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Gopal H. Gaonkar

Bio: Gopal H. Gaonkar is an academic researcher from Florida Atlantic University. The author has contributed to research in topics: Floquet theory & Rotor (electric). The author has an hindex of 13, co-authored 44 publications receiving 575 citations. Previous affiliations of Gopal H. Gaonkar include Indian Institute of Science & Washington University in St. Louis.

Papers
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Journal ArticleDOI
TL;DR: A bilinear formulation of elasto-dynamics is proposed in this article, which admits a larger class of initial-value and boundary-value problems and offers physical insight into the so-called ''trailing terms'' of Hamilton's Law.
Abstract: A bilinear formulation of elasto-dynamics is offered which includes, as a special case, Hamilton's Law of Varying Action. However, the more general bilinear formulation has several advantages over Hamilton's Law. First, it admits a larger class of initial-value and boundary-value problems. Second, in its variational form, it offers physical insight into the so-called \"trailing terms\" of Hamilton's Law. Third, numerical applications (i.e., finite elements in time) can be proven to be convergent under correct application of the bilinear formulation, whereas they can be demonstrated to diverge for specific problems under Hamilton's Law. Fourth, the bilinear formulation offers automatic convergence of the \"natural\" velocity end conditions; while these must be constrained in present applications of Hamilton's Law. Fifth, the bilinear formulation can be implemented in terms of a Lagrange multiplier that gives an order of magnitude improvement in the convergence of velocity. This implies that, in this form, the method is a hybrid finite-element approach.

55 citations


Cited by
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BookDOI
18 Dec 2009
TL;DR: In this article, a simplified HAWT rotor performance calculation procedure was proposed to evaluate the effect of drag and blade number on the optimum performance of wind turbine rotor performance, considering the Betz limit and the ideal horizontal axis wind turbine with wake rotation.
Abstract: Preface Acknowledgements Introduction: Modern wind energy and its origins Modern wind turbines History of wind energy Wind characteristics and resources Introduction General characteristics of the wind resource Characteristics of the atmospheric boundary layer Wind data analysis and resource estimation Wind turbine energy production estimates using statistical techniques Overview of available resource assessment data Wind measurements and instrumentation Advanced topics Aerodynamics of wind turbines General overview One-dimensional momentum theory and the Betz limit Ideal horizontal axis wind turbing with wake rotation' Airfoils and general concepts of aerodynamics Momentum theory and blade element theory Blade shape for ideal rotor without wake rotation General rotor blade shape performance prediction Blade shape for optimum rotor with wake rotation Generalized rotor design procedure Simplified HAWT rotor performance calculation procedure Effect of drag and blade number on optimum performance Advanced aerodynamic topics Mechanics and dynamics Wind turbine rotor dynamics Detailed and specialized dynamic models Electrical aspects of wind turbines Basic concepts of electric power Power transformers Electrical machines Power converters Ancillary electrical equipment Wind turbine design Design procedure Wind turbine topologies Materials Machine elements Wind turbine loads Wind turbine subsystems and components Design evaluation Power curve prediction Wind turbine loads Wind turbine subsystems and components Design evaluation Power curve prediction Wind turbine control Overview of wind turbine control systems Typical grid-connected turbine operation Supervisory control overview and implementation Dynamic control theory and implementation Wind turbine siting, system design and integration Wind turbine siting Installation and operation issues Wind farms Wind turbines and wind farms in electric grids Offshore wind farms Operation in severe climates Hybrid electrical systems Wind energy system economics Overview of economic assessment of wind energy systems Capital costs of wind energy systems Operation and maintenance costs Value of wind energy Economic analysis methods Wind energy market considerations Wind energy systems: environmental aspects and impacts Avian interaction with wind trubines Visual impact of wind turbines Wind turbine noise Electromagnetic interference effects Land-use environmental impacts Other environmental considerations Nomenclature Problems Index

2,354 citations

Journal ArticleDOI
TL;DR: In this article, the aerodynamic properties of wind turbine wakes are studied, focusing on the physics of power extraction by wind turbines, and the main interest is to study how the far wake decays downstream in order to estimate the effect produced in downstream turbines.

1,161 citations

Journal ArticleDOI
TL;DR: In this paper, a tutorial on cyclostationarity oriented towards mechanical applications is presented, with 20 examples devoted to illustrating key concepts on actual mechanical signals and demonstrating how cyclostatarity can be taken advantage of in machine diagnostics, identification of mechanical systems and separation of mechanical sources.

519 citations

Proceedings ArticleDOI
01 Jan 2002
TL;DR: Leishman et al. as mentioned in this paper used complementary experimental measurements and modeling techniques to better understand the aerodynamic problems found on wind turbines, and to develop more rigorous models with wider ranges of application.
Abstract: Many of the aerodynamic phenomena contributing to the observed effects on wind turbines are now known, but the details of the flow are still poorly understood and are challenging to predict accurately, issues discussed herein include the modeling of the induced velocity field produced by the vortical wake behind the turbine, the various unsteady aerodynamic issues associated with the blade sections, and the intricacies of dynamic stall. Fundamental limits exist in the capabilities of all models, and misunderstandings or ambiguities can also arise in how these models should be properly applied. A challenge for analysts is to use complementary experimental measurements and modeling techniques to better understand the aerodynamic problems found on wind turbines, and to develop more rigorous models with wider ranges of application.Copyright © 2002 by J. G. Leishman and ASME

334 citations

Journal ArticleDOI
TL;DR: In this paper, the authors focus on two key areas that need continued serious consideration for wind turbine predictive analyses: the modeling of the rotor wake and the modelling of the unsteady aerodynamics of the blade sections.
Abstract: Many of the aerodynamic phenomena contributing to the observed effects on wind turbines are now known, but the details of the flow are still poorly understood and are challenging to predict accurately. This article emphasizes two key areas that need continued serious consideration for wind turbine predictive analyses: the modelling of the rotor wake and the modelling of the unsteady aerodynamics of the blade sections. Issues discussed herein include the modelling of the induced velocity field produced by the vortical wake behind the turbine, the various unsteady aerodynamic issues associated with the blade sections, and the non-linear intricacies of dynamic stall. Fundamental limits exist in the capabilities of all models, and ambiguities can also arise in how these models should be properly applied. A challenge for analysts of the future is to use complementary experimental measurements and modelling techniques to better understand the aerodynamic problems found on wind turbines, and to develop more rigorous models with wider ranges of application. Copyright © 2002 John Wiley & Sons, Ltd.

316 citations