A Detailed Examination of Gas and Liquid Phase Transient Processes in Convective Droplet Evaporation

1989 ◽  
Vol 111 (2) ◽  
pp. 495-502 ◽  
Author(s):  
R. J. Haywood ◽  
R. Nafziger ◽  
M. Renksizbulut
Keyword(s):  
Liquid Phase ◽  
Numerical Technique ◽  
Detailed Examination ◽  
Droplet Surface ◽  
Transient Effects ◽  
Variable Properties ◽  
Phase Velocities ◽  
Transient Rise ◽  
Transient Variations ◽  
Phase Motion

A finite volume numerical technique has been used to model the evaporation of an n-heptane droplet with an initial Reynolds number of 100 in air at 800 K, 1 atm. The effects of variable thermophysical properties, liquid phase motion and heating, and transient variations in droplet size and velocity are included in the analysis. With appropriate corrections for the effects of variable properties and liquid phase heating, quasi-steady correlations are shown to predict accurately the transient histories of the drag coefficient and Nusselt and Sherwood numbers. For the case investigated here, the transient effects of importance were the variation in droplet velocity, the decline in the liquid phase velocities, and the rise in the droplet surface and volume average temperatures. In spite of the transient rise in the droplet temperature, the nature of the liquid phase heating, as characterised by the liquid Nusselt number, was found to remain constant during most of the droplet lifetime.

The Motion of a Bubble Swarm in Decaying Oscillating-Grid Turbulence and the Modulation of the Liquid-Phase Motion

2011 ◽  
Author(s):  
Yasuyuki Nagami ◽  
Takayuki Saito
Keyword(s):  
Liquid Phase ◽  
Decay Rates ◽  
Bubble Motion ◽  
Stagnant Water ◽  
Phase Velocities ◽  
Decaying Turbulence ◽  
Turbulence Condition ◽  
Condition B ◽  
Phase Motion ◽  
Oscillating Grid

The modulation induced by interaction between bubble motion and liquid-phase motion is important to deeply understand the multi-scale structure of a bubbly flow. In order to quantitatively and systematically clarify the interaction between the bubble swarm and the ambient liquid-phase motion, ideally controlled turbulence and bubble swarm are required. In the present study, we employed the decaying turbulence formed by oscillating grid and a well-controlled bubble swarm launched by hypodermic needles and audio speakers. We formed homogenous isotropic turbulence by using an oscillating grid (oscillating frequency: 4 Hz, stroke: 40 mm) in a cylindrical acrylic pipe (diameter: 149 mm, height: 600 mm) filled with ion-exchanged and degassed water. The decaying turbulence was formed after stopping the oscillating grid. A bubble swarm (: the member bubble rose zigzagging in stagnant water) was launched into the decaying turbulence after two seconds from stop of the oscillating grid. We measured the bubble swarm motion by visualization and did the liquid-phase motion by PIV/LIF system with high-speed video cameras. The measurements were performed under three experimental conditions; the first one is only the decaying turbulence (Condition-O), the second one is the bubble swarm launched into the stagnant water (Condition-B), the third one is the bubble swarm launched into the decaying turbulence (Condition-OB). From the visualization results, it was found out that the positions of the bubbles were expanded in the horizontal direction compared with that under Condition-B. This indicates the transition of the bubble motion from two-dimensional motion to three-dimensional motion was enhanced by the ambient turbulence. We calculated standard deviations of the liquid-phase velocities from the PIV results. When the bubble swarm was launched into the decaying turbulence, the decay rates of the liquid-phase velocities were enhanced; i.e. the decay rates under Condition-OB were larger than those under Condition-O.

Hydrodynamic Studies of Two-Phase Upflow in Vertical Pipelines

1969 ◽  
Vol 184 (3) ◽  
pp. 154-165
Author(s):  
J. C. Jepsen ◽  
J. L. Ralph
Keyword(s):  
Experimental Data ◽  
Liquid Phase ◽  
Mass Flux ◽  
Annular Flow ◽  
Impact Pressure ◽  
Two Phase ◽  
Phase Velocities ◽  
Flow Disturbances ◽  
Liquid Flux ◽  
Liquid Systems

The object of this study was to obtain data on the radial variation of gas- and liquid-phase mass flux profiles in two-phase upflow in vertical pipelines. Experimental data were obtained on the radial gas-liquid flux, impact pressure, and linear liquid-phase velocity profiles for superficial gas- and liquid-phase velocities ranging from 20 to 125 ft/s and from 5 to 15 ft/s, respectively. Studies were made on 1-in, 4-in, and 8·4-in vertical pipelines and in a 1-in i.d. by 8·4-in o.d. vertical annular flow pipeline. Gas-liquid systems studied were air-water, air-aqueous glycerol, and air-tetrabromoethane. In Part 2 time-averaged radial liquid hold-up and linear-phase velocities were estimated from radial mass flux and impact pressure data. Estimates were also made on the magnitude, frequency, and velocity of the flow disturbances. Empirical correlations for mean liquid hold-up and pressure drop were developed from experimental data.

Liquid-phase velocities and the frequency analysis in the vicinity of a single-rising bubble

2004 ◽  
Vol 2004.53 (0) ◽  
pp. 369-370
Author(s):  
Masaki ISHITOBI ◽  
Hiroaki KUSANO ◽  
Yasutaka OCHIAI ◽  
Takayuki SAITO
Keyword(s):  
Liquid Phase ◽  
Frequency Analysis ◽  
Phase Velocities ◽  
Rising Bubble

Raman Amplification in WDM Optical Communication Systems: A System Perceptive

2016 ◽  
Vol 37 (4) ◽  
Author(s):  
Sanjeev Kumar Raghuwanshi ◽  
Talabattula Srinivas
Keyword(s):  
Communication Systems ◽  
Stimulated Raman Scattering ◽  
Group Velocity Dispersion ◽  
Numerical Technique ◽  
Raman Amplification ◽  
Transient Effects ◽  
Coupled Equations ◽  
Optical Communication Systems ◽  
Time Dependent Effect ◽  
Effect Time

AbstractStatistical study on stimulated Raman scattering (SRS) crosstalk has been done by many researchers while ignoring pulse walk-off effect due to analytically unsolvable nonlinear coupled equations. To our knowledge there is no treatise, which deals with pulse walk-off effect except statistically for few cases in case of wideband WDM Raman amplification systems. In this paper, we investigate the effect of group velocity dispersion induced crosstalk. We have tried to solve nonlinear coupled Raman gain equations for few channels by using the numerical technique called finite difference method. Finally we have provided results of the simulation for few cases. It is ever known that pulse walk-off effect (time-dependent effect) is responsible for transient effects hence the modeling has also done in this paper to simulate the effect of abrupt channel addition and removal response.

scholarly journals A Study of Nd:YAG Laser Capsulotomy in the Management of Posterior Capsular Opacification

2016 ◽  
Vol 3 (1) ◽  
pp. 18
Author(s):  
Mrunal Suresh Patil ◽  
Dhiraj Namdeo Balwir ◽  
Swapnil Vidhate
Keyword(s):  
Visual Acuity ◽  
Nd:Yag Laser ◽  
Visual Outcome ◽  
Detailed Examination ◽  
Posterior Capsular Opacification ◽  
Exclusion Criteria ◽  
Posterior Capsulotomy ◽  
Transient Rise ◽  
Nd:Yag Laser Capsulotomy

<strong>Aims:</strong> To study the visual outcome following Nd:YAG laser posterior capsulotomy and to study the complications associated with Nd:YAG laser posterior capsulotomy. <strong>Material and Methods:</strong> The study included a total of 100 eyes of 100 patients who fulfilled the inclusion and exclusion criteria. Once diagnosed to have posterior capsular opacification they were subjected to a detailed clinical examination. All patients underwent Nd:YAG laser capsulotomy. Patients were followed up at 1 hour, 4 hour, 1 day, 1 week, 1 month, 3 month. At every follow up detailed examination was done. BCVA and any complications were noted. <strong>Results:</strong> Post-laser, 87% patients had BCVA 6/12 or more at 3 month follow up. 10% patients had BCVA 6/24 to 6/18. Only 3% patients had visual acuity improved to less than 6/24. Out of 3 patients, 1 patient had visual acuity improved to 6/60&amp;in remaining 2 visual acuity improved to 6/36. The complications were seen in 31 (31%) patients. Most common complication observed was transient rise in IOP. 17 eyes (17%) had transiently raised IOP. Second most common noted was pitting of IOL. Pitting was present in 7 (7%) patients, 3 (3%) patients had ruptured anterior face of vitreous, 2 (2%) patients had iritis, 1 (1%) had hyphema and 1 (1%) developed CME. IOP rise was related to grade of PCO and energy used.<strong> Conclusion:</strong> Improvement in visual acuity after Nd:YAG laser posterior capsulotomy is excellent. Complications associated with Nd:YAG laser capsulotomy are minimal. Nd: YAG laser capsulotomy is a safe method of restoring vision in patients with posterior capsule opacification.

scholarly journals Effects of liquid–liquid phase separation and relative humidity on the heterogeneous OH oxidation of inorganic–organic aerosols: insights from methylglutaric acid and ammonium sulfate particles

2021 ◽  
Vol 21 (3) ◽  
pp. 2053-2066
Author(s):  
Hoi Ki Lam ◽  
Rongshuang Xu ◽  
Jack Choczynski ◽  
James F. Davies ◽  
Dongwan Ham ◽  
...  
Keyword(s):  
Phase Separation ◽  
Liquid Phase ◽  
Gas Phase ◽  
Organic Compounds ◽  
Organic Molecules ◽  
Droplet Surface ◽  
Core Shell ◽  
Oh Radicals ◽  
Liquid Phases ◽  
Heterogeneous Reactivity

Abstract. Organic compounds residing near the surface of atmospheric aerosol particles are exposed to chemical reactions initiated by gas-phase oxidants, such as hydroxyl (OH) radicals. Aqueous droplets composed of inorganic salts and organic compounds can undergo phase separation into two liquid phases, depending on aerosol composition and relative humidity (RH). Such phase behavior can govern the surface characteristics and morphology of the aerosols, which in turn affect the heterogeneous reactivity of organic compounds toward gas-phase oxidants. In this work, we used an aerosol flow tube reactor coupled with an atmospheric pressure ionization source (direct analysis in real time) and a high-resolution mass spectrometer to investigate how phase separation in model aqueous droplets containing an inorganic salt (ammonium sulfate, AS) and an organic acid (3-methylglutaric acid, 3-MGA) with an organic-to-inorganic dry mass ratio (OIR) of 1 alters the heterogeneous OH reactivity. At high RH, 3-MGA/AS aerosols were aqueous droplets with a single liquid phase. When the RH decreased, aqueous 3-MGA/AS droplets underwent phase separation at ∼75 % RH. Once the droplets were phase-separated, they exhibited either a core–shell, partially engulfed or a transition from core–shell to partially engulfed structure, with an organic-rich outer phase and an inorganic-rich inner phase. The kinetics, quantified by an effective heterogenous OH rate constant, was found to increase gradually from 1.01±0.02×10-12 to 1.73±0.02×10-12 cm3 molec.−1 s−1 when the RH decreased from 88 % to 55 %. The heterogeneous reactivity of phase-separated droplets is slightly higher than that of aqueous droplets with a single liquid phase. This could be explained by the finding that when the RH decreases, higher concentrations of organic molecules (i.e., 3-MGA) are present at or near the droplet surface, which are more readily exposed to OH oxidation, as demonstrated by phase separation measurements and model simulations. This could increase the reactive collision probability between 3-MGA molecules and OH radicals dissolved near the droplet surface and secondary chain reactions. Even for phase-separated droplets with a fully established core–shell structure, the diffusion rate of organic molecules across the organic-rich outer shell is predicted to be fast in this system. Thus, the overall rate of reactions is likely governed by the surface concentration of 3-MGA rather than a diffusion limitation. Overall, understanding the aerosol phase state (single liquid phase versus two separate liquid phases) is essential to better probe the heterogenous reactivity under different aerosol chemical composition and environmental conditions (e.g., RH).

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