The Experts below are selected from a list of 60 Experts worldwide ranked by ideXlab platform
Minami Yoda - One of the best experts on this subject based on the ideXlab platform.
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Moderate-aspect-ratio elliptical cylinders in simple shear with inertia
Journal of Fluid Mechanics, 2001Co-Authors: C. M. Zettner, Minami YodaAbstract:The effects of fluid inertia, geometry and flow confinement upon the dynamics of neutrally buoyant elliptical and non-elliptical cylinders over a wide range of aspect ratios in simple shear are studied experimentally for moderate shear-based Reynolds numbers Re. Unlike circular cylinders, elliptical cylinders of moderate aspect ratio cease to rotate, coming to rest at a nearly Horizontal Equilibrium orientation above a critical Reynolds number Recr (‘stationary behaviour’). Simple dynamics arguments are proposed to explain the effects of aspect ratio and flow confinement upon critical Reynolds number and particle dynamics. Experiments confirm results from previous numerical simulations that the normalized rotation period for Re < Recr (‘periodic behaviour’) is proportional to (Recr − Re)−0.5 for small Recr − Re. For periodic behaviour, maximum and minimum angular cylinder speeds both decrease, and period increases, as Recr − Re decreases. For stationary behaviour, the cylinder rotates until it achieves a nearly Horizontal Equilibrium orientation, which increases as the Reynolds number approaches the critical value. The experimental results are in good agreement with previous lattice-Boltzmann simulations for a 0.5 aspect ratio cylinder.Variation in angular speed over a rotation period decreases as aspect ratio increases, while Recr increases as flow confinement and aspect ratio increase. A non-elliptical cylinder of 0.33 aspect ratio also ceases to rotate above a certain Reynolds number. Although Recr is different from the corresponding elliptical case, the scaling of the normalized rotation period for this body as Recr → Re is identical to that for the elliptical cylinder, suggesting that this scaling is independent of particle shape (i.e. ‘universal’, as conjectured in previous numerical studies). The results also demonstrate that a variety of centrosymmetric bodies with aspect ratios below unity transition from periodic to stationary behaviour.
C. M. Zettner - One of the best experts on this subject based on the ideXlab platform.
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Moderate-aspect-ratio elliptical cylinders in simple shear with inertia
Journal of Fluid Mechanics, 2001Co-Authors: C. M. Zettner, Minami YodaAbstract:The effects of fluid inertia, geometry and flow confinement upon the dynamics of neutrally buoyant elliptical and non-elliptical cylinders over a wide range of aspect ratios in simple shear are studied experimentally for moderate shear-based Reynolds numbers Re. Unlike circular cylinders, elliptical cylinders of moderate aspect ratio cease to rotate, coming to rest at a nearly Horizontal Equilibrium orientation above a critical Reynolds number Recr (‘stationary behaviour’). Simple dynamics arguments are proposed to explain the effects of aspect ratio and flow confinement upon critical Reynolds number and particle dynamics. Experiments confirm results from previous numerical simulations that the normalized rotation period for Re < Recr (‘periodic behaviour’) is proportional to (Recr − Re)−0.5 for small Recr − Re. For periodic behaviour, maximum and minimum angular cylinder speeds both decrease, and period increases, as Recr − Re decreases. For stationary behaviour, the cylinder rotates until it achieves a nearly Horizontal Equilibrium orientation, which increases as the Reynolds number approaches the critical value. The experimental results are in good agreement with previous lattice-Boltzmann simulations for a 0.5 aspect ratio cylinder.Variation in angular speed over a rotation period decreases as aspect ratio increases, while Recr increases as flow confinement and aspect ratio increase. A non-elliptical cylinder of 0.33 aspect ratio also ceases to rotate above a certain Reynolds number. Although Recr is different from the corresponding elliptical case, the scaling of the normalized rotation period for this body as Recr → Re is identical to that for the elliptical cylinder, suggesting that this scaling is independent of particle shape (i.e. ‘universal’, as conjectured in previous numerical studies). The results also demonstrate that a variety of centrosymmetric bodies with aspect ratios below unity transition from periodic to stationary behaviour.
Stuart R. Gaffin - One of the best experts on this subject based on the ideXlab platform.
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Ubiquity of the relative Equilibrium line dynamic and amplified cyclicity in Earth sedimentary systems
Climatic Change, 2009Co-Authors: Stuart R. GaffinAbstract:A distinctive feature of Earth’s sedimentary systems is that they all involve the interaction between a nearly-Horizontal “Equilibrium line,” controlling mass supply, and a dynamic sedimentary surface. For glacial systems, this is the snow line or firn line, approximating a zero-degree atmospheric isotherm. For sedimentary basin systems it is sea level or baselevel. For deep ocean carbonate sediments it is the calcite compensation depth or lysocline. First-order considerations in each case suggest a positive feedback on mass supply as the surface builds upwards (and negative feedback if the surface drops). In the first two cases, outstanding paleo-climate problems exist wherein recorded past sedimentary cycles have asymmetric amplitudes that appear too large compared to deduced vertical movements of the respective Equilibrium lines. These problems are familiarly known as the “100-kiloyear Pleistocene ice age cycle” and the “million year high-order Cretaceous relative sea level cycles.” Here, I discuss the emerging commonalities that surround these two amplified cycles, emphasizing the ubiquitous presence of a relative Equilibrium line dynamic, and which for glacial systems has long been seen as providing a mass supply feedback that can reconcile the disparity between the forcing and the response. I suggest that, in the same way that continental ice sheets have been modeled as passive sedimentary systems that can freely oscillate with little or no snowline forcing, sedimentary basin systems may be capable of similar behavior without vertical sea level change and illustrate the concepts with a low-order model. Sedimentary indicators for relative sea level change may be displaying disproportionately large responses to small eustatic sea level changes, due to internal positive feedbacks.
Hiroshi Toyama - One of the best experts on this subject based on the ideXlab platform.
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Low aspect ratio tokamak experiment in University of Tokyo
Fusion Technology, 1995Co-Authors: Kazuaki Hanada, T Oikawa, K Nozawa, H Totsuka, K Shinohara, E Ishiyama, N Shinoda, K. Yamagishi, Hiroshi ToyamaAbstract:A low aspect ratio tokamak device has been designed and constructed in University of Tokyo. A cylindrical vacuum vessel is employed. The vessel is divided toroidally into two parts insulated each other. In the vessel, central core composed of ohmic coils and a part of toroidal coils is installed. The aluminum shell is installed to keep the vertical and Horizontal Equilibrium of the plasma. As the result of several efforts to lower the aspect ratio, the predicted minimum value of the aspect ratio reaches less than 1.2. The predicted advantage of low aspect ratio tokamaks is verified by simulation. The analysis of MHD activities and fluctuations will be carried out, after the assembly is completed. 4 refs., 7 figs.
Paul John Strykowski - One of the best experts on this subject based on the ideXlab platform.
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R439 – Effect of Resistance-Compliance Changes in Fluidic Systems
Otolaryngology–Head and Neck Surgery, 2008Co-Authors: Ryan Dunn, Rick Odland, Paul John StrykowskiAbstract:Problem Previous work has established the relationship of resistance and compliance in a bench-top model of 2 parallel fluid systems representing endolymph and perilymph. The R-C Product is mathematically proportional to the time to Equilibrium. Increasing the resistance to fluid movement in the “endolymph” significantly increased the time to hydrostatic Equilibrium between the systems. The current study was designed to test whether a compensatory change in the R-C Product on the “perilymphatic” side would reduce the time to steady state. Methods As previously described, 2 parallel tubular systems with symmetric resistance and compliance members were perturbed by rotating the model from a Horizontal, Equilibrium condition to an upright, disEquilibrium condition. Time to steady state was video recorded in 4 resistance conditions. The primary test was whether increased resistance to flow on the “endolymph” limb would be negated by an equal increase to resistance to flow on the “perilymph” limb. Results All 4 resistance conditions exhibited differences in time to steady state by ANOVA (p = 3.4 × 10E-12). Mean time to a steady state was reduced when a compensatory change in resistance was applied to the “perilymph” limb (1.0 + 1.1 sec) when compared to high resistance in the “endolymph” alone (2.5 + 1.3 sec, p = .01). Conclusion Compensatory changes in the R-C Product can reduce time to Equilibrium. Significance Improved treatment of vertigo may be possible by application of principles that can affect resistance (fluid pathway diameter or viscosity) or compliance (stiffness of the oval or round window) of the systems. Support University of Minnesota Biomedical Engineering Institute Otolaryngology Interest Group Fund.