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 Time Accurate Aerodynamic Modeling of Synthetic Jets for Projectile Control written by and published by . This book was released on 2004 with total page 7 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 Time Accurate Simulations of Synthetic Jet Based Flow Control for An Axisymmetric Spinning Body written by and published by . This book was released on 2004 with total page 29 pages. Available in PDF, EPUB and Kindle. Book excerpt: This report describes a computational study undertaken to consider the aerodynamic effect of synthetic jets as a means of providing the control authority needed to maneuver a projectile at a low subsonic speed. A time-accurate Navier-Stokes computational technique has been used to obtain numerical solutions for the unsteady jet-interaction flow field for a spinning projectile at a subsonic speed, Mach 0.24, and angle of attack, 0 degree. Numerical solutions have been obtained by Reynolds-averaged Navier-Stokes (RANS) and hybrid RANS-large-eddy simulation turbulence models. Unsteady numerical results show the effect of the jet on the flow field and the aerodynamic coefficients, particularly the lift force. These numerical results are being used to assess if synthetic jets can be used to provide the control authority needed for maneuvering munitions to hit the targets with precision.
Download or read book Time accurate Simulations of Synthetic Jet based Flow Control for an Axisymmetric Spinning Body written by and published by . This book was released on 2004 with total page 21 pages. Available in PDF, EPUB and Kindle. Book excerpt: This report describes a computational study undertaken to consider the aerodynamic effect of synthetic jets as a means of providing the control authority needed to maneuver a projectile at a low subsonic speed. A time-accurate Navier-Stokes computational technique has been used to obtain numerical solutions for the unsteady jet-interaction flow field for a spinning projectile at a subsonic speed, Mach 0.24, and angle of attack, 0 degree. Numerical solutions have been obtained by Reynolds-averaged Navier-Stokes (RANS) and hybrid RANS-large-eddy simulation turbulence models. Unsteady numerical results show the effect of the jet on the flow field and the aerodynamic coefficients, particularly the lift force. These numerical results are being used to assess if synthetic jets can be used to provide the control authority needed for maneuvering munitions to hit the targets with precision.
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 378 pages. Available in PDF, EPUB and Kindle. Book excerpt: Compiles Information from a Multitude of SourcesSynthetic 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.
Download or read book Flow Control Techniques and Applications written by Jinjun Wang and published by Cambridge University Press. This book was released on 2019 with total page 293 pages. Available in PDF, EPUB and Kindle. Book excerpt: Master the theory, applications and control mechanisms of flow control techniques.
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 Direct Computations of a Synthetic Jet Actuator written by Declan Hayes-McCoy and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Synthetic jet actuators have previously been defined as having potential use in both internal and external aerodynamic applications. The formation of a jet flow perpendicular to the surface of an aerofoil or in a duct of diffuser has a range of potential flow control benefits. These benefits can include both laminar to turbulent transition control, which is associated with a drag reduction in aerodynamic applications. The formation and development of zero-net-mass-flux synthetic jets are investigated using highly accurate numerical methods associated with the methodology of Direct Numerical Simulation (DNS). Jet formation is characterised by an oscillating streamwise jet centreline velocity, showing net momentum flux away from the jet orifice. This momentum flux away from the orifice takes the form of a series of vortex structures, often referred to as a vortex train. Numerical simulations of the synthetic jet actuator consist of a modified oscillating velocity profile applied to a wall boundary. The Reynolds numbers used vary from 85 ≤ Re ≤ 300. A complete numerical study of both axisymmetric and fully three-dimensional jet flow is performed. A parametric axisymmetric simulation is carried out in order to study the formation criterion and evolution of zero-net-mass-flux synthetic jets under variations in actuator input parameters. From the results of these simulations the conditions necessary for the formation of the synthetic jet along with the input parameters that provide an optimal jet output are deduced. Jet optimisation is defined by the mass flow, vortex strength and longevity of the vortex train as it travels downstream. Further investigations are carried out on a fully three-dimensional DNS version of the optimised axisymmetric case. Comparisons between the jet evolution and flow-field structures present in both the axisymmetric and three-dimensional configurations are made. This thesis examines the vortex structures, the jet centreline velocities along with time dependent and time averaged results in order to deduce and visualise the effects of the input parameters on the jet formation and performance. The results attained on altering the oscillation frequency of the jet actuator indicated that synthetic jets with zero mean velocity at the inflow behave significantly differently from jets with non-zero mean velocity at the inflow. A study into the evolution and formation of the train of vortex structures associated with the formation of a synthetic jet is performed. This study is accompanied with a series of time averaged results showing time dependent flow-field trends. The time history of the jet centreline velocity, showing the net momentum flux of the fluid away from the orifice of a fully developed synthetic jet, is analysed for both axisymmetric and three-dimensional cases. Differences in the fluid dynamics between the idealised axisymmetric configuration and the three-dimensional case have been identified, where three-dimensional effects are found to be important in the region near the jet nozzle exit. The effect of a disturbance introduced into the three-dimensional simulation in order to break its inherent symmetry around the jet centreline is examined by altering the input frequency of the disturbance. It was found that the effect of this relatively minor disturbance had a major effect on the jet flow field in the region adjacent to the orifice. The effect of which was deemed to be caused by discontinuities in the surface of the jet orifice due to manufacturing tolerances. Although the effects of these disturbances on the jet flow-field are large, they seem to have been neglected from numerical simulations to date. The effect of a synthetic jet on an imposed cross-streamwise velocity profile was examined. It was found that the synthetic jet flow-field resulted in a deformation of the velocity profile in the region downstream of the synthetic jet. It is suggested that this region of deformed flow could interact with coherent structures in a transitional boundary layer in order to delay flow transition to turbulence. The effect of varying the Strouhal number of a synthetic jet in a cross-flow is also analysed. It is clear from the results presented that, in the presence of a cross-flow velocity the Strouhal number effect on the synthetic jet flow field evolution, while dominant in a quiescent fluid is surpassed by the effect of the cross-flow.
Download or read book Synthetic Jets Their Reduced Order Modeling and Applications to Flow Control written by O.K. Rediniotis and published by . This book was released on 1999 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
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 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 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 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 Flow and Heat Transfer of Impinging Synthetic Jets written by Arnau Miró Jané and published by . This book was released on 2019 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Synthetic jets are produced by the oscillatory movement of a membrane inside a cavity, causing fluid to enter and leave through a small orifice. This results in a net jet that is able to transfer kinetic energy and momentum to a fluid medium without the need of an external fluid source. This is why synthetic jets are interesting and will have key roles in a wide range of relevant applications such as active flow control, thermal cooling or fuel mixing. From the phenomenological point of view, synthetic jets are formed by elaborate flow patterns given their non-linear nature and, under certain conditions, unstable complex flows can be observed. The present dissertation is focused on the investigation of the fluid flow and thermal performance of synthetic jets. Two different synthetic jet actuator geometries (i.e., slotted and circular) are studied. The jets in both configurations are confined by two parallel isothermal plates with an imposed temperature difference, and impinge into a heated plate located at a certain distance from the actuator orifice. The unsteady three-dimensional Navier-Stokes equations are solved for a range of Reynolds numbers using time-accurate numerical simulations. Moreover, a detailed model of the actuator that uses Arbitrary Lagrangian-Eulerian (ALE) formulation to account for the movement of the actuator membrane is developed. This model, based on the governing numbers of the flow, is used to conduct the numerical analyses. The flows obtained in both configurations are noticeably different and three-dimensional for almost all the Reynolds numbers considered. The jet in the slotted configuration is formed by a pair of vortices that undergo turbulent transition and eventually coalesce into the jet. The external flow is dominated by two major recirculation structures that find their counterparts inside the actuator cavity. A new vortical structure, observed in confined slotted jets, appears as an interaction of the synthetic jet flow with the bottom wall and results in a change on the jet's heat transfer mechanisms. On the other hand, the jet in the circular configuration presents three different flow regions that have been identified according to the literature: the main vortex ring, the trailing jet and the potential core. In this case, the external flow is dominated by the main vortex ring and the trailing jet, thus presenting a different morphology and heat transfer behavior than the slotted configuration. A detailed analysis of the vortex trajectories has shown that the advected vortices on the circular configuration reach the impingement before their slotted counterparts. Distributions of turbulent kinetic energy at the expulsion and vortex swirl and shear strength have revealed that the flow on the circular jet is mostly concentrated near the jet centerline, while it is more spread for the slotted configuration. For these reasons, at the same jet ejection velocity and actuator geometry, synthetic jet formation on the circular configuration can occur at higher frequencies than on the slotted configuration. The analysis of the synthetic jet outlet temperature has shown that assuming a uniform profile is reasonable if the Reynolds number is high enough. Moreover, the outlet jet temperature is significantly higher than the cold plate temperature. The two configurations present different impinging behaviors due to the differences on the flow. Heat transfer analysis on the hot wall has revealed that the circular configuration reaches a higher heat transfer peak than the slotted configuration, however, heat transfer decays faster in the circular configuration when moving away from the jet centerline. Eventually, correlations for the heat transfer at the hot wall and the outlet temperature with the Reynolds number are proposed. They can be useful to include the cavity effects when using simplified models that do not account for actuator cavity.
Download or read book Large Eddy Simulation of Synthetic Jets in the Context of Flow Control written by and published by . This book was released on 2008 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Modelling Design and Implementation of Synthetic Jets for Flow Control written by Nicholas D. Martin 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 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:
