On the Energy Characteristics of the Aerodynamic Matrix and the Relationship to Possible Flutter

1983 ◽  
Vol 34 (3) ◽  
pp. 212-225 ◽  
Author(s):  
J.G. Jones

SummaryThe problem of energy transfer between an airstream and a wing in sinusoidal motion has been investigated by a series of authors beginning with Frazer who in 1939 considered the power input required to maintain forced oscillations of an aeroplane wing in flight. More recently Nissim introduced an ‘aerodynamic energy concept’ as the basis for the design of active control systems for flutter suppression. In this paper the author reconsiders the energy characteristics of the aerodynamic matrix in terms of the network concepts of resistive and reactive elements, corresponding to energy dissipation and energy storage respectively. A dual formulation of Nissim’s method is described and an extension proposed that takes account of aerodynamic energy storage in addition to aerodynamic energy dissipation.

Author(s):  
Flávio Silvestre ◽  
Mauricio Donadon ◽  
Osmar de Sousa Santos ◽  
Antônio Bernardo Guimarães Neto ◽  
ROBERTO GIL ANNES DA SILVA ◽  
...  

2020 ◽  
Vol 40 (5) ◽  
pp. 373-393 ◽  
Author(s):  
Narendra Singh Chundawat ◽  
Nishigandh Pande ◽  
Ghasem Sargazi ◽  
Mazaher Gholipourmalekabadi ◽  
Narendra Pal Singh Chauhan

AbstractRedox-active polymers among the energy storage materials (ESMs) are very attractive due to their exceptional advantages such as high stability and processability as well as their simple manufacturing. Their applications are found to useful in electric vehicle, ultraright computers, intelligent electric gadgets, mobile sensor systems, and portable intelligent clothing. They are found to be more efficient and advantageous in terms of superior processing capacity, quick loading unloading, stronger security, lengthy life cycle, versatility, adjustment to various scales, excellent fabrication process capabilities, light weight, flexible, most significantly cost efficiency, and non-toxicity in order to satisfy the requirement for the usage of these potential applications. The redox-active polymers are produced through organic synthesis, which allows the design and free modification of chemical constructions, which allow for the structure of organic compounds. The redox-active polymers can be finely tuned for the desired ESMs applications with their chemical structures and electrochemical properties. The redox-active polymers synthesis also offers the benefits of high-scale, relatively low reaction, and a low demand for energy. In this review we discussed the relationship between structural properties of different polymers for solar energy and their energy storage applications.


2021 ◽  
Vol 92 ◽  
pp. 79-93
Author(s):  
N. G. Topolsky ◽  
◽  
S. Y. Butuzov ◽  
V. Y. Vilisov ◽  
V. L. Semikov ◽  
...  

Introduction. It is important to have models that adequately describe the relationship between the integral indicators of the functioning of the system with the particular indicators of the lower levels of management in complex control systems, in particular in RSChS. Traditional approaches based on normative models often turn out to be untenable due to the impossibility of covering all aspects of the functioning of such systems, as well as due to the high variability of the environment and the values of the set of target indicators. Recently, adaptive machine-learning models have proven to be productive, allowing build stable and adequate models, one of the variants of which is artificial neural networks (ANN), based on the solution of inverse problems using expert estimates. The relevance of the study lies in the development of compact models that allow assessing the effectiveness of the functioning of complex multi-level control systems (RSChS) in emergency situations, developing according to complex scenarios, in which emergencies of various types can occur simultaneously. Goals and objectives. The purpose of the article is to build and test the technology for creating compact models that are adequate to the system of indicators of the functioning of hierarchically organized control systems. This goal gives rise to the task of choosing tools for constructing the necessary models and sources of initial data. Methods. The research tools include methods for analyzing hierarchical systems, mathematical statistics, machine learning methods of ANN, simulation modeling, expert assessment methods, software systems for processing statistical data. The research is based on materials from domestic and foreign publications. Results and discussion. The proposed technology for constructing a neural network model of the effectiveness of the functioning of complex hierarchical systems provides a basis for constructing dynamic models of this type, which make it possible to distribute limited financial and other resources during the operation of the system according to a complex scenario of emergency response. Conclusion. The paper presents the results of solving the problem of constructing an ANN and its corresponding nonlinear function, reflecting the relationship between the performance indicators of the lower levels of the hierarchical control system (RSChS) with the upper level. The neural network model constructed in this way can be used in the decision support system for resource management in the context of complex scenarios for the development of emergency situations. The use of expert assessments as an information basis makes it possible to take into account numerous target indicators, which are extremely difficult to take into account in other ways. Keywords: emergency situations, hierarchical control system, efficiency, artificial neural network, expert assessments


2018 ◽  
Vol 857 ◽  
pp. 345-373 ◽  
Author(s):  
Davide Gatti ◽  
Andrea Cimarelli ◽  
Yosuke Hasegawa ◽  
Bettina Frohnapfel ◽  
Maurizio Quadrio

This paper addresses the integral energy fluxes in natural and controlled turbulent channel flows, where active skin-friction drag reduction techniques allow a more efficient use of the available power. We study whether the increased efficiency shows any general trend in how energy is dissipated by the mean velocity field (mean dissipation) and by the fluctuating velocity field (turbulent dissipation). Direct numerical simulations (DNS) of different control strategies are performed at constant power input (CPI), so that at statistical equilibrium, each flow (either uncontrolled or controlled by different means) has the same power input, hence the same global energy flux and, by definition, the same total energy dissipation rate. The simulations reveal that changes in mean and turbulent energy dissipation rates can be of either sign in a successfully controlled flow. A quantitative description of these changes is made possible by a new decomposition of the total dissipation, stemming from an extended Reynolds decomposition, where the mean velocity is split into a laminar component and a deviation from it. Thanks to the analytical expressions of the laminar quantities, exact relationships are derived that link the achieved flow rate increase and all energy fluxes in the flow system with two wall-normal integrals of the Reynolds shear stress and the Reynolds number. The dependence of the energy fluxes on the Reynolds number is elucidated with a simple model in which the control-dependent changes of the Reynolds shear stress are accounted for via a modification of the mean velocity profile. The physical meaning of the energy fluxes stemming from the new decomposition unveils their inter-relations and connection to flow control, so that a clear target for flow control can be identified.


2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Gowtham Venkatraman ◽  
Adam Hehr ◽  
Leon M. Headings ◽  
Marcelo J. Dapino

Purpose Ultrasonic additive manufacturing (UAM) is a solid-state joining technology used for three-dimensional printing of metal foilstock. The electrical power input to the ultrasonic welder is a key driver of part quality in UAM, but under the same process parameters, it can vary widely for different build geometries and material combinations because of mechanical compliance in the system. This study aims to model the relationship between UAM weld power and system compliance considering the workpiece (geometry and materials) and the fixture on which the build is fabricated. Design/methodology/approach Linear elastic finite element modeling and experimental modal analysis are used to characterize the system’s mechanical compliance, and linear system dynamics theory is used to understand the relationship between weld power and compliance. In-situ measurements of the weld power are presented for various build stiffnesses to compare model predictions with experiments. Findings Weld power in UAM is found to be largely determined by the mechanical compliance of the build and insensitive to foil material strength. Originality/value This is the first research paper to develop a predictive model relating UAM weld power and the mechanical compliance of the build over a range of foil combinations. This model is used to develop a tool to determine the process settings required to achieve a consistent weld power in builds with different stiffnesses.


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