ETD at Indian Institute of Science
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 185
A Synergetic Micromechanics Model For Fiber Reinforced Composites - Padhee, Srikant Sekhar
Composite materials show heterogeneity at different length scales. hence concurrent multiscale analysis is the only reliable method to analyze them. But unfortunately there is no concurrent multi-scale strategy that is efficient, and accurate while addressing all kinds of problems. This lack of reliability is partly because there is no micro-mechanical model which inherently keeps all relevent global information with it. This thesis tries to fill this gap. The
presented micro-mechanical model not only homogenizes the micro-structure but also keeps the global information with it. Most of the micro-mechanical models in the literature extract the Representative Volume Element (RVE) from the continuum...
Experimental Study On The Impact Of Water Drops On Groove-Textured Surfaces - Kannan, R
The interaction of a liquid drop with a solid surface is being actively studied to understand practically encountered scenarios such as the impact of fuel spray droplets onto the walls of engine combustion chamber, the formation of thermal barrier coating on the surfaces of turbine blades, the process of ink-jet printing, etc. The surface topography of solid surface is one of the major parameters influencing the dynamics of drop-surface interaction process. Understanding the precise role of surface topography features such as micro asperities and grooves on the spreading and receding processes of impacting liquid drops is crucial for the improvement...
Modeling And Computation Of Turbulent Nonreacting And Reacting Sprays - De, Santanu
Numerical modeling of several turbulent nonreacting and reacting spray jets is carried out using a fully stochastic separated flow (FSSF) approach. As is widely used, the carrier-phase is considered in an Eulerian framework, while the dispersed phase is tracked in a Lagrangian framework following the stochastic separated flow (SSF) model. Various interactions between the two phases are taken into account by means of two-way coupling. Spray evaporation is described using a thermal model with an infinite conductivity in the liquid phase. The gas-phase turbulence terms are closed using the k-� model. In the classical SSF (CSSF) approach the effects of...
Micro-Blast Waves - Obed Samuelraj, I
The near field blast–wave propagation dynamics has been a subject of intense research in recent past. Since experiments on a large scale are difficult to carry out, focus has been directed towards recreating these blast waves inside the laboratory by expending minuscule amounts of energy(few joules),which have been termed here as micro–blast waves. In the present study, micro-blast waves are generated from the open end of a small diameter polymer tube (Inner Diameter of 1.3 mm)coated on its inner side with negligible amounts of HMX explosive (~18 mg/m), along with traces of aluminium powder. Experimental, numerical, and analytical approaches have...
Collision Avoidance And Coalition Formation Of Multiple Unmanned Aerial Vechicles In High Density Traffic Environments - Manathara, Joel George
This thesis addresses the problems of collision avoidance and coalition formation of multiple UAVs in high density traffic environments, proposes simple and efficient algorithms as solutions, and discusses their applications in multiple UAV missions.
First, the problem of collision avoidance among UAVs is considered and deconfliction algorithms are proposed. The efficacy of the proposed algorithms is tested using simulations involving random flights in high density traffic. Further, the proposed collision avoidance algorithms are implemented using realistic six degree of freedom UAV models. The studies in this thesis show that implementation of the proposed collision avoidance algorithms leads to a safer and...
Parametric Analysis Of A Free Piston Stirling Engine For Spacecraft Power Applications With A Radioisotope Heat Source - Bhaskaran, Ramprasad
Stirling engines are promising candidates for applications where air breathing engines cannot be used. Self contained engines capable of operating independently of the environment are required to convert thermal energy into electric power, or to perform other necessary functions. These are ideally suited for power generation onboard spacecrafts with radioisotope heat source. These engines can power interplanetary missions to Mars and beyond.
The problem of parametric analysis, sensitivity and numerical optimization of Stirling cycle engine is discussed and applied to a specific example of a 2kWe free piston Stirling engine. Stirling cycle simulation programs are generated with emphasis and adaptations...
Packed Bed Gasification-Combustion In Biomass Based Domestic Stoves And Combustion Systems - Varunkumar, S
This thesis constitutes fundamental experimental and computational investigations on gasification and combustion in a packed bed of biomass. Packed bed gasification-combustion in counter-current mode is used in two applications -(1) Gasifier stove in reverse downdraft mode (or equivalently, top-lit updraft mode) that constitutes the idea behind efficient and clean burning domestic stoves. (2) Combustion-on moving grate for boiler application, studied widely in Europe. While a large part of the present study is around domestic stoves, a crucial part of the study aims to address the second application as an extension of the approach taken in the first part to clarify...
Experimental Measurement Of Flame Response To Acoustic Oscillations - Alexander, Sam
Acoustic instabilities in a combustion chamber arise due to the coupling of acoustic pressure with in-phase heat-release, and are characterized by large amplitude oscillations of one or more natural modes of combustor. Even though an array of studies, both theoretical and experimental, has been conducted by a number of authors in this field to extract the flame response, most of these are based on kinematic flame models. In this dissertation, an experimental study of a subsonic flame's intrinsic response to acoustic pressure perturbations is performed for the case of a tube closed at one end and the other end opened...
Wave Propagation In Hyperelastic Waveguides - Ramabathiran, Amuthan Arunkumar
The analysis of wave propagation in hyperelastic waveguides has significant applications in various branches of engineering like Non-Destructive Testing and Evaluation, impact analysis, material characterization and damage detection. Linear elastic models are typically used for wave analysis since they are sufficient for many applications. However, certain solids exhibit inherent nonlinear material properties that cannot be adequately described with linear models. In the presence of large deformations, geometric nonlinearity also needs to be incorporated in the analysis. These two forms of nonlinearity can have significant consequences on the propagation of stress waves in solids. A detailed analysis of nonlinear wave propagation...
Role Of Hydrogen Injection Temperature On The Combustion Instability Of Cryogenic Rocket Engine - Biju Kumar, K S
Physical mechanism for high frequency instability in cryogenic engines at low hydrogen injection temperature has been a subject of debate for long time. Experimental and early developmental studies revealed no instabilities and it was only much later when liquid hydrogen at lower initial temperature (~50 to 100 K) was injected into the combustion chamber that instabilities were detected. From the compilations of the experimental data related to the instability of cryogenic engines by Hulka and Hutt, it was found that the instability was strongly connected to the temperature of hydrogen. Experiments conducted with hydrogen temperature ramping from a higher value...
Modelling And Analysis Of Fish Inspired Ionic Polymer Metal Composite Flapping Fins - Karthigan, G
Ionic polymer metal composites (IPMC) are a new class of smart materials that have attractive characteristics such as muscle like softness, low voltage and power consumption, and good performance in aqueous environments. Therefore, there is a significant motivation for research on design and development of IPMC based biomimetic propulsion systems for underwater vehicles. In aerospace, underwater vehicles finds application for forensic studies of spaceship wrecks, missile fragments and any airplane accidents in sea and ocean terrains. Such vehicles can also survey moons and planets that house water oceans. Among biomimetic swimming systems, fish inspired swimming has gained interest since fish...
Evolutionary Optimization For Vibration Analysis And Control - Dutta, Rajdeep
Problems in the control and identification of structural dynamic systems can lead to multimodal optimization problems, which are difficult to solve using classical gradient based methods. In this work, optimization problems pertaining to the vibration control of smart structures and the exploration of isospectral systems are addressed. Isospectral vibrating systems have identical natural frequencies, and existence of the isospectral systems proves non-uniqueness in system identification. For the smart structure problem, the optimal location(s) of collocated actuator(s)/sensor(s) and the optimal feedback gain matrix are obtained by maximizing the energy dissipated by the feedback control system. For the isospectral system problem, both...
Measurement Of Static Pressure Over Bodies In Hypersonic Shock Tunnel Using MEMS-Based Pressure Sensor Array - Ram, S N
Hypersonic flow is both fascinating and intriguing mainly because of presence of strong entropy and viscous interactions in the flow field. Notwithstanding the tremendous advancements in numerical modeling in the last decade separated hypersonic flow still remains an area where considerable differences are observed between experiments and numerical results. Lack of reliable data base of surface static pressures with good spatial resolution in hypersonic separated flow field is one of the main motivations for the present study.
The experiments in hypersonic shock tunnels has an advantage compared to wind tunnels for simulating the total energy content of the flow in...
Inter-laminar Stresses In Composite Sandwich Panels Using Variational Asymptotic Method (VAM) - Rao, M V Peereswara
In aerospace applications, use of laminates made of composite materials as face sheets in sandwich panels are on the rise. These composite laminates have low transverse shear and transverse normal moduli compared to the in-plane moduli. It is also seen that the corresponding transverse strength values are very low compared to the in-plane strength leading to delaminations. Further, in sandwich structures, the core is subjected to significant transverse shear stresses. Therefore the interlaminar stresses (i.e., transverse shear and normal) can govern the design of sandwich structures. As a consequence, the first step in achieving efficient designs is to develop the...
Structural Health Monitoring Of Thin Plate Like Structures Using Active And Passive Wave Based Methods - Gangadharan, R
Aerospace structures comprising of metals and composites are exposed to extreme loading and environmental conditions which necessitates regular inspection and maintenance to verify and monitor overall structural integrity. The timely and accurate detection, characterization and monitoring of structural cracking, corrosion, delaminating, material degradation and other types of damage are of major concern in the operational environment. Along with these, stringent requirements of safety and operational reliability have lead to evolutionary methods for evaluation of structural integrity. As a result, conventional nondestructive evaluation methods have moved towards a new concept, Structural Health Monitoring (SHM). SHM provides in-situ information a bout the...
Experimental Study Of Plasma Actuator Characteristics And Optimization Of Configuration - Pradeep, M
Plasma actuators are devices which function by creating a discharge in air at atmospheric conditions. These devices have been demonstrated to effectively delay flow separation and enhance the lift- drag characteristics of wing sections. They have also been shown to have potential
applications in controlling dynamic stall, flow separation control over turbine blades, flow vectoring, boundary layer manipulation and bluff body flow control.
This study examines the characteristics of the plasma actuator, its working and the optimization of its configuration for its use as a lift enhancing device. A single actuator connected to a high-voltage, high-frequency power supply was studied in quiescent...
A Study On Boundary Layer Transition Induced By Large Freestream Disturbances - Mandal, Alakesh Chandra
The initial slow viscous growth of the Tollmein-Schlichting wave in a canonical boundary layer transition is absent in bypass and wake-induced transitions. Although there have been a great deal of studies pertaining to bypass transition in boundary layers, the underlying breakdown mechanism is not clearly understood and it continues to be a subject of interest. Similarly, a wake-induced transition caused by Karman wake in the freestream remains poorly understood. The breakdown in this case is caused by anisotropic disturbances containing large scale unsteadiness in the freestream. Differing view points among workers on the transition process have also added to the...