Numerical Simulation Of Synthetic Jet Actuators

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Numerical Simulation Of Synthetic Jet Actuators

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Author : Linda D. Kral
language : en
Publisher:
Release Date : 1997

Numerical Simulation Of Synthetic Jet Actuators written by Linda D. Kral and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 1997 with categories.

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.

Numerical Simulation Of The Interaction Of Adjacent Synthetic Jet Actuators

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Author : Dahai Guo
language : en
Publisher:
Release Date : 2000

Numerical Simulation Of The Interaction Of Adjacent Synthetic Jet Actuators written by Dahai Guo and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2000 with categories.

Handbook Of Numerical Simulation Of In Flight Icing

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Author : Wagdi George Habashi
language : en
Publisher: Springer Nature
Release Date : 2023-12-11

Handbook Of Numerical Simulation Of In Flight Icing written by Wagdi George Habashi and has been published by Springer Nature this book supported file pdf, txt, epub, kindle and other format this book has been release on 2023-12-11 with Technology & Engineering categories.

This Handbook of Numerical Simulation of In-Flight Icing covers an array of methodologies and technologies on numerical simulation of in-flight icing and its applications. Comprised of contributions from internationally recognized experts from the Americas, Asia, and the EU, this authoritative, self-contained reference includes best practices and specification data spanning the gamut of simulation tools available internationally that can be used to speed up the certification of aircraft and make them safer to fly into known icing. The collection features nine sections concentrating on aircraft, rotorcraft, jet engines, UAVs; ice protection systems, including hot-air, electrothermal, and others; sensors and probes, CFD in the aid of testing, flight simulators, and certification process acceleration methods. Incorporating perspectives from academia, commercial, government R&D, the book is ideal for a range of engineers and scientists concerned with in-flight icing applications.

Unsteady Numerical Simulations Of Subsonic Flow Over A Projectile With Jet Interaction

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Author : Jabaraj Sahu
language : en
Publisher:
Release Date : 2003

Unsteady Numerical Simulations Of Subsonic Flow Over A Projectile With Jet Interaction written by Jabaraj Sahu and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2003 with Aerodynamics categories.

This report describes a computational study undertaken to consider the aerodynamic effect of synthetic jets as a means to provide the control authority needed to maneuver a projectile at low subsonic speeds. The time-accurate Navier-Stokes computational technique has been used to obtain numerical solutions for the unsteady jet interaction flow field for a projectile at a subsonic speed, Mach = 0.11, and several angles of attack from O deg to 4 deg. Qualitative flow field features show the interaction of the time dependent jet with the free stream flow. Numerical results show the effect of the jet on the flow field, surface pressures and aerodynamic coefficients. Unsteady numerical results have been obtained for a two-dimensional jet flow and compared with experimental data for validation. The same unsteady jet modeling technique has been applied to a subsonic projectile. These numerical results are being assessed to determine if synthetic jets can be used to provide the control authority needed for maneuvering munitions to hit the targets with precision.

Synthetic Jets

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Author : Kamran Mohseni
language : en
Publisher: CRC Press
Release Date : 2014-09-17

Synthetic Jets written by Kamran Mohseni and has been published by CRC Press this book supported file pdf, txt, epub, kindle and other format this book has been release on 2014-09-17 with Science categories.

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.

A Reduced Order Model For Efficient Simulation Of Synthetic Jet Actuators

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Author : National Aeronautics and Space Administration (NASA)
language : en
Publisher: Createspace Independent Publishing Platform
Release Date : 2018-08-29

A Reduced Order Model For Efficient Simulation Of Synthetic Jet Actuators written by National Aeronautics and Space Administration (NASA) and has been published by Createspace Independent Publishing Platform this book supported file pdf, txt, epub, kindle and other format this book has been release on 2018-08-29 with categories.

A new reduced-order model of multidimensional synthetic jet actuators that combines the accuracy and conservation properties of full numerical simulation methods with the efficiency of simplified zero-order models is proposed. The multidimensional actuator is simulated by solving the time-dependent compressible quasi-1-D Euler equations, while the diaphragm is modeled as a moving boundary. The governing equations are approximated with a fourth-order finite difference scheme on a moving mesh such that one of the mesh boundaries coincides with the diaphragm. The reduced-order model of the actuator has several advantages. In contrast to the 3-D models, this approach provides conservation of mass, momentum, and energy. Furthermore, the new method is computationally much more efficient than the multidimensional Navier-Stokes simulation of the actuator cavity flow, while providing practically the same accuracy in the exterior flowfield. The most distinctive feature of the present model is its ability to predict the resonance characteristics of synthetic jet actuators; this is not practical when using the 3-D models because of the computational cost involved. Numerical results demonstrating the accuracy of the new reduced-order model and its limitations are presented.Yamaleev, Nail K. and Carpenter, Mark H.Langley Research CenterACTIVE CONTROL; JET FLOW; FINITE DIFFERENCE THEORY; NAVIER-STOKES EQUATION; ACTUATORS; CAVITY FLOW; THREE DIMENSIONAL MODELS; COMPUTATIONAL GRIDS; TIME DEPENDENCE...

Vortex Rings And Jets

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Author : Daniel T. H. New
language : en
Publisher: Springer
Release Date : 2015-03-26

Vortex Rings And Jets written by Daniel T. H. New and has been published by Springer this book supported file pdf, txt, epub, kindle and other format this book has been release on 2015-03-26 with Technology & Engineering categories.

In this book, recent developments in our understanding of fundamental vortex ring and jet dynamics will be discussed, with a view to shed light upon their near-field behaviour which underpins much of their far-field characteristics. The chapters provide up-to-date research findings by their respective experts and seek to link near-field flow physics of vortex ring and jet flows with end-applications in mind. Over the past decade, our knowledge on vortex ring and jet flows has grown by leaps and bounds, thanks to increasing use of high-fidelity, high-accuracy experimental techniques and numerical simulations. As such, we now have a much better appreciation and understanding on the initiation and near-field developments of vortex ring and jet flows under many varied initial and boundary conditions. Chapter 1 outlines the vortex ring pinch-off phenomenon and how it relates to the initial stages of jet formations and subsequent jet behaviour, while Chapter 2 takes a closer look at the behaviour resulting from vortex ring impingement upon solid boundaries and how the use of a porous surface alters the impingement process. Chapters 3 and 4 focus upon the formation of synthetic jets from vortex ring structures experimentally and numerically, the challenges in understanding the relationships between their generation parameters and how they can be utilized in flow separation control problems. Chapter 5 looks at the use of imposing selected nozzle trailing-edge modifications to effect changes upon the near-field dynamics associated with circular, noncircular and coaxial jets, with a view to control their mixing behaviour. And last but not least, Chapter 6 details the use of unique impinging jet configurations and how they may lend themselves towards greater understanding and operating efficacies in heat transfer problems. This book will be useful to postgraduate students and researchers alike who wish to get up to speed regarding the latest developments in vortex ring and jet flow behaviour and how their interesting flow dynamics may be put into good use in their intended applications.

Direct Computations Of A Synthetic Jet Actuator

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Author : Declan Hayes-McCoy
language : en
Publisher:
Release Date : 2012

Direct Computations Of A Synthetic Jet Actuator written by Declan Hayes-McCoy and has been published by this book supported file pdf, txt, epub, kindle and other format this book has been release on 2012 with categories.

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.

Investigation Of Synthetic Jets Heat Transfer And Flow Field

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Author : Carlo Salvatore Greco
language : en
Publisher: Youcanprint
Release Date : 2015-04-30

Investigation Of Synthetic Jets Heat Transfer And Flow Field written by Carlo Salvatore Greco and has been published by Youcanprint this book supported file pdf, txt, epub, kindle and other format this book has been release on 2015-04-30 with Technology & Engineering categories.

Synthetic jets are devices able to “synthetize” a jet from the ambient in which they are embedded through a simple membrane oscillation inside a cavity with an orifice. Such features make them high reliable, silent and easy to be miniaturized. For these reasons, they are widely investigated as electronic cooling devices. The present research is focused on the design and analysis of a different type of synthetic jet device compared to its single classical configuration. Such a device his experimentally characterized through the study of its free and impinging flow field and the evaluation of its heat transfer performance.