ETD at Indian Institute of Science
(528 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.
Mostrando recursos 1 - 20 de 55
1.
Genetic Programming Based Multicategory Pattern Classification - Kishore, Krishna J
Nature has created complex biological structures that exhibit intelligent behaviour through an evolutionary process. Thus, intelligence and evolution are intimately connected. This has inspired evolutionary computation (EC) that simulates the evolutionary process to develop powerful techniques such as genetic algorithms (GAs), genetic programming (GP), evolutionary strategies (ES) and evolutionary programming (EP) to solve real-world problems in learning, control, optimization and classification. GP discovers the relationship among data and expresses it as a LISP-S expression i.e., a computer program. Thus the goal of program discovery as a solution for a problem is addressed by GP in the framework of evolutionary computation....
2.
NEW PERSPECTIVES FOR ANALYZING THE BREAKUP, ENVIRONMENT, EVOLUTION, COLLISION RISK AND REENTRY OF SPACE DEBRIS OBJECTS - Anilkumar, A K
In the space surrounding the earth there are two major regions where orbital debris causes
concern. They are the Low Earth Orbits (LEO) up to about 2000 km, and Geosynchronous Orbits (GEO) at an altitude of around 36000 km. The impact of the debris accumulations are in principle the same in the two regions; nevertheless they require different approaches and solutions, due to the fact that the perturbations in the orbital decay due to atmospheric drag effects predominates in LEO, gravitational forces including earths oblateness and luni solar
effects dominating in GEO are different in these two regions. In LEO it is...
3.
On The Reduction Of Drag Of a Sphere By Natural Ventilation - Suryanarayana, G K
The problem of bluff body flows and the drag associated with them has been the subject of numerous investigations in the literature. In the two-dimensional case, the flow past a circular cylinder has been most widely studied both experimentally and computationally. As a result, a well documented understanding of the gross features of the near-wake around a circular cylinder exists in the literature. In contrast, very little is understood on the general features of three-dimensional bluff body near-wakes, except that the vortex shedding is known to be less intense.
Control or management of bluff body flows, both from the point of...
4.
An Autonomous Guidance Scheme For Orbital Rendezvous - Shankar, G S
The word 'rendezvous' implies a pre-arranged meeting between two entities for a specific purpose. This term is used in the study of spacecraft operations, to describe a set of maneuvers performed by two spacecraft in order to achieve a match in position and velocity. The term 'orbital rendezvous' applies to rendezvous between spacecraft in earth-centered orbits. Considering its obvious scope for application in the assembly, maintenance and retrieval of earth satellites, the importance of orbital rendezvous towards maintaining a sustained presence in space can be easily appreciated. This particular study deals with the development of a guidance scheme for an...
5.
Turbulent Near Wake Behind An Infinitely Yawed Flat Plate - Subaschandar, N
Near wake is the region of wake flow just behind the trailing edge of the body where the flow is strongly influenced by the upstream flow conditions and also perhaps by the characteristics of the body. The present work is concerned with the study of the development of turbulent near wake behind an infinitely yawed flat plate. The turbulent near wake behind an infinitely yawed flat plate is the simplest of the three-dimensional turbulent near wake flows. The present study aims at providing a set of data on the turbulent near wake behind an infinitely yawed flat plate and also...
6.
Development and Application of Kinetic Meshless Methods for Euler Equations - C, Praveen
Meshless methods are a relatively new class of schemes for the numerical solution of partial differential equations. Their special characteristic is that they do not require a mesh but only need a distribution of points in the computational domain. The approximation at any point of spatial derivatives appearing in the partial differential equations is performed using a local cloud of points called the "connectivity" (or stencil). A point distribution can be more easily generated than a grid since we have less constraints to satisfy.
The present work uses two meshless methods; an existing scheme called Least Squares Kinetic Upwind Method...
7.
Autonomous Orbit Estimation For Near Earth Satellites Using Horizon Scanners - Nagarajan, N
Autonomous navigation is the determination of satellites position and velocity vectors onboard the satellite, using the measurements available onboard. The orbital information of a satellite needs to be obtained to support different house keeping operations such as routine tracking for health monitoring, payload data processing and annotation, orbit manoeuver planning, and prediction of intrusion in various sensors' field of view by celestial bodies like Sun, Moon etc. Determination of the satellites orbital parameters is done in a number of ways using a variety of measurements. These measurements may originate from ground based systems as range and range rate measurements, or...
8.
Experimental And Computational Investigations Of Underexpanded Jets From Elliptical Sonic Nozzles - Rajakuperan, E
Three dimensional nozzles and jet flows have attracted the attention of many researchers due to their potential application to many practical devices. Rectangular nozzles are considered for short/vertical take off and landing aircrafts for achieving powered lift. Axisymmetric nozzles with lobes, tabs or slots and elliptical nozzles are considered for noise reduction in aircrafts and mixing augmentation in airbreathing rockets. Interaction of supersonic jets with solid
surface, as in the case of retro and ullage rockets in launch vehicles and interaction of multiple jets as in the case of launch vehicles with multiple booster rockets/multiple nozzle engines are of practical...
9.
Application Of High Frequency Natural Resonances Extracted From Electromagnetic Scattering Response For Discrimination Of Radar Targets With Minor Variations - Menon, K Rajalakshmi
Radars, as the name suggests, were traditionally used for Radio Detection and Ranging. Nevertheless, advances in high resolution electromagnetic simulations, Ultra Wide-Band sources, signal processing and computer technologies have resulted in a possible perception of radars as sensors for target discrimination. In this thesis, the feasibility of discrimination between targets even with minor variations in structure and material composition on the basis of radar echoes is effectively demonstrated.
It is well-known that the echoes from any target are affected by its natural frequencies which are dependent only on the shape and material composition of the target, and independent of the aspect...
10.
Distributed Computation With Communication Delays: Design And Analysis Of Load Distribution Strategies - Bharadwaj, V
Load distribution problems in distributed computing networks have attracted much attention in the literature. A major objective in these studies is to distribute the processing load so as to minimize the time of processing of the entire load. In general, the processing load can be indivisible or divisible. An indivisible load has to be processed in its entirety on a single processor. On the other hand, a divisible load can be partitioned and processed on more than one processor. Divisible loads are either modularly divisible or arbitrarily divisible. Modularly divisible loads can be divided into pre-defined modules and cannot be...
11.
A Numerical Study On Absolute Instability Of Low Density Jets - Chakravorty, Saugata
A spectacular instability has been observed in low density round jets when the density ratio of jet fluid to ambient fluid falls below a threshold of approximately 0.6. This phenomenon has been observed in non-buoyant jets of helium in air, heated air jets and heated buoyant jets. The oscillation of the flow near the nozzle is extremely regular and periodic and consists of ring vortices. Even the smaller scale structures that appear downstream exhibit similar regularity. A theory for predicting the onset of this oscillation is based on finding regions of absolute instability from linear stability analysis of parallel flow....
12.
A High-Resolution Procedure For Euler And Navier-Stokes Computations On Unstructured Grids - Jawahar, P
A finite-volume procedure, comprising a gradient-reconstruction technique and a multidimensional limiter, has been proposed for upwind algorithms on unstructured grids. The high-resolution strategy, with its inherent dependence on a wide computational stencil, does not suffer from a catastrophic loss of accuracy on a grid with poor connectivity as reported recently is the case with many unstructured-grid limiting procedures. The continuously-differentiable limiter is shown to be effective for strong discontinuities, even on a grid which is composed of highly-distorted triangles, without adversely affecting convergence to steady state. Numerical experiments involving transient computations of two-dimensional scalar convection to steady-state solutions of Euler...
13.
Low Reynolds Number Airfoil Aerodynamics - Srinivasa Murthy, P
In this thesis we describe the development of Reynolds- averaged Navier Stokes code for the flow past two- dimensional configuration. Particularly, emphasis has been laid on the study of low Reynolds number airfoil aerodynamics.
The thesis consists of five chapters covering the back ground history, problem formulation, method of solution and discussion of the results and conclusion.
Chapter I deals with a detailed background history of low Reynolds number aerodynamics, problem associated with it, state of the art, its importance in practical applications in aircraft industries.
Chapter II describes the mathematical model of the flow physics and various levels of approximations. Also it...
14.
A Methodology To Recover Unstable Aircraft From Post Stall Regimes: Design And Analysis - Saraf, Amitabh
This thesis deals with high angle of attack behaviour of a generic delta wing model aircraft. A high angle of attack wind tunnel database has been generated for this aircraft and based upon the bifurcation analysis of the data and the results of extensive simulations, it has been shown in the thesis that the post stall behaviour of this aircraft is both unstable and unpredictable. Unpredictability of aircraft behaviour arises from the fact that the aircraft response is oscillatory and divergent; the aircraft state trajectories do not settle down to any stable limit set and very often exceed valid aerodynamic...
15.
Application Of Controlled Random Search Optimization Technique In MMLE With Process Noise - Anilkumar, A K
Generally in most of the applications of estimation theory using the Method of Maximum Likelihood Estimation (MMLE) to dynamical systems one deals with a situation where only the measurement noise alone is present. However in many present day applications where modeling errors and random state noise input conditions occur it has become necessary for MMLE to handle measurement noise as well as process noise. The numerical algorithms accounting for both measurement and process noise require significantly an order of magnitude higher computer time and memory. Further more, implementation difficulties and convergence problems are often encountered. Here one has to estimate...
16.
Analysis Of Solar Pumped Chemical Oxygen Iodine Laser - Balaji, A
Chemical Oxygen Iodine Laser(COIL) is an electronic transition high energy chemical laser having a wavelength of 1.315 /mi. This is the first chemical laser to operate on an electronic rather than a rotational or vibrational transition. In principle the COIL can be operated either in pulsed or cw mode. Its interest lies in high chemical efficiency, high power and wavelength which is shortest among all the chemical lasers. COIL finds a wide range of applications as its output wavelength at 1.315/zm couples well with the surface of most metals. The applications include surface hardening and modification of metals, welding, drilling...
17.
Implicit Least Squares Kinetic Upwind Method (LSKUM) And Implicit LSKUM Based On Entropy Variables (q-LSKUM) - Swarup, A Sri Sakti
With increasing demand for computational solutions of fluid dynamical problems, researchers around the world are working on the development of highly robust numerical schemes capable of solving flow problems around complex geometries arising in Aerospace engineering. Also considerable time and effort are devoted to development of convergence acceleration devices, for reducing the computational time required for such numerical solutions. Reduction in run times is very vital for production codes which are used many times in design cycle. In this present work, we consider a numerical scheme called LSKUM capable of operating on any arbitrary distribution of points. LSKUM is being...
18.
Computational Studies On Certain Problems Of Combustion Instability In Solid Propellants - Anil Kumar, K R
This thesis presents the results and analyses of computational studies on certain problems of combustion instability in solid propellants. Specifically, effects of relaxing certain assumptions made in previous models of unsteady burning of solid propellants are investigated. Knowledge of unsteady burning of solid propellants is essential in studying the phenomenon of combustion instability in solid propellant rocket motors.
In Chapter 1, an introduction to different types of unsteady combustion investigated in this thesis, such as 1) intrinsic instability, 2) pressure-driven dynamic burning, 3) extinction by depressurization, and 4) L* -instability, is given. Also, a review of previous experimental and theoretical studies...
19.
Experimental And Theoretical Studies On Jet Acoustics - Pundarika, G
A systematic research on aeroacoustics conducted around the world for the last few decades has revealed various inherent characteristics of the jet noise radiation. However, a lot more needs to be done for the theoretical as well as experimental predictions of various jet noise features based on actual flow details. The work reported in the present thesis is an attempt in this direction.
A critical study of existing literature on jet noise shows that none of the general wave equations lends itself easily for predictions of all the jet noise features. It is shown that while LighthilPs classical acoustic analogy approach,...
20.
Artificial Neural Network Approach For Characterization Of Acoustic Emission Sources From Complex Noisy Data - Bhat, Chandrashekhar
Safety and reliability are prime concerns in aircraft performance due to the involved costs and risk to lives. Despite the best efforts in design methodology, quality evaluation in production and structural integrity assessment in-service, attainment of one hundred percent safety through development and use of a suitable in-flight health monitoring system is still a farfetched goal. And, evolution of such a system requires, first, identification of an appropriate Technique and next its adoption to meet the challenges posed by newer materials (advanced composites), complex structures and the flight environment. In fact, a quick survey of the available Non-Destructive Evaluation (NDE)...
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