Browsing by Author "Agrey, Kaden"

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    Coherent Dynamics and Energetics in Thin Flat Plate Wakes
    (2021-08) Agrey, Kaden; Martinuzzi, Robert; Hu, Yaoping; Johansen, Craig; Wan, Richard; Pieper, Jeff
    The dynamics and energetics of two mean two-dimensional wakes behind a flow-normal thin flat plate, induced by inclusion and exclusion of end plates, are studied. Both wakes are characterized by quasi-periodic vortex shedding but differ in mean topology and typical wake characteristics, such as mean base pressure and recirculation length. Energetically optimal proper orthogonal decomposition modes are used to approximate the coherent motion and thus triply decompose the velocity field into a mean, coherent, and residual field. This is utilized to obtain a dynamic characterization of the wakes and to study the large scale coherent structures and their energetic exchanges with other scales of motion. From this, a slow-varying base flow and lateral shear layer flapping are shown to influence the shedding dynamics differently in each wake. These differences in the mean field and coherent dynamics are related to wake turbulence levels and vortex deformation, and thus are at the beginning of the energy cascade and the energy transfer process related to the wake turbulence levels.
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    End effects of nominally two-dimensional thin flat plates
    (2020-09-24) Braun, Eric; Agrey, Kaden; Martinuzzi, Robert John
    Differences in the structure and dynamics of nominally two-dimensional turbulent wakes are investigated experimentally for a thin flat plate, normal to a uniform flow, with two different end conditions: with and without end plates. Both cases are characterized by Karman-like vortex shedding with broadband low frequency unsteadiness. Both wakes evidence a low frequency flapping motion in addition to the slowly drifting base flow common to cylinder wakes. For the case without end plates, an interaction between the drift motion and the vortex formation process is associated with a much stronger modulation of the quasiperiodic vortex shedding amplitude when compared to the case with end plates where a flapping motion is more strongly expressed. These dynamics underlie structural differences in the mean wake and Reynolds stress fields. .