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 29
1.
Investigations On High Rayleigh Number Turbulent Free Convection - Puthenveettil, Baburaj A
High Rayleigh number(Ra) turbulent free convection has many unresolved
issues related to the phenomenology behind the flux scaling, the
presence of a mean wind and its effects, exponential probability
distribution functions, the Prandtl number dependence and the nature
of near wall structures. Few studies have been conducted in the high
Prandtl number regime and the understanding of near wall coherent
structures is inadequate for $Ra > 10^9$. The present thesis deals
with the results of investigations conducted on high Rayleigh
number turbulent free convection in the high Schmidt number(Sc)
regime, focusing on the role of near wall coherent structures.
We use a new method of driving the convection using...
2.
Computational Modelling Of Heat Transfer In Reheat Furnaces - Harish, J
Furnaces that heat metal parts (blooms) prior to hot-working processes such as rolling or forging are called pre-forming reheat furnaces. In these furnaces, the fundamental idea is to heat the blooms to a prescribed temperature without very large temperature gradients in them. This is to ensure correct performance of the metal parts subsequent to reheating. Due to the elevated temperature in the furnace chamber, radiation is the dominant mode of heat transfer from the furnace to the bloom. In addition, there is convection heat transfer from the hot gases to the bloom. The heat transfer within the bloom is by...
3.
The Effect Of Viscosity On The Erosion Of Gradient- Zone In A Laboratory Solar Pond - Pradhan, Sudeep S
Double diffusive phenomena occur in many natural systems and in a variety of engineering applications, such as solar ponds. In a solar pond, the erosion of gradient zone due to convection and diffusion is the main cause of inefficiency and hence, requires lot of maintenance. In this thesis, control of erosion of the gradient zone in a solar pond situation has been studied through experiments and transient numerical simulations. A laboratory solar pond was setup in a tank of size 19cm X 19cm X 19cm, and was heated from below. A polymer additive, Carboxy Methyl Cellulose (CMC) was used to...
4.
Transport Phenomena In Laser Surface Alloying: A Numerical Investigation - Mohan Raj, P
A comprehensive, transient three-dimensional model of a single-pass laser surface alloying process has been developed and used to examine the heat, momentum and species transport phenomena. A numerical study is performed in a co-ordinate system moving with the laser at a constant scanning speed. In this model a fixed grid enthalpy-porosity approach is used, which predicts the evolutionary pool development. In this model two extreme cases of alloying element and base metal combinations are considered based on their relative melting points. One extreme case is for an alloying element with its melting point much lower than that of the base...
5.
Turbulent Mixed Convection - Ramesh Chandra, D S
Turbulent mixed convection is a complicated flow where the buoyancy and shear forces compete with each other in affecting the flow dynamics. This thesis deals with the near wall dynamics in a turbulent mixed convection flow over an isothermal horizontal heated plate. We distinguish between two types of mixed convection ; low-speed mixed convection (LSM) and high-speed mixed convection (HSM). In LSM the entire boundary layer, including the near-wall region, is dominated by buoyancy; in HSM the near-wall region, is dominated by shear and the outer region by buoyancy. We show that the value of the parameter (* = ^...
6.
A Finite Element Investigation Of Brittle Fracture During Spherical Nanoindentation Of Thin Hard Films - Sriram, K
Hard ceramic films of micrometric thickness deposited on a soft metallic substrate have ushered in a new era in the fabrication of structural, tribological, microelectronic and optical components. The mechanical performance of these components is however critically dependent on the strength and toughness of these films as well as on those of the film-substrate interface. Recent studies have shown that cylindrical and radial cracks can propagate through the film during nanoindentation tests with spherically tipped and pointed indenters, resulting in steps in the load versus displacement curve. In this thesis, the mechanics of fracture of thin hard films bonded to...
7.
Development Of A Single Cylinder SI Engine For 100% Biogas Operation - Kapadia, Bhavin Kanaiyalal
This work concerns a systematic study of IC engine operation with 100% biogas as fuel (as opposed to the dual-fuel mode) with particular emphasis on operational issues and the quest for high efficiency strategies. As a first step, a commercially available 1.2 kW genset engine is modified for biogas operation. The conventional premixing of air and biogas is compared with a new manifold injection strategy. The effect of biogas composition on engine performance is also studied.
Results from the genset engine study indicate a very low overall efficiency of the system. This is mainly due to the very low compression ratio...
8.
Studies On Momentum, Heat And Mass Transfer In Binary Alloy Solidification Processes - Chakraborty, Suman
The primary focus of the present work is the development of macro-models for numerical simulation of binary alloy solidification processes, consistent with microscopic phase-change considerations, with a particular emphasis on capturing the effects of non-equilibrium species redistribution on overall macrosegregation behaviour. As a first step, a generalised macroscopic framework is developed for mathematical modelling of the process. The complete set of equivalent single-phase governing equations (mass, momentum, energy and species conservation) are solved following a pressure-based Finite Volume Method according to the SIMPLER algorithm. An algorithm is also developed for the prescription of the coupling between temperature and the melt-fraction.
Based...
9.
An Experimental Study Of Instabilities In Unsteady Separation Bubbles - Das, Shyama Prasad
The present thesis is an experimental study of some aspects of unsteady two dimensional boundary layers subject to adverse pressure gradient. An adverse pressure gradient usually leads to boundary layer separation or an instability which may result in transition to turbulence. Unsteady boundary layer separation is not yet fully understood and there is no specific criterion proposed in literature for its occurrence. The details of separation depend on the Reynolds number, the geometry of the body (streamlined or bluff) and the type of imposed unsteady motion (impulsive, oscillatory etc.). Similarly there are many unknowns with respect to instability and transition...
10.
Design And Analysis Of MEMS Angular Rate Sensors - Patil, Nishad
Design and analysis of polysilicon and single crystal silicon gyroscopes have been carried out. Variations in suspension design have been explored. Designs that utilize in-plane and out-of-plane sensing are studied.
Damping plays an important role in determining the sense response. Reduction in damping directly affects sensor performance. The various damping mechanisms that are prevalent in gyroscopes are studied.
Perforations on the proof mass are observed to significantly reduce the damping in the device when operated in air. The effects of perforation geometry and density have been analyzed. The analysis results show that there is a two orders of magnitude reduction in...
11.
Fundamental Studies On Tribological Response Of Titanium And Copper - Nagaraj, C M
Friction and wear have been observed m mechanical systems when there is a relative motion between two solid bodies Friction mainly results in loss of energy and wear results in matenal loss The proper understanding of friction and wear mechanisms provides practical solutions to tribological related problems Various models are available m tribology literature to calculate function coefficient and wear rate of matenals However, expenments suggest that these models are incomplete and fortuitous as the tnbological response is system dependent
The objective of present investigation is to understand the tribological lesponse of commercially puie titanium and OFHC copper pins sliding on...
12.
Low-Order Laminated Lock-Free Beam And Plate Elements Based On Coupled Displacement Field - Veenaranjini, S M
This study aims to investigate the behaviour of low-order beam and plate elements especially for their application to laminated structures. The merits and dements of the existing elements are brought out and new low-order elements with better interpolation polynomials are proposed.
Two new beam elements are proposed for laminated composite beams that yield better representation of twist due to material coupling. Out of the two elements developed, one is based on the conventional formulation and the other on the coupled-field formulation, both capturing material induced coupling. The beam developed using coupled field formulation shows a novel way of obtaining a fully...
13.
Recognition And Suppression Of Blends In A Tessellated Solid Model - Garg, Anup
Blend recognition and suppression from a tessellated model is important in applications such as model simplification in analysis and collaborative design where tessellated models are being used. This could also be used to pre-process the model before attempting to recognize form features in it.
A procedure is described for recognizing and subsequently suppressing blends (fillets/rounds) in a tessellated model of a part. Earlier efforts on recognizing secondary features such as blends have used the boundary representation (B-Rep) of the part as input. Blend recognition and suppression from a tessellated model has not been addressed to the best of our knowledge. There...
14.
Numerical Study Of Heat Transfer From Pin Fin Heat Sink Using Steady And Pulsated Impinging Jets - Sanyal, Anuradha
The work reported in this thesis is an attempt to enhance heat transfer in electronic devices with the use of impinging air jets on pin-?nned heat sinks. The cooling per-formance of electronic devices has attracted increased attention owing to the demand of compact size, higher power densities and demands on system performance and re-liability. Although the technology of cooling has greatly advanced, the main cause of malfunction of the electronic devices remains overheating. The problem arises due to restriction of space and also due to high heat dissipation rates, which have increased
from a fraction of a W/cm2to 100s of W...
15.
Analysis Of Multiply-Connected Acoustic Filters with Application To Design Of Combination Mufflers And Underwater Noise Control Linings - Panigrahi, Satyanarayan
This thesis endeavors towards developing various concepts employed in analysis and
design of acoustic ?lters for varied applications ranging from combination mufflers for automobiles to complex networks of gas carrying ducts to multiply connected complex automotive silencing devices to the noise control coatings for underwater applications.
A two-dimensional wave modeling approach has been proposed to evaluate sound
attenuation characteristics of dissipative mufflers of ?nite length with/without extended inlet and outlet tubes including very large mufflers. The correctness of the method has been validated through comparison with experimental results from literature. Two other frequently used approximate schemes have been discussed brie?y with reference to...
16.
Analysis And Design Of Spatial Manipulators : An Exact Algebraic Approach Using Dual Numbers And Symbolic Computation - Bandyopadhyay, Sandipan
This thesis presents a uni?ed framework for the analysis of instantaneous kinematics and statics of spatial manipulators. The proposed formulation covers the entire range of kinematic behavior, with kinematic singularity and isotropy appearing as special cases. An analogous treatment of statics is also presented. It is established that the formulations presented are capable of generating exact solutions in closed form for several interesting problems in manipulator analysis. Several such results have been obtained via extensive usage of symbolic computation tools developed for this purpose. The proposed approach is applicable to manipulators of di?erent architectures. However, the focus is on the...
17.
Studies On The Dynamics And Stability Of Bicycles - Basu-Mandal, Pradipta
This thesis studies the dynamics and stability of some bicycles. The dynamics of idealized bicycles is of interest due to complexities associated with the behaviour of this seemingly simple machine. It is also useful as it can be a starting point for analysis of more complicated systems, such as motorcycles with suspensions, frame flexibility and thick tyres. Finally, accurate and reliable analyses of bicycles can provide benchmarks for checking the correctness of general multibody dynamics codes.
The first part of the thesis deals with the derivation of fully nonlinear differential equations of motion for a bicycle. Lagrange’s equations are derived...
18.
Towards Measurement And Simulation Of Elasto-Plastic Deformation - Jain, Praveen Kumar
The stretch forming process is frequently used in the automotive industry (outer pan-
els, inner panels, stiffeners etc.), the packaging industry and household appliances
sector, to manufacture complicated shapes and curvatures. However it requires accurate prediction of tool geometries and manufacturing parameters to avoid the
currently used trial and error approach. Metal forming is also associated with cer-
tain defects like local thinning, wrinkling, tearing etc. Avoiding such defects and
prediction of spring back presumably requires a thorough understanding of the de-
formation mechanics and material behavior beyond the elastic range.
In the stretch forming operation, material essentially passes through the elastic,
yield point and plastic states. Elastic...
19.
Development Of Efficient Modeling Methodologies Of Adhesively Bonded Joints For Crash Simulations - Sureshrao, Malvade Indrajit
In this thesis, a new modeling methodology applicable to adhesively bonded joints for crash simulations is presented. Using this approach, adhesive joints can be modeled without using minute solid elements thus reducing the size of the model. Moreover, coarse mesh can be used for substrates in the overlap region of a joint. Both of these improvements together yield significant reduction in simulation run times in crash analysis when compared to solid element representation of adhesive. The modeling can also capture effects of strain rate for a given ambient temperature.
In order to develop the efficient modeling procedure mentioned above, experimental,...
20.
Development Of An Activated Carbon+ HFC 134a Adsorption Refrigeration System - Nitinkumar, D Banker
The demands facing the refrigeration industry are minimal usage of conventional energy sources for compression and avoidance of ozone depleting substances. One of the approaches to combat these issues is the use of thermally driven solid sorption compression with non-ozone depleting refrigerant. In this context, the research work presented in this thesis is devoted to a comprehensive thermodynamic analysis and development of a laboratory model of an activated carbon+ HFC 134a adsorption refrigeration system. The cooling load catered to by the laboratory model is 2-5 W, mainly for thermal management of electronics.
A complete thermodynamic analysis is carried out for...
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