Mechanical Engineering - Research Publications
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ItemCharacteristics of Reynolds Shear Stress in Adverse Pressure Gradient Turbulent Boundary Layers(Springer, 2021)The focus of the present work is to characterize the features of the turbulent inertia term (the wall-normal gradient of Reynolds shear stress) through the mean momentum balance and the Reynolds shear stress correlation coefficient (ρuv ). Effects of the Reynolds number and Clauser pressure-gradient parameter, β, are discussed. Large eddy simulations of low Reynolds number adverse pressure gradient turbulent boundary layers from Bobke et al. [1], low Reynolds number experimental data from Vila et al. [2] and Volino [3], and newly acquired experimental data at higher Reynolds number from the Flow Physics Facility at The University of New Hampshire are utilized for this analysis. Observations are compared to zero pressure gradient turbulent boundary layer direct numerical simulations of Schlatter and Örlu [4] and Sillero et al. [5], and experimental data from Zimmerman et al. [6] and Zimmerman [7]. These cases show that the correlation coefficient (ρuv ) decreases in magnitude with increasing Reynolds number and β. However, from these initial observations we find that ρuv is more sensitive to changes in the Reynolds number in comparison to the examined range of β. We also find that the location of zero-crossing of the turbulent inertia term seems to scale with δ+ while the minimum of ρuv scales with δ.
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ItemDownstream Recovery of Turbulence Kinetic Energy in the Wake of a Turbulent Boundary Layer Wing-Body Junction Flow(Australasian Fluid Mechanics Society, 2018)A multi-sensor hotwire probe capable of simultaneously measuring all three components of the velocity vector [Zimmerman et al. 2017] has been deployed in the wake of a turbulent boundary layer wing-body junction flow. The wing shape—a 3:2 semi-elliptic nose joined to a NACA 0020 airfoil tail—matches that used in a number of existing studies of wing-body junction wake flow (e.g. see the review of Simpson [2001]). Data have been collected in four spanwise/wall-normal measurement planes ranging from 1 to 33 chord lengths behind the trailing edge of the junction. The measurement planes span a domain over which the unperturbed boundary layer would develop from friction Reynolds number Reτ ≈ 8000 –11000. The downstream extent (per chord length) of the present data is the furthest of any experimental effort to date. Despite having a recovery length many times longer than the typical streamwise wavelength of boundary layer ‘superstructure’ motions [Hutchins and Marusic 2007], the turbulence kinetic energy (TKE) profiles at the furthest downstream station still exhibit spanwise inhomogeneity. Data from the measurement planes closer to the junction offer insight into the momentum and turbulence transporting effects of the trailing ‘horseshoe’ vortex, as well as how these effects propagate downstream.
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ItemVortex Rings in a Stratified Fluid(Australian fluid mechanics society, 2018)