Download or read book Active Flow Control of a Two dimensional NACA 0036 Airfoil with Synthetic Jet Excitations written by Jacob Wilson and published by . This book was released on 2005 with total page 138 pages. Available in PDF, EPUB and Kindle. Book excerpt: An active flow control experiment was conducted on a 2-ft chord NACA 0036 airfoil at 10 degrees angle of attack in the Cal Poly 3' x 4' wind tunnel.
Download or read book Synthetic Jet Flow Control of Two dimensional NACA 65 1 412 Airfoil Flow with Finite Time Lyapunov Exponent Analysis of Lagrangian Coherent Structures written by and published by . This book was released on 2016 with total page 46 pages. Available in PDF, EPUB and Kindle. Book excerpt: Synthetic jet (SJ) control of a low-Reynolds number, unsteady, compressible, viscous flow over a NACA 65-(1)412 airfoil, typical for unmanned air vehicles and gas turbines, has been investigated computationally. A particular focus was placed in the development and control of Lagrangian Coherent Structures (LCS) and the associated Finite-Time Lyapunov Exponent (FTLE) fields. The FTLE fields quantitatively measure of the repulsion rate in forward-time and the attraction rate in backward-time, and provide a unique perspective on effective flow control. A Discontinuous-Galerkin (DG) methods, high-fidelity Navier-Stokes solver performs direct numerical simulation (DNS) of the airfoil flow. Three SJ control strategies have been investigated: immediately downstream of flow separation, normal to the separated shear layer; near the leading edge, normal to the airfoil suction side; near the trailing edge, normal to the airfoil pressure side. A finite difference algorithm computes the FTLE from DNS velocity data. A baseline flow without SJ control is compared to SJ actuated flows. The baseline flow forms a regular, time-periodic, asymmetric von Karman vortex street in the wake. The SJ downstream of flow separation increases recirculation region vorticity and reduces the effective angle of attack. This decreases the time-averaged lift by 2:98% and increases the time-averaged drag by 5:21%. The leading edge SJ produces small vortices that deflect the shear layer downwards, and decreases the effective angle of attack. This reduces the time-averaged lift by 1:80%, and the time-averaged drag by 1:84%. The trailing edge SJ produces perturbations that add to pressure side vortices without affecting global flow characteristics. The time-averaged lift decreases by 0:47%, and the time-averaged drag increases by 0:20%. For all SJ cases, the aerodynamic performance is much more dependent on changes to the pressure distribution than changes to the skin friction distribution. No proposed SJ case improved aerodynamic performance. Some desirable SJ control effects were observed, which may be isolated in a future study by optimizing SJ parameters. Stably increasing recirculation region vorticity, and maintaining or increasing the effective angle of attack are desirable for lift increase, while deflecting the separated shear layer downward is desirable for drag reduction.
Download or read book Active Flow Control on Cambered Airfoils at Ultralow Reynolds Using Synthetic Jets written by Pau Valdepeñas Pujol and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Active flow control methods have been widely studied for more than a decade in order to improve the airfoil's efficiency. This study is focused on fluidic actuation (the addition or subtraction of momentum to/from the boundary layer by blowing and/or sucking fluid). A synthetic jet is a very particular type of fluidic actuation that involves periodic blowing and suction with zero-net-mass-flow over a the full period. Its success as an active flow control device has been extensively reported by several authors. As it can be seen synthetic jet technology provides good results on boundary layer reattachment and therefore, an improvement on the airfoil's efficiency. What is more, is a generic system that can be widespread on multiple types of airfoils such as unmanned aerial vehicles and conventional airplanes airfoils. The effectiveness of control in mitigating boundary separation depends on a number of parameters related both to the flow itself and the control input such as: frequency and amplitude of the excitation, the excitation shape, exit diameter and cavity shape. Since the synthetic jet system has several degrees of freedom and the flux is unpredictable, multiple simulations have to be done in order to assess the best configuration to achieve the maximum airfoil's efficiency. The well-known excitation of the synthetic jet is the zero-net-mass-flow that combines both expulsion and suction periodically. In this study, we also evaluate other types of excitations that imply more or less energy into the system that is characterized with the momentum coefficient. The goal is to assess thoroughly this existent trade-off between the aerodynamics performance and the momentum coefficient. And finally, extract deep conclusions and assess the best synthetic jet configuration where the aerodynamics performances are improved with a low momentum coefficient.. To extract suitably conclusions we pass through a thorough and intricate process that starts with the adapted and generic discretized surface for the synthetic jet that we use to solve the Navier-Stokes equations, then the appropriate conversions to simulate with spectral element framework Nektar++ and finally the detailed extraction of results. Moreover, we adopt to this study a practical approach with an unmanned aerial vehicle (UAV Skywalker x6) airfoil's photogrammetry that we use to simulate.
Download or read book Active Flow Control Over a Naca 0015 Airfoil by Synthetic Jet Actuators written by Pooya Kabiri and published by . This book was released on 2012 with total page 268 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Application of Active Flow Control on Airfoils at Ultralow Reynolds Numbers written by Carlos San Gabriel Romero and published by . This book was released on 2019 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: In a previous research Active Flow Control techniques, such as sweeping jets, applied in an ultra-low Reynolds regime (Re=1000) were found effective to reattach an already separated flow achieving lift enhancements but also inducing a large skin-friction drag increase due to the high velocities near the airfoil surface. In this study, firstly the current actuator configurations have been analyzed with the objective of determining the most important factors involved in the increase of the viscous drag. Then, several hypothesis have been done with the aim of reducing this drag penalty while keeping the lift enhancement. The decision taken in this sense has been to apply geometrical modifications to the the actuators using two control parameters, the jet width and the jet angle in which the fluid is injected. Moreover these modifications have been applied to three different actuation types; blowing, suction and synthetic jets. The simulations have been carried in a 2D NACA0012 airfoil in which a remeshing has been done in order to apply the commented modifications. The obtained results show variations depending on in which actuation type are applied. The jet angle modification has obtained interesting results for the blowing jet, since an angle that maximizes the lift coefficient has been found. The jet width has also obtained an optimum value for a specific momentum coefficient, that moreover is suitable for the three actuations. In conclusion, it has been proved that that besides the momentum coefficient and the jet location the geometrical parameters of the actuator have also a considerable impact on the overall efficiency of the actuation.
Download or read book Active control of the separation region on a two dimensional airfoil written by Julie Anne Lovato and published by . This book was released on 1992 with total page 130 pages. Available in PDF, EPUB and Kindle. Book excerpt: "This experimental analysis presents a comprehensive study of the separating boundary layer over a static airfoil under natural and actively controlled conditions. Near-surface hot-film and surface pressure measurements, as well as flow visualization are used to analyze the large-scale nature of the flow over a two-dimensional NACA-0015 airfoil and determine forcing effects. Results from the static study are then extended for an initial evaluation of unsteady airfoil control. Results show that the fundamental frequency associated with free shear layer instabilities for this case is an integral multiple of the frequency associated with wake structures. The static separating boundary layer response to active control confirms that it is a boundary layer transitioning to a free shear layer. Qualitative analyses show that significant reduction in overall static separation can be achieved under forcing conditions. Upper airfoil surface suction values are also significantly increased over the natural values. Applying tangential pulsed air control at static fundamental frequencies to a dynamic airfoil results in delay of the dynamic stall vortex formation and a delay of dynamic stall. These discoveries indicate that the developed control methodology may prove successful in increasing unsteady aircraft maneuverability. Subject terms: Static Airfoil Control; Separation Control; Unsteady Aerodynamics; Boundary Layer Control."--Report documentation page.
Download or read book Active Flow Control Concepts for Rotor Airfoils Using Synthetic Jets written by Karthikeyan Duraisamy and published by . This book was released on 2002 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Numerical Study of Active Flow Control Using Synthetic Jets written by Jeremy Dennis Roth and published by . This book was released on 2003 with total page 264 pages. Available in PDF, EPUB and Kindle. Book excerpt: Active Flow Control (AFC) using synthetic jets (SJ's) is numerically simulated for several simple aerodynamic shapes at high Reynolds numbers using the Computational Fluid Dynamics (CFD) computer program, CFL3D. AFC is the manipulation of a flow field around a given body in a fluid. AFC is used to improve the resulting flow characteristics bodies produce in regimes of flow separation which result from large pressure gradients. In the AFC device (SJ's) used in this study fluid is periodically displaced from a cavity with an orifice. A SJ relies on the entertainment of the local ambient fluid mass external to the device. Therefore, with the use of SJ's a significant decrease in complexity and weight is possible as compared to other more traditional AFC devices involving mass transfer. The objective of this study is to illustrate how AFC in the form of SJ's can be utilized to enhance the aerodynamic performance of simple aerodynamic shapes such as a circular cylinder, airfoil, and three-dimensional wing in flow conditions which result in boundary layer separation. A flat plate with zero pressure gradient is also analyzed in order to determine the effect of SJ's in the absence of boundary layer separation. In order to provide a fundamental understanding of the enhanced aerodynamic performance an additional investigation of classical boundary layer parameters is performed. Computational results are then presented for the bodies of interest with no AFC and validated with experimental results where available. Secondly, results for the numerical investigations with AFC are presented. The results of this study demonstrate that SJ's enhance the aerodynamic characteristics of the configurations and provide more favorable conditions in those regimes of the flow that are normally highly separated. The present study also revealed that a three-dimensional flow is quite similar in character to two-dimensional flows in the presence of SJ's. Overall, this study illustrates SJ's are effective in boundary layer control, and can be used to improve the aerodynamics of aerospace vehicles.
Download or read book Active Flow Control Applied to an Airfoil written by John F. Donovan and published by . This book was released on 1998 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Two dimensional Investigation of Five Related NACA Airfoil Sections Designed for Rotating wing Aircraft written by Raymond F. Schaefer and published by . This book was released on 1949 with total page 41 pages. Available in PDF, EPUB and Kindle. Book excerpt: Five NACA airfoils intended for use in rotor blades have been designed and the two-dimensional aerodynamics have been determined at three Reynolds numbers up to 2,600,000. The airfoils vary in thickness from 9 to 15 percent chord and in design lift coefficient from 0.3 to 0.7. The relative performance of sample rotors employing the different airfoils is predicted for various flight conditions.
Download or read book Virtual Shaping of a Two dimensional NACA 0015 Airfoil Using Sythetic Jet Actuator written by Fang-Jenq Chen and published by . This book was released on 2002 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Preliminary Study of the Flow on NACA Airfoil for Future Implementation of Active Flow Control written by Jaume Baratech Diaz and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Direct numerical simulations are performed on a NACA 2412 airfoil with an attack angle of 12 degrees and Reynolds numbers between 300 and 35.000. The details of the flow separation, formation and destabilization of the detached shear layer and formation of separation bubbles via flow re- attachment are studied among other phenomena. Results are then post- processed using a data analysis and visualization application. Computational fluid dynamics has proven a handy tool to analyze, characterize and understand the flow over airfoils. A block-structured mesh to run the simulations is created from scratch and presented in this report. The mesh is fully parameterized to save time for future modifications or adaptations. A mesh independence study is undertaken to ensure the mesh does not affect the outcome of the simulations. The lift and drag of the airfoil, as well as the wall shear stress and velocity profiles are calculated and presented in this report. The study is done at varying Re to characterize the transition of the lift and drag coefficients from steady to periodic and then to chaotic. We also present the formation and migration of the separation bubble, which gets closer to the leading edge as the Re increases. Open source software distributed under open public licensing (GPL) is exclusively exploited. The mesh has been created using Gmsh, the simulations have been done with OpenFOAM and the post-processing is done with paraView and grace.
Download or read book Two dimensional Circulation Control Tests on an Naca 23015 Airfoil Equipped with a Sealed and Slotted Flap to Determine Jet Momentum Loss Over the Flap written by D. L. CRUSE and published by . This book was released on 1958 with total page 170 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Two dimensional Investigation of Boundary layer Control by Suction on an N A C A 23015 Airfoil with a Single slotted Flap written by Virgil L. Razak and published by . This book was released on 1952 with total page 188 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Flow Control of a NACA 0015 Airfoil Using a Chordwise Array of Synthetic Jets written by Kevin Bales and published by . This book was released on 2003 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Flow Control on a NACA 4418 Airfoil Using Streamwise Synthetic Jet Actuators written by Yves Daniel Loretz and published by . This book was released on 2001 with total page 170 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Feedback Control of the Flow Over a Two dimensional Airfoil written by Julie A. Lovato and published by . This book was released on 1995 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
