Quantitative analysis of take-off forces in birds

The increasing interest on Unmanned Air Vehicles (UAV’s) and their several utilities blended with the need of easy carrying and also the stealth, lead to the need to create the concept of Micro Air Vehicles (MAV’s) and the Nano Air Vehicles (NAV’s). Due to the current interest and the present lack of knowledge on the insect’s and bird’s flight, this study was intended to interpret the forces involved on the moment of the take-off of a bird, recurring to an experiment involving a fast data acquisition force sensor and high speed camera, in addition known facts from earlier studies. In order to do that a bibliographic revision was done, to know what was already studied and to find what could yet be studied. That way could be formed a link on the factors involved on the propulsion of a bird at the moment of take-off. The main conclusions obtained by this work is that the bird can produce movements that will enhance the total moment when the bird stretches its neck forward and moving head down followed by stretching even more its neck and moving head up impelling himself into the air, resulting in a main role on the mechanical forces (against perch) for the bird first moments momentum. Columba livia can generate about 4 times its weight worth mechanic force (against perch) and above 8 times its weight during the 2nd downstroke.O interesse crescente nos Veículos Aéreos não Tripulados “Unmanned Air Vehicles (UAV’s)” e suas diversas utilidades em conjunto com a necessidade de seu fácil transporte e furtividade, levaram à necessidade de criar o conceito dos Micro Veículos Aéreos “Micro Air Vehicles (MAV’s)” e os Nano Veículos Aéreos “Nano Air Vehicles (NAV’s)”. Este tipo de veículos tem como fonte inspiradora os insetos e aves devido à necessária produção simultânea de sustentação e propulsão. Tal como no voo convencional, também no voo animal podem ser identificadas as fases de levantamento (descolagem) e aterragem como diferenciadas do voo longe de uma superfície de apoio. Este trabalho é dedicado ao estudo da fase de levantamento de voo de uma ave columba livia. Foram realizadas experiências para medir a força inicial produzida pela ave para iniciar o voo e a respetiva trajetória na zona próxima do ponto de apoio inicial. Estas medidas foram efetuadas com um sensor de força dotado de elevada velocidade de aquisição de dados e uma camara de alta velocidade. As principais conclusões obtidas com a realização deste trabalho é o facto de que a ave consegue produzir movimentos, que aumentar o momento total quando a ave estica o pescoço para a frente e movendo a cabeça para baixo seguido por continuação de esticamento do pescoço e movimento da cabeça para cima impelindo-se para o ar, resultando num papel principal relativamente às forças mecânicas (contra o poleiro) para o momento linear actuante nos primeiros momentos. Columba livia consegue gerar cerca de 4 vezes o seu peso em força mecânica e acima de 8 vezes o seu peso durante o 2º downstroke

3D locomotion biomimetic robot fish with haptic feedback

This thesis developed a biomimetic robot fish and built a novel haptic robot fish system based on the kinematic modelling and three-dimentional computational fluid dynamic (CFD) hydrodynamic analysis. The most important contribution is the successful CFD simulation of the robot fish, supporting users in understanding the hydrodynamic properties around it

Consultants Second Report, Volume 2: Technical Appraisal Of The Devices - Part 1

This report is the second general assessment prepared by the Consultants for the Wave Energy Steering Committee, the first having been submitted in August 1977. The primary objective of this report is to present to those responsible for directing the U.K. wave energy programme a full assessment of the devices now under development from the point of view of their potential for large scale implementation. The Consultants have attempted to assemble as firm a basis of factual information as is possible at this stage, to guide future decision making. The report is presented in three volumes, Volume 1 is an Executive Summary and includes the conclusions for the whole report. Volume 2 is the main body of the report and deals with the technical assessment, Volume 3 contains the costing information. The report assesses devices and not Device Teams. The Consultants have tried to present as fair a picture as possible of the devices as conceived by the Teams, and the Teams are of course the principal source of information. However, the text also refers to work from other sources. Every effort has been made to identify the inherent strengths and weaknesses of the devices independently of the work of the development Teams. It is recognised that at some stage certain devices will be dropped from the programme to allow concentration of effort on the more promising schemes. The Consultants have therefore given special prominence to those topics which are likely to have most influence on such decisions. An important limitation imposed on this report is its timing. It finds many Device Teams halfway through planned programmes of work, and in many areas detailed information necessary for a complete assessment is missing. In these areas attention is drawn to those factors which may later modify the stated conclusions on particular aspects of devices. However, the Consultants feel that it is now possible to reach reliable conclusions on many of the broader aspects of device development. Seven devices are included in the assessment. Some are much further advanced than others, and some are much more complex. The depths of the assessments carried out reflect these factors. Chapters 4 to 10 of this Volume present for each device a Reference Design which has been used as the basis of assessment. Table 1.1 sets out the key parameters of the Reference Designs. These designs have either been produced in their entirety by the Device Teams, or have been in part worked up by the Consultants in consultation with the Device Teams. The devices are described and assessed technically in terms of their material and workmanship content, and in terms of their annual average power output (termed 'productivity' in this report). For each device a brief summary of the fundamental mechanism of wave power extraction is given as general information, and for comparison between devices. There is a strong link between these fundamentals and the most important engineering problems, including costs. Except where it is directly applicable to the assessment, this report does not deal in any detail with the extensive programme of support work which has been initiated in areas of interest to all devices. This work is undertaken by Technical Advisory Groups (TAGS) and their work is documented in numerous separate reports

Bioinspired fluid-structure interaction problems: gusts, load mitigation and resonance

Mención Internacional en el título de doctorNature often serves as a reference for the design and development of sustainable solutions in numerous different fields. The recent development of small-scale robotic vehicles, asMicro-Air Vehicles (MAVs), is not an exception, and has had an increasingly important impact on society, proposing new alternatives in areas as surveillance or planetary exploration. Trying to mimic the flight of insects and small birds, these devices try to offer more efficient designs and with higher manoeuvrability abilities than the already existing designs. It happens similar with robotic swimmers, with many different existing prototypes. Indeed, it is even possible to find designs of bioinspired small-scale wind turbines based on auto-rotating seeds looking for a more efficient energy harvesting. Besides, in order to develop sustainable designs, increasing their lifetime and reducing the maintenance costs are crucial factors. Depending on the device to design, different methodologies may be followed in order to achieve these two goals while meeting the design requirements. One clear example can be found in the development of wind turbines. Their blades must be designed to withstand not only maximum loads and stresses but also the fatigue caused by the fluctuations around the load required to operate correctly. Reducing fatigue issues by limiting the amplitude of those fluctuations using passive or active control is a viable option to improve their lifetime. The aimof this dissertation is to contribute to the understanding of the underlying physics in biolocomotion. To this end, direct numerical simulations of different examples and problems at low Reynolds number, Re, have been performed using an existing fluid-structure interaction (FSI) solver. This FSI solver relies on the coupling of an incompressible-flow solver with robotic algorithms for the computation of the dynamics of a system of connected rigid bodies. The particularities of this solver are detailed in the thesis. The second part of the thesis includes the analysis of these examples and problems mentioned above.More in detail, the aerodynamic and aeroelastic behaviour of airfoils and wings at Re Æ 1000 in various conditions and environments has been analysed. Natural flyers and swimmers are immersed in turbulent and gusty environments which affect their aerodynamic behaviour. The first problem that has been studied is that of the unsteady response of airfoils impacted by vortical gusts. This first example focuses on how the impact of viscous vortices of different size and intensity on two-dimensional airfoils modify their response. Although in a simplified framework, this analysis allows to gather relevant information about the aerodynamic performance of the airfoils. This aerodynamic response is seen to be self-similar, and the work proposes a semi-empirical model to determine the temporal evolution of the lifting forces based on an integral definition of the vertical velocity induced by the gust, which can be known a priori. The target of the second problem is to analyse the load that can be mitigated in airfoils undergoing oscillations in the angle of attack using passive-pitching trailing edge flaps. This corresponds, for example, to a simplification of the problem of load mitigation in small-scale wind turbines. The use of passive-pitching trailing edge flaps is a strategy that has recently been recently proposed for large-scale wind turbines. Here, we investigate the validity of this strategy on a completely different scenario. Contrary to what happens in experiments at higher Reynolds numbers, whose results match the predictions of a quasi-steady linear model when the kinematics are within the range of applicability of this model, the load mitigation obtained in this work differs from the values of this theory. The load mitigated is larger or smaller than the predicted values depending on the amplitude of the oscillations in the angle of attack. However, the results of this work show that an increase in the length of the flap while the chord of the airfoil is kept constant leads to an equal change in the reduction of load, in line with the predictions of the quasi-steady model. The development of vortical structures is clearly affected by the flap when it is sufficiently large, which also involves changes in the dynamics of the flap and the forces seen by the airfoil. The repercussion that several of the variables defining the parametric space have on the aerodynamic behaviour of the foil and the dynamics of the flap are analysed. This allows to gather more information for an appropriate selection of those variables. Finally, the third and fourth problems involve the study of the effects of spanwise flexibility on both isolated wings and pairs of wings arranged in horizontal tandem undergoing flapping motions. The wings are considered to be rectangular flat plates, and the spanwise flexibility is modelled discretizing these flat plates in a finite number of rigid sub-bodies that are connected using torsional springs. The wings are considered to be rigid in the chordwise direction. Isolated spanwise-flexible wings find an optimal propulsive performance when a fluid-structural resonance occurs. At this flexibility, the time-averaged thrust is maximum and twice the value yielded by the rigid case, and the increment in efficiency is around a 15%. Flexibility and the generation of forces are coupled, such that the structural response modifies the development of the vortical structures generated by the motion of the wing, and vice versa. The optimal performance comes from a combination of larger effective angles of attack, properly timed with the pitching motion such that the projection of the forces is maximum, with a delayed development of the vortical structures. Besides, while aspect ratio effects are important for rigid wings, this effect becomes small when compared to flexibility effects when the wings become flexible enough. In fact, while the increase in thrust coefficient for rigid wings with aspect ratio 4 is 1.2 times larger than that provided by rigid wings with aspect ratio equal to 2, the value of this coefficient for resonant wings is twice the value yielded by rigid wings of aspect ratio 4. While forewings of the tandem systems are found to behave similarly to isolated wings, the aeroelastic response of the hindwings is substantially affected by the interaction with the vortices developed and shed by the forewings. This wake capture effect modifies the flexibility at which an optimal propulsive behaviour is obtained. This wake capture effect is analysed through an estimation of the effective angle of attack seen by both forewings and hindwings, linking the optimal behaviour with the maximisation of the effective angle of attack at the right instants. Based on the obtained results, a proof-of-concept study has been carried out analysing the aerodynamic performance of tandem systems made of wings with different flexibility, which suggests that the latter could outperformsystems of equally flexible wings.This thesis has been carried out in the Aerospace Engineering Department at Universidad Carlos III de Madrid. The financial support has been provided by the Universidad Carlos III de Madrid through a PIPF scholarship awarded on a competitive basis, and by the Spanish Ministry of Economy and Competitiveness through grant DPI2016-76151-C2-2-R (AEI/FEDER, UE).Programa de Doctorado en Mecánica de Fluidos por la Universidad Carlos III de Madrid; la Universidad de Jaén; la Universidad de Zaragoza; la Universidad Nacional de Educación a Distancia; la Universidad Politécnica de Madrid y la Universidad Rovira i VirgiliPresidente: José Ignacio Jiménez González.- Secretaria: Andrea Ianiro.- Vocal: Manuel Moriche Guerrer

Submerged Floating Tunnels: A review and study of their use for strait crossings

Se trata de desarrollar un estudio comparativo entre la construcción de túneles sumergidos y túneles flotante

From conception to interpretation; a new angle on smart tags for reef inhabitants

Length and direction are the two parameters that define animal movement, from the scale of the limbs to whole-body animal navigation through their environment. However, although step lengths have been considered widely, the effect of angles is rarely documented. This thesis considers some of the ways in which directionality operates to define processes within marine communities, particularly reef-based inhabitants, using animal-attached technology. Rapid improvements in device power, size and utility has led to ubiquitous use of such technology in animal movement and behaviour research. Working within a setting of a proposed multi-species, mass tagging effort of a Red Sea coral reef’s inhabitants, this thesis works within the context of angles to evaluate the inherent challenges and areas of opportunities in studying both less- and more-mobile species. It begins by describing a novel system for attaching tags to the dorsal fin of elasmobranchs using a magnetic clip. The angles between the clip halves, as well as between fin and clip, determine the external forces applied to the system and, therefore, the ability of the clip to remain on the animal without causing injury. Despite significant progress in development, there is some way to go to finalise the system. In the second chapter the clip, equipped with a tri-axial accelerometer, was deployed on various captive shark species to investigate the behavioural implications of attachment. Negative reactions to attachment were most notable in whole-body roll angle, due to fleeting chafing behaviours, a reaction that would otherwise be missed by other common, non-angular, tag-derived measures. The thesis then examined the hypothesis that energy expenditure can be represented by rotational (and not necessarily dynamic) movements using invertebrates as a model. Static respirometry methods with spider conchs (Lambis truncata) showed this was valid, with important implications for our ability to quantify the energy expenditure of free-living, slow-moving animals. The next chapter found that spider conchs, despite being ostensibly relatively simplistic movers, have probabilistic movement rules, including in terms of directionality, predicted by previous movement as well as the ambient environment. Finally, gape angles of free-living giant clams (Tridacna maxima) on a Red Sea coral reef were used to infer the effect of anthropogenic noise on their behaviour, suggesting that post-tagging recovery was hindered by boat passes

The aerodynamic loading on an oscillating control

SIGLEAvailable from British Library Document Supply Centre- DSC:DX73942/87 / BLDSC - British Library Document Supply CentreGBUnited Kingdo

Dynamic stability of space vehicles. Volume 12 - Re-entry vehicle landing ability and control

Control and stability aspects prior to spacecraft landing, and propulsive assist to landing spacecraf