scholarly journals Active control of liquid film flows: beyond reduced-order models

2021 ◽  
Vol 104 (1) ◽  
pp. 267-287
Author(s):  
Radu Cimpeanu ◽  
Susana N. Gomes ◽  
Demetrios T. Papageorgiou
Keyword(s):  
Liquid Film ◽  
Information Transfer ◽  
Analytical Models ◽  
Feedback Controls ◽  
Reduced Order ◽  
Modelling Framework ◽  
Theoretical Approaches ◽  
Active Feedback ◽  
Feedback Strategies ◽  
Set Up

AbstractThe ability to robustly and efficiently control the dynamics of nonlinear systems lies at the heart of many current technological challenges, ranging from drug delivery systems to ensuring flight safety. Most such scenarios are too complex to tackle directly, and reduced-order modelling is used in order to create viable representations of the target systems. The simplified setting allows for the development of rigorous control theoretical approaches, but the propagation of their effects back up the hierarchy and into real-world systems remains a significant challenge. Using the canonical set-up of a liquid film falling down an inclined plane under the action of active feedback controls in the form of blowing and suction, we develop a multi-level modelling framework containing both analytical models and direct numerical simulations acting as an in silico experimental platform. Constructing strategies at the inexpensive lower levels in the hierarchy, we find that offline control transfer is not viable; however, analytically informed feedback strategies show excellent potential, even far beyond the anticipated range of applicability of the models. The detailed effects of the controls in terms of stability and treatment of nonlinearity are examined in detail in order to gain understanding of the information transfer inside the flows, which can aid transition towards other control-rich frameworks and applications.

A Physics-Based Dynamic Model for Boilers: Part 2 — Model Reduction in a Cogeneration Application

2017 ◽  
Author(s):  
Matthew J. Blom ◽  
Michael J. Brear ◽  
Chris G. Manzie ◽  
Ashley P. Wiese
Keyword(s):  
Model Reduction ◽  
Gas Turbine ◽  
Dynamic Model ◽  
Reduction Process ◽  
Singular Perturbation Theory ◽  
Reduced Order Models ◽  
Reduced Order ◽  
One Dimensional ◽  
Time Scale Separation ◽  
Modelling Framework

This paper is the second part of a two part study that develops, validates and integrates a one-dimensional, physics-based, dynamic boiler model. Part 1 of this study [1] extended and validated a particular modelling framework to boilers. This paper uses this framework to first present a higher order model of a gas turbine based cogeneration plant. The significant dynamics of the cogeneration system are then identified, corresponding to states in the gas path, the steam path, the gas turbine shaft, gas turbine wall temperatures and boiler wall temperatures. A model reduction process based on time scale separation and singular perturbation theory is then demonstrated. Three candidate reduced order models are identified using this model reduction process, and the simplest, acceptable dynamic model of this integrated plant is found to require retention of both the gas turbine and boiler wall temperature dynamics. Subsequent analysis of computation times for the original physics-based one-dimensional model and the candidate, reduced order models demonstrates that significantly faster than real time simulation is possible in all cases. Furthermore, with systematic replacement of the algebraic states with feedforward maps in the reduced order models, further computational savings of up to one order of magnitude can be achieved. This combination of model fidelity and computational tractability suggest suggests that the resulting reduced order models may be suitable for use in model based control of cogeneration plants.

A New Bump-Type Foil Bearing Structure Analytical Model

2007 ◽  
Vol 129 (4) ◽  
pp. 1047-1057 ◽  
Author(s):  
Sébastien Le Lez ◽  
Mihaï Arghir ◽  
Jean Frene
Keyword(s):  
Analytical Model ◽  
Degrees Of Freedom ◽  
Load Capacity ◽  
Reaction Force ◽  
Analytical Models ◽  
Experimental Investigations ◽  
Underlying Structure ◽  
Static System ◽  
Theoretical Approaches ◽  
Foil Bearing

A gas bearing of bump foil type comprises an underlying structure made of one or several strips of corrugated sheet metal covered by a top foil surface. The fluid film pressure needs to be coupled with the behavior of the structure for obtaining the whole bearing characteristics. Unlike in classical elasto-aerodynamic models, a foil bearing (FB) structure has a very particular behavior due to friction interfaces, bump interactions, and nonisotropic stiffness. Some authors have studied this complex behavior with the help of three-dimensional finite element simulations. These simulations evidenced a lack of reliable analytical models that can be easily implemented in a FB prediction code. The models found in the literature tend to overestimate the foil flexibility because most of them do not consider the interactions between bumps that are highly important. The present work then develops a model that describes the FB structure as a multidegree of freedom system of interacting bumps. Each bump includes three degrees of freedom linked with elementary springs. The stiffnesses of these springs are analytically expressed so that the model can be adjusted for any dimensions and material properties. Once the stiffness matrix of the whole FB structure is obtained, the entire static system is solved taking friction into account. Despite its relative simplicity, comparisons with finite elements simulations for various static load distributions and friction coefficients show a good correlation. This analytical model has been integrated into a foil bearing prediction code. The load capacity of a first generation foil bearing was then calculated using this structure model as well as other simplified theoretical approaches. Significant differences were observed, revealing the paramount influence of the structure on the static and dynamic characteristics of the foil bearing. Some experimental investigations of the static stiffness of the structure were also realized for complete foil bearings. The structure reaction force was calculated for a shaft displacement with zero rotation speed, using either the multidegree of freedom model or the usual stiffness formulas. The comparisons between theoretical and experimental results also tend to confirm the importance of taking into account the bump interactions in determining the response of the structure.

Linear and nonlinear active feedback controls for vortex-induced vibrations of circular cylinders

2012 ◽  
Vol 20 (8) ◽  
pp. 1137-1147 ◽  
Author(s):  
A Mehmood ◽  
A Abdelkefi ◽  
I Akhtar ◽  
AH Nayfeh ◽  
A Nuhait ◽  
...  
Keyword(s):  
Circular Cylinders ◽  
Feedback Controls ◽  
Vortex Induced Vibrations ◽  
Active Feedback ◽  
Linear And Nonlinear

scholarly journals Lidar measurements of yawed-wind-turbine wakes: characterization and validation of analytical models

2020 ◽  
Vol 5 (4) ◽  
pp. 1253-1272
Author(s):  
Peter Brugger ◽  
Mithu Debnath ◽  
Andrew Scholbrock ◽  
Paul Fleming ◽  
Patrick Moriarty ◽  
...  
Keyword(s):  
Wind Turbine ◽  
Cross Sections ◽  
Wake Flow ◽  
Analytical Models ◽  
Power Coefficient ◽  
Doppler Lidar ◽  
Scada System ◽  
Lidar Measurements ◽  
Set Up ◽  
Yaw Angle

Abstract. Wake measurements of a scanning Doppler lidar mounted on the nacelle of a full-scale wind turbine during a wake-steering experiment were used for the characterization of the wake flow, the evaluation of the wake-steering set-up, and the validation of analytical wake models. Inflow-scanning Doppler lidars, a meteorological mast, and the supervisory control and data acquisition (SCADA) system of the wind turbine complemented the set-up. Results from the wake-scanning Doppler lidar showed an increase in the wake deflection with the yaw angle and that the wake deflection was not in all cases beneficial for the power output of a downstream turbine due to a bias of the inflow wind direction perceived by the yawed wind turbine and the wake-steering design implemented. Both observations could be reproduced with an analytical model that was initialized with the inflow measurements. Error propagation from the inflow measurements that were used as model input and the power coefficient of a waked wind turbine contributed significantly to the model uncertainty. Lastly, the span-wise cross section of the wake was strongly affected by wind veer, masking the effects of the yawed wind turbine on the wake cross sections.

scholarly journals A Comprehensive Study and Analysis of LEACH and HEED Routing Protocols for Wireless Sensor Networks – With Suggestion for Improvements

2018 ◽  
Vol 9 (3) ◽  
pp. 778 ◽  
Author(s):  
G. Anitha ◽  
V. Vijayakumari ◽  
S. Thangavelu
Keyword(s):  
Information Transfer ◽  
Data Transfer ◽  
Routing Algorithm ◽  
Local Network ◽  
Wireless Data ◽  
The World ◽  
End Of The World ◽  
Set Up ◽  
Point To Point ◽  
5 Ghz

<p>The main interesting aspect of the digital era is the widely spread ease of communication from one end of the world to the other end of the world. There is a revolution in communication, digitalization, globalization, video calling, wireless data transfer and this is possible due to networking. Initially computer networks is the data sharing where data such as documents, file, reports, presentation files, videos, images etc can be shared within a local network or remotely connected networks. Traditional data networking is to empower end-to-end information transfer. The data in such networks are carried across point-to-point links and the intermediate nodes just forward the packets, where the payload of the packets is not modified. Traditional LANs need wires, which may be difficult to set up in some situations.</p><p>It is very much understandable and clearly visible that wired communication is being completely overtaken by wireless technologies in the recent past. Wireless LANs, by its very nature, empowers with increased mobility and flexibility. Wi-Fi devices get connected to the internet through WLAN and access points. 2.4 GHz and 5 GHz ISM bands are used by Wi-Fi. Also, it is to be understood that, a wireless adhoc network is distributed in its nature. It is also to be noted that, the adhoc nature makes these network to rely on any of the pre-existing infrastructure. The data forwarding shall happen from the nodes very much dynamically based on the connectivity and the routing algorithm used.  </p>

scholarly journals Determination of Factors and Indicators of Efficient Port Functioning

2021 ◽  
pp. 105-109
Author(s):  
M. Makarenko ◽  
◽  
I. Barskiy ◽  
V. Popov ◽  
◽  
...  
Keyword(s):  
Comparative Analysis ◽  
Performance Indicators ◽  
Negative Consequences ◽  
Unified Approach ◽  
Cross Sectional ◽  
Theoretical Approaches ◽  
Port Efficiency ◽  
Set Up ◽  
Clear Idea ◽  
The Impact

The article emphasizes the lack of a systematic and unified approach to measuring the performance of ports with different properties. The analysis of practical and theoretical approaches and the comparative analysis of indicators of efficiency of port are carried out. Measuring efficiency plays a significant role in assessing production in its current and future state. With the appropriate performance measurement, the system in the organization can be set up to move in the desired direction by analyzing behavioral responses and understanding the impact of different performance indicators on port performance. However, incorrectly defined performance indicators will lead the organization in the wrong direction and cause unforeseen negative consequences. Port efficiency can have a major impact on the region's economic growth, as ports connect maritime transport and inland transport. They are also important suppliers for ships, cargo and inland transport. Port performance analysis gives operators a clear idea of how much port resources are being used and helps them compare their strengths and weaknesses. Measuring port efficiency improves port development and maintains its competitiveness in an increasingly competitive commercial environment. Therefore, it is important to first conduct a comprehensive study to determine the performance of the port, relevant to the activities of ships, cargo and terminals. By assessing the efficiency of ports using certain indicators, you can get an idea of comparing their efficiency, even internationally. A review of practical and theoretical approaches to the comparative analysis of port efficiency indicators over the past three decades and summarized the main differences in these studies found the lack of a systematic and unified approach to measuring the performance of ports with different properties. Recent studies have aimed to analyze the performance of port terminals, as they are the most important component of ports, operations for the transfer of berths and court operations in the terminals fundamentally determine the efficiency of the port. Port bandwidth is one of the most widely used indicators of port efficiency. Productivity growth is seen as direct evidence of port activity. One of the most important aspects of measuring seaport efficiency is performance, and the popular database analysis (DEA) method is commonly used to evaluate it. There are several other models used for cross-sectional and panel data, such as software. To assess port efficiency, this study examines the analysis of the DEA and FDH database through its ability to analyze multiple outputs and inputs simultaneously.

scholarly journals USOS Y ABUSOS DEL INTERNET EN LOS ALUMNOS UNIVERSITARIOS DE LA DIVISIÓN ACADÉMICA DE CIENCIAS ECONÓMICO ADMINISTRATIVAS

2014 ◽  
Vol 19 (53) ◽  
pp. 25-32
Author(s):  
Gladys Hernández Romero
Keyword(s):  
Information And Communication Technologies ◽  
Internet Use ◽  
Communication Technologies ◽  
Simple Random Sampling ◽  
The Internet ◽  
Negative Effects ◽  
Theoretical Approaches ◽  
Internet Abuse ◽  
Information And Communication ◽  
Set Up

RESUMEN Objetivo: Este trabajo analiza los usos y abusos del Internet en los jóvenes universitarios de la Licenciatura en Administración de Empresas de la Universidad Juárez Autónoma de Tabasco, con sede en Villahermosa Tabasco, mostrando evidencias de la manera en que el uso de Internet ha influido en su desempeño académico; ya que el modelo global entre sus mecanismos más sugestivos trajo consigo las denominadas Tecnologías de la Información y Comunicación, (TICs) las cuales tienen la particularidad de que una vez incorporadas a la vida cotidiana del sujeto resultan imprescindibles y en algunos casos crean dependencia entre sus usuarios. Material y método: El instrumento que se empleó fue entrevista no estructurada focalizada, con la particularidad de concentrarse en el tema Usos y Abusos del Internet en los alumnos de la División Académica de Ciencias Económico Administrativas, aplicado a una muestra de dieciocho alumnos que fungieron como informantes. Se empleó un enfoque cualitativo como método general de la investigación bajo el muestreo aleatorio simple que permite llevar a cabo el contraste o correlación de los planteamientos teóricos del problema. Resultados: Los resultados obtenidos dieron un panorama general del uso y abuso de Internet en los mencionados alumnos; quienes no reconocieron abusar del Internet en la redacción de sus trabajos de investigación. Conclusiones: Finalmente, se establecieron conclusiones y recomendaciones que pueden contribuir a minimizar los efectos negativos del uso de Internet y las aplicaciones que le dan a éste. ABSTRACT Objetive: This paper analyzes the internet use and abuse from young university Business Administration degree students of the Universidad Juarez Autónoma de Tabasco, that is located in the city of Villahermosa in the state of Tabasco, showing evidence on the way how the internet use has influenced the academic performance of those students, because one of the most suggestive mechanisms that the global model brought, are the so-called Information and Communication Technologies (ICT) which have the particularity that once they are incorporated into the daily life of the individuals, they become essential, and in some cases, create dependency among their users. Material and method: The instrument used was a focused unstructured interview, with the particularity to focus on the topic of Internet Use and Abuse from students of the Academic Division of Economics and Administrative Sciences. This interview was applied to a sample of eighteen students who acted as informants. A qualitative approach was used as a general method of research under simple random sampling that allowed the researcher to carry out the contrast or correlation of the problem theoretical approaches. Results: The given results provided an overview of the use and abuse of the Internet in the above mentioned students, who did not recognize Internet abuse in the drafting of their research. Conclusions: Finally, conclusions and recommendations were set up so that they can help minimize the negative effects that the use and abuse of internet is given by the students.

Guidelines for Reduced-Order Thermal Modeling of Multifinger GaN HEMTs

2020 ◽  
Vol 142 (2) ◽  
Author(s):  
Robert Pearson ◽  
Bikramjit Chatterjee ◽  
Samuel Kim ◽  
Samuel Graham ◽  
Alexander Rattner ◽  
...  
Keyword(s):  
Gallium Nitride ◽  
Heat Generation ◽  
Composite Layer ◽  
High Electron Mobility Transistors ◽  
Heat Fluxes ◽  
Analytical Models ◽  
High Electron ◽  
Reduced Order ◽  
Electron Mobility Transistors ◽  
Channel Temperature

Abstract The increasing demand for tightly integrated gallium nitride high electron mobility transistors (HEMT) into electronics systems requires accurate thermal evaluation. While these devices exhibit favorable electrical characteristics, the performance and reliability suffer from elevated operating temperatures. Localized device self-heating, with peak channel and die level heat fluxes of the order of 1 MW cm−2 and 1 kW cm−2, respectively, presents a need for thermal management that is reliant on accurate channel temperature predictions. In this publication, a high-fidelity multiphysics modeling approach employing one-way electrothermal coupling is validated against experimental results from Raman thermometry of a 60-finger gallium nitride (GaN) HEMT power amplifier under a set of direct current (DC)-bias conditions. A survey of commonly assumed reduced-order approximations, in the form of numerical and analytical models, are systematically evaluated with comparisons to the peak channel temperature rise of the coupled multiphysics model. Recommendations of modeling assumptions are made relating to heat generation, material properties, and composite layer discretization for numerical and analytical models. The importance of electrothermal coupling is emphasized given the structural and bias condition effect on the heat generation profile. Discretization of the composite layers, with temperature-dependent thermal properties that are physically representative, are also recommended.

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