Study of a Crossflow over a Zero-Net-Mass-Flux Synthetic Jet Driven by a Vibrating Diaphragm

2011 ◽  
Vol 27 (4) ◽  
pp. 503-509 ◽  
Author(s):  
L.-Y. Tseng ◽  
A.-S. Yang ◽  
J.-C. Lin
Keyword(s):  
Boundary Layer ◽  
Flow Control ◽  
Turbulent Flows ◽  
Mass Flux ◽  
Moving Boundary ◽  
Active Flow Control ◽  
Flow Characteristics ◽  
Synthetic Jet ◽  
Computational Domain ◽  
Zero Net Mass Flux

ABSTRACTMiniature synthetic jet actuators are low operating power, zero-net-mass-flux and very compact devices which have demonstrated their capability in modifying the subsonic flow characteristics for boundary layer flow control. In order to improve the design active flow control systems, the present study aims to examine the formation and interaction of unsteady flowfield of a synthetic jet with external crossflow. In view of a single synthetic jet emitting into a turbulent boundary layer crossflow via a circular orifice, the theoretical model utilized the transient three-dimensional conservation equations of mass and momentum for compressible, turbulent flows with a negligible temperature variation over the computational domain. The motion of a movable membrane plate was also treated as the moving boundary by prescribing the displacement on the plate surface. The predictions by the computational fluid dynamics (CFD) software ACE+®were compared with the measured transient phase-averaged velocities in literature for code validation. The predictions showed the time evolution of the large vortical structure originating from the jet orifice and its successive interaction with the crossflow to change the flow structure inside the boundary layer.

Use of Micro Synthetic Jet Actuators for Boundary Layer Flow Control

2009 ◽  
Vol 74 ◽  
pp. 157-160
Author(s):  
Jing Chuen Lin ◽  
An Shik Yang ◽  
Li Yu Tseng
Keyword(s):  
Boundary Layer ◽  
Flow Control ◽  
Turbulent Flows ◽  
Boundary Layer Flow ◽  
Moving Boundary ◽  
Active Flow Control ◽  
Flow Characteristics ◽  
Synthetic Jet ◽  
Layer Flow ◽  
Active Flow

The main purpose of active flow control research is to develop a cost-effective technology that has the potential for inventive advances in aerodynamic performance and maneuvering compared to conventional approaches. It can be essential to thoroughly understand the flow characteristics of the formation and interaction of a synthetic jet with external crossflow before formulating a practicable active flow control strategy. In this study, the theoretical model used the transient three-dimensional conservation equations of mass and momentum for compressible, isothermal, turbulent flows. The motion of a movable membrane plate was also treated as the moving boundary by prescribing the displacement on the plate surface. The predictions by the computational fluid dynamics (CFD) code ACE+® were compared with measured transient phase-averaged velocities of Rumsey et al. for software validation. The CFD software ACE+® was utilized for numerical calculations to probe the time evolution of the development process of the synthetic jet and its interaction within a turbulent boundary layer flow for a complete actuation cycle.

Active Flow Control With an Oscillating Backward Facing Step in a Shallow Open Channel

2012 ◽  
Author(s):  
Sertac Cadirci ◽  
Hasan Gunes
Keyword(s):  
Boundary Layer ◽  
Flow Control ◽  
Flow Separation ◽  
Open Channel ◽  
Recirculation Zone ◽  
Active Flow Control ◽  
Computational Domain ◽  
Backward Facing Step ◽  
Induced Flow ◽  
Active Flow

An oscillatory, zero-net-mass flux actuator system, Jet and Vortex Actuator (JaVA), is implemented on the step wall of a backward facing step. JaVA can energize the boundary layer by creating jets or vortices thus it may delay flow separation when used properly. The main part of JaVA is a rectangular cavity with a moving actuator plate. The actuator plate is mounted asymmetrically inside the cavity of the JaVA box, such that there are one narrow and one wide gap between the plate and the box. The main governing parameters are the actuator plate’s width (b), the amplitude (a) and the operating frequency (f). The main target of the control with active jets on the step wall is to influence directly the main recirculation zone, thus as the actuator plate or the step’s vertical wall moves periodically in horizontal direction, a jet emerges into the recirculation zone. Non-dimensional numbers such as the scaled amplitude (Sa = 2πa/b) and the jet Reynolds number (ReJ = 4abf/ν) as well as the cross flow parameter characterize the JaVA-induced flow types and the effects on the recirculation zone. One period consists of one blowing and one suction phase into the recirculation zone. Boundary layer profiles extracted from time-averaged flow fields of the not actuated (f = 0) and actuated cases at various operating frequencies indicate the effect of active flow control. The interaction between JaVA-induced flow regimes and the boundary layer is investigated numerically in an open channel with a BFS. The computational domain consists of a moving zone along the channel and the motion of the actuator plate is generated by a moving grid imposing appropriate boundary conditions with User-Defined-Functions and the calculations are carried out by a commercial finite-volume-based unsteady, laminar, incompressible Navier-Stokes solver. Numerical simulations and comparisons reveal the JaVA-boundary layer interaction for various governing parameters. Reynolds numbers based on the step height for the shallow open channel flow are Reh = 225 and 450. The proposed control method based on suction and blowing with an oscillating vertical step seems to be effective in shortening the recirculation zone length and delaying the flow separation downstream of the backward facing step.

scholarly journals Unsteady Simulation of a Synthetic Jet Actuator with Cylindrical Cavity Using a 3-D Lattice Boltzmann Method

2018 ◽  
Vol 2018 ◽  
pp. 1-9 ◽  
Author(s):  
Hongbin Mu ◽  
Qingdong Yan ◽  
Wei Wei ◽  
Pierre E. Sullivan
Keyword(s):  
Lattice Boltzmann Method ◽  
Mass Flux ◽  
Lattice Boltzmann ◽  
Cylindrical Cavity ◽  
Active Flow Control ◽  
Control Device ◽  
Synthetic Jet ◽  
Synthetic Jet Actuator ◽  
Zero Net Mass Flux ◽  
Boltzmann Method

A synthetic jet actuator is a zero-net mass-flux device that imparts momentum to its surroundings and has proved to be a useful active flow control device. Using the lattice Boltzmann method (LBM) with the Bhatnagar-Gross-Krook (BGK) collision models, a 3-D simulation of a synthetic jet with cylindrical cavity employing a sinusoidal velocity inlet boundary condition was conducted. The velocity distributions are illustrated and discussed, and the numerical results are validated against previous experimental data. The computed results show the ingestion and expulsion flow over one working cycle as well as the evolution of vortices important to the control of the separated shear layer. Zero-net mass-flux behavior is confirmed.

Flow Characteristics and Novel Applications of Synthetic Jets - A Review

2021 ◽  
Author(s):  
Pratik Walimbe ◽  
Amit Agrawal ◽  
Mangesh B. Chaudhari
Keyword(s):  
Flow Control ◽  
Active Flow Control ◽  
Acoustic Streaming ◽  
Flow Characteristics ◽  
Electronics Cooling ◽  
Synthetic Jets ◽  
Jet Flows ◽  
Impingement Heat Transfer ◽  
Zero Net Mass Flux ◽  
Novel Applications

Abstract Synthetic jets, often abbreviated as 'SJs' or 'Synjets' are a type of Zero Net Mass Flux (ZNMF) jets which have gained popularity due to their ability to transfer momentum without transferring mass. This property distinguishes SJs from their counterpart traditional continuous jets. Over a stretch of time, SJs have been employed extensively in applications such as active flow control, impingement heat transfer, miniature electronics cooling, etc. However, researchers are now slowly extending the frontiers of SJ research and making efforts to utilize excellent properties of SJs in novel applications such as AUVs, marine systems, bio-inspired propulsion systems, etc. This paper strives to identify the gaps in the current research and the areas which have remained unexplored yet. The article begins with a discussion of the origin of SJs i.e. 'acoustic streaming'. The resulting segments talk about the formation criteria and the recent works employing various configurations of orifices and cavities. The paper discusses critical concepts such as JIF, volumetric efficiency, and propulsive efficiency of synthetic jets. It is followed by the introduction of novel flow control systems employing SJs such as gurney flaps, bumps, and electroactive synthetic jets. Finally, the most innovative applications of SJs such as AUVs, UAVs, jetting cavities. Pulsatile jet flows found in jellyfish, cephalopod, squid and salp have been discussed in great detail. The exhaustive discussion on future prospects strives not only to provide reader with comprehensive insights into SJs, but also to motivate future researchers to overcome the gaps identified in this paper.

Piezoelectric Controlled Pulsed Microjet Actuation

2009 ◽  
Author(s):  
Fei Liu ◽  
Josh Hogue ◽  
William Oates ◽  
John Solomon ◽  
Farrukh Alvi
Keyword(s):  
Flow Control ◽  
Mass Flux ◽  
Active Flow Control ◽  
Flow Characteristics ◽  
Impinging Jets ◽  
Fluid Behavior ◽  
Pulsed Flow ◽  
Active Flow ◽  
Actuator Design ◽  
Piezoelectric Stack Actuator

A piezohydraulic actuator has been designed and tested for broadband flow control of a microjet actuator. This actuator is under development to understand fundamental flow characteristics near a pulsed flow microjet for active flow control on a number of aircraft structures including impinging jets, cavities, and jet inlets. Recent research has shown substantial reductions in flow separation and noise reduction using steady blowing microjets. This approach often leads to inefficiencies due to excessive mass flux that is typically bled off of an aircraft compressor. Reductions in mass flux without performance losses are desired by actively pulsing the microjet. A piezohydraulic actuator design is presented to investigate this concept. The actuator includes a piezoelectric stack actuator and hydraulic circuit to achieve sufficient displacement amplification to throttle a 400 μm diameter microjet. This system is shown to provide broadband pulsed flow actuation up to 900 Hz. Key parameters contributing to dynamic actuation are shown to include hydraulic fluid behavior, biased microjet air pressure, and voltage inputs to the stack actuator.

Numerical Investigations of Synthetic Jet Control for TAU0015 Airfoil

2014 ◽  
Vol 598 ◽  
pp. 562-567
Author(s):  
Xiao Ping Xu ◽  
Zhou Zhou ◽  
Rui Wang
Keyword(s):  
Flow Control ◽  
Control Method ◽  
Active Flow Control ◽  
Flow Characteristics ◽  
Aerodynamic Performance ◽  
Synthetic Jet ◽  
Airfoil Surface ◽  
Momentum Coefficient ◽  
Jet Control ◽  
Active Flow

The aerodynamic performance of TAU0015 airfoil was investigated with synthetic jet control method. The simplified mathematical model of the active flow control was established with unsteady velocity boundary condition at the specific location of airfoil surface. The aerodynamic performance was simulated with synthetic jet and the efficiency of jet momentum coefficient was conducted. The result shows that the flow control model could perform the minor jet flow characteristics and higher jet momentum coefficient result better control efficiency.

Numerical Investigation of JaVA-Induced Flow in Quiescent Water

2013 ◽  
Author(s):  
Sertac Cadirci ◽  
Hasan Gunes ◽  
Ulrich Rist
Keyword(s):  
Flow Control ◽  
Active Flow Control ◽  
Flow Characteristics ◽  
Flow Fields ◽  
Control Device ◽  
Flow Control Device ◽  
Induced Flow ◽  
Wide Gap ◽  
Zero Net Mass Flux ◽  
Quiescent Fluid

A Jet and Vortex Actuator (JaVA) is an oscillatory, zero-net-mass flux active flow control device which has been investigated numerically in quiescent water. JaVA consists of a vertically moving actuating plate and ejects jets or vortices into the quiescent fluid. Main JaVA-induced flow regimes include jets to different orientations and vortex mode. In this paper, we investigate the effect of the wide gap on the flow characteristics. Three cases consisting of two jets and one vortex mode are presented in detail where the jet-Reynolds number and the scaled amplitude are kept constant. Computational results have been reported to depict instantaneous fields and reveal temporal behavior of JaVA-induced flows in quiescent fluid. In addition, the phase-averaged flow fields have been obtained for suction and blowing phases. The velocity profiles extracted from phase-averaged flow fields across the wide gap supply further insight into the JaVA-induced flow regime and their effectiveness in flow control.

scholarly journals Some aspects of aerodynamic flow control using synthetic-jet actuation

2011 ◽  
Vol 369 (1940) ◽  
pp. 1476-1494 ◽  
Author(s):  
Ari Glezer
Keyword(s):  
Flow Control ◽  
Spatial Scales ◽  
Active Flow Control ◽  
Cross Flow ◽  
Synthetic Jet ◽  
Base Flow ◽  
Bluff Bodies ◽  
Actuation Frequency ◽  
Zero Net Mass Flux ◽  
Aerodynamic Flow Control

Aerodynamic flow control effected by interactions of surface-mounted synthetic (zero net mass flux) jet actuators with a local cross flow is reviewed. These jets are formed by the advection and interactions of trains of discrete vortical structures that are formed entirely from the fluid of the embedding flow system, and thus transfer momentum to the cross flow without net mass injection across the flow boundary. Traditional approaches to active flow control have focused, to a large extent, on control of separation on stalled aerofoils by means of quasi-steady actuation within two distinct regimes that are characterized by the actuation time scales. When the characteristic actuation period is commensurate with the time scale of the inherent instabilities of the base flow, the jets can effect significant quasi-steady global modifications on spatial scales that are one to two orders of magnitude larger than the scale of the jets. However, when the actuation frequency is sufficiently high to be decoupled from global instabilities of the base flow, changes in the aerodynamic forces are attained by leveraging the generation and regulation of ‘trapped’ vorticity concentrations near the surface to alter its aerodynamic shape. Some examples of the utility of this approach for aerodynamic flow control of separated flows on bluff bodies and fully attached flows on lifting surfaces are also discussed.

Active Flow Control Techniques on a Stator Compressor Cascade: A Comparison Between Synthetic Jet and Plasma Actuators

2012 ◽  
Author(s):  
Maria Grazia De Giorgi ◽  
Stefania Traficante ◽  
Carla De Luca ◽  
Daniela Bello ◽  
Antonio Ficarella
Keyword(s):  
Boundary Layer ◽  
Flow Control ◽  
Active Flow Control ◽  
Pressure Ratio ◽  
Boundary Layer Separation ◽  
Synthetic Jet ◽  
Plasma Actuators ◽  
Compressor Cascade ◽  
Control Techniques ◽  
Active Flow

In this work a CFD analysis is applied to study the suppression of the boundary layer separation into a highly-loaded subsonic compressor stator cascade, by different active flow control techniques. Active flow control techniques have the potential to delay separation and to increase the pressure ratio. In particular three different techniques have been applied: the actuation by steady jet, by zero net mass flux Synthetic Jet (SJA) and by plasma actuator. Several works have investigated the use of synthetic jet and plasma actuators on the airfoil, but only few studies have compared the effect of these devices. Concerning the synthetic jet actuator, a suction/blowing type boundary condition is used, imposing a prescribed sinusoidal velocity depending on velocity amplitude, jet frequency and jet angle of ejection with respect to the wall. Concerning the plasma actuation, the effect is modeled into numerical flow solvers by adding the paraelectric force that represents the plasma force into the momentum equation. The plasma, generated by Dielectric Barrier Discharge, acts as a momentum source to the boundary layer allowing it to remain attached throughout a larger portion of the airfoil. The time-averaged body force component, acting on the fluid, depends on the frequency and on the applied voltage, the charge density, the electrical field and the dimensional properties of the actuator, like width of the electrodes and gap between the electrodes. Using this numerical model, the effect of plasma actuators to suppress the flow separation over the blade has been investigated, increasing the turbo-machinery performance too. Finally, the comparison between the different actuation devices shows that, reducing the secondary flow structures, each actuation technique beneficially affects the performance of the stator compressor cascade, even if in the steady jet the costs are relevant.

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