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Leading-Edge active flow control Enabled by Curved Fluidic Oscillators

AIAA JOURNAL 2023年第4期61卷 1675-1686页

作者： Spens, Alexander Pisano, Anthony P. Bons, Jeffrey P. Ohio State Univ Mech & Aerosp Engn Columbus OH 43210 USA Ohio State Univ AIAA Columbus OH 43210 USA

A new design of fluidic oscillator, in which the oscillator is curved along its primary flow direction, allows for a sweeping jet to be placed near the leading edge of a wing as an active flow control device. Previous studies of fluidic oscillator applications have shown their promise as an active flow control device by increasing the lift over a wing and preventing flow separation. However, the planar extent of the flat fluidic oscillators creates challenges when trying to optimally implement them in a confined geometry. The application of these new curved oscillators is experimentally investigated on the leading edge of an upswept NACA0018 airfoil full-span wing. Global load cell measurements of lift, drag, and pitching moment are presented and analyzed using suction surface static pressure taps, and particle image velocimetry data are presented. The effects of active flow control on lift, drag, and stall at a Reynolds number of 100,000 are documented for a variety of oscillator chordwise locations near the leading edge and compared to traditional vortex-generating jets. While further aft-positioned oscillators produced a larger increase in maximum lift, more forward locations resulted in better poststall performance and delayed flow separation over the wing.

关键词： active flow control Strouhal Number Fluid Mechanics Critical Angle of Attack flow control (Fluid) Fluidic Oscillator Sweeping Jet Actuators Vortex Generators Post Stall

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Numerical investigation of active flow control using zero-net-mass-flux jets around a high-lift morphing cambered wing-flap system

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INTERNATIONAL JOURNAL OF NUMERICAL METHODS FOR HEAT & FLUID flow 2023年第4期33卷 1475-1488页

作者： Truong, Hung Marouf, Abderahmane Gehri, Alain Vos, Jan Braza, Marianna Hoarau, Yannick Univ Strasbourg ICUBE Strasbourg France EPFL Innovat Pk CFS Engn Lausanne Switzerland CNRS INPT UMR N 5502 Inst Mecan Fluides Toulouse Toulouse France

PurposeThis study aims to investigate the physical mechanisms of the use of active flow control (AFC) for a high-lift wing-flap configuration. Design/methodology/approachBy means of high-fidelity numerical simulations, the flow dynamics around a high-lift wing-flap system at high Reynolds number (Re/c = 4.6 million) is studied. Adapted turbulence models based on the URANS approach are used to capture the flow separation and the subsequent development of coherent structures. The present study focuses on the use of AFC using a synthetic jet known as zero-net-mass-flux (ZNMF) using the blowing-suction approach. Different parameters (geometry, frequency and velocity) of a ZNMF placed at the cambered flap's chord are optimized to obtain the most efficient parameter settings to suppress the flow separation. FindingsA synthetic jet with the optimal shape and orientation enforces the flow reattachment on the wing-flap surface. This leads to an improvement of the aerodynamic performance of the system. The wake thickness was reduced by 30%, and an increase of 17.6% in lift-to-drag ratio was obtained. Concerning the ZNMF location, they should be installed upstream of the separation point to achieve the best performance. Originality/valueThe effectiveness of ZNMF devices integrated on a high-lift wing-flap configuration was studied in real flight conditions at high Reynolds number. A detailed analysis of the wake dynamics explains how AFC forces the reattachment of the boundary layer and attenuates the predominant wake instabilities up to -20 dB.

关键词： active flow control Zero-net-mass-flux High-lift system CFD Aerodynamics Turbulence

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Comparison between synthetic jets and continuous jets for active flow control: Application on a NACA 0015 and a compressor stator cascade

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AEROSPACE SCIENCE AND TECHNOLOGY 2015年 43卷 256-280页

作者： De Giorgi, M. G. De Luca, C. G. Ficarella, A. Marra, F. Univ Salento Dipartimento Ingn Innovaz I-73100 Lecce Italy

A numerical investigation is performed to analyse the suppression of the boundary layer separation first on a NACA 0015 airfoil and subsequently in a highly loaded subsonic compressor stator cascade using two different active flow control techniques: synthetic jet actuators (SJA) and continuous jet actuators (CJA). In particular, the effort is concentrated towards understanding the physics of the phenomenon, which makes one configuration perform better than the other one as an active flow control (AFC) system. The analysis of the interaction of the jet with the boundary layer was performed, with a description of the vortical structures, which are beneficial for the mixing of the boundary layer and the entrainment of energy from the external flow towards the most inner layers. Regarding airfoils, the comparisons of the SJA with the CJA were performed considering two similarity conditions: identical momentum coefficients and identical amounts of energy fed into the cross flow. Finally, the flow behaviour and the topology structure in a highly loaded compressor cascade with and without AFC are examined. active flow control using synthetic jet actuators proved to be attractive because it could exploit the unsteady phenomena, inhibit the separation, improve and control the aerodynamics of the flow in both external aerodynamics and turbomachinery components. Furthermore, comparing the CJA and the SJA for active flow control on the compressor at similar momentum coefficients shows that the relative reduction of the total pressure losses for the SJA is approximately twice as large as that for the CJA. It should also be remarked that even if the two AFC configurations present similar effects on the reduction of secondary flow structures, the SJA is more advantageous than the CJA from the regaining energy viewpoint. (C) 2015 Elsevier Masson SAS. All rights reserved.

关键词： active flow control Synthetic jet actuator Compressor cascade Steady jet actuator

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Numerical studies of active flow control on wing tip extension

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AIRCRAFT ENGINEERING AND AEROSPACE TECHNOLOGY 2019年第2期91卷 346-352页

作者： Vrchota, Petr Prachar, Ales Peng, Shia-Hui Tormalm, Magnus Eliasson, Peter VZLU Czech Aerosp Res Ctr Dept Aerodynam Prague Czech Republic Swedish Res Agcy FOI Stockholm Sweden Saab AB Dept Aeronaut Stockholm Sweden

Purpose - In the European project AFLoNext, active flow control (AFC) measures were adopted in the wing tip extension leading edge to suppress flow separation. It is expected that the designed wing tip extension may improve aerodynamic efficiency by about 2 per cent in terms of fuel consumption and emissions. As the leading edge of the wing tip is not protected with high-lift device, flow separation occurs earlier than over the inboard wing in the take-off/landing configuration. The aim of this study is the adoption of AFC to delay wing tip stall and to improve lift-to-drag ratio. Design/methodology/approach - Several actuator locations and AFC strategies were tested with computational fluid dynamics. The first approach was "standard" one with physical modeling of the actuators, and the second one was focused on the volume forcing method. The actuators location and the forcing plane close to separation line of the reference configuration were chose to enhance the flow with steady and pulsed jet blowing. Dependence of the lift-to-drag benefit with respect to injected mass flow is investigated. Findings - The mechanism of flow separation onset is identified as the interaction of slat-end and wing tip vortices. These vortices moving toward each other with increasing angle of attack (AoA) interact and cause the flow separation. AFC is applied to control the slat-end vortex and the inboard movement of the wing tip vortex to suppress their interaction. The separation onset has been postponed by about 2 degrees of AoA;the value of ift-to-drag (LID) was improved up to 22 per cent for the most beneficial cases. Practical implications - The AFC using the steady or pulsed blowing (PB) was proved to be an effective tool for delaying the flow separation. Although better values of L/D have been reached using steady blowing, it is also shown that PB case with a duty cycle of 0.5 needs only one half of the mass flow. Originality/value - Two approaches of different levels of complex

关键词： CFD Aerodynamics active flow control flow separation control

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Multivariable Closed-Loop active flow control of a Compressor Stator Cascade

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AIAA JOURNAL 2017年第10期55卷 3371-3380页

作者： Kiesner, Matthias King, Rudibert Tech Univ Berlin Dept Measurement & Control D-10623 Berlin Germany

This paper presents a multivariable closed-loop active flow control strategy to control the pressure rise and the wake size of a compressor stator cascade. For flow control, a combination of two actuator concepts, trailing-edge and sidewall blowing, was applied to a linear stator cascade. Detailed five-hole probe measurements of the downstream flowfield at a Reynolds number of 6x105 were carried out to reveal the effect of the actuation on the cascade flow. An increase in the pressure rise coefficient by 5% and a significant reduction of the wake size could be achieved with the investigated actuation amplitudes of c values up to 2.5%. Principal component analysis was used to find coherent structures in the full measurement data set. Based on this analysis, a real-time estimation of the complex downstream flowfield with only three pressure sensors was realized. With this estimation, linear dynamic black-box models for the pressure rise coefficient and the wake size were identified. Variable reference signals with a Strouhal number of 0.03, specified by a later application in a pressure gain combustion system, were successfully tracked, leading to small experimental control errors.

关键词： active flow control Closed Loop control Compressor Efficiency Trailing Edges flow Conditions Actuators Strouhal Number Pressure Sensors Combustion System Black Box

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Effects of Input Voltage and Freestream Velocity on active flow control of Passage Vortex in a Linear Turbine Cascade Using Dielectric Barrier Discharge Plasma Actuator

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ENERGIES 2020年第3期13卷 764页

作者： Matsunuma, Takayuki Segawa, Takehiko Natl Inst Adv Ind Sci & Technol 1-2-1 Namiki Tsukuba Ibaraki 3058564 Japan

Passage vortex exists as one of the typical secondary flows in turbomachines and generates a significant total pressure loss and degrades the aerodynamic performance. Herein, a dielectric barrier discharge (DBD) plasma actuator was utilized for an active flow control of the passage vortex in a linear turbine cascade. The plasma actuator was installed on the endwall, 10 mm upstream from the leading edge of the turbine cascade. The freestream velocity at the outlet of the linear turbine cascade was set to range from U-FS,U-out = 2.4 m/s to 25.2 m/s, which corresponded to the Reynolds number ranging from Re-out = 1.0 x 10(4) to 9.9 x 10(4). The two-dimensional velocity field at the outlet of the linear turbine cascade was experimentally analyzed by particle image velocimetry (PIV). At lower freestream velocity conditions, the passage vortex was almost negligible as a result of the plasma actuator operation (U-PA,U-max/U-FS,U-out = 1.17). Although the effect of the jet induced by the plasma actuator weakened as the freestream velocity increased, the magnitude of the peak vorticity was reduced under all freestream velocity conditions. Even at the highest freestream velocity condition of U-FS,U-out = 25.2 m/s, the peak value of the vorticity was reduced approximately 17% by the plasma actuator operation at V-AC = 15 kV(p-p) (U-PA,U-max/U-FS,U-out = 0.18).

关键词： active flow control plasma actuator turbine cascade passage vortex particle image velocimetry velocity turbulence intensity vorticity

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Detached-Eddy Simulations for active flow control

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AIAA JOURNAL 2018年第4期56卷 1447-1462页

作者： Wang, Liang Hu, Ruyun Li, Liying Fu, Song Tsinghua Univ Dept Engn Mech Beijing 100084 Peoples R China Shanghai Jiao Tong Univ Sch Mech Engn Shanghai 200240 Peoples R China

The present study conducted improved delayed detached-eddy simulations of actively controlled flows with a harmonic actuation on a backward-facing step and pulsed blowing on a pitching airfoil for reattachment and separation controls. Spectra analyses based on the unexcited flowfield data were carried out by using dynamic mode decomposition to identify spatial structures corresponding to the different Strouhal frequencies. The characteristic physical modes have been extracted for both cases. With better understanding of unsteady flow features, effective control practices were illustrated. For the backward-facing step case, the optimal excitation frequency was found to be identical with the step-mode frequency of the baseline flow. Such harmonic actuation enhanced the pairing process, forming the largest-scale spanwise coherent structures in the free shear layer, resulting in a 40% maximum reduction of the bubble length. For the airfoil case, with the optimum excitation frequency determined by the vortex-shedding mode of the baseline flow, a 194% increase of the lift-to-drag ratio was obtained;the pulsed blowing with the jet orifices in an antiphased manner was found to be very effective to damp the fluctuations of the lift around its mean value, though it led to a small decrease in mean lift.

关键词： Direct Numerical Simulation active flow control Boundary Layer Separation Strouhal Numbers Pitching Airfoil Lift to Drag Ratio flow Conditions Reynolds Averaged Navier Stokes flow Characteristics Lift Coefficient

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control of a miniducted-fan unmanned aerial vehicle using active flow control

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JOURNAL OF AIRCRAFT 2002年第4期39卷 561-571页

作者： Fung, PHY Amitay, M Georgia Inst Technol Sch Mech Engn Atlanta GA 30332 USA Georgia Tech Res Inst Aerosp Transportat & Adv Syst Lab Smyrna GA 30080 USA

An experimental study of the control of the flowfield around the stator vanes of a new miniducted-fan unmanned aerial vehicle (UAV) using synthetic jet actuators is presented. As a result, a new control approach of the UAV is proposed in which active flow control can be used instead of moving control surfaces and articulated rotor blade. Therefore, the UAV's propulsion and control systems are reduced to a single moving part, a fixed pitch propeller. This mechanical simplicity makes the active How control application particularly attractive for development of mini- and micro-UAVs. The directional and rotational control of the UAV (0.5 m in diameter and 0.15 m in height) can be obtained by controlling the flow within the duct. This can be achieved by the activation of surface fluidic actuators based on synthetic jet technology that are located downstream from a miniature passive obstruction. The synthetic jets are Hush mounted on a set of four fixed stators located downstream from the propeller. In the present work the flowfield around the stator vanes is studied using particle image velocimetry at different radial locations, where the geometrical angle of attack of the stator vanes is fixed at 10 deg and the propeller rotational speed is either 4300 or 6200 rpm. Velocity measurements in the near wake are also obtained, and the data show that as a result of the Actuation the cross-stream extent of the wake and its velocity deficit are significantly reduced and the How is quasi-steady.

关键词： UAV active flow control Propellers Actuators Aerodynamic Performance Particle Image Velocimetry Articulated Rotor Propulsion control System control Surfaces Vortex Sheet

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Plasma actuator scaling down to improve its energy conversion efficiency for active flow control in modern turbojet engines compressors

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APPLIED THERMAL ENGINEERING 2016年 106卷 334-350页

作者： De Giorgi, M. G. Pescini, E. Marra, F. Ficarella, A. Univ Salento Dipartimento Ingn Innovaz Via Monteroni I-73100 Lecce Italy

The present work was performed to investigate the employment of micro dielectric barrier discharge plasma actuators for mitigating separation, thereby decreasing wake losses and increasing efficiency, on a highly loaded compressor cascade. To this aim, the experimental characterization of the control device was initially done. A dedicated activity was devoted to microelectronic technology adoption for micro plasma actuator fabrication, together with batch production of electrodes with photolithographic techniques. The actuation effect on quiescent flow was evaluated by measuring the induced wall-jet with particle image velocimetry. The actuator power consumption was estimated by recording the applied voltages and resulting currents. Experimental results were then used to calibrate a multi-physics numerical model, for the prediction of the body forces induced by plasma actuator. Different algebraic models were compared. Numerical modelling was applied to predict the capability of micro plasma actuation to suppress flow separation into a highly-loaded subsonic compressor stator cascade. At first, simulations of the compressor cascade without active flow control were carried out and the results were compared with the literature experimental data. A good agreement was found between the experimental and the numerical results. active flow control by the micro plasma actuator was then tested under different sinusoidal voltage amplitudes. It was found that the compressor pressure losses were reduced by increasing the applied voltage;actuation brought to a reduction in the pressure loss coefficient up to 14% and to an increase in static pressure up to 3%. When the actuator was on, the isosurface of the Q-criteria showed the reduction of secondary flow structures and the shape factor at the trailing edge of the midspan section was always lower than 2.2, confirming a reattachment of the flow. Furthermore, a conventional macro actuator found in the literature was also modelled

关键词： active flow control Micro plasma actuator CFD Compressor cascade

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Development of piezoelectric actuators for active flow control

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AIAA JOURNAL 2001年第8期39卷 1562-1568页

作者： Cattafesta, LN Garg, S Shukla, D High Technol Corp Hampton VA 23666 USA

The development of piezoelectric actuators for active flow control is discussed. The type of actuators considered consists of a single sheet of piezoceramic material bonded to the underside of a shim: a "unimorph" flap design. Existing theoretical beam models are extended to incorporate a linear strain distribution in the composite unimorph beam structure. This model is combined with an optimization scheme to design a flap that maximizes the tip deflection per unit voltage for a given bandwidth. The optimization model is then used to design a piezoelectric actuator. The model predictions compare favorably to measurements of the actuator frequency response function. A sample application to control of separated flow from a backward-facing step is also described, in which the actuator is installed at the origin of the free shear layer. Detailed hot-wire measurements, together with dimensional analysis, reveal the physical mechanism responsible For the fluid-structure coupling. A quasi-static model based on the solid-body displacement of the incoming shear layer accurately describes the peak streamwise velocity perturbations produced by the actuator. This model leads to a proportional relationship between the flap tip displacement, the incoming boundary-layer profile parameters, and the streamwise velocity fluctuations produced by the actuator.

关键词： .consists displacement frequency response per unit piezoceramic tip bonded hot-wire linear strain optimization scheme Development of Piezoelectric active flow control unimorph

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