,000 and angle of attack (AoA) 4-degree. The aerofoil A7 is redesigned from E387 by removing the irregularities in the surface curvature distributions and keeping a nearly identical geometry. Flow vorticity magnitude of both aerofoils, along with the spectra of the vertical fluctuating velocity component and noise level, are analysed to demonstrate the bubble flapping process near the trailing edge (TE) and the vortex shedding phenomenon. Findings This paper provides quantitative insights about how the flapping process of the laminar separation bubble (LSB) within the boundary layer near the TE affects the aerofoil self-noise. It is found that the aerofoil A7 with smooth curvature distributions presents a 10% smaller LSB compared to the aerofoil E387 at Reynolds number 100,000 and AoA 4-degree. The LES results also suggest that curvature distribution smoothing leads to a 6.5% reduction in overall broadband noise level. Originality/value This paper fulfils an identified need to reveal the unknown flow structure and the boundary layer characteristics that resulted in the self-noise reduction phenomenon yielded by curvature distribution smoothing.

A cyclist is a vulnerable road user whose interaction with the road infrastructure depends on several factors, including variable environmental conditions of lighting and meteorological road surface. This paper is concerned with nanoscopic crash modelling under the riskiest environmental conditions. There are very few works in the literature dealing with such modelling. An intelligent methodological framework consisting of the data collection unit and a knowledge processing unit (KPU) is proposed. In the knowledge processing unit, a combination of a) Statistical, b) Data learning and c) Casual inference methods are applied for investigating crashes on the study area of Tyne and Wear county in North-East of England. Three predictive nanoscopic road safety models are constructed (with 86% accuracy) using a) Spatial, b) Personal, and c) Infrastructure input variables. The importance of each of the identified input variable is estimated by deep learning and statistically validated through chi-square test and Cramer's V statistic. It is found that unsafeness of interaction between rider and infrastructure depends on lighting and road surface meteorological conditions. Different environmental conditions present a varying degree of risk to different types of infrastructure. The riskiest environment conditions are significantly affected by rider's gender and age, traffic flow regime, specific riding manoeuvre, and the road hierarchy difference. The increase in the number of variables, a rider encounters during his entire trip, imparts risky riding behaviour, affecting its safe interaction with the infrastructure. A novel infrastructure variable, i.e. `functional road hierarchy level and direction' introduced in this work, is found to be a critical road safety variable. A shift in road safety analysis towards nanoscopic modelling can help achieve zero-vision road traffic fatality. The study reinforces the need to plan and design infrastructure to move towards a more holistic approach while considering this vulnerable road user's limitations.

To create a safe bicycle infrastructure system, this article develops an intelligent embedded learning system using a combination of deep neural networks. The learning system is used as a case study in the Northumbria region in England’s northeast. It is made up of three components: (a) input data unit, (b) knowledge processing unit, and (c) output unit. It is demonstrated that various infrastructure characteristics influence bikers’ safe interactions, which is used to estimate the riskiest age and gender rider groups. Two accurate prediction models are built, with a male accuracy of 88 per cent and a female accuracy of 95 per cent. The findings concluded that different infrastructures pose varying levels of risk to users of different ages and genders. Certain aspects of the infrastructure are hazardous to all bikers. However, the cyclist’s characteristics determine the level of risk that any infrastructure feature presents. Following validation, the built learning system is interoperable under various scenarios, including current heterogeneous and future semi-autonomous and autonomous transportation systems. The results contribute towards understanding the risk variation of various infrastructure types. The study’s findings will help to improve safety and lead to the construction of a sustainable integrated cycling transportation system.

The paper aimed at studying the peculiarities of boundary layer on a rotating body. Rotation of axisymmetric bodies is often used for their stabilization at a high velocity motion in the atmosphere. Presented are calculation of boundary layer flow on a rotating cone at zero angle of attack. Longitudinal and full enthalpy profiles in the laminar boundary layer obtained as a result of calculations were used to determine upstream disturbances propagation velocity. New integral relation was determined to find out disturbances propagation velocity for the regime of weak hypersonic viscous-inviscid interaction. Effects of surface rotation velocity along with the temperature factor influence were investigated.

Over the last several decades advancement in UAV technology has formed an important part of recent research. Nowadays, these flying robots are a great aid and even replace humans in many types of critical activities such as surveillance, fire protection, search & rescue (SAR), etc. In this paper, we study the design of SAR system using autonomous quadrotors UAVs. The developed system attempts to maximize the probability of target detection and minimize the expected search time while also minimizing the number of UAVs required. It is also adapted to counter UAV failures by re-configuring the UAVs to optimally continue the mission. Furthermore the SAR system algorithms are designed to accomplish the mission with a minimum amount of control information to be passed between UAVs. Finally a case study of survivor search and rescue operations is provided along with the obtained results which confirm the efficiency of the designed system.

This paper proposes a novel nonlinear feedback control strategy for velocity and attitude control of fixed wing aircrafts. The key feature of the control design strategy is the introduction of a virtual control input in order to deal with the underactuation property of such vehicles and to indirectly control the orientation of the aircraft. As such, the proposed strategy consists of three control loops each realizing a specific task. Simulations are carried out by using the jetstream-3102 aircraft in a real-time virtual Simulation Platform for the development of Aircraft Control Systems (SP-ACS). The proposed approach of control is model-based for which we have introduces an identification part before test and validation. We use the Total Least Squares Estimation (TLSE) technique to identify the aerodynamic parameters, which are unknown, variable and classified. Each aerodynamic coefficient is defined as the mean of its numerical values. All other variations are considered as modeling uncertainties that will be compensated by the robustness of the piloting law. Simulation results on Jetstream-3102 aircraft show very good performance in terms of convergence towards the desired reference trajectories and in terms of robustness with respect to modeling uncertainties.

A study of shock train self-excited oscillation in an isolator with background waves was implemented through a wind tunnel experiment. Dynamic pressure data were captured by high-frequency pressure measurements and the flow field was recorded by the high-speed Schlieren technique. The shock train structure was mostly asymmetrical during self-excited oscillation, regardless of its oscillation mode. We found that the pressure discontinuity caused by background waves was responsible for the asymmetry. On the wall where the pressure at the leading edge of the shock train was lower, a large separation region formed and the shock train deflected toward to the other wall. The oscillation mode of the shock train was related to the change of wall pressure in the oscillation range of its leading edge. The oscillation range and oscillation intensity of the shock train leading edge were affected by the wall pressure gradient induced by background waves. When located in a negative pressure gradient region, the oscillation of the leading edge strengthened; when located in a positive pressure gradient region, the oscillation weakened. To find out the cause of self-excited oscillation, correlation and phase analyses were performed. The results indicated that the instability of the separation region induced by the leading shock was the source of perturbation that caused self-excited oscillation, regardless of the oscillation mode of the shock train.

Protecting an anode from deterioration during charging/discharging has been seen as one of the key strategies in achieving high-performance lithium (Li)–O2 batteries and other Li–metal batteries with a high energy density. Here, we describe a facile approach to prevent the Li anode from dendritic growth and chemical corrosion by constructing a SiO2/GO hybrid thin layer on the surface. The uniform pore-preserving layer can conduct Li ions in the stripping/plating process, leading to an effective alleviation of the dendritic growth of Li by guiding the ion flux through the microstructure. Such a preservation technique significantly enhances the cell performance by enabling the Li–O2 cell to cycle up to 348 times at 1 A·g–1 with a capacity of 1000 mA·h·g–1, which is several times the cycles of cells with pristine Li (58 cycles), Li–GO (166 cycles), and Li–SiO2 (187 cycles). Moreover, the rate performance is improved, and the ultimate capacity of the cell is dramatically increased from 5400 to 25,200 mA·h·g–1. This facile technology is robust and conforms to the Li surface, which demonstrates its potential applications in developing future high-performance and long lifespan Li batteries in a cost-effective fashion.

A comprehensive computational study of the aerodynamic performance and stability characteristics of corrugated airfoils has been conducted at the Low-Reynolds number corresponding to the flight regime of micro-aerial vehicles (MAVs). This research aims to explore the applicability of bio-inspired airfoils in the design of MAVs and to study the effect of corrugations, and thus the entrapped vortices on the inherent tendency of airfoils to diminish flight disturbances. Computational fluid dynamics (CFD) analyses have been performed on three dragonfly-based corrugated airfoils, flat plate, and a "smoothened version" of a pleated airfoil; a comparison of their aerodynamic coefficients is discussed. The stability aspect of these airfoils is studied by estimating dynamic longitudinal damping coefficients at different angles of attack. These damping coefficients are calculated by inducing forced sinusoidal oscillations centered at the quarter-chord of each airfoil while maintaining the reduced frequency (k) in a quasi-steady aerodynamic regime. The interlink relation of the time-step size of transient simulations with the angular frequency of oscillations is also discussed concisely. The aerodynamic results show little-to-no difference between the pleated and smoothened version of the airfoil; thus, further strengthening the notion of the existence of a "switch-over" region from pleated airfoil to smoothened airfoil near Reynolds number (Re) of 100,000. Similarly, the perusal of dynamic damping coefficients of airfoils also suggests a negligible effect of corrugations or entrapped vortices on the stability behavior of airfoil.

This paper is concerned with modelling cyclist road safety by considering various factors including infrastructure, spatial, personal and environmental variables affecting cycling safety. Age is one of the personal attributes, reported to be a significant critical variable affecting safety. However, very few works in the literature deal with such a problem or undertaking modelling of this variable. In this work, we propose a hybrid approach by combining statistical and supervised deep learning with neural network classifier, and gradient descent backpropagation error function for road safety investigation. The study area of Tyne and Wear County in the north-east of England is used as a case study. An accurate dynamic road safety model is constructed, and an understanding of the key parameters affecting the cyclist safety is developed. It is hoped that this research will help in reducing the cyclist crash and contribute towards sustainable integrated cycling transportation system, by making use of cut above methodologies such as deep learning neural network.

This paper is concerned with the development of intelligent safety modelling for cycling safety at the nanoscopic level. The present models are primarily focused on the motorists modelling at an aggregate level. In this work a framework for safety analysis is proposed consisting of a) Data collection unit, b) Data storage unit, and c) Knowledge processing unit. The predictive safety model is developed in the knowledge processing unit using supervised deep learning with neural network classifier, and gradient descent backpropagation error function. This framework is applied to a case study in Tyne and Wear county in England's northeast by using the crash database. An accurate safety model (88 accuracy) is developed with the output of the riskiest age and gender group, based upon the specific input variables. The most critical variables affecting the safety of an individual belonging to a particular age and gender groups, are the journey purpose, traffic flow regime and variable environmental conditions it is subjected to. It is hoped that the proposed framework can help in better understanding of cycling safety, aid the transportation professional for the design and planning of intelligent road infrastructure network for the cyclists

The standard inertial Navier–Stokes equations consisting of the conservation equations for mass, momentum and energy are often used to investigate the motion of a compressible fluid around an object that is in arbitrary motion. The non-inertial form of the Navier–Stokes equations can be used to accurately capture the acceleration effects that arise from the unsteady motion. The acceleration source terms that arise in the conservation equation for momentum have been extensively documented. In this paper, an Eulerian approach for deriving the apparent forces is presented to transform the governing conservation equation for energy into a non-inertial reference frame that is in arbitrary motion. The Eulerian approach is based on successive Galilean transformations between an inertial frame, an orientation-preserving non-inertial frame and a rotating non-inertial frame. The paper demonstrates that for an object in arbitrary motion, the rate of work done due to fictitious forces affects the rate of change of the total energy. The fictitious work arises in the kinetic energy equation while the internal energy and enthalpy equations remain invariant in the non-inertial frame. The present derivation is a step towards quantifying the contribution of the fictitious work terms to the heat transfer of a body that is accelerating/decelerating.

Nowadays, most of the recent researches are focusing on the use of multi-UAVs in both civil and military applications. Multiple robots can offer many advantages compared to a single one such as reliability, time decreasing and multiple simultaneous interventions. However, solving the formation control and obstacles avoidance problems is still a big challenge. This paper proposes a distributed strategy for UAVs formation control and obstacles avoidance using a consensus-based switching topology. This novel approach allows UAVs to keep the desired topology and switch it in the event of avoiding obstacles. A double loop control structure is designed using a backstepping controller for tracking of the reference path, while a Sliding Mode Controller (SMC) is adopted for formation control. Furthermore, collaborative obstacles avoidance is assured by switching the swarm topology. Numerical simulations show the efficiency of the proposed strategy.

Purpose – this paper aims to investigate the different analytical methods used to predict the performance of seaplanes in the wing-in-ground effect region. This was achieved by comparing between the analytical methods available in the literature. The paper also addresses the weaknesses in each method and states which of them can be expanded to include the nonlinear effects.\ud \ud Design/methodology/approach – first of all, the elemental hydrodynamic characteristics of seaplanes are discussed. Secondly, five different analytical methods are reviewed. The advantages and disadvantages of each method are stated. After that, the heave and pitch equations of seaplane motion are illustrated. The procedure of obtaining the solution of the heave and pitch equations of seaplane motion is explained. Finally, the results obtained from the most common methods are compared.\ud \ud Findings – the results show that the current analytical methods available are based on different assumptions and considerations. As a result, no method is optimal for all types of seaplanes. Moreover, some of the analytical methods do not study the stability of the seaplane which is a major issue in the design stage. Also, no method takes in consideration the nonlinear effects of motion of seaplanes in heave and pitch axes.\ud \ud Practical Implications – the previous work has many limitations and only applicable under some assumptions. There was insufficient work to define the motion of the craft in the in-ground effect region where the craft experiences nonlinear characteristics. In order to be able to define the motion in this region, the analytical methods available have to be investigated and compared.\ud \ud Originality/value – the information provided in the research paper can be used by seaplane designers to distinguish between the analytical methods available and gives them valuable insight into the dynamic stability of seaplanes. The work can also be extended to provide better understanding of the wing-in-ground effect phenomenon.

PurposeAircraft noise is dominant for residents near airports when planes fly at low altitudes such as during departure and landing. Flaps, wings, landing gear contribute significantly to the total sound emission. This paper aims to present a passive flow control (in the sense that there is no power input) to reduce the noise radiation induced by the flow over the cavity of the landing gear during take-off and landing.Design/methodology/approachThe understanding of the noise source mechanism is normally caused by the unsteady interactions between the cavity surface and the turbulent flows as well as some studies that have shown tonal noise because of cavity resonances; this tonal noise is dependent on cavity geometry and incoming flow that lead us to use of a sinusoidal surface modification application upstream of a cavity as a passive acoustics control device in approach conditions.FindingsIt is demonstrated that the proposed surface waviness showed a potential reduction in cavity resonance and in the overall sound pressure level at the majority of the points investigated in the low Mach number. Furthermore, optimum sinusoidal amplitude and frequency were determined by the means of a two-dimensional computational fluid dynamics analysis for a cavity with a length to depth ratio of four.Research limitations/implicationsThe noise control by surface waviness has not implemented in real flight test yet, as all the tests are conducted in the credible numerical simulation.Practical implicationsThe application of passive control method on the cavity requires a global aerodynamic study of the air frame is a matter of ongoing debate between aerodynamicists and acousticians. The latter is aimed at the reduction of the noise, whereas the former fears a corruption of flow conditions. To balance aerodynamic performance and acoustics, the use of the surface waviness in cavity leading edge is the most optimal solution.Social implicationsThe proposed leading-edge modification it has important theoretical basis and reference value for engineering application it can meet the demands of engineering practice. Particularly, to contribute to the reduce the aircraft noise adopted by the “European Visions 2020”.Originality/valueThe investigate cavity noise with and without surface waviness generation and propagation by using a hybrid approach, the computation of flow based on the large-eddy simulation method, is decoupled from the computation of sound, which can be performed during a post-processing based on Curle’s acoustic analogy as implemented in OpenFOAM.

The use of second- and third-order classical piston theory [1] (CPT) is commonplace, with the role of the higher-order terms being well understood [2]. The advantages of local piston theory (LPT) relative to CPT have been demonstrated previously [3]. Typically, LPT has been used to perturb a mean-steady solution obtained from the Euler equations, and recently, from the Navier-Stokes equations [4]. The applications of LPT in the literature have been limited to first-order LPT [5–7]. The reasoning behind this has been that the dynamic linearization used assumes small perturbations. The present note clarifies the role of higher-order terms in LPT. It is shown that second-order LPT makes a non-zero contribution to the normal-force prediction, in contrast to second-order CPT.

Similar to MXene, MAB is a group of 2D ceramic/metallic boride materials which exhibits unique properties for various applications. However, these 2D sheets tend to stack and therefore lose their active surface area and functions. Herein, an amorphous cobalt nickel boride (Co–Ni–B) nanocomposite is prepared with a combination of 2D sheets and nanoparticles in the center to avoid agglomeration. This unique structure holds the 2D nano-sheets with massive surface area which contains numerous catalytic active sites. This nanocomposite is prepared as an electrocatalyst for borohydride electrooxidation reaction (BOR). It shows outstanding catalytic activity through improving the kinetic parameters of BH4− oxidation, owing to abundant ultrathin 2D structure on the surface, which provide free interspace and electroactive sites for charge/mass transport. The anode catalyst led to a 209 mW/cm2 maximum power density with high open circuit potential of 1.06 V at room temperature in a miniature direct borohydride fuel cell (DBFC). It also showed a great longevity of up to 45 h at an output power density of 64 mW/cm2, which is higher than the Co–B, Ni–B and PtRu/C. The cost reduction and prospective scale-up production of the Co–Ni–B catalyst are also addressed.

Transportation negatively affects the environment due to a high carbon footprint associated with travel. In this paper, we estimate the commuter travel emissions of an out-of-town centre and evaluate the modelled emission against the targets set out by the UK government for 2030 (Climate Change Act), and 2050 (Committee on Climate Change, Kyoto protocol). For the study, primary data is provided by a leading retail centre in the UK in the form of home postcode, and mode selected by its staff for the commute. Each trip’s details are extracted using a macro code linking the journey details with google map. An emission model is constructed through the Department for Transport’s, Transport Appraisal Guidelines. Modelling for: a) Present mode share, b) Car only, and c) Bus only, with horizon modelling from 2010-2030. There are 3,444 staff working in the centre, 1743 (51%) use a car and 1701 (49%) bus for the everyday commute. Presently the average emission per person is 3 kg CO2e, modelled to decrease to 2.3 kg CO2e per journey by 2050. It is concluded from the study that a) average emissions for the same trip are expected to decrease, b) the emissions for bus journey are much lower than that of car, c) the targets set out for 2030, and 2050 will not be met if the present travel patterns continue. The modelling has considered advancements in technology, cleaner fuels, and electric vehicles' uptake. The deviation from 2030 and 2050 target is modelled as 29% and 56% respectively. The setout emissions targets are achievable only if a significant change in travel behaviour occurs supplemented by the uptake of sustainable transport modes such as cycling. This study endorses the adverse effects of travel on the environment and makes a case for stronger actions to reduce the travel carbon footprint.

This paper is concerned with the modelling of cyclist road traffic crashes by considering multiple factors affecting the safety of cyclists. There are very few works in the literature dealing with such a problem. The available models in the literature are only based upon the probabilistic function of human error. In this study, we propose an intelligent safety system for modelling cycling infrastructure. The historic crash dataset for the Tyne and Wear County, north-east of England is used as a case study. There are five predictive road safety models develops using the Artificial Neural Network, with the output for the riskiest road type infrastructure. The study demonstrates that infrastructure, spatial variables, personal characteristics, and environmental conditions affect safety, which can also be used for predicting safety. These identified variables are modelled both individually and in combination with each other, and a plausible high accuracy is achieved in all the five models (> 85% accuracy). This demonstrates the benefit of using ANN for effective and efficient modelling of the safety variable for infrastructure design and planning. It is hoped that the proposed model can help in designing better cyclist infrastructure and contribute towards the development of a sustainable transportation system.

This paper studies an approach for detecting cyber attacks against networked cooperative systems (NCS) that are assumed to be working in a cyber-physical environment. NCS are prone to anomalies both due to cyber and physical attacks and faults. Cyber-attacks being more hazardous given the cooperative nature of the NCS may lead to disastrous consequences and thus need to be detected as soon as they occur by all systems in the network. Our approach deals with two types of malicious attacks aimed at compromising the stability of the NCS: intrusion attacks/local malfunctions on individual systems and deception/cyber-attacks on the communication between the systems. In order to detect and identify such attacks under switching communication topologies, this paper proposes a new distributed methodology that solves global state estimation of the NCS where the aim is identifying anomalies in the networked system using residuals generated by monitoring agents such that coverage of the entire network is assured. A cascade of predefined-time sliding mode switched observers is introduced for each agent to achieve a fast estimate of the global state whereby the settling time is an a priori defined parameter independently of the initial conditions. Then, using the conventional consensus algorithm, a set of residuals are generated by the agents that is capable of detecting and isolating local intrusion attacks and communication cyber-attacks in the network using only locally exchanged information. In order to prove the effectiveness of the proposed method, the framework is tested for a velocity synchronization seeking network of mobile robots.

Drone jamming platforms are faced with a significant constraint on bandwidth limitation compared to the broadband spectrum used by remote control radio links in view of implementing the advanced techniques of spread spectrum on these devices. In this work, we propose a hardware solution to overcome the bandwidth limitation of drone jamming platforms by using the dual AD9361 transceiver integrated on the AD-FMCOMMS5-EBZ radio prototyping platform. The hyperchaotic generator of random digital signals and the custom control architecture have been implemented on the ZC706 FPGA development board. A versatile real time chaotic signals generation IP have been developed and integrated on the FMCOMMS5-EBZ HDL reference design considering timing constraints related to the AD9361 data exchange and the AXI-LITE bus interface. The experimental results showed a coverage capacity of more than 100 MHz of bandwidth, which made it possible to guarantee an integral coverage of the WIFI band and consequently to neutralize any potential threat evolving on this band.

This paper is concerned with the modelling of cyclist road traffic crashes by considering the personal attributes, i.e. gender and age of the cyclists. There are 21 different types of variables considered for each crash, which broadly fall into spatial, infrastructure, and environment categories. The study area of Tyne and Wear county in the north-east of England is selected for investigation. Six deep learning-based safety models are constructed using historic crash data. The effectiveness of deep learning methodology for road safety analysis is demonstrated, and it is found that spatial, infrastructural, and environmental conditions affect the safety interactions of a particular cyclist. These variables can be used for determining/predicting safety for a rider at a location. The model can predict age and gender of the rider, which is likely to be the most unsafe based upon the specific input variables. The significant accuracy is obtained for the constructed models with an overall accuracy of 84%. It is hoped that the proposed models can help in better designing of cyclist network, design, and planning, which will contribute to a sustainable transportation system.

The suitability of local piston theory for modeling static loads on a deforming low-aspect-ratio wing in the presence of aerodynamic interference is investigated. Predictions using Euler-based loca...

Cogeneration of power-and-water is one of the potential solutions for ever-rising energy and freshwater demand. These systems have shown superior thermodynamic and economic performance compared to their standalone counterparts because of processes synergy and shared utilities resources. The current study investigates a multi-effect distillation system operated on bleed-out steam from the last stages of low-pressure steam turbine of a combined cycle gas turbine power plant (CCGT + MED). For this purpose, a component-based exergoeconomic investigation integrated with normalized sensitivity analysis for energy, exergy, and economic evaluation. The performance indicators include specific fuel consumption, thermal efficiency, exergy destruction, exergy efficiency, stream cost, and product cost (electricity and freshwater). The analysis showed that the cogeneration scheme reduced the electricity cost by 16.8% and freshwater production cost by 24.5% compared to the standalone power plant and MED systems. Moreover, the payback period for the MED system is calculated as 2.59 years with freshwater selling at $1.6 /m3. The sensitivity analysis showed that the electricity and the freshwater production cost are the most sensitive to gas turbine efficiency, fuel cost, and fuel heating value with normalized sensitivity coefficients of 1.71, 0.86, and 0.80 for electricity and 0.76, 0.42 and 0.40, for freshwater cost, respectively. While the other parameters such as interest rate, cost index factor, steam turbine efficiencies etc. showed a remarkably low impact on the cost of the products.

Indirect evaporative cooling technology has emerged as an energy-efficient, low-cost, and sustainable alternative to conventional air conditioning systems for space cooling. This is because of its significant (40–50%) energy-saving potential compared to ventilation, vapor compression cooling, and desiccant cooling systems. The current paper presents a novel humidifier-assisted regenerative indirect evaporative cooler that eliminates the use of hydrophilic surfaces within the system and mitigates the fouling propensity and water management issues. A generic cell of the proposed system is fabricated and tested for different operating scenarios along with the uncertainty propagation analysis. Thereafter, a normalized sensitivity analysis is performed to identify the most influential parameters on the cooler performance. The experimental data shows an effective cooling performance with a temperature drop of 20 °C of outdoor air and cooling capacity of 175 watts of 1800 mm × 300 mm generic cell. The cooling coefficient of performance was calculated as 44 and maximum effectiveness of 83.82% for the proposed configuration. The sensitivity analysis reveals scaling trends of the coefficient of performance in the following order of primary air inlet temperature > primary air outlet temperature > primary air velocity and the cooler effectiveness as secondary air outlet temperature > primary air inlet temperature > primary air humidity > primary air outlet.

The paper presents an Eulerian derivation of the non-inertial Navier–Stokes equations as an alternative to the Lagrangian fluid parcel approach. To the best knowledge of the authors, this is the first instance where an Eulerian approach is used for such a derivation. This work expands on the work of Kageyama and Hyodo (2006) who derived the incompressible momentum equation in constant rotation for geophysical applications. In this paper the derivation is done for the full set of Navier–Stokes equations in incompressible flow for pure rotation. It is shown that the continuity equation as well as the conservation of energy equation are invariant under transformation from the inertial frame to the rotational frame. From these equations the non-inertial boundary layer equations for flow on a flat plate subjected to rotation is derived in both the Cartesian and cylindrical co-ordinate systems.

Purpose This paper aims to propose a new multi-layered optimal navigation system that jointly optimizes the energy consumption, improves the robustness and raises the performance of a quadrotor unmanned aerial vehicle (UAV). Design/methodology/approach The proposed system is designed as a multi-layered system. First, the control architecture layer links the input and the output spaces via quaternion-based differential flatness equations. Then, the trajectory generation layer determines the optimal reference path and avoids obstacles to secure the UAV from collisions. Finally, the control layer allows the quadrotor to track the generated path and guarantees the stability using a double loop non-linear optimal backstepping controller (OBS). Findings All the obtained results are confirmed using several scenarios in different situations to prove the accuracy, energy optimization and the robustness of the designed system. Practical implications The proposed controllers are easily implementable on-board and are computationally efficient. Originality/value The originality of this research is the design of a multi-layered optimal navigation system for quadrotor UAV. The proposed control architecture presents a direct relation between the states and their derivatives, which then simplifies the trajectory generation problem. Furthermore, the derived differentially flat equations allow optimization to occur within the output space as opposed to the control space. This is beneficial because constraints such as obstacle avoidance occur in the output space; hence, the computation time for constraint handling is reduced. For the OBS, the novelty is that all controller parameters are derived using the multi-objective genetic algorithm (MO-GA) that optimizes all the quadrotor state’s cost functions jointly.

The building sector consumes around half of the global energy produced and air-conditioning processes guzzle over 55% of building sector energy. The conventional refrigerant-based chillers, covering over 90% of the current cooling market, are not only energy-intensive but also have high ozone depletion and global warming potentials. Indirect evaporative coolers were introduced but they were difficult to commercialize due to their practical lower achievable temperature limits. All existing indirect evaporative coolers use hydrophilic interface to provide wet surfaces for evaporative potential. These hydrophilic surfaces not only increase heat transfer resistance but also provide excellent conditions, wet and damp surface, for mold formation. The treatment of mold is almost impossible as the height of the channel is only 3–5 mm and the fungus can be dangerous to health. Therefore, we proposed an innovative indirect evaporative cooling cycle in which there are no hydrophilic surfaces inside the system. The humidification of the working air is carried out before it is introduced into the wet channel. Also, the interface between dry and wet channel is only a thin aluminium foil that boosts heat transfer from supply air to working air in the transverse direction. A generic cell of 1800 mm long and 280 mm wide can produce 182.5 W cooling capacity. The measured coefficient of performance and effectiveness are 45 and 80% respectively for sensible cooling. This basic information of the proposed innovative indirect evaporative cooling system can be used to design a commercial unit as the total capacity is based on number of generic cells.

The time-averaged behavior of gap flow between two stationary side-by-side circular cylinders immersed in the subcritical Reynolds number regime and its variation with gap spacing are presented. A series of experiments and numerical simulations are performed. Results reveal that gap flow, which is the flow passing between the cylinders, can be classified broadly into pressure- and momentum-driven regimes, depending on the spacing ratio (T/D), where T is the transverse center-to-center spacing between the cylinders and D is the cylinder diameter. The pressure-driven regime occurs for roughly T/D 1.25. Within the pressure-driven regime, subtransitions of the gap flow are further classified, based on distinct changes in the circumferential static pressure distribution, as well as the velocity profile, ...

The present work presents a brief review of some of the notable contributions to piston theory and of its theoretical basis. A generalized formulation of piston theory is given, applicable to both local and classical piston theory. A consistent generalized formulation of the downwash equation is given, accounting for arbitrary motion in the plane of the airfoil. The formulation reduces to established downwash equations through appropriate definition of the cylinder orientation. The theoretical range of validity of classical piston theory is examined, and the relative accuracy of a number of approximate theories encapsulated by the formulation as applied to a planar wedge is considered. The relative importance of higher order terms in piston theory is examined, with the significance of recent literature extending the fidelity of the first-order term highlighted. It is subsequently suggested that current implementations of local piston theory may be improved through the use of a first-order term of suitable...

A novel lead-free luminescent ferroelectric (FE) ceramic, B i 0.5 N a 0.5 T i O 3 − 0. 06 B a T i O 3 − 0. 055 S r 0.7 B i 0.18 E r 0.02 ◻ 0.1 T i O 3 (BNT-BT-SBET), is developed with an adiabatic temperature change ( Δ T ) of 0.7 K under an electric field ( E ) of 60 kV/cm at room temperature, an anti-Stokes fluorescence cooling, and a maximum optical T sensitivity of 0.0055 K − 1 at 522 K. Interestingly, the electrocaloric response reaches a saturation at permittivity shoulder T of 100°C; meanwhile, the maximized emission intensity of 2 H 11 / 2 → 4 I 15 / 2 occurs. T - and E -tunable enhancement of 2 H 11 / 2 → 4 I 15 / 2 emission intensity is due to the population inversion from the 4 S 3 / 2 to 2 H 11 / 2 states caused by an incoherent regime consisting of FE phase and polar nanoregions in a relaxor matrix.

Unmanned Aerial Vehicles (UAVs) swarming has took an important part of the recent researches. Multiple robots offer many advantages when comparing to a single one such as reliability, time decreasing and multiple simultaneous interventions. This paper proposes a new scheme for trajectory tracking of multiple quadrotors UAVs under a centralized leader-followers formation strategy. Attitude stability and position control are assured using a double loop control structure based on the Linear Quadratic Regulator (LQR), moreover the leader-followers formation is maintained via a Sliding Mode Controller (SMC) controller. Many scenarios are proposed within this work. Simulation results proof the energy optimization and formation controller’s robustness and accuracy.

Over the past several years, a growing interest in UAV's has been shown, since they are widely used for military as well as civilians applications. Quadrotors are a type of VTOL systems. They are capable of hover, forward flight and vertical takeoff landing, as a drawback, the nonlinear, underactuated dynamic system and the high energy consumption can be mentioned. This work introduces a new concept of quadrotors modeling by developing a nonlinear dynamic model that takes in consideration the energy limitation, then apply a set of linear commands in a real time simulation in order to choose the most adequate for a real application.

An aeroelastic prediction framework in MATLAB with modularity in the quasi-steady aerodynamic methodology is developed. Local piston theory (LPT) is integrated with quasi-steady methods including shock-expansion theory and the Supersonic Hypersonic Arbitrary Body Program (SHABP) as a computationally inexpensive aerodynamic solver. Structural analysis is performed using bilinear Mindlin–Reissner quadrilateral plate elements. Strong coupling of the full-order system and linearization of the modal-order system are implemented. The methodology is validated against published experimental data in the literature and benchmarked against Euler computation in the Edge CFD code. The flutter dynamic pressure is predicted to be within 10% of the experimental value for 140 times lower computational cost compared to CFD. Good agreement in other cases is obtained with the industry-standard ZONA7 and ZONA7U codes.

This study aimed to observe the effect of a novel concept (referred to as the flap extension) implemented on the leading edge of the flap of a three element high lift device. The high lift device, consisting of a flap, main element and slat is designed around an Airbus research profile for sufficient take off and landing performance of a large commercial aircraft. The concept is realised on the profile and numerically optimised to achieve an optimum geometry. Two different optimisation approaches based on Genetic Algorithm optimisations are used: a zero order approach which makes simplifying assumptions to achieve an optimised solution: as well as a direct approach which employs an optimisation in ANSYS DesignXplorer using RANS calculations. Both methods converge to different optimised solutions due to simplifying assumptions. The solution to the zero order optimisation showed a decreased stall angle and decreased maximum lift coefficient against angle of attack due to early stall onset at the flap. The DesignXplorer optimised solution matched that of the baseline solution very closely. The concept was seen to increase lift locally at the flap for both optimisation methods.

This research is based on the investigation into the dynamic stability associated with seaplanes during takeoff. Various forces acting on a hydroplaning hull form have been empirically defined. Such empirical data have shown that, under a certain set of conditions, a hydroplaning hull will begin to porpoise: an instability oscillation in both the vertical direction and about the center of gravity. To investigate the porpoising motion, a shallow water flume was used. It was the first time that such a facility had been used to simulate the dynamic motion of hydroplaning hull forms. An experimental method derived from the store release experiments was derived for the dynamics measurements. The equipment developed led to an analysis of a flat-plate hull porpoising in a supercritical channel. The porpoising limit was then very well defined.

A combined computational and experimental analysis was performed on a tangent ogive body with very low aspect ratio wings in the ‘+’ (plus) orientation at Mach numbers 0.1, 0.2 and 0.3, with the aim of developing a database of global force and moment loads. Three different span to body diameter ratios were tested with aspect ratios of 0.022, 0.044 and 0.067. Aerodynamic loads were obtained and flow visualization was performed to gain an understanding of the lee side flow features. It was found that the global loads were independent of Mach number as is expected at incompressible speeds. The numerical centre-of-pressure predictions were validated experimentally for angles of attack higher than 6 degrees. The correlation below 6 degrees was only reasonable due to the relative higher balance uncertainties. Vortex separation was observed for all three span to body diameter configurations, whose locations did not correlate to that of an impulsively started flow for a flat plate. This indicated possible configuration specific phenomena or body-wing interactions.

Passive and active flow control methods are used to manipulate flow fields to reduce acoustic signature, aerodynamic drag and heating experienced by blunt bodies flying at supersonic and hypersonic speeds. This paper investigate the use of active opposing jet concept in combination with geometric variations of the opposing jet nozzle to alleviate high wave drag formation. A numerical study is conducted to observe the effects of simple jet as well as jet emanating from a divergent nozzle located at the nose of a blunt hemispherical body. An initial discussion is presented of the complex shock wave pattern flow physics occurring when opposing jet ejected from a nozzle under various operating conditions interacts with the free stream flow. The complex flow physics that include long penetration and short penetration mode is studied in conjunction with effect on drag. The numerical setup consists of supersonic free stream flow interacting with an opposing sonic jet under varying pressure ratios. Initial computational results are validated by identifying prominent flow features as well as comparing available experimental data of surface pressure distributions. Preliminary validation is followed by the introduction of a divergent nozzle in the blunt body nose region. A series of numerical iterations are performed by varying nozzle geometric parameters that include nozzle divergent angle and nozzle length for a certain jet pressure ratio. Long penetration mode, short penetration mode as well as flow separations are captured accurately during the analysis. The results show a considerable reduction in drag by the use of a divergent nozzle. Specifically, 46% and 56% reduction in drag coefficient is achieved at pressure ratio of 0.6 and 0.8 respectively in the divergent nozzle cases as compared to the simple blunt body without any nozzle.

A quadrotors is a type of Unmanned Aerial Vehicles (UAV) systems that attract the researchers in the control field since it's a highly nonlinear, underactuated system. In this paper, a non-linear dynamic model based on quaternions is developed. Differential flatness is an approach that enables the optimization to occur within the output space and therefore simplifies the problem of the trajectory tracking. This work aim to combine both methods in order to create a differential flatness-quaternion based approach that enables the quadrotors to follow a desired optimal path and avoid any singularities that can occur. The trajectory tracking is assured by a double loop control structure based on the LQR controller.