scholarly journals The coalescence of liquid drops in a viscous fluid: interface formation model

2014 ◽  
Vol 751 ◽  
pp. 480-499 ◽  
Author(s):  
James E. Sprittles ◽  
Yulii D. Shikhmurzaev
Keyword(s):  
Drop Size ◽  
Experimental Studies ◽  
Fluid Interface ◽  
Formation Model ◽  
Ambient Fluid ◽  
Interface Formation ◽  
Coalescence Process ◽  
Conventional Model ◽  
Internal Interface ◽  
Liquid Drops

AbstractThe interface formation model is applied to describe the initial stages of the coalescence of two liquid drops in the presence of a viscous ambient fluid whose dynamics is fully accounted for. Our focus is on understanding (a) how this model’s predictions differ from those of the conventionally used one, (b) what influence the ambient fluid has on the evolution of the shape of the coalescing drops and (c) the coupling of the intrinsic dynamics of coalescence and that of the ambient fluid. The key feature of the interface formation model in its application to the coalescence phenomenon is that it removes the singularity inherent in the conventional model at the onset of coalescence and describes the part of the free surface ‘trapped’ between the coalescing volumes as they are pressed against each other as a rapidly disappearing ‘internal interface’. Considering the simplest possible formulation of this model, we find experimentally verifiable differences with the predictions of the conventional model showing, in particular, the effect of drop size on the coalescence process. According to the new model, for small drops a non-monotonic time dependence of the bridge expansion speed is a feature that could be looked for in further experimental studies. Finally, the results of both models are compared to recently available experimental data on the evolution of the liquid bridge connecting coalescing drops, and the interface formation model is seen to give a better agreement with the data.

Dynamic fluid interface formation in microfluidics: Effect of emulsifier structure and oil viscosity

2018 ◽  
Vol 45 ◽  
pp. 215-219 ◽  
Author(s):  
Kelly Muijlwijk ◽  
Xuezhu Li ◽  
Claire Berton-Carabin ◽  
Karin Schroën
Keyword(s):  
Fluid Interface ◽  
Oil Viscosity ◽  
Interface Formation

scholarly journals Characterization and Simulation of a Low-Pressure Rotator Spray Plate Sprinkler Used in Center Pivot Irrigation Systems

Water ◽  
2019 ◽  
Vol 11 (8) ◽  
pp. 1684 ◽  
Author(s):  
Cruz Octavio Robles Rovelo ◽  
Nery Zapata Ruiz ◽  
Javier Burguete Tolosa ◽  
Jesús Ramiro Félix Félix ◽  
Borja Latorre
Keyword(s):  
Drag Coefficient ◽  
Distribution Pattern ◽  
Size Distribution ◽  
Water Distribution ◽  
Drop Size ◽  
Low Pressure ◽  
Drop Size Distribution ◽  
Energy Losses ◽  
Conventional Model ◽  
The Impact

Spray sprinklers enable to operate at low pressures (<103 kPa) in self-propelled irrigation machines. A number of experiments were performed to characterize the water distribution pattern of an isolated rotator spray plate sprinkler operating at very low pressure under different experimental conditions. The experiments were performed under two pressures (69 kPa and 103 kPa) and in calm and windy conditions. The energy losses due to the impact of the out-going jet with the sprinkler plate were measured using an optical technique. The adequacy to reproduce the measured water distribution pattern under calm conditions of two drop size distribution models was evaluated. A ballistic model was used to simulate the water distribution pattern under wind conditions evaluating three different drag models: (1) considering solid spherical drops; (2) a conventional model based on wind velocity and direction distortion pattern, and (3) a new drag coefficient model independent of wind speed. The energy losses measured with the optical method range from 20% to 60% from higher to lower nozzle sizes, respectively, for both evaluated working pressures analyzing over 16,500 droplets. For the drop size distribution selected, Weibull accurately reproduced the water application with a maximum root mean square error (RMSE) of 19%. Up to 28% of the RMSE could be decreased using the wind-independent drag coefficient model with respect to the conventional model; the difference with respect to the spherical model was 4%.

The jet density exponent issue for the noise of heated subsonic jets

1974 ◽  
Vol 64 (3) ◽  
pp. 611-622 ◽  
Author(s):  
R. Mani
Keyword(s):  
Speed Of Sound ◽  
Plug Flow ◽  
Experimental Studies ◽  
Acoustic Power ◽  
Point Of View ◽  
Ambient Fluid ◽  
Simple Assumption ◽  
Exit Velocity ◽  
Radiative Efficiency ◽  
Flow Round

The subject of the present study is the question of how the sound power of a jet of constant exit velocity would vary if the jet exit density were varied. Changes in jet exit density would inevitably be accompanied in a real experiment by changes in the speed of sound (temperature) in the jet, so that both effects must be considered simultaneously. The point of view advanced at the end of the study is that experimentally observed results in this area seem to admit an explanation based on how the radiative efficiency of moving acoustic sources is affected by the shrouding effect of a jet flow whose velocity, temperature and density differ from those of the ambient fluid. This change in efficiency is calculated with the aid of a simple model as follows. We determine the acoustic power output of a convected monopole source, simple harmonic in its own frame of reference, moving along the axis of a plug-flow round jet whose velocity is the same as that of the source. The jet is doubly infinite and the source is assumed to have an infinite lifetime. The density and temperature of the jet are allowed to differ from those of the ambient fluid though the specific-heat ratio of the jet fluid is assumed to be the same as that of the ambient. The requirement of equality of the static pressure inside and outside the jet then calls for a certain restraint on how the jet density and temperature vary. For a specific value of the jet exit velocity, the variation of acoustic power with the ratio of jet to ambient density along with a simple assumption on how the source strength varies with jet density are employed to deduce theoretically the ‘jet density exponent for jets which are subsonic with respect to the ambient speed of sound. The jet density exponent is found to depend both on the jet Mach number and even more strongly on a source frequency parameter. The theoretical results are compared with some experimental studies of this problem. Encouraging agreement is obtained both for the detailed observed effects on the power spectrum and the exponent for the overall power.

A New Concept in Design of Rheolytic Thrombectomy Devices: The Coanda Effect

2009 ◽  
Author(s):  
Cheng-Shiu Chung ◽  
Sergio L. Cornejo ◽  
Ming Huo ◽  
Ender A. Finol
Keyword(s):  
Pressure Distribution ◽  
High Speed ◽  
Experimental Studies ◽  
Pressure Sensors ◽  
Surface Velocity ◽  
Coanda Effect ◽  
Ambient Fluid ◽  
Mixing Rate ◽  
Coandǎ Effect ◽  
Coanda Flow

The Coanda effect, which was first named by Henri Coanda in 1910, is the phenomenon when a fluid, gas or liquid, attaches to a solid surface, called the Coanda surface. The direction of this adhered flow changes along with the surface because of the Van der Walls forces or surface tension. Therefore, the pressure distribution of the ambient fluid is also altered due to the bent attached Coanda flow. The fluid material properties, Coanda flow velocity, curvature of the Coanda surface, velocity of the ambient fluid flow, and distance to the wall above the Coanda flow are the primary factors affecting this pressure distribution. In experimental studies, Panitz and Wasan [1] evaluated the pressure distribution of the Coanda effect by using pressure sensors on the Coanda surface and a colored dye solution in the flow. By means of photographs and experimental data, they describe the influence of different heights of the shroud (a sheath plate above the Coanda surface) and the secondary flow entrainment (flow of ambient fluid) on the pressure profiles. Vortices occur beneath the Coanda flow when the height of the shroud is lower than a specified reference. Cutbill et al. [2] developed a high speed Coanda flow k-ε turbulence model in the application of PHOENICS to improve the prediction of the mixing rate, shock wave structure and flow separation. The pressure drop occurs near the Coanda surface in both experimental and computational prediction results.

Experimental Studies in Fluid Mechanics and Materials Science Using Acoustic Levitation

1986 ◽  
Vol 87 ◽  
Author(s):  
E. H. Trinh ◽  
J. Robey ◽  
A. Arce ◽  
M. Gaspar
Keyword(s):  
Materials Science ◽  
Acoustic Radiation ◽  
Measurement Techniques ◽  
Experimental Studies ◽  
Direct Application ◽  
Acoustic Levitation ◽  
Low Gravity ◽  
Liquid Drops ◽  
Radiation Forces ◽  
Freely Suspended

AbstractGround-based and short-duration low gravity experiments have been carried out with the use of ultrasonic levitators to study the dynamics of freely suspended liquid drops under the influence of predominantly capillary and acoustic radiation forces. Some of the effects of the levitating field on the shape as well as the fluid flow fields within the drop have been determined. The development and refinement of measurement techniques using levitated drops with size on the order of 2mm in diameter have yielded methods having direct application to experiments in microgravity. In addition, containerless melting, undercooling, and freezing of organic materials as well as low melting metals have provided experimental data and observation on the application of acoustic positioning techniques to materials studies.

A Novel Method for Evaluation of the Flow Field Effects on Mean Drop Size in a Multiphase CFB

2015 ◽  
Vol 4 (2) ◽  
pp. 13-36
Author(s):  
Ali Akbar Jamali ◽  
Shahrokh Shahhosseini ◽  
Yaghoub Behjat
Keyword(s):  
Drop Size ◽  
Orifice Diameter ◽  
Injection Velocity ◽  
Structural Parameter ◽  
Liquid Drops ◽  
Riser Reactor ◽  
Proposed Model ◽  
Liquid Injection ◽  
Novel Method ◽  
Current Flows

Prompt evaporation of injected liquid drops near the injectors locating in the FCC unit riser reactor has considerable impacts on the gas–solid mixing phenomena. To investigate influencing various parameters on the injected liquid species in the riser, conservation equations are primarily needed. A novel model to predict droplet mean diameter (DMD) due to computing penetration depth of the jet flowing through the riser was proposed. The proposed model is able to indirect predict DMD based on direct computation of spray tip penetration (STP). The model has been validated by some empirical correlations. In this study, influencing gas superficial velocity, liquid injection velocity, jet angle and nozzle diameter on DMD were investigated. The results for both concurrent and counter-current flows showed that the decrease of jet angle and injection velocity improves DMD. In addition, increasing orifice diameter (as a structural parameter) arising mean drop size can decline performance of atomizing. It also displayed close agreement between the model predictions and experimental data. In this work, the measurement error associated with STP was determined up to 2.7 mm, and the mean relative error with respect to detecting STP is 4.3%.

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