Active decoupling of the axisymmetric body wake response to a pitching motion

Lambert, Thomas; Vukašinović, Bojan; Glezer, Ari

doi:10.1016/j.jfluidstructs.2015.08.017

Cited by 6 publications

(9 citation statements)

References 28 publications

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“…Hybrid flow control was also demonstrated by Nagib et al (1985) who combined a short backward-facing step with a jet to control local separation. The earlier works of Lambert et al (2014Lambert et al ( , 2015aLambert et al ( , 2015b demonstrated that the aerodynamic loads induced by an azimuthal array of hybrid synthetic jet actuators (each utilizing a Coanda surface and a backward-facing step) on an axisymmetric bluff body are comparable to the corresponding flow-induced aerodynamic loads that are generated during pitch rotation over a broad range of frequencies in the absence of actuation. In addition, vortex shedding could be excited in pitch, and such actuation is implemented in the present work for trajectory control of the free moving 3-DOF body.…”

Section: Technical Backgroundmentioning

confidence: 99%

Aerodynamic Flow Control of Wake Dynamics Coupled to a Moving Bluff Body

Lambert

Vukašinović

Glezer

2016

8th AIAA Flow Control Conference

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The dynamic motion of an axisymmetric bluff body that is free to precess in pitch, yaw, and roll as a response to flow-induced aerodynamic loads is investigated in open-and closed-loop flow control wind tunnel experiments at Re D < 2·10 5 . The body is coupled to an upstream wire-mounted sting through a low-friction hinge bearing within its front end that enables nearlyfree rotations in pitch (15), yaw (18), and roll (180). The attitude and displacement of the sting are dynamically manipulated in 6-DOF using eight support wires that are each connected to a servo actuator through an in-line load cell for monitoring the instantaneous tension. The aerodynamic loads on the body, and thereby its motion, are controlled through fluidic modification of its aerodynamic coupling to its near wake using four independently-controlled aft mounted synthetic jet actuators that effect azimuthally-segmented flow attachment over the model's tail end. The effects of actuation-induced, transitory changes in the model's aerodynamic loads are measured by its motion response using image tracking (600 fps) and the coupled evolution of the near-wake flow captured by high-speed (500 fps) stereo PIV. Flow control authority is demonstrated by feedbackcontrolled manipulation of the model's dynamic response when the sting is held stationary or when it is subjected to commanded transitory pitch-yaw trajectory disturbances. It is shown that this flow control approach can modify the stability and damping of the model's motion when the sting is stationary (e.g., suppression or amplification of its natural oscillations), and impose a desired directional attitude that is decoupled from the moving sting using actuation-effected disturbance rejection.

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Section: Technical Backgroundmentioning

confidence: 99%

Aerodynamic Flow Control of Wake Dynamics Coupled to a Moving Bluff Body

Lambert

Vukašinović

Glezer

2016

8th AIAA Flow Control Conference

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“…For the purposes of testing of the traverse, the model used as an example case study is an axisymmetric body, as shown in Figure 3, which has been of interest in prior investigations (e.g., [12][13][14]). This axisymmetric wind tunnel model ( Figure 3) is assembled using stereo-lithographed (SLA) and aluminum components (D = 90 mm, L = 165 mm, m = 0.53 kg).…”

Section: Case Study: Axisymmetric Modelmentioning

confidence: 99%

“…It should be also noted that the wires do not only affect aerodynamic measurements, but also present additional sources of vorticity in the flow. However, increased levels of the flow fluctuations behind the wires do not appear to alter the dominant body wake dynamics, and the coupling between the two is deemed insignificant (see Lambert et al [14]). Once the force on a centered stationary model is characterized, three canonical motions are investigated: dynamic pitch, plunge, and streamwise displacement.…”

Section: Force Responsementioning

confidence: 99%

“…Figure 10a Figure 10e,j,o). For reference, the values of the C D , C L , and C M for a static model at varying fixed angles of attack with the same geometry [14] are superimposed in Figure 10a,f,k. The baseline C D vs. α y presented in Figure 10a has a quadratic shape with a minimum of C D = 0.24 at α y = 0 and a change in magnitude of around 25% (0.24 to 0.3).…”

Section: Force Responsementioning

confidence: 99%

“…The current study extends the methodology for a thin wire support, aimed at minimizing flow interference with a traverse that can affect dynamic motion of a wind tunnel model at low flow speeds, and is primarily influenced by earlier studies of Abramson et al [12,13] and Lambert et al [14]. The present work investigates a wire-mounted body on a programmable six degrees of freedom (6-DOF) (x/y/z-translation and roll/pitch/yaw) eight-wire traverse that is electromechanically driven by a dedicated feedback controller to remove the parasitic mass and inertia of the dynamic support system and of the model.…”

Section: Introductionmentioning

confidence: 99%

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A Six Degrees of Freedom Dynamic Wire-Driven Traverse

2016

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A novel support mechanism for a wind tunnel model is designed, built, and demonstrated on an aerodynamic platform undergoing dynamic maneuvers, tested with periodic motions up to 20 Hz. The platform is supported by a 6-DOF (six degrees of freedom) traverse that utilizes eight thin wires, each mounted to a servo motor with an in-line load cell to accurately monitor or control the platform motion and force responses. The system is designed such that simultaneous control of the servo motors effects motion within˘50 mm translations,˘15˝pitch,˘9˝yaw, and˘8˝roll at lower frequencies. The traverse tracks a desired trajectory and resolves the induced forces on the platform at 1 kHz. The effected motion of the platform is measured at 0.6 kHz with a motion capture system, which utilizes six near-infrared (NIR) cameras for full spatial and temporal resolution of the platform motion, which is used for feedback control. The traverse allows different platform model geometries to be tested, and the present work demonstrates its capabilities on an axisymmetric bluff body. Programmable timed outputs are synchronized relative to the model motion and can be used for triggering external systems and processes. In the present study, particle image velocimetry (PIV) is used to characterize the realized wakes of the platform undergoing canonical motions that are effected by this new wind tunnel traverse.

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