Characterization of the leading-edge vortex dynamics using cyber-physical systems

Onoue, Kyohei

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Year:: 2016
Contributor:: Onoue, Kyohei (creator); Breuer, Kenneth (Director); Mandre, Shreyas (Reader); Franck, Jennifer (Reader); Brown University. ENGINEERING: Fluids and Thermal Sciences (sponsor)
Genre:: theses
Subject:: Leading-edge vortex; fluid-structure interactions; cyber-physical system; vortex dynamics; Energy harvesting
Extent:: xxx, 103 p.
DOI: https://doi.org/10.7301/Z0SN07CK

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Abstract:: We present experimental investigations aimed at characterizing the flow physics associated with strong fluid-structure interactions that drive large-scale oscillations of an elastically-supported wing in a uniform airflow. All experiments are performed using a cyber-physical system in which the structural characteristics of the system are emulated using a digital controller that monitors the motion of the structure in real time. Provided that the formation of the leading-edge vortex (LEV) plays an important role in driving large-scale oscillations, much of our effort has been devoted into characterizing the dynamical properties of the LEV. Towards this end, we first analyzed the phase-plane representation of the aeroelastic instability to follow and deduce from the measured motion and aerodynamic torque the formation time and separation dynamics of the LEV. The insight gained from the phase portraits are subsequently confirmed and directly quantified using 2D Particle Image Velocimetry (PIV). We demonstrate that the LEV stability, formation time and circulation scale robustly with the characteristic velocity of the feeding shear layer emanating from the leading edge, and the connection between this scaling and the concept of optimal vortex formation number is discussed. We developed a quasi-steady potential flow model to elucidate a quantitative connection between the location and strength of the LEV core and the resulting aerodynamic torque on the elastic structure. In the final phase of this work, we implemented tomographic PIV to characterize the three-dimensionality of the LEV core on 2D and 3D wings, and to identify important vorticity transport mechanisms responsible for regulating the LEV growth. Through systematic assessments of vortex stability, three-dimensional vorticity dynamics and vortex energy, we found that the stability of the LEV can be improved by (i) increasing the reduced frequency, (ii) moderating the LEV circulation via the process of vorticity annihilation and (iii) suppressing the formation of an arch-shaped LEV. We conclude this study by presenting a unified scaling for vortex formation on 2D and 3D pitching wings that effectively accounts for the variations in the physical configuration of the vortex generator, wing kinematics and Reynolds number.
Notes:: Thesis (Ph.D. -- Brown University (2016)

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Citation

Onoue, Kyohei, "Characterization of the leading-edge vortex dynamics using cyber-physical systems" (2016). Fluid, Thermal, and Chemical Processes Theses and Dissertations. Brown Digital Repository. Brown University Library. https://doi.org/10.7301/Z0SN07CK

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Fluid, Thermal, and Chemical Processes Theses and Dissertations

Theses and Dissertations for the Fluid, Thermal, and Chemical Processes department.
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