Bubble Length (bubble + length)

Distribution by Scientific Domains

Selected Abstracts

Shape of isolated bubble in intermittent flows in a horizontal pipe

Gu Hanyang
Abstract An experimental study on the shape of a single bubble similar to those observed in a horizontal plug/slug flow was performed using visual observation and conductance probes. The results indicated that the shapes of the bubble nose and the bubble body depend on the Froude number defined by gas/liquid mixture velocity, whereas the shape of the back region of the bubble depends on both the Froude number and bubble length. The photographic images showed that the structural feature of the bubble head is related to the motion characteristics of the bubble. The transition from plug flow to slug flow occurs when the tail of the bubble changes from a staircase to hydraulic jump pattern with the increasing of the Froude number and bubble length. 2007 Wiley Periodicals, Inc. Heat Trans Asian Res, 36(5): 276, 285, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.20161 [source]

Laminar separation bubble on an Eppler 61 airfoil

Samir B. Savaliya
Abstract Laminar separation bubble that occurs on the suction side of the Eppler 61 airfoil at Re=46000 is studied. The incompressible flow equations are solved using a stabilized finite element method. No turbulence model is used. The variation of the bubble length and its location, with the angle of attack (,), is studied in detail. An abrupt increase in the lift coefficient is observed at ,,4.5. It is found to be related to a sudden decrease in the separation bubble length at the trailing edge of the airfoil. Significant differences are observed in the results from the 2D and 3D computations. Stall is observed in 3D simulations, but is found to be absent in 2D. The laminar bubble, which fails to reattach in 3D for ,>14, continues to reattach for , as large as 20 in the 2D computations. Reynolds stress calculations in both 2D and 3D indicate the extent to which the outer flow is affected by the presence of bubble. It is found that the Reynolds stress components and are of comparable order of magnitude indicating that spanwise fluctuations are significant. The effect of the time window used to compute the time-averaged aerodynamic coefficients is studied. The time-averaged and root mean square (rms) value of the aerodynamic coefficients are calculated for both 2D and 3D computations and compared with the previously published experimental results. The 3D computations show good agreement with the earlier data. The variation of the rms value of the aerodynamic coefficients with angle of attack shows certain peaks. The cause of their appearance is investigated. The effect of Reynolds number is studied. The increase in Re at ,=10 is found to reduce the bubble length and cause it to move closer to the leading edge. Copyright 2009 John Wiley & Sons, Ltd. [source]

Influence of processing conditions and part design on the gas-assisted injection molding process

Nan-Shing Ong
Gas-assisted injection molding has been developed to solve the problems that the conventional injection molding process is not able to. It is believed that the new process is able to produce final parts with higher quality at a more effective cost. Warpage and sink marks are reduced and there is material-savings to be reaped. This research aims to investigate some of the processing parameters that come with this new process. They include shot size, gas delay time, gas pressure, and melt temperature. The influence of part design is also looked into. Five designs were used in the research and compared. The responses evaluated include gas bubble length, residual wall thickness, bending strength, warpage, and fingering. 2001 John Wiley & Sons, Inc. Adv Polym Techn 20: 270,280, 2001 [source]

Hydrogenation of 2-ethylanthraquinone under Taylor flow in single square channel monolith reactors

AICHE JOURNAL, Issue 3 2009
Dingsheng Liu
Abstract The hydrogenation of 2-ethylanthraquinone (EAQ) to 2-ethylanthrahydroquinone (EAHQ) was carried out under Taylor flow in single square channel monolith reactors. The two opening ends of opaque reaction channel were connected with two circular transparent quartz-glass capillaries, where Taylor flow hydrodynamics parameters were measured and further used to obtain practical flow state of reactants in square reaction channels. A carefully designed gas-liquid inlet mixer was used to supply steady gas bubbles and liquid slugs with desired length. The effects of various operating parameters, involving superficial gas velocity, superficial liquid velocity, gas bubble length, liquid slug length, two-phase velocity and temperature, on EAQ conversion were systematically researched. Based on EAQ conversion, experimental overall volumetric mass transfer coefficients were calculated, and also studied as functions of various parameters as mentioned earlier. The film model, penetration model, and existing semi-empirical formula were used to predict gas-solid, gas-liquid, and liquid-solid volumetric mass transfer coefficients in Taylor flow, respectively. The predicted overall volumetric mass transfer coefficients agreed well with the experimental ones. 2009 American Institute of Chemical Engineers AIChE J, 2009 [source]