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 175
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...
Studies On Shock Wave Attenuation In Liquids - Bhaskar, K
The attenuation mechanism of shock waves of arbitrary strength propagating in air has been reasonably well understood. On the other hand, very little is known about the precise mechanism of shock wave attenuation and energy dissipation in liquids. The equation of state for shock propagation in water is empirical in nature and considerable differences exist with reference to the exact value of various constants even in the cast of Tait’ s equation of state, which is popularly used by researchers to describe the shock wave propagating through water. In recent times, considerable attention is being focused by researchers on shock...
Momentum And Enthalpy Transfer In Packed Beds - Experimental Evaluation For Unsteady Inlet Temperature At High Reynolds Numbers - Srinivasan, R
Solid propellant gas generators that have high gas capacity are used for fast pressurization of inflatable devices or elastic shells. However, many applications such as control surface actuation, air bottle pressurization in rocket engines and safety systems of automobiles (airbags) require exit gases at near ambient temperature. A scheme suitable for short duration applications is passive cooling of gas generator gases by using a packed bed as compact heat exchanger. A study indicated that the mass flow rates of solid propellant gas generators for applications such as air bottle pressurization and control system actuators were of the order of 1...
Structural Modeling And Analysis Of Insect Scale Flapping Wing - Mukherjee, Sujoy
Micro Air Vehicles (MAVs) are defined as a class of vehicles with their larger dimension not exceeding 15 cm and weighing 100 gm. The three main approaches for providing lift for such vehicles are through fixed, rotating and flapping wings. The flapping wing MAVs are more efficient in the low Reynolds-number regime than conventional wings and rotors. Natural flapping ﬂyers, such as birds and insects, serve as a natural source of inspiration for the development of MAV. Flapping wing design is one of the major challenges to develop an MAV because it is not only responsible for the lift, but...
Differential Evolution Based Interceptor Guidance Law - Raghunathan, T
Kinematics based guidance laws like the proportional navigation (PN) and many other linear optimal guidance laws perform well in near-collision course conditions. These have been studied thoroughly in the literature from all aspects, ranging from optimality to capturability, for planar or two dimensional interceptor-target engagements, and to a lesser extent, for three dimensional engagements. But guidance in widely off-collision course conditions like high initial heading errors has been relatively less studied. This is probably due to the inherently high nonlinearity of the problem, which makes it a far more difficult problem to solve. However, with increasing speed and agility of...
Effect Of Cross-sectional Nonlinearities On Anisotropic Strip-based Mechanisms - Pollayi, Hemaraju
The goal of this work is to develop and demonstrate a comprehensive analysis of single and multi-body composite strip-beam systems using an asymptotically-correct geometrically nonlinear theory. The comprehensiveness refers to the two distinguishing features of this work, namely the unified framework for the analysis and the inclusion of the usually ignored cross-sectional nonlinearities in thin-beam and multi-beam analyses.
The first part of this work stitches together an approach to analyse generally anisotropic composite beams. Based on geometrically exact nonlinear elasticity theory, the nonlinear 3-D beam problem splits into either a linear (conventionally considered) or nonlinear (considered in this work) 2-D...
Strength Prediction And Fatigue De-Bond Growth In Bonded Joints In Metallic And Composite Structures - Sahoo, Pradeep Kumar
Large scale structures such as those in aerospace flight vehicles are made in parts and assembled. Joints are inevitable in these systems and they are potential threats to the structural integrity of the flight vehicles. Fastener and bonded joints are the most commonly used methods of joining in these structures. Among these, adhesive bonding has become more popular with the advent of composite structures, due to the presence of less number of points of stress concentration and the resulting benefit for static strength and fatigue life. In modern aircraft in which maximum percentage of composite materials are being employed due...
Novel Finite Element Formulations For Dynamics Of Acoustic Fluids - Kishor, Dubasi Krishna
Fluid-structure interaction (FSI) as the name suggests, is the study of dynamic interaction of both fluid and structure motions. Fluid-structure interaction exists in almost all engineering and science fields. Moreover, the random loading caused by fluid motions in uncertain environment conditions present new challenges to the designers. The objective of the present research work is to develop efficient and robust finite element models to solve fluid structure interaction problems effectively. A key advantage of the displacement based FE M is the flexibility and easiness in modifying the existing efficient numerical solvers, and can also be extended easily to a number...
System Identification And Control Of Helicopter Using Neural Networks - Vijaya Kumar, M
The present work focuses on the two areas of investigation: system identification of helicopter and design of controller for the helicopter.
Helicopter system identification, the first subject of investigation in this thesis, can be described as the extraction of system characteristics/dynamics from measured flight test data. Wind tunnel experimental data suffers from scale effects and model deficiencies. The increasing need for accurate models for the design of high bandwidth control system for helicopters has initiated a renewed interest in and a more active use of system identification. Besides, system identification is likely to become mandatory in the future for model validation...
Thermal Behaviour Of Mono-Fibre Composites And Hybrid Composites At Cryogenic Temperatures - Praveen, R S
Hybrid composites forms an important field of research in the area of composite science and engineering as it gives the advantage of avoiding complex lay-up designs and provides better tuning compatibility to get desired properties in comparison with their mono-fiber counterpart.
Further, utilization of composites for low temperature structures has been hindered by inconsistency of material property data and not much is reported on thermal characteristics of hybrid composites at cryogenic temperatures.
This research work is focused on development of carbon-glass epoxy hybrid composite and to study the thermal behavior of these materials in comparison to its mono-fiber counterparts especially...