Control Of Flow Separation From The Deflected Flap Of A High Lift Airfoil Using Multiple Dielectric Barrier Discharge Dbd Plasma Actuators
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Control Of Flow Separation From The Deflected Flap Of A High Lift Airfoil Using Multiple Dielectric Barrier Discharge Dbd Plasma Actuators
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Author : Kristine L. McElligott
language : en
Publisher:
Release Date : 2010
Control Of Flow Separation From The Deflected Flap Of A High Lift Airfoil Using Multiple Dielectric Barrier Discharge Dbd Plasma Actuators written by Kristine L. McElligott and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2010 with categories.
Abstract: In current wing design, multiple flaps are incorporated into the trailing edge to allow mixing of high and low pressure sides to reduce flow separation. These flaps reduce the efficiency by adding weight and complexity to the aircraft. A single hinged flap would reduce these inefficiencies but is more susceptible to flow separation. Active flow control is a means by which the fluid flow over a body is deliberately altered and can be altered such that it becomes less likely to separate from the object. By energizing the flow, the degree of separation of the flow can be controlled, and this inherently controls lift. Dielectric barrier discharge (DBD) plasma actuators are a form of active flow control. These actuators are created by asymmetrically aligning two electrodes and adding a dielectric layer between the electrodes. When the electrodes are electrically connected, ionized air (plasma) travels from the exposed electrode towards the covered electrode. Collisions occur between the plasma and neutral air over the body, and momentum is transferred to the neutral air, effectively energizing it. The purpose of this study is to examine the lift enhancement and flow control authority that multiple DBD plasma actuators have on a high-lift airfoil when compared to the flow exhibited by non-controlled and single DBD plasma actuator controlled cases. Electrodes were mounted onto a simplified NASA Energy Efficient Transport airfoil near the flap. The airfoil was tested in a closed, recirculating wind tunnel operating at a Reynolds number of 240,000, 20° flap deflection angle and 0° degree angle of incidence. The actuators were independently powered in order to determine the most effective input parameters. Using multiple actuators operated in-phase has increased the lift and has delayed flow separation on the trailing edge flap when compared to baseline and single actuation cases.
High Lift Airfoil Separation Control With Dielectric Barrier Discharge Plasma Actuators
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Author : Jesse Little
language : en
Publisher:
Release Date : 2010
High Lift Airfoil Separation Control With Dielectric Barrier Discharge Plasma Actuators written by Jesse Little and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2010 with categories.
Abstract: This work examines the performance of dielectric barrier discharge (DBD) plasma actuators for controlling separation from the leading edge and trailing edge flap shoulder of a supercritical high-lift airfoil. DBD plasma actuators driven by both typical AC voltages (AC-DBD) and more developmental nanosecond duration pulses (NS-DBD) are investigated. Characterization of the two actuators shows that very different behavior is created when exciting the plasma discharge using these two waveforms. The AC-DBD plasma actuator functions through electrohydrodynamic effects that introduce zero net mass, but nonzero net momentum into the flow. Conversely, the electrohydrodynamic effects of the NS-DBD are quite weak suggesting thermal effects from rapid localized heating by the plasma are responsible for control authority. The performance of both devices as separation control actuators is tested on a high-lift airfoil system. The AC-DBD is effective for controlling turbulent boundary layer separation from a deflected trailing edge flap between Reynolds numbers of 240,000 and 750,000. Momentum coefficients for the AC-DBD plasma actuator are generally an order of magnitude lower than those usually employed for such studies yet control authority is still realized through amplification of natural vortex shedding from the flap shoulder. The corresponding lift enhancement is primarily due to upstream effects from increased circulation around the entire model rather than full separated flow reattachment to the deflected flap surface. Lift enhancement via instability amplification is found to be relatively insensitive to changes in angle of attack provided that the separation location and underlying dynamics do not change. Control authority decreases with increasing Reynolds number and flap deflection highlighting the necessity for further optimization of AC-DBD plasma actuators for use in realistic takeoff and landing transport aircraft applications. As a whole, these findings compare favorably to studies on a similar high-lift platform using piezoelectric driven zero net mass flux actuation. The NS-DBD plasma actuator is ineffective for controlling separation from the deflected trailing edge flap. However, the device is found to be superior to the tested AC-DBD plasma actuators for controlling leading edge separation and rivals the performance of a passive droop by extending the stall angle by six degrees in the Reynolds number range 750,000-1,000,000. Detailed flow diagnostics show the NS-DBD plasma actuator functions as an active trip for pre-stall incidence angles and generates coherent spanwise vortices that entrain freestream momentum into the separated region at post-stall angles. These structures are generated across all surveyed frequencies, but optimal dimensionless frequencies for controlling separation are in the range four to six depending on the incidence angle. The contrasting performance of the NS-DBD plasma actuator at the leading and trailing edge in comparison to the AC-DBD is discussed and recommendations for future work are provided.
Encyclopedia Of Plasma Technology Two Volume Set
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Author : J. Leon Shohet
language : en
Publisher: CRC Press
Release Date : 2016-12-12
Encyclopedia Of Plasma Technology Two Volume Set written by J. Leon Shohet and has been published by CRC Press this book supported file pdf, txt, epub, kindle and other format this book has been release on 2016-12-12 with Technology & Engineering categories.
Technical plasmas have a wide range of industrial applications. The Encyclopedia of Plasma Technology covers all aspects of plasma technology from the fundamentals to a range of applications across a large number of industries and disciplines. Topics covered include nanotechnology, solar cell technology, biomedical and clinical applications, electronic materials, sustainability, and clean technologies. The book bridges materials science, industrial chemistry, physics, and engineering, making it a must have for researchers in industry and academia, as well as those working on application-oriented plasma technologies. Also Available Online This Taylor & Francis encyclopedia is also available through online subscription, offering a variety of extra benefits for researchers, students, and librarians, including: Citation tracking and alerts Active reference linking Saved searches and marked lists HTML and PDF format options Contact Taylor and Francis for more information or to inquire about subscription options and print/online combination packages. US: (Tel) 1.888.318.2367; (E-mail) [email protected] International: (Tel) +44 (0) 20 7017 6062; (E-mail) [email protected]
Flow Control Techniques And Applications
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Author : Jinjun Wang
language : en
Publisher: Cambridge University Press
Release Date : 2018-12-13
Flow Control Techniques And Applications written by Jinjun Wang and has been published by Cambridge University Press this book supported file pdf, txt, epub, kindle and other format this book has been release on 2018-12-13 with Science categories.
Master the theory, applications and control mechanisms of flow control techniques.
Physics And Control Of Flow Over A Thin Airfoil Using Nanosecond Pulse Dbd Actuators
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Author : Ghasemi Esfahani Ata
language : en
Publisher:
Release Date : 2017
Physics And Control Of Flow Over A Thin Airfoil Using Nanosecond Pulse Dbd Actuators written by Ghasemi Esfahani Ata and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2017 with Aerodynamics categories.
Flow separation leading to stall imposes considerable performance penalties on lifting surfaces. Limitations in flight envelope and loss of control are among the chief reasons for the interest in the aeronautical research community for better understanding of this phenomenon. Modern flow control techniques explored in this work can potentially alleviate the performance penalties due to flow separation. Experiments were designed to investigate excitation of flow over an airfoil with leading edge separation at a post-stall angle of attack with nanosecond pulse dielectric barrier discharge actuators. The subject airfoil is designed with a small radius of curvature that potentially challenges the task of flow control as more centrifugal acceleration around leading is required to successfully reattach the flow. The Reynolds number based on the chord was fixed at 5·105, corresponding to a freestream flow of approximately 37 m/s. An angle of attack of 19° was used and a single plasma actuator was mounted near the leading edge of the airfoil. Fully separated flow on the suction side extended well beyond the airfoil with naturally shed vortices generated at a Strouhal number of 0.60. Excitation at very low to moderate (~1) Strouhal numbers at the leading edge generated organized coherent structures in the shear layer over the separated region with a shedding Strouhal number corresponding to that of the excitation, synchronizing the vortex shedding from leading and trailing edges. Excitation around the shedding Strouhal number promoted vortex merging while excitation at higher Strouhal numbers resulted in smaller, weaker structures that quickly developed and disintegrate over the airfoil. The primary mechanism of control is the excitation of instabilities associated with the vortices shed from leading edge. The excitation generates coherent large-scale structures that entrain high-momentum fluid into the separation region to reduce the separation and/or accelerate the flow over the airfoil and to modify the lift and drag properties. The baseline showed some spanwise non-uniformity both on and off the surface. Excitation at low Strouhal numbers (0.3
Development Of Dielectric Barrier Discharge Plasma Actuators And Their Application At Subsonic Speeds
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Author : Craig Hale
language : en
Publisher:
Release Date : 2012
Development Of Dielectric Barrier Discharge Plasma Actuators And Their Application At Subsonic Speeds written by Craig Hale and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2012 with categories.
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°.
Aeronautics And Astronautics
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Author : Max Mulder
language : en
Publisher: BoD – Books on Demand
Release Date : 2011-09-12
Aeronautics And Astronautics written by Max Mulder and has been published by BoD – Books on Demand this book supported file pdf, txt, epub, kindle and other format this book has been release on 2011-09-12 with Technology & Engineering categories.
In its first centennial, aerospace has matured from a pioneering activity to an indispensable enabler of our daily life activities. In the next twenty to thirty years, aerospace will face a tremendous challenge - the development of flying objects that do not depend on fossil fuels. The twenty-three chapters in this book capture some of the new technologies and methods that are currently being developed to enable sustainable air transport and space flight. It clearly illustrates the multi-disciplinary character of aerospace engineering, and the fact that the challenges of air transportation and space missions continue to call for the most innovative solutions and daring concepts.
Parameters Governing Separation Control With Sweeping Jet Actuators
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Author : Rene Woszidlo
language : en
Publisher:
Release Date : 2011
Parameters Governing Separation Control With Sweeping Jet Actuators written by Rene Woszidlo and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2011 with categories.
Parameters governing separation control with sweeping jet actuators over a deflected flap are investigated experimentally on a generic "Multiple Flap Airfoil" (MFA). The model enables an extensive variation of geometric and aerodynamic parameters to aid the scaling of this novel flow control method to full-size applications. Sweeping jets exit from discrete, millimeter-scale nozzles distributed along the span and oscillate from side-to-side. The sweeping frequency is almost linearly dependent on the supplied flowrate per actuator. The measured thrust exerted by a row of actuators agrees well with vectored momentum calculations. Frequency and thrust measurements suggest that the jet velocity is limited to subsonic speeds and that any additional increase in flowrate causes internal choking of the flow. Neither the flowrate nor the momentum input is found to be a sole parameter governing the lift for varying distance between adjacent actuators. However, the product of the mass flow coefficient and the square root of the momentum coefficient collapses the lift onto a single curve regardless of the actuator spacing. Contrary to other actuation methods, separation control with sweeping jets does not exhibit any hysteresis with either momentum input or flap deflection. A comparison between sweeping and non-sweeping jets illustrates the superior control authority provided by sweeping jets. Surface flow visualization on the flap suggests the formation of counter-rotating pairs of streamwise vortices caused by the interaction of neighboring jets. The actuation intensity required to attach the flow increases with increasing downstream distance from the main element's trailing edge and increasing flap deflection. No obvious dependence of the ideal actuation location on actuator spacing, flap deflection, angle of attack, or actuation intensity is found within the tested range. Comparisons between experimental and numerical results reveal that the inviscid flow solution appears to be a suitable predictor for the effectively and efficiently obtainable lift of a given airfoil configuration. The flap size affects the achievable lift, the accompanying drag, and the required flap deflection and actuation intensity. By controlling separation, the range of achievable lift coefficients is doubled without significant penalty in drag even when considering a safety margin for the maximum applicable incidence.
Unsteady Flow Separation Control Over A Naca 0015 Using Ns Dbd Plasma Actuators
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Author : Achal Sudhir Singhal
language : en
Publisher:
Release Date : 2017
Unsteady Flow Separation Control Over A Naca 0015 Using Ns Dbd Plasma Actuators written by Achal Sudhir Singhal and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2017 with categories.
Flow field surrounding a moving body is often unsteady. This motion can be linear or rotary, but the latter will be the primary focus of this thesis. Unsteady flows are found in numerous applications, including sharp maneuvers of fixed wing aircraft, biomimetics, wind turbines, and most notably, rotorcraft. Unsteady flows cause unsteady loads on the immersed bodies. This can lead to aerodynamic flutter and mechanical failure in the body. Flow control is hypothesized to reduce the load hysteresis, and is achieved in the present work via nanosecond pulse driven dielectric barrier discharge (NS-DBD) plasma actuators. These actuators have been effective in the delay or mitigation of static stall. The flow parameters were varied by Reynolds number (Re=167,000-500,000), reduced frequency (k=0.025-0.075), and excitation Strouhal number (Ste=0-10). It was observed that the trends of Ste were similar for all combinations of Re and k, and three major conclusions were drawn. It was first observed that low Strouhal number excitation (Ste0.5) results in oscillatory aerodynamic loading in the stalled stage of dynamic stall. At high Strouhal number excitation (Ste2), this behavior is not observed, as in the static stall cases. Second, all excitation resulted in earlier flow reattachment. Lastly, it was shown that excitation resulted in reduced aerodynamic hysteresis and dynamic stall vortex strength. The decrease in the strength of the dynamic stall vortex is achieved by the formation of excited structures that bleed the leading edge vorticity prior to the ejection of the dynamic stall vortex. At sufficiently high excitation Strouhal numbers (Ste ̃10), the dynamic stall vortex was suppressed.
Numerical Investigation Of Plasma Actuator Configurations For Flow Separation Control At Multiple Angles Of Attack
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Author : Thomas Kelsey West
language : en
Publisher:
Release Date : 2012
Numerical Investigation Of Plasma Actuator Configurations For Flow Separation Control At Multiple Angles Of Attack written by Thomas Kelsey West and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2012 with Computational fluid dynamics categories.
"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.