Download or read book CFD Study of a Bidirectional Synthetic Jet as an Aerodynamic Flow Control Device written by Jaime Rodrigo Fisher Fernandez and published by . This book was released on 2018 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Aerodynamic Flow Control Using Synthetic Jet Technology written by Michael Amitay 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 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 Aerodynamic Flow Control of a High Lift System with Dual Synthetic Jet Arrays written by Robert Bruce Alstrom and published by . This book was released on 2014 with total page 378 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Study of the Boundary Layer Flow Control Using Synthetic Jets by Means of Spectro consistent Discretizations written by David Duran Perez and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This report presents a study of the interaction of AFC (specifically, synthetic jets) with the laminar boundary layer of a NACA 0012 airfoil. First of all, in order to understand the phenomenology of Navier-Stokes equations, a spectro-consistent Computational Fluid Dynamics (CFD) code has been developed from scratch. By using a spectro-consistent discretization, the fundamental symmetry properties of the underlying differential operators are preserved. This code also helps to understand how the energy is transported from big to small scales. After solving a paradigmatic problem (TGV) using the aforementioned code, a mature CFD code (Alya) is used to simulate the flow around the NACA 0012 airfoil. Alya software also uses a spectro-consistent code but in Finite Element Method (FEM). Once the reference cases are solved for different angles of attack, a boundary condition representing an idealized synthetic jet is implemented. A systematic parametrization of the synthetic jet has been performed in order to assess the level of flow control in the boundary layer. Results demonstrate that, by selecting a correct combination of actuator frequency and momentum coefficient, the lift coefficient increases while the drag coefficient decreases producing a better lift-to-drag ratio. This aerodynamic improvement implies that a better circulation control is achieved, less noise is produced and less fuel consumption is required. It is also worth noting that, for high angles of attack, it is necessary to perform 3D flow simulations in order to capture the entire physics of the problem.
Download or read book Time Accurate Aerodynamic Modeling of Synthetic Jets for Flow Control written by and published by . This book was released on 2003 with total page 9 pages. Available in PDF, EPUB and Kindle. Book excerpt: This paper describes a computational study undertaken to determine the aerodynamic effect of tiny unsteady synthetic jets as a means to provide the control authority needed to maneuver a spinning projectile at low subsonic speeds. Advanced Navier-Stokes computational techniques have been developed and used to obtain numerical solutions for the unsteady jet-interaction flow field at subsonic speeds and small angles of attack. Unsteady numerical results show the effect of the jet on the flow field and on the aerodynamic coefficients. The unsteady jet is shown to substantially alter the flow field both near the jet and the base region of the projectile that in turn affects the forces and moments even at zero degree angle of attack. The results have shown the potential of computational fluid dynamics to provide insight into the jet interaction flow fields and provided guidance as to the locations and sizes of the jets to generate the maximum control authority to maneuver a projectile to hit its target with precision.
Download or read book Unsteady Aerodynamics of Airfoils and Characterization and Modeling of Axisymmetric Synthetic Jets written by Xi Xia and published by . This book was released on 2018-11-29 with total page 288 pages. Available in PDF, EPUB and Kindle. Book excerpt: Abstract: This thesis has two main parts. The aerodynamic part is motivated by the interest in unveiling the flying secrets of natural fliers, e.g. birds and insects. The understandings will provide insights in the design and control of micro air vehicles (MAVs) for improved aerodynamic performance. The second part of the thesis focuses on the study of synthetic jets for aerodynamic flow control over MAVs. This is motivated by the promising effects of synthetic jets in enhancing mixing and controlling flow separation. The thesis starts with the unsteady aerodynamic modeling of a flat plate based on the Joukowski transformation and vortex method. The analytical solution includes both translational and rotational motions of the flat plate. The force calculation suggests that the lift generation caused by a stabilized leading edge vortex is a combined effect of the motions of both leading-edge and trailing-edge vortices. To extend this model to an arbitrarily-shaped airfoil, the wall boundary condition on the airfoil is enforced by introducing a bound vortex sheet at the location of the airfoil boundary. Furthermore, an analytical vortex-sheet formation condition is proposed to accurately evolve the wake vortices, and is based on the conservation laws of mass and momentum as well as Kelvin's circulation theorem. This condition resolves the paradox of the Giesing-Maskell model, which does not recover the steady-state Kutta condition. The thesis continues with an investigation of synthetic jets in a quiescent environment. An effective-eddy-viscosity concept is adopted to provide a unified modeling approach for the entrainment and mixing of any round jet, continuous or synthetic. The experimental study is focused on characterizing the spreading and decay features in the transitional region and far field of synthetic jets. The far-field momentum flux of a synthetic jet is modeled by calculating the hydrodynamic impulse of the vortical structure formed in the near field. Synthetic jets issuing into a crossflow are also studied and a self-similar model is developed for the trajectory and velocity of the midplane flow field. It is found that the crossflow velocity is enhanced in the near field due to the induced effect of the tilted vortex rings. This finding provides an auxiliary explanation for the mechanism of a synthetic jet in flow-separation control. Dissertation Discovery Company and University of Florida are dedicated to making scholarly works more discoverable and accessible throughout the world. This dissertation, "Unsteady Aerodynamics of Airfoils and Characterization and Modeling of Axisymmetric Synthetic Jets" by Xi Xia, was obtained from University of Florida and is being sold with permission from the author. A digital copy of this work may also be found in the university's institutional repository, IR@UF. The content of this dissertation has not been altered in any way. We have altered the formatting in order to facilitate the ease of printing and reading of the dissertation.
Download or read book The Isolated Synthetic Jet in Crossflow written by Norman W. Schaeffler and published by BiblioGov. This book was released on 2013-08 with total page 40 pages. Available in PDF, EPUB and Kindle. Book excerpt: An overview of the data acquisition, reduction, and uncertainty of experimental measurements made of the flowfield created by the interaction of an isolated synthetic jet and a turbulent boundary layer is presented. The experimental measurements were undertaken to serve as the second of three computational fluid dynamics validation databases for Active Flow Control. The validation databases were presented at the NASA Langley Research Center Workshop on CFD Validation of Synthetic Jets and Turbulent Separation Control in March, 2004. Detailed measurements were made to document the boundary conditions for the flow and also for the phase-averaged flowfield itself. Three component Laser-Doppler Velocimetry, 2-D Particle Image Velocimetry, and Stereo Particle Image Velocimetry were utilized to document the phase-averaged velocity field and the turbulent stresses.
Download or read book Transverse and Near tangent Synthetic Jets for Aerodynamic Flow Control written by Ahmed A. Hassan and published by . This book was released on 2000 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Study of the Passive Flow Control in Aerodynamic Devices written by David Guiu Soler and published by . This book was released on 2018 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The principal aim of this study is to analyse how the boundary layer separation can becontrolled in a tridimensional cylinder with the application of a passive flow control deviceon its surface.The study is carried out by means of CFD techniques, so the secondary objectives ofthe study are to develop CFD skills as well as learning how to manage the different pro-grammes and methodologies required to conduct the analysis, regarding the geometry andmesh generation and the interpretation of the post-processed results.
Download or read book Recent Development of Aerodynamic Design Methodologies written by Kozo Fujii and published by Springer Science & Business Media. This book was released on 2013-04-17 with total page 228 pages. Available in PDF, EPUB and Kindle. Book excerpt: Computational Fluid Dynamics (CFD) has made remarkable progress in the last two decades and is becoming an important, if not inevitable, analytical tool for both fundamental and practical fluid dynamics research. The analysis of flow fields is important in the sense that it improves the researcher's understanding of the flow features. CFD analysis also indirectly helps the design of new aircraft and/or spacecraft. However, design methodologies are the real need for the development of aircraft or spacecraft. They directly contribute to the design process and can significantly shorten the design cycle. Although quite a few publications have been written on this subject, most of the methods proposed were not used in practice in the past due to an immature research level and restrictions due to the inadequate computing capabilities. With the progress of high-speed computers, the time has come for such methods to be used practically. There is strong evidence of a growing interest in the development and use of aerodynamic inverse design and optimization techniques. This is true, not only for aerospace industries, but also for any industries requiring fluid dynamic design. This clearly shows the matured engineering need for optimum aerodynamic shape design methodologies. Therefore, it seems timely to publish a book in which eminent researchers in this area can elaborate on their research efforts and discuss it in conjunction with other efforts.
Download or read book Investigation of Co Flow Jet Flow Control and Its Applications written by Alexis Michel Lefebvre and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis investigates the performance of co-flow jet (CFJ) flow control and its applications using experimental testing and computational fluid dynamics (CFD) simulations. First, the study examines the CFJ energy expenditure, lift enhancement, drag reduction, stall margin increase, dynamic stall removal, and performance variation with Mach number. These investigations are conducted for a variety of stationary airfoils, pitching airfoils, and 3D CFJ wings. Then, the CFJ airfoil is applied to design an ultra-high wing loading general aviation electric airplane (EA). For a stationary airfoil and wing, CFJ increases the lift coefficient (CL), reduces the drag and may produce thrust at a low angle of attack (AoA). The maximum lift coefficient is substantially increased for a 2D CFJ airfoil and reaches a value of 4.8 at C[mu] = 0.30. The power consumption of the CFJ pump, measured by the power coefficient (Pc), is influenced by a variety of parameters, including themomentum coefficient (C[mu] ), the AoA, the injection slot location, and the internal cavity configuration. A low C[mu] of 0.04 produces a rather small Pc in the range of 0.01 - 0.02 while a higher C[mu] rapidly increases the Pc. Due to the stronger leading edge suction effect, increasing the AoA decreases the Pc. That is until the flow is near separation, within about 2°- 3° of the stall AoA. An injection slot location within 2% - 5% chord from the leading edge very effectively reduces the power coefficient since the leading edge suction effect is typically the strongest within this range. An internal cavity design with no separation is crucial to minimize the CFJ power consumption. When the Mach number is increased from 0.03 to 0.3, the suction pressure behind the airfoil leading edge is lowered due to the compressibility effect. This increases the CFJ airfoil maximum lift coefficient and decreases the power coefficient because of the lower required jet injection pressure. The drag coefficient remains fairly stable within this range of Mach numbers. At Mach 0.4, as the AoA increases, the flow on the suction surface becomes transonic. Consequently, a strong shock wave interrupts the jet and triggers a boundary-layer separation. The shock wave boundary-layer interaction and wave drag increase the total drag and the power coefficient significantly due to a large increase in entropy. Overall, the CFJ effectiveness is enhanced with an increasing Mach number as long as the flow remains subsonic, typically with free stream Mach number less than 0.4. For a pitching airfoil, CFJ is able to remove the dynamic stall with a substantial lift increase and drag decrease. Two pitching airfoil oscillations with dynamic stall are studied in this thesis, namely the mild dynamic stall and the deep dynamic stall. At Mach 0.3, the CFJ with a relatively low C[mu] of 0.08 removes the mild dynamic stall. Thereby, the timeaveraged lift is increased by 32% and the time-averaged drag is decreased by 80%. The resulting time-averaged aerodynamic (L/D)ave, which does not take the pumping power into account, reaches 118.3. When C[mu] is increased, the time-averaged drag becomes negative, which demonstrates the feasibility of a CFJ to propel helicopter blades using its pump as the only source of power. The deep-stall is mitigated at C[mu] = 0.12 and completely removed at C[mu] = 0.20 with a great (L/D)ave increase. At Mach 0.4, the CFJ mitigates the mild dynamic stall. However, the energy consumption is higher than at Mach 0.3 due to the appearance of shock waves in the flow. A 3D CFJ wing based on NACA 6415 airfoil with an aspect ratio of 20 produces a maximum L/D of 38.5 at a remarkably high cruise CL of 1.20 with an AoA of 5.0° and a low C[mu] of 0.04. The takeoff and landing performance is also excellent with a maximum CL of 4.7 achieved at C[mu] of 0.28 and AoA of 40.0°. When the wing thickness is increased from 15% to 21%, not only the lift is increased by about 5% but the structural strength is also improved. Overall the CFJ wing efficiency is found to be similar to that of conventional wings, but the lift coefficient at cruise condition is much higher, typically by 2-3 times. Hence CFJ is particularly suitable to design a compact wing with high wing loading. In the final study of this thesis, a CFJ Electric Aircraft (CFJ-EA) is designed for the general aviation. The aircraft has a high wing loading so that it can carry more battery and reach a longer range with a relatively small wing size. The CFJ-EA mission is to carry 4 passengers at a cruise Mach number of 0.15 with a range of 315nm. The CFJ-EA cruises at a very high CL of 1.3, which produces a wing loading of 182.3kg/m2, about 3 times higher than that of a conventional general aviation airplane. To determine the aircraft range and endurance, we introduce the corrected aerodynamic efficiency (L/D)c defined as (L/D)c = L/(D+P/Vinf), where the L and D are the aerodynamic lift and drag, P is the CFJ pumping power and Vinf is the free stream velocity. The (L/D)c of the CFJ-EA is excellent with a cruise value of 23.5 at a low C[mu] of 0.04. Takeoff and landing distances are also good due to a very high maximum CL of 4.8, achieved with a high C[mu] of 0.28. During takeoff and landing, the wing pivots around its 1/4 chord axis so that it can achieve an AoA of 25.0° with the fuselage rotated by only 5.0°. Based on a measure of merit defined as MPS=Miles*Passengers/S, where S is the wing planform area, the MPS of the present EA design is about half that of a conventional reciprocating engine general aviation airplane, and is 1.5 to 2.5 times greater than the MPS of the state of the art EA. This suggests that, compared to the conventional EA, a same size CFJ-EA has a far greater range, or a smaller CFJ-EA achieves the same range. Therefore, the CFJ-EA concept may open the door to a new class of general aviation EA designs. The same CFJ airfoil flow control technology is also suitable for airplanes and rotorcraft using conventional propulsion systems including high altitude planform, general aviation, commercial aviation or military transport to improve the range, reduce the wing size and/or reduce the takeoff and landing distances.
Download or read book The Current Status of Unsteady CFD Approaches for Aerodynamic Flow Control written by Mark H. Carpenter 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 Synthetic Jets written by Kamran Mohseni and published by CRC Press. This book was released on 2014-09-17 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Compiles Information from a Multitude of Sources Synthetic jets have been used in numerous applications, and are part of an emergent field. Accumulating information from hundreds of journal articles and conference papers, Synthetic Jets: Fundamentals and Applications brings together in one book the fundamentals and applications of fluidic actuators. Clearly and thoroughly explaining the mechanisms of underlying synthetic jet behavior—from aerospace to mechanical engineering—this book addresses a variety of aspects, and provides a holistic, systematic approach of the subject. Covers Fundamental Principles, Analysis Techniques, and Applications Designed as a starting point for newcomers, the book is divided into three parts: fundamentals, techniques, and applications, and focuses on a class of incompressible jet flows where the jet is made up of the surrounding fluid. It explores fluid dynamics, hydrodynamic modeling, acoustics, and fabrication. It covers key measurement techniques, computational modeling, and synthetic jet design. In addition to highlighting the concepts and applications of synthetic jets, (in particular their uses in flow control and thermal management in electronic devices), the book explores attempts to improve and accelerate the design and optimization processes (from flow control to electronic cooling and propulsion) involved in a wealth of applied knowledge. Features prominent experts in the field Surveys the state of the art Details a pathway to future advances in the industry Synthetic Jets: Fundamentals and Applications can be used as a guidebook for researchers, graduate students, and upper-level undergraduate students.
Download or read book Study written by Carlos Martínez Segarra and published by . This book was released on 2020 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: A synthetic jet is formed by the oscillating movement of a membrane located inside a cavity. Such movement allows ambient fluid to be dragged inside and outside, hence producing a jet that is able to transfer both linear momentum and kinetic energy into the system without any external mass flux. It offers multiple interesting applications, the most relevant being active flow control and thermal control of electronic devices. This work focuses on the study of a discharge of a slotted synthetic jet actuator into an opened external medium. Numerical simulations using Large Eddy Simulations have been performed to analyze the jet behavior and vortex dynamics. Three mesh densities and two different cases based on the SJA governing parameters have been evaluated during the analysis. This study reveals that the advected vortex pair reaches a higher altitude before becoming the jet as the jet formation criteria becomes greater. This causes a bigger gradient on turbulent kinetic energy at higher altitudes which is closely related to the distance from the actuator orifice in which the vortex pair starts coalescing into the jet. Vortex penetration also increases with the jet formation criteria as such parameter is directly related to the actuator membrane deflection. A bigger jet formation criteria allows the membrane to deflect more, hence more fluid is dragged downstream resulting in the increase of the linear momentum contribution to the system. Such phenomenon straightaway affects the jet half-width which also increases with the jet formation criteria. This study also reveals that both cases share the same potential core which suggests that the ingestion and expulsion dynamics of a synthetic jet are independent of the jet formation criteria.
Download or read book Inherent and Model form Uncertainty Analysis for CFD Simulation of Synthetic Jet Actuators written by Daoru Han and published by . This book was released on 2011 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: "A mixed aleatory (inherent) and epistemic (model-form) uncertainty quantification (UQ) analysis method was applied to a computational fluid dynamics (CFD) modeling problem of synthetic jet actuators. A test case, (Case 3, flow over a hump model with synthetic jet actuator control) from the CFDVAL2004 workshop was selected to apply the Second-Order Probability framework implemented with a stochastic response surface obtained from Quadrature-Based Non-Intrusive Polynomial Chaos (NIPC). Three uncertainty sources were considered: (1) epistemic uncertainty in turbulence model, (2) aleatory uncertainty in free stream velocity and (3) aleatory uncertainty in actuation frequency. Uncertainties in both long-time averaged and phase averaged quantities were quantified using a fourth order polynomial chaos expansion (PCE). Results were compared with experimental data available. A global sensitivity analysis with Sobol indices was utilized to rank the importance of each uncertainty source to the overall output uncertainty. The results indicated that for the long-time averaged separation bubble size, the uncertainty in turbulence model had a dominant contribution, which was also observed in the long-time averaged skin friction coefficients at three selected locations. For long-time averaged pressure coefficient, the contributions from free stream velocity and turbulence model are depending on the locations. The mixed UQ results for phase averaged x-velocity distributions at three selected locations showed that the 95% confidence intervals (CI) could generally envelope the experimental data. The Sobol indices showed that near the wall, the turbulence model had a main influence on the x-velocity, while approaching the main stream, the uncertainty in free stream velocity became a larger contributor. The uncertainty in frequency was found to have a very small contribution to both long-time averaged and phase averaged quantities with the range of variance considered"--Abstract, leaf iii
Download or read book An Experimental Study of ASTOVL Related Jet Flows to Produce CFD Code Validation Data written by P. Behrouzi and published by . This book was released on 1992 with total page 56 pages. Available in PDF, EPUB and Kindle. Book excerpt:
