Download or read book Active Control of High Speed Subsonic Cavity Flow Using Plasma Actuators written by Douglas Alan Mitchell and published by . This book was released on 2007 with total page 242 pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: The study and control of cavity flow fields began in the 1950's and has remained an active area of research for the past fifty years. Grazing flow over an open cavity which leads to resonance is a common occurrence generated by the flow-acoustic coupling mechanism. When the natural instabilities in the shear layer phase match with the acoustic waves generated from the impingement of the structures in the shear layer at the trailing edge of the cavity, high amplitude background noise and discrete cavity tones are generated in the form of high amplitude pressure fluctuations. Common examples of this phenomenon are aircraft landing gear openings, aircraft weapons bays, and engine air intakes. Unchecked cavity flow resonance can lead to weapon stores damage and incorrect deployment, reduction in lift, increase in drag, and structural fatigue. Initial research concentrated on using a compression driver as a synthetic jet type actuator to reduce acoustic resonance peaks, to operate the actuator at optimal forcing frequencies using reduced order modeling in order to shrink the peaks without triggering adjacent tones, and to develop logic based controls to damp pressure fluctuations within the system. The compression driver was ultimately limited by its frequency bandwidth and power output. The limited capabilities of the compression driver led to the development of the localized arc filament plasma actuator which is capable of high bandwidth and high amplitude actuation. The focus of this research was on the development of a high speed subsonic cavity flow facility and its control using localized arc filament plasma actuators (LAFPA). A cavity flow facility was designed and fabricated which allowed for the study of both baseline and forced cavity flows. The baseline flow characteristics were studied using flow visualization techniques in the form of particle image velocimetry (PIV) and schlieren photography, dynamic surface pressure measurements, and instantaneous and time-averaged dynamic pressure correlations to gain further understanding in cavity flow physics. Once the flow was sufficiently understood, LAFPAs were then used to force the flow into different modes or non-preferred frequencies in order to reduce the cavity tones or reduce the overall sound pressure level. Resonant, non-resonant, and multi-mode resonance are studied and actuated at various forcing frequencies, duty cycles, and modes. Furthermore, several different plasma actuator platforms were developed and tested to determine an optimal electrode arrangement during actuation.
Download or read book Active Control of Subsonic Cavity Flow Using Plasma Actuators written by Nathan George Kamps and published by . This book was released on 2007 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: Due to the prevalence of stealth technology on increasing numbers of new aircraft, weapons and electronics that had previously been stored under the aircraft wings are now being stored in weapons bays inside the fuselage. When these bays are opened however, a damaging flow situation can arise to create high amplitude pressure fluctuations capable of damaging structures and systems of the aircraft and the weapons stored in the bay. Thus a major area of research at the Gas Dynamics and Turbulence Laboratory (GDTL) has been focused on the suppression of these pressure fluctuations. Previous results using active flow control and a compression driver showed good flow authority up to Mach 0.40, when actuator effectiveness was lost. Other research at the GDTL has focused on the use of localized arc filament plasma actuators (LAFPA's) to control flow instabilities in a high Mach number free jet. The focus of this research was to incorporate the plasma actuators in a cavity flow facility and investigate their effectiveness at suppressing the tone generated by flows of higher Mach numbers. The results presented in this paper detail the results of testing several different actuator configurations on Mach 0.69 flow over a shallow cavity.
Download or read book Compressibility Turbulence and High Speed Flow written by Thomas B. Gatski and published by Academic Press. This book was released on 2013-03-05 with total page 343 pages. Available in PDF, EPUB and Kindle. Book excerpt: Compressibility, Turbulence and High Speed Flow introduces the reader to the field of compressible turbulence and compressible turbulent flows across a broad speed range, through a unique complimentary treatment of both the theoretical foundations and the measurement and analysis tools currently used. The book provides the reader with the necessary background and current trends in the theoretical and experimental aspects of compressible turbulent flows and compressible turbulence. Detailed derivations of the pertinent equations describing the motion of such turbulent flows is provided and an extensive discussion of the various approaches used in predicting both free shear and wall bounded flows is presented. Experimental measurement techniques common to the compressible flow regime are introduced with particular emphasis on the unique challenges presented by high speed flows. Both experimental and numerical simulation work is supplied throughout to provide the reader with an overall perspective of current trends. - An introduction to current techniques in compressible turbulent flow analysis - An approach that enables engineers to identify and solve complex compressible flow challenges - Prediction methodologies, including the Reynolds-averaged Navier Stokes (RANS) method, scale filtered methods and direct numerical simulation (DNS) - Current strategies focusing on compressible flow control
Download or read book Active Flow Control written by Rudibert King and published by Springer Science & Business Media. This book was released on 2007-05-31 with total page 441 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book contains contributions presented at the Active Flow Control 2006 conference, held September 2006, at the Technische Universität Berlin, Germany. It contains a well balanced combination of theoretical and experimental state-of-the-art results of Active Flow Control. Coverage combines new developments in actuator technology, sensing, robust and optimal open- and closed-loop control and model reduction for control.
Download or read book Active Control of Massively Separated High speed base Flows with Electric Arc Plasma Actuators written by and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Investigation of Magnetohydrodynamic Plasma Actuators for Aerodynamic Flow Control written by Brent Joel Pafford and published by . This book was released on 2013 with total page 88 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis describes the analysis, fabrication and testing of a novel magnetohydrodynamic plasma actuator for aerodynamic flow control, specifically, retreating blade stall. A magnetohydrodynamic plasma actuator is comprised of two parallel rail electrodes embedded chord-wise on the upper surface of an airfoil. A pulse forming network generates a low-voltage, high-current repetitive pulsed arc. Self-induced electromagnetic fields force the pulsed arc along the length of the rail electrodes at high velocities, transferring momentum to the surrounding air, creating a high-velocity pulsed air wall jet. A systematic experimental investigation of the effect of plasma actuators on the surrounding air is conducted in stagnant air conditions to gain an understanding of the physical characteristics. These characteristics include voltage and current measurements, pulsed arc velocity measurements, and high speed video imaging. The results show typical pulsed arc velocities of about 100 m/s can be induced with discharge energies of about 300 J per pulse. Additional experimental studies are conducted to quantify the performance of the pulsed arc for potential use in subsonic flow control applications. To gain an estimate of the momentum transferred from the pulsed arc to the surrounding air the plasma actuator is placed in a subsonic open-circuit wind tunnel at a Reynolds number of 4.5 x 105. The induced velocity of the pulsed wall jet is measured using a Laser Doppler Anemometer. The measurements show that the pulsed arc creates a high-velocity pulsed wall jet that extends 40 mm above the airfoils surface and has an induced velocity of 15 m/s greater than the unaltered air flow over the airfoil, with peak velocities of 32 m/s. The magnetohydrodynamic plasma actuator proved to induce velocities an order of magnitude greater than the velocities attained by current state-of-the-art plasma actuators. Moreover, the RailPAc is found to posses the potential for alleviation of retreating blade stall. Future work will include experiments to gain a detailed understanding of the improvements to the static stall angle, the optimal actuator geometry, excitation duty cycle, magnetic field augmentation, and behavior of the plasma armature at high Mach/Reynolds numbers. Particle Image Velocimetry (PIV) will be utilized to improve the induced flow velocity measurements acquired with the LDA.
Download or read book Direct and Large Eddy Simulation IX written by Jochen Fröhlich and published by Springer. This book was released on 2015-01-27 with total page 656 pages. Available in PDF, EPUB and Kindle. Book excerpt: This volume reflects the state of the art of numerical simulation of transitional and turbulent flows and provides an active forum for discussion of recent developments in simulation techniques and understanding of flow physics. Following the tradition of earlier DLES workshops, these papers address numerous theoretical and physical aspects of transitional and turbulent flows. At an applied level it contributes to the solution of problems related to energy production, transportation, magneto-hydrodynamics and the environment. A special session is devoted to quality issues of LES. The ninth Workshop on 'Direct and Large-Eddy Simulation' (DLES-9) was held in Dresden, April 3-5, 2013, organized by the Institute of Fluid Mechanics at Technische Universität Dresden. This book is of interest to scientists and engineers, both at an early level in their career and at more senior levels.
Download or read book Electric Aircraft Dynamics written by Ranjan Vepa and published by CRC Press. This book was released on 2020-07-29 with total page 274 pages. Available in PDF, EPUB and Kindle. Book excerpt: Electric Aircraft Dynamics: A Systems Engineering Approach surveys engineering sciences that underpin the dynamics, control, monitoring, and design of electric propulsion systems for aircraft. It is structured to appeal to readers with a science and engineering background and is modular in format. The closely linked chapters present descriptive material and relevant mathematical modeling techniques. Taken as a whole, this ground-breaking text equips professional and student readers with a solid foundation for advanced work in this emerging field. Key Features: Provides the first systems-based overview of this emerging aerospace technology Surveys low-weight battery technologies and their use in electric aircraft propulsion Explores the design and use of plasma actuation for boundary layer and flow control Considers the integrated design of electric motor-driven propellers Includes PowerPoint slides for instructors using the text for classes Dr. Ranjan Vepa earned his PhD in applied mechanics from Stanford University, California. He currently serves as a lecturer in the School of Engineering and Material Science, Queen Mary University of London, where he has also been the programme director of the Avionics Programme since 2001. Dr. Vepa is a member of the Royal Aeronautical Society, London; the Institution of Electrical and Electronic Engineers (IEEE), New York; a Fellow of the Higher Education Academy; a member of the Royal Institute of Navigation, London; and a chartered engineer.
Download or read book Active Control of the Turbulent Flow Downstream of a Backward Facing Step with Dielectric Barrier Discharge Plasma Actuators written by Patricia Sujar Garrido and published by . This book was released on 2014 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis is part of an international project (MARS) to improve air transport efficiency by active flow control strategy. In this context, the presented experimental works are focused on a surface Dielectric Barrier Discharge (DBD) as a solution to control the turbulent flow separation downstream a backward-facing step (BFS) at Reh = 30000. Two different plasma discharges are investigated: an ac-DBD resulting in a electrohydrodynamic force and a ns- DBD producing a pressure wave. Thanks to the versatility of plasma discharges and in order to optimize its effects on the flow, different locations of the DBD actuator have been investigated. Furthermore, an extended parametric study regarding the input variables of the discharge has been carried out by stereoscopic PIV. Among the obtained results, the mean reattachment length has been reduced up to 20%. In addition, other averaged quantities such as Reynolds stress components, the kinetic energy and the vorticity thickness of the separated shear layer have been analyzed to provide more extended information about the effects of the DBD actuator. The last part includes a dynamical analysis of the modifications produced by an optimal actuation. For that aim, the dominant structures are investigated by their signature in the frequency domain and by proper orthogonal decomposition (POD). All the results lead to the definition of an optimal actuation for which the mean reattachment position is reduced and the vortex shedding street can be reinforced by a lock-on control mechanism.
Download or read book Machine Learning Control Taming Nonlinear Dynamics and Turbulence written by Thomas Duriez and published by Springer. This book was released on 2016-11-02 with total page 229 pages. Available in PDF, EPUB and Kindle. Book excerpt: This is the first textbook on a generally applicable control strategy for turbulence and other complex nonlinear systems. The approach of the book employs powerful methods of machine learning for optimal nonlinear control laws. This machine learning control (MLC) is motivated and detailed in Chapters 1 and 2. In Chapter 3, methods of linear control theory are reviewed. In Chapter 4, MLC is shown to reproduce known optimal control laws for linear dynamics (LQR, LQG). In Chapter 5, MLC detects and exploits a strongly nonlinear actuation mechanism of a low-dimensional dynamical system when linear control methods are shown to fail. Experimental control demonstrations from a laminar shear-layer to turbulent boundary-layers are reviewed in Chapter 6, followed by general good practices for experiments in Chapter 7. The book concludes with an outlook on the vast future applications of MLC in Chapter 8. Matlab codes are provided for easy reproducibility of the presented results. The book includes interviews with leading researchers in turbulence control (S. Bagheri, B. Batten, M. Glauser, D. Williams) and machine learning (M. Schoenauer) for a broader perspective. All chapters have exercises and supplemental videos will be available through YouTube.
Download or read book Wind Tunnels and Experimental Fluid Dynamics Research written by Jorge Colman Lerner and published by BoD – Books on Demand. This book was released on 2011-07-27 with total page 728 pages. Available in PDF, EPUB and Kindle. Book excerpt: The book "Wind Tunnels and Experimental Fluid Dynamics Research" is comprised of 33 chapters divided in five sections. The first 12 chapters discuss wind tunnel facilities and experiments in incompressible flow, while the next seven chapters deal with building dynamics, flow control and fluid mechanics. Third section of the book is dedicated to chapters discussing aerodynamic field measurements and real full scale analysis (chapters 20-22). Chapters in the last two sections deal with turbulent structure analysis (chapters 23-25) and wind tunnels in compressible flow (chapters 26-33). Contributions from a large number of international experts make this publication a highly valuable resource in wind tunnels and fluid dynamics field of research.
Download or read book Modeling of Dielectric Barrier Discharge Plasma Actuators for Flow Control Simulations written by Denis Palmeiro and published by . This book was released on 2011 with total page 198 pages. Available in PDF, EPUB and Kindle. Book excerpt: Single-dielectric-barrier-discharge (SDBD) plasma actuators have shown much promise as an actuator for active flow control. Proper design and optimization of plasma actuators requires a model capable of accurately predicting the induced flow for a range of geometrical and excitation parameters. A number of models have been proposed in the literature, but have primarily been developed in isolation on independent geometries, frequencies and voltages. This study presents a comparison of four popular plasma actuator models over a range of actuation parameters for three different actuator geometries typical of actuators used in the literature. The results show that the hybrid model of Lemire & Vo (2011) is the only model capable of predicting the appropriate trends of the induced velocity for different geometries. Additionally, several modifications of this model have been integrated into a new proposed model for the plasma actuator, introducing a number of improvements.
Download or read book AIAA Journal written by American Institute of Aeronautics and Astronautics and published by . This book was released on 2007 with total page 960 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Numerical Investigation of Plasma Actuator Configurations for Flow Separation Control at Multiple Angles of Attack written by Thomas Kelsey West and published by . This book was released on 2012 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: "The primary objective of the study presented in this thesis was to analyze the effectiveness of aerodynamic plasma actuators as a means of active flow control over a low speed airfoil at multiple angles of attack each corresponding to two different flow separation mechanisms (i.e., laminar separation bubble and turbulent flow separation at stall conditions). Detailed parametric studies based on steady and unsteady Navier-Stokes simulations, modified to include the body force term created by the plasma actuator, were performed for a NACA 0012 airfoil at a chord Reynolds number of 105. In particular, parametric studies were performed to investigate the influence of the number, the location, the imposed body force magnitude (power input) and steady vs. unsteady operation of plasma actuators on the flow control effectiveness. First, the effectiveness of plasma actuators was studied when applied to the airfoil at a relatively low angle of attack, which involved the development of a laminar separation bubble (LSB). Next, the effectiveness of plasma actuators was analyzed at a high angle of attack where the stall of the airfoil occurs with a fully turbulent flow assumption. The results show that plasma actuators can provide significant improvement in aerodynamic performance for the flow conditions considered in this study. For LSB control, as much as a 50% improvement in the lift to drag ratio was observed. Results also show that the same improvement can be achieved using an unsteady or multiple actuators, which can require as much as 75% less power compared to a single, steady actuator. For the stalled airfoil case, as much as a 700% improvement in L/D was observed from a single, steady actuator. Note that this was achieved using a power input eight times higher than what was used for LSB control. Also, unsteady and multiple actuator configurations do not provide the same enhancement as the single, steady actuators. This was found to be due to the nature of the turbulent separation (trailing edge separation) at the stall condition that occurs for the selected airfoil and Reynolds number"--Abstract, leaf iii
Download or read book Aeroacustic and Vibroacoustic Advancement in Aerospace and Automotive Systems written by Roberto Citarella and published by MDPI. This book was released on 2018-06-26 with total page 181 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book is a printed edition of the Special Issue "Advances in Vibroacoustics and Aeroacustics of Aerospace and Automotive Systems" that was published in Applied Sciences
Download or read book Development of Dielectric Barrier Discharge Plasma Actuators and Their Application at Subsonic Speeds written by Craig Hale and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Plasma actuators are electrical devices that generate a wall bounded jet without the use of any moving parts. For aerodynamic applications they can be used as flow control devices to delay separation and augment lift on a wing. The aim of this project is to initially develop a system capable of generating and sustaining a plasma that generates a wall bounded jet. The next step is to investigate the effect of varying the number and distribution of encapsulated electrodes in the dielectric layer. Finally the best case design is applied at the leading edge and flap shoulder of a NACA0015 aerofoil with a 20% flap. Utilising a transformer cascade, plasma has been generated for a variety of input voltages. In the quiescent environment of a Faraday cage the velocity flow field is recorded using particle image velocimetry (PIV). Through understanding of the mechanisms involved in producing the wall jet and the importance of the encapsulated electrode a novel actuator design was investigated. The actuator design distributes the encapsulated electrode throughout the dielectric layer. The experiments have shown that actuators with shallow initial encapsulated electrodes induce velocities greater than the baseline case at the same voltage. Actuators with a deep initial electrode are able to induce the highest velocities as they can operate at higher voltages without breakdown of the dielectric. The best actuator case is applied to the aerofoil for Reynolds numbers of 1:97x105, 2:63x105 and 3:29x105. The lift and drag are recorded using pressure measurements around the aerofoil surface and across the aerofoil's wake. PIV is utilised to visualise the flow field. The trailing edge actuator produces a step increase in lift for pre-stall angles of attack and delays stall by 1° at Re = 1:97x105. The leading edge actuator has limited impact on the flow for the no flap deflection case due to the actuator location. As the flap deflection increases the leading edge actuator is able to influence the flow. Repositioning of the leading edge actuator has the ability to reattach the flow around the fore portion of the aerofoil at a post stall angle of alpha = 18°.
Download or read book Case Study written by Nihar H. Chhatiawala and published by . This book was released on 2018 with total page 80 pages. Available in PDF, EPUB and Kindle. Book excerpt: Boundary Labs, LLC is an early-stage company composed of three students at Case Western Reserve University which aimed to evaluate the feasibility of commercialization of a novel dielectric barrier discharge (DBD) plasma actuator as an active flow control (AFC) method in wind turbines. The hypothesized benefits of DBD plasma actuators for AFC include improved energy capture from wind, low cost, and ease of implementation. This thesis is a two-part case study. The first part emulates a Small Business Innovation Research (SBIR) Phase I Proposal for the technology and includes discussions arguing that a strong commercial potential for the proposed technology exists in the United States and that technical development is feasible. The second part includes miscellaneous sections outside the scope of an SBIR proposal, leading to a discussion of the Boundary Labs team decision to discontinue development of this technology.
