Browsing by Subject "seals"
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Item Comparative Analysis of the Morphology and Materials Properties of Pinniped Vibrissae(2012-02-14) Ginter, Carly C.Vibrissae (whiskers) are important components of the mammalian tactile sensory system, and primarily function as detectors of environmental vibrotactile cues. Pinnipeds possess the largest and most highly innervated vibrissae among mammals and their vibrissae demonstrate a diversity of shapes and likely mechanical properties. These two characteristics are important for vibrotactile sensory perception. Vibrissae of most phocid seals exhibit a beaded morphology with repeated sequences of crests and troughs along their length. I comparatively characterized differences in vibrissae morphologies among phocid species with a beaded profile, phocid species with a smooth profile, and otariids with a smooth profile using traditional and geometric morphometric methods to test the hypothesis that vibrissal morphologies are species-specific manipulations of a common pattern. The traditional and geometric morphometric datasets were subsequently combined by mathematically scaling each to true rank, followed by a single eigendecomposition. Quadratic discriminant function analysis demonstrated that 79.3, 97.8 and 100% of individuals could be correctly classified to taxon based on vibrissal shape variables in the traditional, geometric and combined morphometric analyses, respectively. At least three separate morphologies were identified since phocids with beaded vibrissae, phocids with smooth vibrissae, and otariids each occupied distinct morphospace in the geometric morphometric and combined data analyses. Another important characteristic that influences the transduction of vibrotactile information to the mechanoreceptors in the follicle-sinus complex is the materials properties of the vibrissae. Vibrissae were modeled as cantilever beams and flexural stiffness (EI) was measured to test the hypotheses that the shape of beaded vibrissae reduces flexural stiffness and that vibrissae are anisotropic (orientations differ in EI). Species were significantly different and smooth vibrissae were generally stiffer than beaded vibrissae. Beaded vibrissae decrease vibrations in flow, which, combined with lower flexural stiffness values, may enhance detection of small changes in flow from swimming prey. The anterior plane of the vibrissae is likely the most biologically significant in tracking hydrodynamic trails but had lower flexural stiffness values than the dorsoventral orientation. There is likely a complex interaction between shape and mechanical properties in pinniped vibrissae but the ecological and functional implications are currently unknown.Item Experimental measurement of phase averaged wall-pressure distributions for a 25% eccentric whirling annular seal(Texas A&M University, 2006-08-16) Cusano, DomenicInstantaneous wall-pressure data were recorded for a 25% eccentric whirling annular seal for rotor speeds of 1800RPM and 3600RPM, axial Reynolds numbers of 24000 and 12000, and whirl ratios of 0.1-1.0 following the procedure set forth by Winslow (1994), Robic (1999) and Suryanarayanan (2003). Overall, the phase averaged wall-pressure distributions were consistent with previous results. The ??switch?? in the pressure distribution measured by Suryanarayanan (2003) and Robic (1999) from pressure to suction between the seal entrance and exit occurs at and above a whirl ratio of 0.7 for 1800RPM and 0.4 for 3600RPM. For both rotor speeds, decreasing the flow rate by one-half also decreases the wall pressure fluctuation distributions by one-half. For whirl ratios less than 0.5, the phase averaged pressure field was relatively constant which leads to minimal forces being imparted on the rotor by the fluid in the annulus. Talyor-Gortler vortices are measured for 1800RPM and Re=24000 at whirl ratios 0.1 and 0.3-0.7. As the whirl ratio increases past 0.5, longitudinal vortices begin to emerge in the pressure contours and skew axially with 180?? shifts occurring when the Taylor-Reynolds ratio is large enough. Longitudinal vortices were measured for both rotor speeds when the whirling motion is greater than 1400RPM for Re=12000 and greater than 1600RPM for Re=24000. Attempts were made to apply Childs (1983) procedure for finding the rotordynamic coefficients of annular seals; however, the seal moves in a non-circular orbit about the seal??s center so Childs analysis cannot be applied.