Numerical Study On Active Flow Control Using Synthetic Jet Actuators Over A Naca 4421 Airfoil
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Numerical Study On Active Flow Control Using Synthetic Jet Actuators Over A Naca 4421 Airfoil
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Author : Xavier Guerrero Pich
language : en
Publisher:
Release Date : 2015
Numerical Study On Active Flow Control Using Synthetic Jet Actuators Over A Naca 4421 Airfoil written by Xavier Guerrero Pich and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2015 with categories.
This study is focused on evaluating the effects of using a Zero Net Mass Flux (ZNMF) actuator on a NACA 4421 airfoil for active flow control. First part of the study presents the fundamentals of boundary layer and a study of the available devices which are more used for flow control, focusing on the ZNMF. The steps for creating the mesh to perform numerical simulations of the airfoil are explained, and the results of the CFD simulations are compared with experimental data as a vaseline balidation. In the secord part, the ZNMF is studied in order to set the parameters of the actuator and to simulate its effect on CFD, and moreover the numerical simulations of the airfoil with the ZNMF set up are performed and the results are evaluated. The evaluation will show the most optimum parameters for the actuator, as well as the effects that the ZNMF has on the airfoil's behaviour.
Computational Study Of A Naca4415 Airfoil Using Synthetic Jet Control
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Author : Omar Dario Lopez Mejia
language : en
Publisher:
Release Date : 2009
Computational Study Of A Naca4415 Airfoil Using Synthetic Jet Control written by Omar Dario Lopez Mejia and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2009 with categories.
Synthetic jet actuators for flow control applications have been an active topic of experimental research since the 90's. Numerical simulations have become an important complement of that experimental work, providing detailed information of the dynamics of the controlled flow. This study is part of the AVOCET (Adaptive VOrticity Control Enabled flighT) project and is intended to provide computational support for the design and evaluation of closed-loop flow control with synthetic jet actuators for small scale Unmanned Aerial Vehicles (UAVs). The main objective is to analyze active flow control of a NACA4415 airfoil with tangential synthetic jets via computational modeling. A hybrid Reynolds-Averaged Navier-Stokes/Large Eddy Simulation (RANS/LES) turbulent model (called Delayed Detached-Eddy Simulation-DDES) was implemented in CDP, a kinetic energy conserving Computational Fluid Dynamics (CFD) code. CDP is a parallel unstructured grid incompressible flow solver, developed at the Center for Integrated Turbulence Simulations (CITS) at Stanford University. Two models of synthetic jet actuators have been developed and validated. The first is a detailed model in which the flow in and out of the actuator cavity is modeled. A second less costly model (RSSJ) was also developed in which the Reynolds stress produced by the actuator is modeled, based on information from the detailed model. Several static validation test cases at different angle of attack with modified NACA 4415 and Dragon Eye airfoils were performed. Numerical results show the effects of the actuators on the vortical structure of the flow, as well as on the aerodynamic properties. The main effect of the actuation on the time averaged vorticity field is a bending of the separation shear layer from the actuator toward the airfoil surface, resulting in changes in the aerodynamic properties. Full actuation of the suction side actuator reduces the pitching moment and increases the lift force, while the pressure side actuator increases the pitching moment and reduces the lift force. These observations are in agreement with experimental results. The effectiveness of the actuator is measured by the change in the aerodynamic properties of the airfoil in particular the lift ([Delta]C[subscript t]) and moment ([Delta]C[subscript m]) coefficients. Computational results for the actuator effectiveness show very good agreement with the experimental values (over the range of -2° to 10°). While the actuation modifies the global pressure distribution, the most pronounced effects are near the trailing edge in which a spike in the pressure coefficient (C[subscript p]) is observed. The local reduction of C[subscript p], for both the suction side and pressure side actuators, at x/c = 0.96 (the position of the actuators) is about 0.9 with respect to the unactuated case. This local reduction of the pressure is associated with the trapped vorticity and flow acceleration close to the trailing edge. The RSSJ model is designed to capture the synthetic jet time averaged behavior so that the high actuation frequencies are eliminated. This allows the time step to be increased by a factor of 5. This ad hoc model is also tested in dynamic simulations, in which its capacity to capture the detail model average performance was demonstrated. Finally, the RSSJ model was extended to a different airfoil profile (Dragon Eye) with good results.
Numerical Study Of Active Flow Control Using Synthetic Jets
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Author : Jeremy Dennis Roth
language : en
Publisher:
Release Date : 2003
Numerical Study Of Active Flow Control Using Synthetic Jets written by Jeremy Dennis Roth and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2003 with categories.
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.
Numerical Studies Of The Application Of Active Flow Control To Subsonic And Transonic Airfoil Flows Using A Synthetic Jet Actuator
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Author : Jose L. Vadillo
language : en
Publisher:
Release Date : 2005
Numerical Studies Of The Application Of Active Flow Control To Subsonic And Transonic Airfoil Flows Using A Synthetic Jet Actuator written by Jose L. Vadillo and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2005 with categories.
Flow Control Simulation With Synthetic And Pulsed Jet Actuator
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Author : Sol Keun Jee
language : en
Publisher:
Release Date : 2010
Flow Control Simulation With Synthetic And Pulsed Jet Actuator written by Sol Keun Jee 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.
Two active flow control methods are investigated numerically to understand the mechanism by which they control aerodynamics in the presence of severe flow separation on an airfoil. In particular, synthetic jets are applied to separated flows generated by additional surface feature (the actuators) near the trailing edge to obtain Coanda-like effects, and an impulse jet is used to control a stalled flow over an airfoil. A moving-grid scheme is developed, verified and validated to support simulations of external flow over moving bodies. Turbulent flow is modeled using detached eddy simulation (DES) turbulence models in the CFD code CDP (34) developed by Lopez (54). Synthetic jet actuation enhances turbulent mixing in flow separation regions, reduces the size of the separation, deflects stream lines closer to the surface and changes pressure distributions on the surface, all of which lead to bi-directional changes in the aerodynamic lift and moment. The external flow responds to actuation within about one convective time, which is significantly faster than for conventional control surfaces. Simulation of pitching airfoils shows that high-frequency synthetic jet affects the flow independently of the baseline frequencies associated with vortex shedding and airfoil dynamics. These unique features of synthetic jets are studied on a dynamically maneuvering airfoil with a closed-loop control system, which represents the response of the airfoil in wind-tunnel experiments and examines the controller for a rapidly maneuvering free-flight airfoil. An impulse jet, which is applied upstream of a nominal flow separation point, generates vortices that convect downstream, interact with the separating shear layer, dismantle the layer and allow following vortices to propagate along the surface in the separation region. These following vortices delay the separation point reattaching the boundary layer, which returns slowly to its initial stall condition, as observed in wind-tunnel experiments. A simple model of the impulse jet actuator used herein is found to be sufficient to represent the global effects of the jet on the stalled flow because it correctly represents the momentum injected into the flow.
Numerical Study Of Virtual Aerodynamic Shape Modification Of An Airfoil Using A Synthetic Jet Actuator
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Author : Jose L. Vadillo
language : en
Publisher:
Release Date : 2002
Numerical Study Of Virtual Aerodynamic Shape Modification Of An Airfoil Using A Synthetic Jet Actuator written by Jose L. Vadillo and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2002 with categories.
Flow Control Via Synthetic Jet Actuation
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Author : Adam Cole Miller
language : en
Publisher:
Release Date : 2005
Flow Control Via Synthetic Jet Actuation written by Adam Cole Miller and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2005 with categories.
An experimental investigation was undertaken to determine the ability of Synthetic Jet Actuators to control the aerodynamic properties of a wing. The Synthetic Jet Actuator (SJA) was placed at two separate positions on a wing comprised of a NACA0015 airfoil. The first of the jet positions is located at 12% of the chord, hereby referred to as the leading edge Synthetic Jet Actuator. The second exit position is located at 99% chord of an airfoil and hereby is referred to as the trailing edge Synthetic Jet Actuator. The two locations produced different benefits as the angle of attack of the wing was increased. The leading edge Synthetic Jet Actuator delayed the onset of stall of an airfoil, suppressing stall up to 25 degrees angle of attack. The control of the aerodynamic characteristics was achieved by influencing the amount of the separated flowfield region. The effects of the dynamic stall vortex were investigated with wind tunnel testing during the pitching motion of an airfoil to determine how the flow reacts dynamically. The trailing edge synthetic jet actuator was investigated as a form of low angle "hingeless" control. The study investigated the effect of the jet momentum coefficient on the ability of the synthetic jet to modify the lifting and pitching moment produced from the wind tunnel model. The data indicates that, with the present implementation, the SJA-jet flap generates moderate lift and moment coefficient increments that should be suitable for hinge- less control. It was also shown that, for the current experimental setup and a given jet momentum coefficient, continuous blowing is more effective than oscillatory blowing/sucking. The data shows that combining the SJA with a Gurney flap does not result in performance enhancement.
Hingeless Flow Control Over An Airfoil Via Distributed Actuation
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Author : Anmol Agrawal
language : en
Publisher:
Release Date : 2007
Hingeless Flow Control Over An Airfoil Via Distributed Actuation written by Anmol Agrawal and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2007 with categories.
An experimental investigation was undertaken to test the effectiveness of a novel design for controlling the aerodynamics of an airfoil. A synthetic jet actuator (SJA) was placed inside a NACA 0015 airfoil with its jet at 12.5% of the chord length, hereby referred to as the leading edge actuator. Four centrifugal fans across the span were mounted at 70%of the chord and the jet formed by them was located at 99% of the chord, hereby referred to as the trailing edge actuator. The effects of these actuators on the aerodynamic properties were studied, separately and then in conjunction, with varying angles of attack. The leading edge actuator delays the onset of stall up to 24 degrees, the maximum angle of attack that could be attained. The control of the aerodynamics was achieved by controlling the amount of separated region. There was no effect of the actuation at lower angles of attack. The trailing edge actuator provides aerodynamic control at both low and high angles of attack. The study investigated the effect of jet momentum coefficient on the aerodynamic properties for various angles of attack. The data obtained shows that lift control (in both positive and negative direction) was achieved even at low angles. The actuator enhances the aerodynamic properties by changing the pressure distribution as well as by delaying flow separation. Study of the combined actuation shows that the synthetic jet actuator was very effective in delaying stall when the trailing edge jet was ejected from the upper surface. For the case when the jet is ejected from the lower surface, there is less control. This can be accounted for by the difference in aerodynamic loading for both cases.
Advances In Effective Flow Separation Control For Aircraft Drag Reduction
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Author : Ning Qin
language : en
Publisher: Springer Nature
Release Date : 2019-10-17
Advances In Effective Flow Separation Control For Aircraft Drag Reduction written by Ning Qin and has been published by Springer Nature this book supported file pdf, txt, epub, kindle and other format this book has been release on 2019-10-17 with Technology & Engineering categories.
This book presents the results of a European-Chinese collaborative research project, Manipulation of Reynolds Stress for Separation Control and Drag Reduction (MARS), including an analysis and discussion of the effects of a number of active flow control devices on the discrete dynamic components of the turbulent shear layers and Reynolds stress. From an application point of view, it provides a positive and necessary step to control individual structures that are larger in scale and lower in frequency compared to the richness of the temporal and spatial scales in turbulent separated flows.
Numerical Simulation Of Synthetic Jets
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Author : Alejandra Lorenzo Mora
language : en
Publisher:
Release Date : 2017
Numerical Simulation Of Synthetic Jets written by Alejandra Lorenzo Mora 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.
Synthetic jet actuators (SJA) or zero-net mass flux (ZNMF) actuators are devices consisting of a cavity with a small orifice or slot, inside of which is a moving oscillator. Thecavity is connected to the external medium by means of a neck. The oscillator drivercan be a diaphragm, whose periodic movement makes the fluid leave and enter the cav-ity. When the flow exits from the neck a train of vortices is formed, to be able to obtainthe jet, these vortices cannot be swallowed back into the cavity when the membrane is moving down. To ensure that this is not happening the parameter jet formation criteria(JFC) is defined. The JFC only depends on geometrical parameters as the longitudeand the amplitude of the membrane, when the movement of the membrane is periodic.When the jet is successfully formed, it is able to transfer kinetic energy and momentumto the fluid without a mass addition. Several potential applications of this technologyexist, e.g, active flow control (AFC), cooling and fuel mixing.The present work solves a SJA impinged into a hot wall. The case at low Reynolds(Re= 50) is considered to be laminar and incompressible. Four different neck longitudes are compared to see which is the importance of the neck length. The strategy to solve these cases is running three meshes with different densities. The simulationwith the less dense mesh can run more cycles spending less computational time, theresults of this mesh are the inputs of the denser mesh. The case is configured usingmoving mesh techniques for the actuator membrane. In this situation, the decouplingof velocity and frequency is no longer possible and other strategies need to be applied.Velocity and temperature are found to reach a steady state after about 50 actuatorcycles, however, the Nusselt number features a low frequency that makes the whole case longer to converge. It is estimated that a number of around 200 actuator cyclesare needed for the Nusselt number to reach the steady state. This fact complicates theflow, despite the fact that the Reynolds number is low. The effect of changing the necklength has a direct effect on the velocity but has little influence on the temperature orthe Nusselt number.