Bulletin of the American Physical Society
63rd Annual Meeting of the APS Division of Fluid Dynamics
Volume 55, Number 16
Sunday–Tuesday, November 21–23, 2010; Long Beach, California
Session QE: General Fluid Dynamics IV |
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Chair: Jean Hertzberg, University of Colorado, Boulder Room: Long Beach Convention Center 102C |
Tuesday, November 23, 2010 12:50PM - 1:03PM |
QE.00001: Light dragging phenomenon and expanding wormholes Hristu Culetu The null geodesic congruence for the Lorentzian version of Hawking's wormhole is studied, in spherical Rindler coordinates. One finds that the wormhole throat, where the stress energy is mostly located, expands exponentially and the flare - out condition is satisfied. The expanding fluid is anisotropic and has a mean pressure that is one third of the energy density, as for a null fluid. A time reversal is equivalent with an inversion applied to the radial coordinate. Far from the throat (the light cone in Cartesian coordinates) the energy density of the fluid no longer depends on the Newton constant G and acquires an expression similar with the Casimir energy density between two perfectly reflecting plates. [Preview Abstract] |
Tuesday, November 23, 2010 1:03PM - 1:16PM |
QE.00002: The mass, energy, space and time systemic theory-MEST-quantum gravitational field Dayong Cao Not only thing has the mass-energy of itself, but also thing has the space-time of itself. The spcac is from the amplitude. The time is from the frequence. $S=P(r)={f^2}$, $T=P(t)=ln(1+\frac{1}{t})=2\pi\nu$. Among it, S: the space, T: the time, t: date, r: distance, f: the amplitude of wave, $\nu$: the frequence of wave, P(x): Probability function. There is the Wave-particle duality; there is a mass-energy duality. $E=h\nu$, $m=\frac{h}{{\lambda}{c}}$ Among it, E: the energy of particle, m: the mass of particle, c: the velocity of particle, $\nu$: the frequence of particle, h: the Planck constant. $E'{\psi}=i{\hbar}\frac{\partial{\psi}}{{\partial}t}$, $m'{\psi}=-i{\hbar}\frac{{\partial}{\psi}{\partial}t} {{(\partial}x)^2}.$ Among it, E$'$: the energy of wave, m$'$: the mass of wave, c$'$: the velocity of wave, ${\psi}$: the Wave Functions. In the solar system, sun radiate the repulsive (energy) wave and absorb the absorptive (mass) wave. and there is a energy balance system.The paper suppose that unlike mass repel each other; unlike energy attract. $E+E'{\psi}=mc^2+m'c'^2, (\frac{({\partial}x)^2}{({\partial}t)^2}=c'^2)$. Everything has a system; anything can not exist without the system. The quark and Gluons are made up of the system of quark confinement. [Preview Abstract] |
Tuesday, November 23, 2010 1:16PM - 1:29PM |
QE.00003: Seeing Fluid Physics: Outcomes From a Course on Flow Visualization Jean Hertzberg Since 2003, a course on flow visualization has been offered to mixed teams of engineering and fine arts photography students at the University of Colorado. The most significant outcome of the course is the impact on students' perceptions; they \textit{see} fluid physics as ubiquitous in the environment after taking the course. A survey instrument has been developed that explores student perceptions of fluid physics, and has been administered to students in the flow visualization course, and in a traditional junior level fluid mechanics course. Survey results indicate that the students in the flow visualization course notice fluid physics in daily life at an increased rate, and their attitude (affect) towards fluids is improved compared to students in the traditional course. The use of photography in improving student perceptions is being extended to a course on perception of design; preliminary results from a survey on attitudes towards design will be presented. Examples of student images from both courses will be presented as well. [Preview Abstract] |
Tuesday, November 23, 2010 1:29PM - 1:42PM |
QE.00004: New Ways of Teaching Upper-division courses: Descriptions and Results Rachel Pepper, Stephanie Chasteen, Steven Pollock, Michael Dubson, Paul Beale, Katherine Perkins Over the past three years, the physics faculty at the University of Colorado have worked to transform two core courses in our upper-division undergraduate physics curriculum, Electricity and Magnetism and Quantum Mechanics, with the goals of (a) improving student learning and (b) developing materials and approaches that other faculty may adopt or adapt to their teaching environment. The transformation of our upper-division physics courses may serve as a model for transformation of other upper-division courses, such as fluid mechanics courses. This work began with faculty working groups meeting regularly to define explicit course learning goals. These learning goals served as the foundation for the course transformations that applied the principles of active engagement and learning theory to these upper-division courses. The development of the full curriculum was guided by the results of observations, interviews, and analysis of student work. In this talk, we will outline the reforms -- including consensus learning goals, ``clicker'' questions, tutorials, modified homeworks, and more -- and present evidence of the effectiveness of these reforms relative to traditional courses. Some research-based fluid mechanics instructional materials will also be discussed. All of our curriculum materials are available at http://www.colorado.edu/sei/departments/physics.htm. [Preview Abstract] |
Tuesday, November 23, 2010 1:42PM - 1:55PM |
QE.00005: Oscillatory motion of flat square wall-hinged winglets inside a turbulent boundary layer Amir Elzawawy, Yiannis Andreopoulos An experiment in a wind tunnel has been designed to investigate the augmented force generation acting on winglets during periodic rotation between zero and ninety degrees angle to the flow. Square and triangular flaps hinged at the wall beneath the flow have been used which were rotated with angular velocities between 10 and 150 rad/s. Strouhal numbers between 0.05 and 1.1 and Stokes numbers between 6300 and 95000 were achieved. Time-resolved Particle Image Velocimetry was implemented by using a continuous laser and fast frame-rate camera to provide qualitative and quantitative information of the flow field. The dynamic lift and drag force coefficients during the periodic motion of the winglet are different than the corresponding coefficients under stationary conditions at the same deployment angle after adjusting for inertial effects. These effects are enhanced with increasing Strouhal number and decrease with increasing boundary layer thickness. A highly intermittent thin boundary layer developing over the forward moving surface of the winglet separates into a shear layer which wraps around to form a large scale vortex which is causing the force augmentation. [Preview Abstract] |
Tuesday, November 23, 2010 1:55PM - 2:08PM |
QE.00006: Combined experimental and computational investigation of sterile air flows in surgical environments James McNeill, Jean Hertzberg, Zhiqiang Zhai Surgical environments in hospitals utilize downward, low-turbulence, sterile air flow across the patient to inhibit transmission of infectious diseases to the surgical site. Full-scale laboratory experiments using particle image velocimetry were conducted to investigate the air distribution above the patient area. Computational fluid dynamics models were developed to further investigate the air distribution within the operating room in order to determine the impact of ventilation design of airborne infectious disease pathways. Both Reynolds-averaged Navier-Stokes equations and large eddy simulation techniques are currently being used in the computational modeling to study the effect of turbulence modeling on the indoor air distribution. CFD models are being calibrated based on the experimental data and will be used to study the probability of infectious particles entering the sterile region of the room. [Preview Abstract] |
Tuesday, November 23, 2010 2:08PM - 2:21PM |
QE.00007: The incorporation of computational fluid dynamics (CFD) capabilities with RISK, an indoor air quality zonal model developed by the U.S. EPA David Marr Individual exposure to indoor contaminant concentrations is often estimated using assumptions of fully mixed conditions. The applicability of such an assumption can vary significantly based on the ventilation design and contaminant of interest. To solve for gradients in the contaminant concentration field, a CFD solver has been added to RISK, the primary indoor air quality model developed by the U.S. Environmental Protection Agency. The RISK model was created to solve for ``zonal'' concentrations based on emission characteristics of indoor materials and emission sources. Current updates to this model allow for a greater resolution and therefore more detailed view of risk and exposure in the indoor environment towards risk management. CFD results are compared to particle image velocimetry (PIV) experimental databases acquired at the U.S. EPA and Syracuse University. This presentation includes a brief overview of the model capabilities, steps towards validation of the model output, and examples of indoor contaminant transport from common indoor material emissions. [Preview Abstract] |
Tuesday, November 23, 2010 2:21PM - 2:34PM |
QE.00008: Flow-Induced Stress Distribution in Porous Scaffolds Dimitrios Papavassiliou, Roman Voronov, Samuel VanGordon, Vassilios Sikavitsas Flow-induced stresses help the differentiation and proliferation of mesenchymal cells cultured in porous scaffolds within perfusion bioreactors. The distribution of stresses in a scaffold is thus important for understanding the tissue growth process in such reactors. Computational results for flow through Poly-L-Lactic Acid porous scaffolds that have been produced with salt-leaching techniques, and for scaffolds that have been constructed with nonwoven fibers, indicate that the probability density function (pdf) of the wall stress, when normalized with the mean and the standard deviation of the pdf, appears to follow a single type of pdf. The scaffolds were imaged with micro-CT and the simulations were run with lattice Boltzmann methods. The parameters of the distribution can be obtained using Darcy's law and the Blake-Kozeny-Carman equation. Experimental results available in the literature appear to corroborate the computational findings, leading to the conclusion that stresses in high-porosity porous materials follow a single distribution. [Preview Abstract] |
Tuesday, November 23, 2010 2:34PM - 2:47PM |
QE.00009: Microfluidic Production of Monodisperse Perfluorocarbon Microdroplets David Li, Kevin Schalte, J. Brian Fowlkes, Joseph Bull Acoustic droplet vaporization (ADV) is process in which liquid perfluorocarbon (PFC) microdroplets are vaporized using focused ultrasound to form gas bubbles that are approximately 125 times larger in volume. Gas embolotherapy is a novel cancer treatment that uses ADV in vivo to strategically form gas emoboli, which can lodge in the microcirculation and starve tumors. Current methods to produce PFC microdroplets, such has high speed shaking or sonication, result in polydisperse droplet distributions where a fraction of droplets fall within the 2-10 microns range. In the clinical application with such a droplet distribution, large droplets are filtered by the lungs and small droplets result in bubbles that are too small to lodge in the tumor vasculature. Consequently, there is a need for a monodisperse droplet distribution. A microfluidic based device has been developed in order to produce such monodisperse PFC microdroplets. The device used hydrodynamic flow focusing to create droplets with a mean diameter less than 10 microns in diameter. This work is supported by NIH grant R01EB006476. [Preview Abstract] |
Tuesday, November 23, 2010 2:47PM - 3:00PM |
QE.00010: The Effect of Nonuniform Inlet Conditions on Annular Diffusers Angelina Padilla, Chris Elkins, John Eaton Most practical diffusers have complex 3D geometries and may have highly disturbed inlet flows. The performance of diffusers designed for optimum pressure recovery is governed by flow separation which can be very sensitive to inlet perturbations. We are examining the effect of upstream disturbances on the performance of practical annular diffusers. Experiments are conducted in an annular diffuser sector containing a single NACA 0015 airfoil shaped support strut. Three component, time averaged velocities are measured using magnetic resonance velocimetry and static pressure data are measured with conventional wall taps. We are testing four inlet conditions: a uniform velocity profile with thin boundary layers and relatively low turbulence intensity, a similar case with higher turbulence levels, a mean profile with uniform velocity except for a high velocity wall jet at the outer radius, and a nonuniform profile in which the mean velocity decreases with increasing radius. Generally, the results show that the diffuser acts to increase flow distortion. For the case with the radial velocity gradient, passing through the diffuser strongly increases the velocity gradient. The wall jet on the outer (diffusing) wall eliminates flow separation resulting in higher pressure recovery and thicker wall boundary layers on the other three walls. Interestingly, the separated wake of the support strut closes more rapidly for the case with the radial velocity gradient. [Preview Abstract] |
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