Hydrodynamic Stability of Inverted Annular Flow in an Adiabatic Simulation

1986 ◽  
Vol 108 (1) ◽  
pp. 84-92 ◽  
Author(s):  
G. De Jarlais ◽  
M. Ishii ◽  
J. Linehan
Keyword(s):  
Annular Flow ◽  
Liquid Jets ◽  
Droplet Flow ◽  
Free Jet ◽  
Jet Stability ◽  
Water Jets ◽  
Droplet Stability ◽  
Droplet Sizes ◽  
Data Points ◽  
Turbulent Water

Inverted annular flow was simulated adiabatically with turbulent water jets, issuing downward from large aspect ratio nozzles, enclosed in gas annuli. Velocities, diameters, and gas species were varied, and core jet length, shape, breakup mode, and dispersed core droplet sizes were recorded at approximately 750 data points. Inverted annular flow destabilization led to inverted slug flow at low relative velocities, and to dispersed droplet flow at high relative velocities. For both of these transitions from inverted annular flow, core breakup length correlations were developed by extending work on free liquid jets to include this coaxial, jet disintegration phenomenon. The results show length dependence upon DJ, ReJ, WeJ, α, and WeG,rel. Correlations for core shape, breakup mechanisms, and dispersed core droplet size were also developed, by extending the results of free jet stability, roll wave entrainment, and churn turbulent droplet stability studies.

Comparative study on interfacial oscillations of rectangular and elliptical liquid jets

2020 ◽  
Vol 234 (7) ◽  
pp. 1272-1286 ◽  
Author(s):  
Amin Jaberi ◽  
Mehran Tadjfar
Keyword(s):  
Aspect Ratio ◽  
Weber Number ◽  
High Speed ◽  
Nozzle Geometry ◽  
Liquid Jets ◽  
High Speed Photography ◽  
Aspect Ratios ◽  
Water Jets ◽  
Switching Phenomenon ◽  
Axis Switching

The instability characteristics and flow structures of water jets injected from rectangular and elliptical nozzles with aspect ratios varying from 2 to 6 were experimentally studied and compared. Shadowgraph technique was employed for flow visualization, and structures on the liquid jet surface were captured using high speed photography. It was found that disturbances originating from the nozzle geometry initially perturbed the liquid column, and then, at high jet velocities, disturbances generated within the flow dominated the jet surface. It was also found that rectangular nozzles introduced more disturbances into the flow than the elliptical ones. The characteristic parameters of axis-switching phenomenon including wavelength, frequency, and amplitude were measured and compared. Axis-switching wavelength was found to increase linearly with Weber number. Also, the wavelengths of rectangular jets were longer than the elliptical jets. Further, the frequency of axis-switching was shown to be reduced with increase of both Weber number and aspect ratio. It was observed that the axis-switching amplitude increased monotonically, reached a peak, and then decreased gradually. It was also found that the axis-switching amplitude varied with Weber number. At lower values of Weber number, the rectangular nozzles had higher amplitude than the elliptical nozzles. However, at higher values of Weber number, this relation was reversed, and the elliptical nozzles had the higher axis-switching amplitudes. This reversal Weber number decreased with the orifice aspect ratio. The reversal Weber number for aspect ratio of 4 was about 289, and it had decreased to 144 for the aspect ratio of 6.

Scour by jets in cohesionless and cohesive soils

2007 ◽  
Vol 34 (6) ◽  
pp. 744-751 ◽  
Author(s):  
Kerry A Mazurek ◽  
Tanvir Hossain
Keyword(s):  
Impinging Jets ◽  
Coarse Grained ◽  
Cohesive Soils ◽  
Wall Jets ◽  
Fine Grained ◽  
Water Jets ◽  
Turbulent Wall Jets ◽  
Turbulent Wall ◽  
Turbulent Water ◽  
Unified Method

A technique is developed in this paper to unify the methods of analyzing scour by turbulent water jets in cohesionless and cohesive soils. Data from previous studies using circular turbulent impinging jets and circular turbulent wall jets are used to compare the scour in low void ratio cohesive soils to that in uniform sands and gravels. Scour by these jets is related to the dimensionless excess stress on the soil bed. It is seen that this parameter will likely work well for developing a method to predict scour for circular wall jets that is applicable to both materials. However, a circular impinging jet appears to vary appreciably in its interaction with the bed between the two types of soil, which makes developing a unified method to predict scour by impinging jets more difficult. Key words: erosion, scour, water jets, cohesionless sediments, cohesive sediments, fine-grained soils, coarse-grained soils.

Curved Non-Newtonian Liquid Jets With Surfactants

2009 ◽  
Vol 131 (9) ◽  
Author(s):  
Jamal Uddin ◽  
Stephen P. Decent
Keyword(s):  
Free Surface ◽  
Shear Thickening ◽  
Linear Instability ◽  
Liquid Jets ◽  
Liquid Jet ◽  
Long Wavelength ◽  
Droplet Sizes ◽  
Wavelength Approximation ◽  
Steady Solutions ◽  
Linear Instability Analysis

Applications of the breakup of a liquid jet into droplets are common in a variety of different industrial and engineering processes. One such process is industrial prilling, where small spherical pellets and beads are generated from the rupture of a liquid thread. In such a process, curved liquid jets produced by rotating a perforated cylindrical drum are utilized to control drop sizes and breakup lengths. In general, smaller droplets are observed as the rotation rate is increased. The addition of surfactants along the free surface of the liquid jet as it emerges from the orifice provides a possibility of further manipulating breakup lengths and droplet sizes. In this paper, we build on the work of Uddin et al. (2006, “The Instability of Shear Thinning and Shear Thickening Liquid Jets: Linear Theory,” ASME J. Fluids Eng., 128, pp. 968–975) and investigate the instability of a rotating liquid jet (having a power law rheology) with a layer of surfactants along its free surface. Using a long wavelength approximation we reduce the governing equations into a set of one-dimensional equations. We use an asymptotic theory to find steady solutions and then carry out a linear instability analysis on these solutions.

scholarly journals On the Determination Method of Entrained Droplet Flow Rate in the Disturbance Wave Region of Annular Flow

1985 ◽  
Vol 28 (240) ◽  
pp. 1105-1112 ◽  
Author(s):  
Kotohiko SEKOGUCHI ◽  
Osamu TANAKA ◽  
Takashi UENO
Keyword(s):  
Flow Rate ◽  
Annular Flow ◽  
Determination Method ◽  
Disturbance Wave ◽  
Droplet Flow ◽  
Wave Region

Deposition of Thin Alumina Films from Supercritical Water Jets

1988 ◽  
Vol 131 ◽  
Author(s):  
J. I. Brand ◽  
D. R. Miller
Keyword(s):  
Supercritical Water ◽  
Silicon Substrate ◽  
Free Jet ◽  
Alumina Films ◽  
Water Jets ◽  
Substrate Temperatures

ABSTRACTThin alumina films are grown on a silicon substrate, in vacuum, at a rate of about 10 Å per second, and at substrate temperatures below 1500C. Alumina is dissolved in supercritical water and the resulting solution expanded in a supersonic free jet, which is directed at the substrate. The films are characterized by ESCA and FTIR.

scholarly journals High-speed IR thermography of submerged turbulent water jets

2016 ◽  
Author(s):  
I. Znamenskaya ◽  
E. Koroteeva ◽  
A. Novinskaya ◽  
N. Sysoev
Keyword(s):  
High Speed ◽  
Ir Thermography ◽  
Water Jets ◽  
Turbulent Water

Design and Operation of a Droplet Deposition System for Freeform Fabrication of Metal Parts

1999 ◽  
Author(s):  
Ampere A. Tseng ◽  
Munhee Lee ◽  
Bosen Zhao
Keyword(s):  
Linear Stability ◽  
Stability Theory ◽  
Linear Stability Theory ◽  
Liquid Jets ◽  
Droplet Generator ◽  
Droplet Deposition ◽  
Generator System ◽  
Freeform Fabrication ◽  
Wide Range ◽  
Droplet Sizes

Abstract Based on a linear stability theory for liquid jets, the design of a droplet generator system is presented for freeform fabrication. The linear stability theory of forming droplets is first reviewed and its suitability to the present droplet deposition system is then discussed. The analytical formulae for predicting droplet size and break-up length at optimal conditions are developed. Based on the present formulation, a droplet generator is designed and built to make wax and tin alloy droplets. Experiments have been conducted at a wide range of jet velocities, frequencies, and droplet sizes. Good agreements are found between the analytical predictions based on the linear theory and experimental results. It has also been found that using the present design and procedure recommended, the droplet sizes can be controlled having a size deviation of less than 3 % and the variation of the deposited layer can be managed within 3% of its width deposited.

Evaporative Annular Flow in Micro/Minichannels: A Simple Heat Transfer Model

2013 ◽  
Vol 5 (3) ◽  
Author(s):  
Zan Wu ◽  
Bengt Sundén ◽  
Wei Li ◽  
Vishwas V. Wadekar
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Flow Regime ◽  
Annular Flow ◽  
Bubble Flow ◽  
New Model ◽  
Error Band ◽  
Data Points

The present study collected and analyzed flow boiling data points which fall in the annular flow regime with an increasing heat transfer coefficient h - vapor quality x trend (h increases with increasing x) in small diameter channels (0.1 < dh < 3.1 mm) for halogenated refrigerants, CO2 and water. In this annular flow regime, heat transfer coefficient also depends on both heat flux and mass flux. It is proposed that the heat flux dependence comes mainly through its effect on interfacial waves and the fact that bubble growth and coalescence in isolated bubble flow and elongated bubble flow propagate oscillations downwards into the annular flow. In other words, heat flux affects the heat transfer coefficient in the annular flow regime by upstream effects or historical effects. A semi-empirical model for annular flow was developed by starting with pure thin film evaporation and then corrections were applied based on the Boiling number and the liquid Reynolds number. The resulting simple model can predict about 89.1% of the entire database within a ± 30% error band. Almost all data points can be predicted within a ± 50% error band. It is shown that the parametric trends are well captured by the new model. Besides, no noticeable macro-to-micro/miniscale transition was observed for the entire database of annular flow. Therefore, the new model can be applied to model annular flow covering from microchannels to relatively large channels.

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