Recursos de colección

ETD at Indian Institute of Science (3.494 recursos)

Repository of Theses and Dissertations of Indian Institute of Science, Bangalore, India. The repository has been developed to capture, disseminate and preserve research theses of Indian Institute of Science.

Aerospace Engineering (aero)

Mostrando recursos 1 - 20 de 160

  1. Design and Development of 75 mm Fixed-Wing Nano Air Vehicle

    Pushpangathan, Jinraj V
    This thesis deals with the design and development of a 75 mm fixed-wing nano-air vehicle (NAV). The NAV is designed to fit inside a cube with each side measuring 75 mm. The range and endurance of the NAV are 300 m and 2-3 minutes, respectively. The high-wing horizontal tailless NAV has a take-off weight of 19.5 g. The battery-powered single propeller NAV has two control surfaces in the form of elevator and rudder. This thesis contains a detailed account of the airfoil selection, selection of the configuration of NAV and the longitudinal, lateral and directional aerodynamic characterization of the NAV. The...

  2. A Design Procedure for Flapping Wings Comprising Piezoelectric Actuators, Driver Circuit, and a Compliant Mechanism

    Chattaraj, Nilanjan
    Flapping-wing micro air vehicle (MAV) is an emerging micro-robotic technology, which has several challenges toward its practical implementation. Inspired by insect flight, researchers have adopted bio-mimicking approach to accomplish its engineering model. There are several methods to synthesize such an electromechanical system. A piezoelectric actuator driven flapping mechanism, being voltage controlled, monolithic, and of solid state type exhibits greater potential than any conventional motor driven flapping wing mechanism at small scale. However, the demand for large tip deflection with constrained mass introduces several challenges in the design of such piezoelectric actuators for this application. The mass constraint restricts the geometry,...

  3. Impact Angle Constrained Guidance Using Cubic Splines

    Dhabale, Ashwin
    In this thesis the cubic spline guidance law and its variants are derived. A detailed analysis is carried out to find the initial conditions for successful interception. The results are applied to three dimensional guidance design and for solving waypoint following problems. The basic cubic spline guidance law is derived for intercepting a stationary target at a desired impact angle in a surface-to-surface engagement scenario. The guidance law is obtained using an inverse method, from a cubic spline curve based trajectory. For overcoming the drawbacks of the basic cubic spline guidance law, it is modified by introducing an additional parameter....

  4. Large Eddy Simulation of Multiphase Flows

    Deevi, Sri Vallabha
    Multiphase flows are a common phenomenon. Rains, sediment transport in rivers, snow and dust storms, mud slides and avalanches are examples of multiphase flows occurring in nature. Blood flow is an example of multiphase flow in the human body, which is of vital importance for survival. Multiphase flows occur widely in industrial applications from hydrocarbon extrac-tion to fuel combustion in engines, from spray painting to spray drying, evaporators, pumps and pneumatic conveying. Predicting multiphase flows is of vital importance to understand natural phenomenon and to design and improve industrial processes. Separated flows and dispersed flows are two types of multiphase...

  5. Time-Optimal Guidance for Impact Angle Constrained Interception of Moving Targets

    Akhil, G
    Various unmanned missions deploy vehicles such as missiles, torpedoes, ground robots, and unmanned aerial vehicles. Guidance strategies for these vehicles aim to intercept a target point and satisfy additional objectives such as specifications on impact angle and interception time. Certain impact angles are crucial for a greater warhead effectiveness, and minimizing the interception time is important for vehicles with limited endurance time and for reducing the probability of detection. This thesis considers the time-optimal impact angle constrained guidance problem for interception of moving targets. In the first part of the thesis, a Dubins paths–based guidance methodology for minimum-time lateral interception of...

  6. Edge Effect of Semi-Infinite Rectangular Posts on Impacting Drops

    Umashankar, Viverjita
    The inhibiting effect of a sharp edge on liquid spreading is well observed during drop interaction with textured surfaces. On groove-textured solid surfaces comprising unidirectional parallel grooves, the edge effect of posts results in the squeezing of drop liquid in the direction perpendicular to the grooves and the stretching of drop liquid along the grooves leading to anisotropy in drop flow, popularly known as wetting anisotropy which has been employed in several engineering applications. A recent study observed that the energy loss incurring at the edges of posts via contact angle hysteresis is primarily responsible for the anisotropic spreading of...

  7. A Study on the Effect of Inhomogeneous Phase of Shape Memory Alloy Wire

    Manna, Sukhendu Sekhar
    The present study in this thesis has attempted to resolve one of the key aspects of enhancing predictability of macroscopic behavior of Shape Memory Alloy (SMA) wire by considering variation of local phase inhomogeneity. Understanding of functional fatigue and its relation with the phase distribution and its passivation is the key towards tailoring thermal Shape Memory Alloy actuators’ properties and performance. Present work has been carried out in two associated areas. First part has covered solving a coupled thermo-mechanical boundary value problem where initial phase fractions are prescribed at the gauss points and subsequent evolution are tracked over the loading...

  8. A Numerical Study of Changes to Flow Organization and their Prognostic Measures

    Kamin, Manu
    Flow induced self-oscillations cause acoustic pressure oscillations of large amplitude in pipe flows. If Reynolds number is treated as a parameter, these floinduced oscillations occur only at discrete and critical values of Reynolds number. However, for a small range of Reynolds numbers around such a critical value, such periodic oscillations may appear intermittently. If intermittency, which is a precursor to these self-oscillations, can be detected, prediction of an impending instability may be possible. In experiments done by Vineeth and Sujith (Int. J. Aeroacoustics, 2016) on flow in a duct orifice arrangement, where flow enters through the duct inlet, and leaves...

  9. A Ghost Fluid Method for Modelling Liquid Jet Atomization

    Kiran, S
    Liquid jet atomisation has a wide variety of application in areas such as injectors in automobile and launch vehicle combustors, spray painting, ink jet printing etc. Understanding physical mechanisms involved in the primary regime of atomisation in combustors is extremely challenging due to the lack of experimental techniques that can reliably provide measurements of gas and liquid velocity fields in this region. Experimental studies have so far been mostly restricted to conditions at atmospheric conditions rather than technically relevant operating pressures. We present a computational fluid dynamics based modelling approach that can capture the evolution of the flow field in...

  10. Analysis of Unsteady Incompressible Potential Flow Over a Swimming Slender Fish and a Swept Wing Tail

    Nathan, Vinay
    This thesis deals with computing the pressure distribution around a swimming slender fish and the thrust generated by its flapping motion. The body of the fish is modeled as a missile like slender body to which a tail is attached that is modeled as a swept wing. The tail is attached to the tip of the slender body and maintains its slope with it. The motion for the swimming fish is prescribed. The fluid flow is modeled as an unsteady potential flow problem with the flow around the slender body modeled as flow over an array of cylinders of varying radii...

  11. Vision-based Strategies for Landing of Fixed Wing Unmanned Aerial Vehicles

    Marianandam, Peter Arun
    Vision-based conventional landing of a fixed wing UAV is addressed in this thesis. The work includes mathematical modeling, interface to a software for rendering the outside scenery, image processing techniques, control law development and outdoor experimentation. This research focuses on detecting the lines or the edges that flank the landing site, use them as visual cues to extract the geometrical parameters such as the line co-ordinates and the line slopes, that are mapped to the control law, to align and conventionally land the fixed wing UAV. Pre-processing and image processing techniques such as Canny Edge detection and Hough Transforms have...

  12. Hybird Central Solvers for Hyperbolic Conservation Laws

    Maruthi, N H
    The hyperbolic conservation laws model the phenomena of nonlinear waves including discontinuities. The coupled nonlinear equations representing such conservation laws may lead to discontinuous solutions even for smooth initial data. To solve such equations, developing numerical methods which are accurate, robust, and resolve all the wave structures appearing in the solutions is a challenging task. Among several discretization techniques developed for solving hyperbolic conservation laws numerically, Finite Volume Method (FVM) is the most popular. Numerical algorithms, in the framework of FVM, are broadly classified as upwind and central discretization methods. Upwind methods mimic the features of hyperbolic conservation laws very well. However, most...

  13. Structural Modeling and Damage Detection in a Non-Deterministic Framework

    Chandrashekhar, M
    Composite structures are extremely useful for aerospace, automotive, marine and civil applications due to their very high specific structural properties. These structures are subjected to severe dynamic loading in their service life. Repeated exposure to these severe loading conditions can induce structural damage which ultimately may precipitate a catastrophic failure. Therefore, an interest in the continuous inspection and maintenance of engineering structures has grown tremendously in recent years. Sensitive aerospace applications can have small design margins and any inadequacy in knowledge of the system may cause design failure. Structures made from composite materials posses complicated failure mechanism as compared to...

  14. Three Dimensional Computational Fluid Dynamic Simulation and Analysis of a Turbocharger Compressor

    Sharma, Ashutosh
    This thesis constitutes detailed computational investigation on ow through the passages of a centrifugal compressor used for turbocharging applications. Given the dynamic nature of operation of the turbocharger, it becomes necessary to under- stand the ow that occurs within the blade passages and its e ect on performance. CFD is an established computational technique wherein the ow is dissected to fun- damental levels and a detailed picture is presented, application of this technique with limited and diverse sense towards understanding of ows through a turbocharger compressor has been successfully carried out by many before. This work presented attempts to address...

  15. Accurate and Efficient Algorithms for Star Sensor Based Micro-Satellite Attitude and Attitude Rate Estimation

    Pal, Madhumita
    This dissertation addresses novel techniques in determining gyroless micro-satellite attitude and attitude rate. The main objective of this thesis is to explore the possibility of using commercially available low cost micro-light star sensor as a stand-alone sensor for micro-satellite attitude as well as attitude rate determination. The objective is achieved by developing accurate and computationally efficient algorithms for the realization of onboard operation of a low fidelity star sensor. All the algorithms developed here are tested with the measurement noise presented in the catalog of the sensor array STAR-1000. A novel accurate second order sliding mode observer (SOSMO) is designed for...

  16. Analysis and Detection of Ionospheric Depletions over the Indian Region in the Context of Satellite Navigation

    Joshi, Prachi
    Satellites have revolutionized navigation by making it more universal, accessible and ac- curate. Global Positioning System (GPS) is the most widely used satellite navigation system in the world. However, it is prone to errors from various sources such as the ionosphere, troposphere and clock biases. In order to make the system very accurate and reliable, especially to meet the requirements of safety-critical applications, Satellite Based Augmentation Systems (SBAS) have recently been designed in various countries to augment the GPS by providing corrections for its errors. An Indian SBAS called GAGAN (GPS Aided Geo Augmented Navigation), developed for the Airports Authority...

  17. Experimental Investigations on Supersonic Ejectors

    Srisha Rao, M V
    A supersonic ejector is used to pump a secondary gas using a supersonic primary gas flow by augmentation of momentum and energy in a variable area duct. The internal compressible flow through an ejector has many complex gas dynamic features, like compressible shear layers and associated shock interactions. In many practical applications, ejectors are operated in the choked flow regimes where higher operating pressure ratios and mass flow rates are encountered. On the other hand, rather low entrainment and subsonic secondary flow dynamics (referred as the mixed regime of operation) dominate the dilution and purging applications of ejectors. The fundamental...

  18. Shock Tunnel Investigations on Hypersonic Impinging Shock Wave Boundary Layer Interaction

    Sriram, R
    The interaction of a shock wave and boundary layer often occurs in high speed flows. For sufficiently strong shock strengths the boundary layer separates, generating shock patterns in the contiguous inviscid flow (termed strong interactions); which may also affect the performances of the systems where they occur, demanding control of the interaction to enhance the performances. The case of impinging shock wave boundary layer interaction is of fundamental importance and can throw light on the physics of the interaction in general. Although various aspects of the interaction are studied at supersonic speeds, the complexities involved in the interaction at hypersonic...

  19. A Computational Study of Structural and Thermo-Mechanical Behavior of Metallic Nanowires

    Sutrakar, Vijay Kumar
    This thesis is an attempt to understand ways to improve thermo-mechanical and structural properties of nano-structured materials. A detailed study on computational design and analysis of metallic nanowires is carried out. Molecular dynamic simulation method is applied. In particular, FCC metallic nanowires, NiAl, and CuZr nanowires are studied. Various bottom-up approaches are suggested with improved structural and thermo¬mechanical properties. In the first part of the thesis, Cu nanowires are considered. Existence of a novel and stable pentagonal multi-shell nanobridge structure of Cu under high strain rate tensile loading is reported. Such a structure shows enhanced mechanical properties. A three-fold pseudo-elastic-plastic...

  20. Optimal Trajectory Planning for Fixed-Wing Miniature Air Vehicles

    Hota, Sikha
    Applications such as urban surveillance, search and rescue, agricultural applications, military applications, etc., require miniature air vehicles (MAVs) to fly for a long time. But they have restricted flight duration due to their dependence on battery life, which necessitates optimal path planning. The generated optimal path should obey the curvature limits prescribed by the minimum turn radius/ maximum turn rate of the MAV. Further, in a dynamically changing environment, the final configuration that the MAV has to achieve may change en route, which demands the path to be replanned by an airborne processor in real-time. As MAVs are small in...

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