Download or read book Leading edge Flow Separation Control Over a NACA 0012 Aerofoil with DBD Plasma Actuators written by Longfei Song and published by . This book was released on 2018 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Physics and Control of Flow Over a Thin Airfoil Using Nanosecond Pulse DBD Actuators written by Ghasemi Esfahani Ata and published by . This book was released on 2017 with total page 192 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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
Download or read book Airfoil Leading and Trailing Edge Separation Control Using SDBD Plasma Actuators written by Christopher L. Kelley and published by . This book was released on 2013 with total page 129 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Experimental and Computational Analysis of Separation Bubble Behavior for Compressible Steady and Oscillatory Flows Over a NACA 0012 Airfoil M written by and published by . This book was released on 1997 with total page 202 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this thesis, the separation bubble behavior and its effect on the steady and dynamic stall characteristics of a thin airfoil in a compressible flow at a transitional Reynolds number was studied. For such flows, laminar separation occurs near the airfoil leading edge, but turbulent reattachment occurs within a short distance downstream, forming a separation bubble in the underlying region. Two experimental techniques, point diffraction interferometry (PDI) and laser doppler velocimetry (LDV), were used to acquire detailed flowfield information that showed the development of the leading-edge separation bubble and its subsequent bursting at higher angles of attack. The initiation of the stall process from the leading-edge separation bubble as opposed to trailing-edge flow reversal pointed to the need for transitional flow analysis. Both in the boundary layer and Reynolds-averaged, Navier-Stokes (N-S) analysis methods, transition models were incorporated to determine the location and extent of the transition zone that best modeled the measured separation bubble behavior. Computed results for steady flow gave remarkable agreement with the measurements.
Download or read book Experimental and Computational Analysis of Separation Bubble Behavior for Compressible Steady and Oscillatory Flows Over a NACA 0012 Airfoil M written by and published by . This book was released on 1997 with total page 202 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this thesis, the separation bubble behavior and its effect on the steady and dynamic stall characteristics of a thin airfoil in a compressible flow at a transitional Reynolds number was studied. For such flows, laminar separation occurs near the airfoil leading edge, but turbulent reattachment occurs within a short distance downstream, forming a separation bubble in the underlying region. Two experimental techniques, point diffraction interferometry (PDI) and laser doppler velocimetry (LDV), were used to acquire detailed flowfield information that showed the development of the leading-edge separation bubble and its subsequent bursting at higher angles of attack. The initiation of the stall process from the leading-edge separation bubble as opposed to trailing-edge flow reversal pointed to the need for transitional flow analysis. Both in the boundary layer and Reynolds-averaged, Navier-Stokes (N-S) analysis methods, transition models were incorporated to determine the location and extent of the transition zone that best modeled the measured separation bubble behavior. Computed results for steady flow gave remarkable agreement with the measurements.
Download or read book Experimental and Computational Analysis of Separation Bubble Behavior for Compressible Steady and Oscillatory Flows Over a NACA 0012 Airfoil M 0 3 Re 540 000 written by Robert D. Van Dyken and published by . This book was released on 1997-03-01 with total page 202 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this thesis, the separation bubble behavior and its effect on the steady and dynamic stall characteristics of a thin airfoil in a compressible flow at a transitional Reynolds number was studied. For such flows, laminar separation occurs near the airfoil leading edge, but turbulent reattachment occurs within a short distance downstream, forming a separation bubble in the underlying region. Two experimental techniques, point diffraction interferometry (PDI) and laser doppler velocimetry (LDV), were used to acquire detailed flowfield information that showed the development of the leading-edge separation bubble and its subsequent bursting at higher angles of attack. The initiation of the stall process from the leading-edge separation bubble as opposed to trailing-edge flow reversal pointed to the need for transitional flow analysis. Both in the boundary layer and Reynolds-averaged, Navier-Stokes (N-S) analysis methods, transition models were incorporated to determine the location and extent of the transition zone that best modeled the measured separation bubble behavior. Computed results for steady flow gave remarkable agreement with the measurements.
Download or read book Airfoil Separation Control with Plasma Actuators written by Shawn Fleming and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Design and Development of a Dynamically Deforming Leading Edge Airfoil for Unsteady Flow Control written by and published by . This book was released on 1997 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: A novel approach to unsteady flow separation and dynamic stall control using a dynamically deforming leading edge airfoil is described. The design details of a carbon-fiber composite skin airfoil having a thickness of 0.002 in. at the leading edge and capable of deforming at 20 Hz in unsteady flow at freestream Mach numbers of up to 0.45, are discussed. Implementation of the scheme at model scales places extraordinary demands on the design, material and fabrication of such an airfoil. Rate scaling further requires very-rapid-response instrumentation, measurement techniques and data acquisition schemes. The special instrumentation control system developed for these experiments as well as the fluid dynamic results of successful flow control that was achieved using this method, are also discussed.
Download or read book Flow Separation Induced by Periodic Aerodynamic Interference written by E. E. Covert and published by . This book was released on 1984 with total page 8 pages. Available in PDF, EPUB and Kindle. Book excerpt: Analysis of experimental surface pressure distributions on an NACA 0012 airfoil has revealed four flow states: attached, separated, borderline, and dynamically separated. The important parameters that determine the flow state are Reynolds number, reduced frequency, airfoil angle of attack, and surface condition at the leading edge. Testing was done at Re=700,000, .5
Download or read book Transition and Turbulence Structure in the Boundary Layers of an Oscillating Airfoil written by J. DeRuyck and published by . This book was released on 1989 with total page 102 pages. Available in PDF, EPUB and Kindle. Book excerpt: Objectives of this investigation were: 1) to identify the conditions under which a sinusoidally oscillating NACA 0012 airfoil operates with a leading edge separation bubble and the conditions under which it operates with leading edge stall; 2) to conduct complete boundary layer and near wake survey in the presence of the leading edge separation bubble; and 3) to investigate the flow near the trailing edge and in the near wake while the airfoil was undergoing leading edge stall. The airfoil oscillates about an axis at 25% chord from the leading edge, with a nominal reduced frequency of 0.3 and Reynolds number of 300,000. Experiments were made at 4 to 14, 5 to 15, 6 to 16 and 8 to 18 deg angle of attack. It was found that the most probable cause of leading edge stall was due to the leading edge separation bubble burst which occurred soon after static stall limit was exceeded. Leading edge stall is not due to the rapid upstream movement of the trailing edge separation. The velocity vectors and the Reynolds stress tensors were measured using a slanted rotating single sensor hot-wire. The complete suction side boundary layer profile and the near wake was surveyed at 5-15 deg oscillation where no interaction is observed between leading edge and trailing edge flows. Keywords: Unsteady aerodynamics; Dynamic stall; High angle of attack; Flow separation; Rotorcraft; Wake; Unsteady flow transition; Belgium. (EDC).
Download or read book Robust Feedback Control of Flow Separation Using Plasma Actuators written by Laura Pasquale and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Computational Investigations of a NACA 0012 Airfoil in Low Reynolds Number Flows written by and published by . This book was released on 1992 with total page 147 pages. Available in PDF, EPUB and Kindle. Book excerpt: A steady flow analysis is conducted for a NACA 0012 airfoil in low Reynolds number flows ranging from 540,000 to 1,000,000. Emphasis is placed on prediction and location of the separation bubble. Computational methods include the direct boundary layer method, the viscous-inviscid interaction method, and the time-averaged Navier-Stokes method. Characteristic trends in skin friction coefficient, displacement thickness, and boundary layer velocity profiles with increasing angle of attack are observed. Computational results are compared to each other and to experimental photographs visualizing the density flowfield using Point Diffraction Interferometry. Both the viscous-inviscid method and the Navier-Stokes method failed to accurately represent leading edge separation bubbles. The direct boundary layer method, usually considered of very limited usefulness due to a singularity in the underlying equations at separation, is shown to exhibit unexpected recovery behavior for small amounts of separation. Furthermore, the results near the leading edge, where separation bubbles were computed, were validated by the experiment. Boundary layer, Separation bubble.
Download or read book An Experimental Investigation of Leading edge Flow Separation from a 4 Percent Thick Two dimensional Biconvex Aerofoil written by Aeronautical Research council and published by . This book was released on 1958 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book An Experimental Investigation of Leading edge Flow Separation from a 4 Percent Thick Two dimensional Biconvex Aerofoil written by Aeronautical Research council and published by . This book was released on 1958 with total page 17 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Active Control of Separation on a Low Reynolds Number Airfoil Using Synthetic Jet Actuation written by Mark Feero and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book An Experimental Investigation of Leading edge Flow separation from a 4 Thick Two dimensional Biconvex Aerofoil written by B. D. Henshall and published by . This book was released on 1957 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Natural Laminar Flow and Laminar Flow Control written by R. W. Barnwell and published by . This book was released on 1992 with total page 432 pages. Available in PDF, EPUB and Kindle. Book excerpt: Research on laminar flow and its transition to turbulent flow has been an important part of fluid dynamics research during the last sixty years. Since transition impacts, in some way, every aspect of aircraft performance, this emphasis is not only understandable but should continue well into the future. The delay of transition through the use of a favorable pressure gradient by proper body shaping (natural laminar flow) or the use of a small amount of suction (laminar flow control) was recognized even in the early 1930s and rapidly became the foundation of much of the laminar flow research in the U.S. and abroad. As one would expect, there have been many approaches, both theoretical and experimental, employed to achieve the substantial progress made to date. Boundary layer stability theories have been formu lated and calibrated by a good deal of wind tunnel and flight experiments. New laminar now airfoils and wings have been designed and many have been employed in aircraft designs. While the early research was, of necessity, concerned with the design of subsonic aircraft interest has steadily moved to higher speeds including those appropriate to planetary entry. Clearly, there have been substantial advances in our understanding of transition physics and in the development and application of transition prediction methodolo gies to the design of aircraft.
