Search results for "BUBBLE"
showing 10 items of 167 documents
A preliminary method for the numerical prediction of the behavior of air bubbles in the design of Air Cavity Ships
2016
Air-cavity ships (ACS) are advanced marine vehicles that use air injection under hull to improve the vessel’s hydrodynamic characteristics. Although the concept of drag reduction by supplying gas under the ship’s bottom was proposed in the 19th century by Froude and Laval, at this time there are not many systematic studies on this subject. This paper is a preliminary work with the purpose of being a basic tool for the design of the ACS with computational fluid dynamic methods. The study aims to conduct a series of computational tests to compare the numerical models of bubble with experimental data. The first step of this study was to investigate the behavior of free bubble in water, conside…
Analysis of the bubbling behaviour of 2D gas solid fluidized beds
2008
Abstract In the field of gas–solid fluidization, bubbles, and all features regarding them, have a very great importance, as they significantly affect the process performance. Numerous experimental studies on bubbles, and their formation, evolution, and properties, have been performed in the past. These investigations appear particularly difficult, due to the nature of these systems, since the gas phase is distributed in both the bubble and the emulsion phase. Several experimental approaches have been developed to tackle this study. Among these, the Digital Image Analysis Technique purposely developed in Part I of the present work, based on the use of a video camera for monitoring the phenom…
Bubble formation at variously inclined nozzles
2014
Bubble formation at variously inclined submerged nozzles, fed with a continuous gas flow rate, is investigated. Results confirm previous findings, such as a substantial independence of bubble size of nozzle diameter and its dependence on the cubic root of gas flow rate at sufficiently high values of this parameter. Nozzle inclination in the range between 0 and 135° from the vertical upward orientation is found to have a negligible effect on bubble size. Observed bubble rise velocities lead to an estimation of the average liquid velocity induced by bubbles motion, leading in turn to a very simple correlation for the estimation of the liquid velocities induced by the repeated passage of bubbl…
Free surface oxygen transfer in large aspect ratio unbaffled bio-reactors, with or without draft-tube
2015
Abstract It is widely accepted that animal cell damage in aerated bioreactors is mainly related to the bursting of bubbles at the air–liquid interface. A viable alternative to sparged bioreactors may be represented by uncovered unbaffled stirred tanks, which have been recently found to be able to provide sufficient mass transfer through the deep free surface vortex which takes place under agitation conditions. As a matter of fact, if the vortex is not allowed to reach impeller blades, no bubble formation and subsequent bursting at the free-surface, along with relevant cells damage, occurs. In this work oxygen transfer performance of large aspect ratio unbaffled stirred bioreactors, either e…
Stability criteria, atomization and non-thermal processes in liquids
2008
Analyzing the first equation in the BBGKY chain of equations for an equilibrium liquid-gas system, we derived the analytical expression for the atom work function from liquid into gas. The coupling between the atom work function from liquid into vacuum and the stability criterion of liquid in limiting points of the first type was shown (using I.Z.. Fisher classification). As it turned out, Fisher's criterion corresponds to the condition of atomization. We have expressed the state equation in terms of the atom work function from liquid into vacuum and performed calculations of the limiting line of stability composed of limiting points of the first type for argon. Our model discovers an inter…
Resolving gas bubbles ascending in liquid metal from low-SNR neutron radiography images
2021
We demonstrate a new image processing methodology for resolving gas bubbles travelling through liquid metal from dynamic neutron radiography images with an intrinsically low signal-to-noise ratio. Image pre-processing, denoising and bubble segmentation are described in detail, with practical recommendations. Experimental validation is presented—stationary and moving reference bodies with neutron-transparent cavities are radiographed with imaging conditions representative of the cases with bubbles in liquid metal. The new methods are applied to our experimental data from previous and recent imaging campaigns, and the performance of the methods proposed in this paper is compared against our p…
Monitoring the Growth of a Microbubble Generated Photothermally onto an Optical Fiber by Means Fabry-Perot Interferometry.
2021
In the present paper, we show the experimental measurement of the growth of a microbubble created on the tip of a single mode optical fiber, in which zinc nanoparticles were photodeposited on its core by using a single laser source to carry out both the generation of the microbubble by photothermal effect and the monitoring of the microbubble diameter. The photodeposition technique, as well as the formation of the microbubble, was carried out by using a single-mode pigtailed laser diode with emission at a wavelength of 658 nm. The microbubble’s growth was analyzed in the time domain by the analysis of the Fabry–Perot cavity, whose diameter was calculated with the number of interference frin…
The invisible setting of digital space: the Facebook case
2018
La neutralidad en la red no existe. El espacio digital puede ser adaptado de forma automática al perfil de cada usuario. Sin que este tenga que identificarse, las empresas de gestión de contenidos en Internet disponen de suficientes datos de cualquier individuo para poder filtrar los resultados de su búsqueda y personalizarlos, sin previo aviso, condicionando así su experiencia en la red. Esta investigación, de carácter exploratorio, aborda en primer lugar la descripción del espacio público digital. En segundo lugar, plantea una tipología de espacios digitales que se definen en función del grado de adaptación de los contenidos al usuario. Finalmente, presenta un análisis de caso de espacio …
MHT-X: Offline Multiple Hypothesis Tracking with Algorithm X
2021
An efficient and versatile implementation of offline multiple hypothesis tracking with Algorithm X for optimal association search was developed using Python. The code is intended for scientific applications that do not require online processing. Directed graph framework is used and multiple scans with progressively increasing time window width are used for edge construction for maximum likelihood trajectories. The current version of the code was developed for applications in multiphase hydrodynamics, e.g. bubble and particle tracking, and is capable of resolving object motion, merges and splits. Feasible object associations and trajectory graph edge likelihoods are determined using weak mas…
Phase boundary dynamics of bubble flow in a thick liquid metal layer under an applied magnetic field
2020
Dynamic neutron radiography is used to observe the effect of a transverse magnetic field on argon bubbles rising through a thick layer of liquid gallium without interactions with the container walls.