Bulletin of the American Physical Society
60th Annual Meeting of the Divison of Fluid Dynamics
Volume 52, Number 12
Sunday–Tuesday, November 18–20, 2007; Salt Lake City, Utah
Session NI: Material Processing and Industrial Applications |
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Chair: Douglas Bohl, Clarkson University Room: Salt Palace Convention Center 250 C |
Tuesday, November 20, 2007 11:35AM - 11:48AM |
NI.00001: Classification of Particle by Size Using Aerodynamic Vectoring Zachary Humes, Barton Smith, Angela Minichiello An experimental and numerical demonstration of a non-contact particle sorting and particle concentration technique called Aerodynamic Vectoring Particle Sorting (AVPS) is presented. AVPS uses secondary suction control flows to sharply turn a planar, particle-laden jet. As the jet is turned, particles present in the flow experience a resultant drag force dependent upon their size. Since the balance of the drag and inertia determines the particle's trajectory, turning the flow leads to a separation of particles. This simple, low-pressure-drop sorting technique classifies and concentrates particles with less risk of damage or contamination than currently available sorting devices.~AVPS also allows multiple cuts simultaneously. Particle size and trajectory are measured using the Shadowgraphy method.~ Numerical simulations are performed to calculate the 2D turbulent vectored jet flow field using a RANS approach. Currently, AVPS is capable of a cut sharpness of .8 and .9 for industrial and laboratory particles respectively. A concentration factor of 9.5 for particles between 7 and 10 micron has also been achieved. [Preview Abstract] |
Tuesday, November 20, 2007 11:48AM - 12:01PM |
NI.00002: Experimental Study of Mixing Characteristics of a Flat Plate Paddle Mixer Douglas Bohl, Naratip Santitissadeekorn, Erik Bollt In this work a flat rectangular plate is rotated along its long axis and parallel to the z-axis of a circular cylinder. The blade position is varied with respect to the cylinder wall to allow investigation of the effect of the no slip boundary on the flow structure and mixing field. The cylinder is filled with a Newtonian fluid, glycerin, and driven at a Reynolds number of 8 based on the cylinder diameter. Particle Image Velocimetry is used to measure the velocity in the plane perpendicular to the rotation of the plate (i.e. in the r-$\theta $ plane of the cylinder). The experimental velocity field is used to numerically determine the motion of 100,000 simulated particle tracers for up to 25 cycles of the blade. Mixing rates and length scales are determined by noting the distribution of the particle tracers. Results show that when the paddle blade is centered in the tank there are three distinct regions in the flow. In the region where the blade sweeps there is no mixing and further no transport into or out of this region. At the tip of the blade there is a region of high mixing. However, towards the wall a moderate amount of mixing is observed. [Preview Abstract] |
Tuesday, November 20, 2007 12:01PM - 12:14PM |
NI.00003: Mixing Topology in a Flat Plate Paddle Mixer Naratip Santitissadeekorn, Erik Bollt, Douglas Bohl Using the experimental velocity field from a mixer with a flat plate impeller we aim to quantify the mixing in various notions and use it to study regions of strong mixing in our model. We would like to understand if there is some coherent structure that partitions regions corresponding to qualitatively different motions, such as the Lagrangian coherent structure (LCS). It is believed that understanding of transport and mixing can be accomplished by analysis the LCS based on the finite-time Lyapanov exponent (FTLE). For a steady flow, the LCSs give and empirical understanding of stable and unstable invariant manifolds of hyperbolic fix points. Stable and unstable manifolds which are co-dimension-1 constitute barriers to transport and, therefore, mixing in dynamical systems. LCS can be used to empirically infer such structures from experimental data. Specifically, two points straddling a repelling (contracting) LCS will eventually separate exponentially in a forward (backward) time. [Preview Abstract] |
Tuesday, November 20, 2007 12:14PM - 12:27PM |
NI.00004: Hole Collapse During the Drawing Process for a Hollow Optical Fiber Jing Yang, Yogesh Jaluria Hollow fibers are of interest in many applications, such as disgnostics, telecommunications and power delivery. The collapse of the hole is of particular interest in the drawing process for these optical fibers because it changes their basic characteristics. An analytical and numerical model is developed for the flow of glass and inert gases under typical drawing conditions. The zonal method is employed to simulate the radiative transport in the material. The transport processes are investigated and changes in the hole diameter are calculated. The ratio of the diameter of the hole at the end of the draw process to that in the starting glass cylinder, or perform, is determined. The results show that the collapse ratio is strongly dependent on surface tension effects. The radius ratio in the preform and the drawing speed are found to be relatively weak effects. A high difference in pressure between the hole and the ambient medium, high feeding speed, low surface tension, and low furnace temperature help in curbing the collapse of the hollow fiber during the drawing process. A comparison between the results for a polymer (PMMA) and a silica fiber shows that polymer fibers have an advantage over silica fibers in the preservation of the shape due to the relatively low surface tension. [Preview Abstract] |
Tuesday, November 20, 2007 12:27PM - 12:40PM |
NI.00005: Reactive wetting and spreading in metal/metal systems Y. Sun, B.T. Murray, T.J. Singler, A. Chauhan, L. Yin, E. Webb Wetting, phase change and reaction in high temperature systems, such as when a liquid metal drop spreads spontaneously on a metal substrate, are fundamental to many materials processing applications. Rapidly melted solid drops are typically used to study the wetting and spreading behavior of low melting point alloys on a solid metal as a model of soldering processes in microelectronics fabrication. Kinetics, e.g., contact line motion, dissolution and intermetallic compound formation, are frequently very fast, requiring high speed video imaging to resolve the temporal evolution of the drop spreading. Phase change at the liquid/solid interface leads to more complex spreading behavior (e.g., contact line morphology) that is not observed in inert spreading. In order to better understand the phenomena observed in the drop spreading experiments, multiscale models are employed. Molecular dynamics simulations on the nanometric scale exhibit many characteristics observed in millimetric scale laboratory experiments. Two types of continuum models are employed: a primarily diffusive transport model and a phase-field model coupled to hydrodynamic transport. Both models simulate the wetting and dissolution of the spreading drop at the scales of the experiments. The model results for the extent of spreading are compared to the experiments. [Preview Abstract] |
Tuesday, November 20, 2007 12:40PM - 12:53PM |
NI.00006: VIV Diagnostics for Fatigue Damage Estimation in the Field Yahya Modarres-Sadeghi, Michael Triantafyllou, Franz Hover We apply systematic diagnostics obtained form laboratory experiments at MIT to the strain and acceleration signals of model scale experiments on a riser, in order to assess the predictability of the response, and also extract the contribution of the higher-harmonic force components. The displacement signals are cut into small sub-signals and the cross flow displacement in each sub-signal is plotted versus the in-line displacement, showing a figure-eight or crescent-like motion. For linearly sheared flow cases, the trajectories are counterclockwise (moving upstream at the lateral extremes) figure-eights at high flow region and change to crescent-like and clockwise figure-eight ones at low flow region. A large third-harmonic contribution is observed for the majority of uniform flow cases, suggesting the importance of considering the influence of higher harmonic force components, when analyzing the fatigue life of a riser. The region of excitation for various sheared flow cases remains almost constant, independent of the maximum sheared flow, suggesting about half of the riser is excited. The excited part covers the region where counterclockwise figure-eight motions are observed. These results can be directly compared with the results of the experiments on a flexibly mounted rigid cylinder, showing good agreement especially in sheared flow cases. [Preview Abstract] |
Tuesday, November 20, 2007 12:53PM - 1:06PM |
NI.00007: Squeeze Film Damping in the Limit of High Frequency Matthew Sullivan, Antoine Fornari, Philip Dryden, Hua Chen, Kai Hsu, Fredric Marty, Bruno Mercier, Christopher Harrison We present experimental evidence that the drag associated with squeeze film damping in the inertia-dominated regime scales like the inverse cube of the gap. The experiments were performed by measuring the resonant spectrum of vibrating plates fabricated with Micro Electro Mechanical Systems (MEMS) technology and studying their mechanical properties in near proximity to a wall. The resonant frequency and quality factor were measured from which the real and imaginary portions of the drag were calculated. By modeling the system as a simple harmonic oscillator with complex drag it was found that the inertial component dominated for $h>R$ and that the drag scaled as $R^3/h^3$, where $R$ and $h$ correspond to the effective plate radius and the gap respectively. In this regime the plate can be modeled with steady potential dipoles which have a pressure field that decays in the same manner with distance. [Preview Abstract] |
Tuesday, November 20, 2007 1:06PM - 1:19PM |
NI.00008: Flow Measurement in Liquid Aluminium Using Lorentz Force Velocimetry Andre Thess, Yurii Kolesnikov, Christian Karcher, Vitaly Minchenya We report a series of non-contact flow measurements in molten aluminium using a novel technique called Lorentz force velocimetry (LFV). This technique consists in exposing the flow to a magnetic field and measuring the force that acts on the magnet system. We explain the basic physical principles of the technique and show that it permits one to obtain reliable and accurate contactless flow measurements in a variety of materials processing applications. [Preview Abstract] |
Tuesday, November 20, 2007 1:19PM - 1:32PM |
NI.00009: ABSTRACT WITHDRAWN |
Tuesday, November 20, 2007 1:32PM - 1:45PM |
NI.00010: Measuring mixing efficiency Charles R. Doering, Takahide Okabe The mixing efficiency or stirring effectiveness of a flow can be quantified in terms of the suppression of concentration variance of a passive scalar sustained by steady sources and sinks. The mixing efficiency defined this way is the ratio of the scalar variance mixed by molecular diffusion alone to the (statistically steady state) variance in the presence of stirring. This measure of the effectiveness of the stirring is naturally related to the enhancement factor of the equivalent eddy diffusivity over molecular diffusion. This mixing efficiency naturally depends on the P\'eclet number, but it was recently noted that the maximum possible mixing efficiency at a given P\'eclet number depends as well on the structure of the sources and sinks. That is, in general it does not make sense to talk about the mixing effectiveness or eddy diffusion of a flow without also specifying the source-sink structure of whatever is being stirred. We present the results of particle-based numerical simulations quantitatively confirming the source-sink dependence of the mixing efficiency as a function of P\'eclet number for a model flow. [Preview Abstract] |
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