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 CK: Free Surface Flows: Macro-Scale Phenomena |
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Chair: Gaozhu Peng, Corning Inc. Room: Long Beach Convention Center 201B |
Sunday, November 21, 2010 1:00PM - 1:13PM |
CK.00001: Dragging a floating horizontal cylinder Duck-Gyu Lee, Ho-Young Kim A cylinder immersed in a fluid stream experiences a drag, and it is well known that the drag coefficient is a function of the Reynolds number only. Here we study the force exerted on a long horizontal cylinder that is dragged perpendicular to its axis while floating on an air-water interface with a high Reynolds number. In addition to the flow-induced drag, the floating body is subjected to capillary forces along the contact line where the three phases of liquid/solid/gas meet. We first theoretically predict the meniscus profile around the horizontally moving cylinder assuming the potential flow, and show that the profile is in good agreement with that obtained experimentally. Then we compare our theoretical predictions and experimental measurement results for the drag coefficient of a floating horizontal cylinder that is given by a function of the Weber number and the Bond number. This study can help us to understand the horizontal motion of partially submerged objects at air-liquid interface, such as semi-aquatic insects and marine plants. [Preview Abstract] |
Sunday, November 21, 2010 1:13PM - 1:26PM |
CK.00002: The submarine's wake Adrien Benusiglio, Marrie Le Merrer, Christophe Clanet An object moving under water creates a wake at the surface. We mesure the amplitude of the wake and the additive drag it creates on a sphere moving horizontally at different dephts an speeds. We isolate two different comportements at high and low depht. Can we deduce the size and depht of a submarine from it's wake? [Preview Abstract] |
Sunday, November 21, 2010 1:26PM - 1:39PM |
CK.00003: Experimental Investigation of Slamming Loads on a Flat Plate David Jeon, Francisco Huera-Huarte, Matthew Fu, Mory Gharib Slamming loads on marine structures and vessels pose a hazard, with the potential for structural failure from the high momentary loads. With interest in higher speed vessels, exterior panels face tremendous impact loads from both wave impact and slamming. We have designed an experimental apparatus that can slam a variety of objects into a free surface at a range of deadrise angles and impact speeds. This system is instrumented with load cells to give us the force history of the impact, rather than the pressure on the face of the panel. Impact speeds over 5 m/s have been tested, with impact angles ranging from 1-25 degrees, using a foam core composite panel. We have documented the cushioning effect of trapped air between the plate and the free surface at small impact angles. We have also seen a correlation between the impact duration and the total force. The authors would like to thank the Office of Naval Research for their support of this experiment through award number N00014-06-1-0730. In addition, FJHH would like to acknowledge the support given by the European Commission through the Marie Curie IOF for actions for individuals (PIOF-GA-2008-219429). [Preview Abstract] |
Sunday, November 21, 2010 1:39PM - 1:52PM |
CK.00004: A comparison of model-scale experimental measurements and computational predictions for a large transom-stern wave Thomas T. O'Shea, Kristy L.C. Beale, Kyle A. Brucker, Donald C. Wyatt, David Drazen, Anne M. Fullerton, Tom C. Fu, Douglas G. Dommermuth Numerical Flow Analysis (NFA) predictions of the flow around a transom-stern hull form are compared to laboratory measurements collected at NSWCCD. The simulations are two-phase, three-dimensional, and unsteady. Each required 1.15 billion grid cells and 200,000 CPU hours to accurately resolve the unsteady flow and obtain a sufficient statistical ensemble size. Two speeds, 7 and 8 knots, are compared. The 7 knots ($Fr=Uo /\sqrt{gLo}=0.38$) case is a partially wetted transom condition and the 8 knots ($Fr=0.43$) case is a dry transom condition. The results of a detailed comparison of the mean free surface elevation, surface roughness (RMS), and spectra of the breaking stern-waves, measured by Light Detection And Ranging (LiDAR) and Quantitative Visualization (QViz) sensors, are presented. All of the comparisons showed excellent agreement. The concept of height-function processing is introduced, and the application of this type of processing to the simulation data shows a $k^{-5/3}$ power law behavior for both the 7 and 8 knot cases. The simulations also showed that a multiphase shear layer forms in the rooster-tail region and that its thickness depends on the Froude number. [Preview Abstract] |
Sunday, November 21, 2010 1:52PM - 2:05PM |
CK.00005: Computation of two-dimensional standing water waves Jon Wilkening, Jia Yu, Chris Rycroft We develop a quasi-Newton trust-region shooting algorithm for solving two-point boundary value problems governed by nonlinear PDEs. We use our method to compute families of (time-periodic) standing water waves in two dimensions. To evolve the water wave in time, we use a spectrally accurate boundary integral collocation method. As a starting guess, we use analytically determined time-periodic solutions of the linearized problem about a flat surface. We then use our numerical method to continue these solutions beyond the realm of linear theory to explore the topology and bifurcation structure of a two-parameter family of standing waves (with mean depth and wave amplitude as parameters). Preliminary results suggest that if limiting wave profiles exist, they have more complicated singularities than the 90 degree angles previously conjectured. [Preview Abstract] |
Sunday, November 21, 2010 2:05PM - 2:18PM |
CK.00006: Computation of three-dimensional standing water waves Chris Rycroft, Jon Wilkening We develop a method for computing three-dimensional gravity-driven water waves, which we use to search for time-periodic standing wave solutions. We simulate an inviscid, irrotational, incompressible fluid bounded below by a flat wall, and above by an evolving free surface. The computations make use of spectral derivatives on the surface, but also require computing a velocity potential in the bulk, which we carry out using a finite element method with fourth order elements that are curved to match the free surface -- this computationally expensive step is solved using a parallel multigrid algorithm which we have developed. We search for time-periodic solutions using the trust-region shooting method that was previously used to find two-dimensional standing water waves. [Preview Abstract] |
Sunday, November 21, 2010 2:18PM - 2:31PM |
CK.00007: Energy Transfer into Cross-Waves by Wavemakers Tatyana Krasnopolskaya, Viatcheslav Meleshko, Viacheslav Spektor In the long channels, the cross-waves derive their energy directly from wavemaker not only from basic flow. In the present talk we show how cross-waves are generated in long rectangular channels by wavemaker even without having to take into account the presence of any basic flow waves. Here we apply Lam\`e's method of superposition for the first time in such channel geometry. This method allows one to construct a simple mathematical model, which shows how the cross-waves can be generated directly by the wavemaker motion. This mathematical model of the resonant cross-wave excitation is the easiest way to study pattern formation on fluid free surface. Our experimental observations agree with the theoretical results. [Preview Abstract] |
Sunday, November 21, 2010 2:31PM - 2:44PM |
CK.00008: Experimental Study of Free Surface Magnetohydrodynamic Flow J. Rhoads, E. Edlund, P. Sloboda, E. Spence, H. Ji Free surface MHD flows contain many interesting phenomena due to the interplay between the free boundary condition at the surface and the effects of the external magnetic field. This interaction can produce features distinct from other types of flow. The Liquid Metal Experiment (LMX) is designed to investigate the effects of a strong magnetic field applied orthogonal to the flow direction of an electrically conducting fluid. In order to study heat transfer under these conditions, a resistive heater and an infrared camera have been installed. Changes in the vortex street from the cylindrical heater have been observed as the field is increased. Additionally, the modification of underlying turbulent structures can be tracked using two position-sensitive diodes. This diagnostic records fluctuations of the surface from which the k-spectra can be extracted by using cross-correlation techniques. Lastly, a local velocity diagnostic is under development which should have the capability of mapping the velocity profile as a function of the magnetic field. An overview of the experiment and preliminary results will be presented. [Preview Abstract] |
Sunday, November 21, 2010 2:44PM - 2:57PM |
CK.00009: Experimental investigation of orbitally shaken bioreactor hydrodynamics Martino Reclari, Matthieu Dreyer, Mohamed Farhat The growing interest in the use of orbitally shaken bioreactors for mammalian cells cultivation raises challenging hydrodynamic issues. Optimizations of mixing and oxygenation, as well as similarity relations between different culture scales are still lacking. In the present study, we investigated the relation between the shape of the free surface, the mixing process and the velocity fields, using specific image processing of high speed visualization and Laser Doppler velocimetry. Moreover, similarity parameters were identified for scale-up purposes. [Preview Abstract] |
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