Bulletin of the American Physical Society
61st Annual Meeting of the APS Division of Fluid Dynamics
Volume 53, Number 15
Sunday–Tuesday, November 23–25, 2008; San Antonio, Texas
Session HR: General Fluid Mechanics: Experiments |
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Chair: Roi Gurka, Ben-Gurion University Room: 203A |
Monday, November 24, 2008 10:30AM - 10:43AM |
HR.00001: ABSTRACT WITHDRAWN |
Monday, November 24, 2008 10:43AM - 10:56AM |
HR.00002: Falling Spheres in Stratified Fluids Joyce Lin, Roberto Camassa, Claudia Falcon, Richard McLaughlin Low settling rates are observed for small particulate matter in strongly, stably stratified fluid. As the particle passes through an interface between two layers of fluid, it entrains lighter, upper fluid. The significance of this entrained fluid in the low Reynolds regime, along with a model for the behavior of the particle, has not yet been fully explored. We present careful measurements performed in stratified corn syrup showing the effects of the enhanced drag due to entrained fluid on the sphere at low Reynolds. We explore the theory for modeling sphere behavior and also discuss the hydrodynamics, which involve a strong coupling between the variable density fluid and moving solid boundary. [Preview Abstract] |
Monday, November 24, 2008 10:56AM - 11:09AM |
HR.00003: Experimental Investigation of Vortex Ring Evolution at Low Reynolds Number Lauren Couch, Paul Krueger Evolution of low Reynolds number vortex rings in an infinite fluid has been well studied numerically and analytically, but the vortex formation process is typically ignored in these studies. In the present investigation, vortex rings were studied experimentally to determine the effects of formation conditions on vortex ring evolution as Reynolds number is decreased. Vortex rings were generated using a mechanical piston-cylinder vortex ring generator for jet Reynolds numbers in the range 10 to 1000 and piston stroke to jet diameter ratios between 0.5 to 2.0. The vortex rings were imaged using planar laser induced fluorescence and using dye visualization, both recorded with a digital camera. The images were used to obtain the vortex ring velocity and net displacement. The results show increased ring velocity and displacement with higher stroke ratios. Additionally, lower Reynolds numbers resulted in quicker deceleration and decreased maximum displacement. The experimental results will be compared with analytical models of viscous vortex rings traveling in an infinite fluid. [Preview Abstract] |
Monday, November 24, 2008 11:09AM - 11:22AM |
HR.00004: Pressure Distribution and Velocity Profiles Around Smooth and Corrugated Cylinders of Finite Span Mike Parker, Doug Bohl In this work the pressure distribution and velocity profiles around two finite aspect ratio (AR$\sim $1) cylinders is investigated for Reynolds numbers ranging from 1x10$^{5}$ to 9x10$^{5}$. The first cylinder is smooth, while the second cylinder has a corrugated surface with channels cut in the r-$\theta $ plane. The channels are approximately half the diameter in depth and twenty percent of the diameter in width. The apparent aspect ratio was increased by the addition of endplates and the resulting pressure and velocity distributions were compared. The results show that the cylinder with corrugations has a significantly higher minimum pressure coefficient compared to the smooth cylinder at all Reynolds numbers tested. Adding end plates to the cylinders caused the minimum pressure coefficients to decrease and approach that of an infinitely long smooth circular cylinder. Velocity profiles indicate that the corrugated cylinder has a significantly thicker viscous/separated region compared to the smooth cylinder. A strong dependence on Reynolds number was shown for both pressure and velocity in the range investigated. [Preview Abstract] |
Monday, November 24, 2008 11:22AM - 11:35AM |
HR.00005: A Hele-Shaw study of brachistochrones in potential flow past rigid bodies Ashwin Vaidya, Roberto Camassa, Richard McLaughlin, Mathew Moore, Derrek Spronk, David Skewrer, Sean Skewrer The potential flow of an unbounded, viscous, incompressible fluid past a rigid body in two and three dimensions has been theoretically shown to possess a brachistochrone path which is absent in the case of Stokes flow past the same object. In this talk, we present some experimental verification of the brachistochrone by means of a Hele-Shaw experiment which simulates the two dimensional potential flow past an obstacle in the presence of walls. The experiments are also compared with some numerical studies comparing Stokes and potential flow past symmetric bodies in bounded and undounded domains. [Preview Abstract] |
Monday, November 24, 2008 11:35AM - 11:48AM |
HR.00006: Experimental investigation of low Reynolds number and laminar mixing in a tilted-rotating tank Thomas Ward, William Hourigan A tilted-partially filled rotating tank is investigated experimentally at O($1$) Reynolds and small ($\ll 1$) capillary numbers, to study the mixing of a viscous homogeneous fluid. Of particular interest is the transition from a previously studied low Reynolds number flow regime (Ward and Metchik, Chem. Engng. Sci., 2007), that exhibited two large vortices, to the laminar flow regime. In the laminar Reynolds number O ($1$) limit the two primary vortices, generated by a liquid rotation axis, interact with the bottom wall, generating two secondary vortices, via a cascade that is qualitatively similar to the well known Moffatt (Moffatt, J. Fluid Mech., 1964) vortices in Stokes flow. While the secondary vortices aid in transporting material from the walls to the bulk, they also intensify in magnitude with increasing rotation rate leading to de-mixing through the appearance of KAM-like surfaces (Alvarez- Hern\'andez et al., Chem. Engng. Sci., 2002). Experiments are performed using a 90\% glycerol, 10\% water mixture at two volume portions with angles ranging between 25$^{\circ}$ to 65$^ {\circ}$ measured from the horizontal. Laser fluorescence is used to illuminate the vortices via experimental Poincar\'e mapping (Fountain et al., Science, 1998), and the resulting images are analyzed to determine the mixed cross sectional area versus elapsed time. [Preview Abstract] |
Monday, November 24, 2008 11:48AM - 12:01PM |
HR.00007: Chaos in VIV Yahya Modarres-Sadeghi, Michael Triantafyllou In this study the existence of chaotic oscillations in signals from vortex induced vibrations is investigated using some experimental data of flexible risers. VIV is traditionally known as a periodic phenomenon for which the oscillations are mainly at a fundamental frequency of oscillations. As observed recently, in many VIV signals, there is a second peak at three times the fundamental frequency, which represents the existence of a third harmonic oscillation. This view is based on analyzing a statistically stationary region of experimental VIV signals. The original non-filtered signals, however, do not show a statistically stationary behavior in the entire period of oscillations. Practically, the major part of the signal illustrates non-stationary behavior. Here, we do not limit our analysis to the statistically stationary regions; instead, we use the entire experimental signal. The time histories, PSD and phase plane plots, and Poincar\'{e} maps of analyzed signals show cases where the signal is (i) mainly periodic/quasiperiodic or (ii) periodic/quasiperiodic with bursts of chaos or (iii) entirely chaotic. [Preview Abstract] |
Monday, November 24, 2008 12:01PM - 12:14PM |
HR.00008: Temporally irregular surface switching of rotating flow in a cylinder; influence of surface tension and aspect ratio Yuji Tasaka, Makoto Iima We have investigated experimentally the recent reported phenomena called ``surface switching'' that occur in the flow driven by a rotating disk in a cylindrical open vessel (Suzuki et al., 2006). It shows temporally irregular vertical motion of the surface with changing its shape between an axisymmetric shape and a non-axisymmetric shape. There are four control parameters to describe the phenomena; Reynolds number ($Re$), Froude number ($Fr$), Weber number ($We$) and aspect ratio ($A$) between the radius of the cylinder and the height of the fluid layer. In a restricted condition on the working fluid and aspect ratio (Water, $A = 0.95$), behaviors of the phenomena for $Re$ and $Fr$ were discussed. This issue reports influence of other uninvestigated parameter, $We$ and $A$, by using some kind of working fluid (water, Silicone oil and liquid gallium) and by changing surface height. 10 cSt Silicone oil layer has an axisymmetric shape even at a small rotating speed, and corresponding velocity fluctuation shows larger value than that in water at the same rotating speed. But it has never showed the irregular surface switching after it attaches to the bottom in spite of large deformation of the surface. It would be insufficient on the Reynolds number due to its 10 times large viscosity of water. [Preview Abstract] |
Monday, November 24, 2008 12:14PM - 12:27PM |
HR.00009: Innovative Method of Greatly Reducing Flow Resistance Weiyi Lin In this paper, firstly, the aerated pipe flow experiment is introduced. And some experimental research on comparison between different volumes of air entrained is presented. Secondly, the technical characteristics of gravity pipe flow under the action of Torricelli's vacuum, shortly called as GPFUTV are dissertated, including creative and functional design, fundamental principle and the strange energy loss phenomena, etc. Thirdly, an appeal in relation to the experimental research, the applied studies and basic theory research is given. For instance, Reynolds' experiment under GPFUTV condition, the potential for GPFUTV to be developed for deep seawater suction technology and lifting technology for deep ocean mining, flow stability and flow resistance under GPFUTV condition, etc. [Preview Abstract] |
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