Bulletin of the American Physical Society
65th Annual Meeting of the APS Division of Fluid Dynamics
Volume 57, Number 17
Sunday–Tuesday, November 18–20, 2012; San Diego, California
Session R28: General Fluids III |
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Chair: Alfonso Ganan-Calvo, ESI, Universidad de Sevilla Room: 32A |
Tuesday, November 20, 2012 1:00PM - 1:13PM |
R28.00001: Thermodynamics of continuous media with permanent electric polarisation and magnetisation Sylvain Brechet, Jean-Philippe Ansermet The thermodynamics of an electrically charged, multicomponent fluid with permanent electric polarisation, permanent magnetisation and intrinsic vorticity is analysed in the presence of electromagnetic fields with magnetoelectric coupling in the classical limit. Three equations characterising the fluid are derived: a thermostatic equilibrium equation, a reversible and an irreversible thermodynamic evolution equation. These equations are obtained by taking into account the first and second laws of thermodynamics, the chemical reactions, the second law of Newton in translation and in rotation, the local time evolution of the permanent polarisation and the permanent magnetisation, and Maxwell's equations. Explicit expressions for the temperature and the chemical potentials are derived in terms of the electromagnetic fields, the permanent electric polarisation, the permanent magnetisation, the intrinsic vorticity and the magnetoelectric coupling. The analysis of the irreversible thermodynamics yields novel dissipative equations accounting in particular for dielectrophoresis, magnetophoresis, the relaxation of the permanent electric polarisation and the permanent magnetisation, and other properties of electrorheological and magnetorheological fluids. [Preview Abstract] |
Tuesday, November 20, 2012 1:13PM - 1:26PM |
R28.00002: Physical symmetries of Taylor cone-jets: foundations of scaling laws Alfonso M. Ganan-Calvo, Jose M. Montanero, Noelia Rebollo-Munoz In this work, we aim to establish the scaling laws for the liquid rate of flow naturally ejected by quasi-steady Taylor cone-jets. To this end, we utilize an ample literature in the field reporting precise measurements of the electric current transported and the resulting droplet size as a function of liquid properties and flow rate. The projection of thousands of experimental conditions onto an appropriate non-dimensional parameter space maps a region bounded by the minimum rate of flow attainable in steady state. In this limit, a theoretical model here proposed teaches that a remarkable system of symmetries rises at the geometrical transition from the cone to the jet. This system of symmetries determines an inescapable scaling for the minimum flow rate and related variables. If the flow rate is further decreased, those symmetries break down (the system bifurcates: global instability \& dripping). Our model predicts the minimum flow rates reached in experiments reported so far in the literature, including all ranges of liquid properties. The existing literature and a set of new experiments performed for this specific purpose confirms our predictions. [Preview Abstract] |
Tuesday, November 20, 2012 1:26PM - 1:39PM |
R28.00003: The Minimum Flow Rate Scaling in Taylor Cone-Jets William Scheideler, Chuan-Hua Chen A minimum flow rate is required to maintain steady electrohydrodynamic Taylor cone-jets, and is empirically known to be inversely proportional to the electrical conductivity of the working fluid in the electrospraying literature. Here, we show that this scaling law governed by the charge relaxation process is only applicable to low-viscosity liquids. At higher viscosities, the minimum flow rate is governed by the capillary-inertial process and exhibits a strong dependence on the nozzle diameter instead of the liquid conductivity. The two scaling laws are demarcated by the Ohnesorge number based on the nozzle diameter. [Preview Abstract] |
Tuesday, November 20, 2012 1:39PM - 1:52PM |
R28.00004: Stability of a viscous pinching thread Jens Eggers We consider the dynamics of a fluid thread near pinch-off, in the limit that inertial effects can be neglected. There exists an infinite hierarchy of similarity solutions corresponding to pinch-off. Only one of the similarity solutions (the ``ground state'') is stable, all other solutions are linearly unstable to perturbations, and thus cannot be observed. Eigenvalues and eigenfunctions are calculated analytically. [Preview Abstract] |
Tuesday, November 20, 2012 1:52PM - 2:05PM |
R28.00005: Laboratory experiments on stratified flow through a suspended porous fence Sarah Delavan, Roger Nokes, David Plew This study explores stratified flow through a suspended, porous, fence-like obstacle to simulate flow through fish farm cages, mussel farm rope suspensions, flow through suspended aquatic vegetation, underwater energy production structures, or windbreak and wave break fencing. Laboratory experiments were performed in a density stratified, stationary flume with a suspended porous fence model using a particle tracking velocimetry (PTV) system. Experiments explored the effect on the fluid of the fence depth to total depth ratio, the system Richardson number, and the porosity of the fence. Preliminary results suggest that the density stratification of the fluid inhibits vertical fluid motion, that fence porosity greatly controls the vertical mixing of the fluid, and that there may be an optimal fence depth to total depth ratio for full development of the system flow structures. [Preview Abstract] |
Tuesday, November 20, 2012 2:05PM - 2:18PM |
R28.00006: Solutions to separated and quasi-laminarized pressure gradient boundary layers via similarity analysis Riki Minoru Hopkins, Raul Bayoan Cal Numerical solutions have been found through a characteric equation. This equation was first obtained via similarity analysis of the equations of motion. The equations are analyzed for limiting pressure gradient cases, namely quasi-laminarization and separation. It is also found that the profiles for the laminar case and experimental data for a quasi-laminarized case do not collapse thus showing the effects and remnants of turbulence. The experimental data considered was first reported by Warnack and Fernholz as well as Jones et al. The equation contains two key parameters which are the pressure parameter as obtained via similarity analysis as well as the Pohlhausen parameter. Further investigation is done for the skin friction coefficient. [Preview Abstract] |
Tuesday, November 20, 2012 2:18PM - 2:31PM |
R28.00007: Surface waves generated by a moving electromagnetic force on electrolytes Gerardo Alcal\'a, Sergio Cuevas We present an experimental study of the gravity-capillary waves generated in the liquid-air interface of a shallow electrolytic layer (NaHCO$_3$) due to an electromagnetic force created by the interaction an applied direct electric current and a traveling magnetic field. The field is generated by a permanent magnet traveling in straight line externally to the bottom of the fluid container, and having a dominant component perpendicular to the plane spanned by the surface at equilibrium. Through long parallel electrodes, the current is applied transversally to the motion of the magnet so that the electromagnetic force points in favor or against the movement of the magnet, according to the polarity of either the electrodes or the magnet. The electromagnetic force acts as an obstacle for the flow (a magnetic obstacle) and, analogously to a moving solid body, generates a stationary wave pattern, which is reconstructed for various speeds of the magnet using optical methods. Differences in wave patterns are discussed for when the electromagnetic force points either in favor or against the movement of the magnet. [Preview Abstract] |
Tuesday, November 20, 2012 2:31PM - 2:44PM |
R28.00008: Avoid Earth Extinction Dayong Cao In 2011, the author supposes: the dark hole will take the dark comet to impact our solar system in 20 years. (see Dayong Cao, BAPS.2011.DFD.LA.24, BAPS.2012.APR.K1.78 and BAPS.2011.APR.K1.17) Asteroid 2011 AG5 will impact on Earth in 2040. (See Donald K. Yoemans, ``Asteroid 2011 AG5 - A Reality Check,'' NASA-JPL, 2012) The dark Asteroid 2011 AG5 (as a dark comet) is made of the dark matte. Sun and its companion-dark hole are a binary system (Their systemic model- SDS for short there in after). The dark hole has a dark comet belt. The dark hole and dark comet are made of the dark matter which has a space-time (as frequence-amplitude square) center- a different systemic model from solar systemic model. Because it absorb the space-time and wave. So it is ``dark.'' When the dark hole goes near the sun every 25-27 million years, it will take its dark comet belt to go into the solar system to impact our earth. In a other hand, it can change all of our systemic model and code which are controled by the SDS, such as the orbit both of the asteroid belt and planet (such as Jupiter), our atomic structure and our genetic code. It can trigger periodic Mass Extinction. We will use the dark matter to change the SDS to avoid forthcoming extinction. [Preview Abstract] |
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