Bubble Breakup Phenomena in a Venturi Tube

2007 ◽  
Author(s):  
A. Fujiwara ◽  
K. Okamoto ◽  
K. Hashiguchi ◽  
J. Peixinho ◽  
S. Takagi ◽  
...  
Keyword(s):  
High Speed ◽  
Bubbly Flow ◽  
Bubble Diameter ◽  
Pressure Change ◽  
Venturi Tube ◽  
Large Bubble ◽  
Breakup Process ◽  
Bubble Behavior ◽  
Bubble Breakup ◽  
Unstable Surface

Microbubble generation techniques have been proposed in former investigations. Here, we study an effective technique using air bubbly flow into a convergent-divergent nozzle (venturi tube). Pressure change in the diverging section induces bubble breakup. The purpose of this study is to clarify the effect of flow velocity at the throat with respect to the bubble breakup process and the bubble behavior in a venturi tube. Relations between generated bubble diameter and bubble breakup process are also described. Using high speed camera for detailed observation of bubble behavior, the following features were obtained. The velocity at the throat is expected to be of the order of the magnitude of the speed of sound of bubbly flow and a drastic bubble expansion and a shrink is induced. Besides, a liquid column appeared after the bubble flowing into the throat, and it grew up to stick to the bubble like in the form of a jet. This jet induced both unstable surface waves and the breakup of a single large bubble into several pieces.

Study on Bubble Breakup Mechanism in a Venturi Tube

2011 ◽  
Author(s):  
Yasumichi Nomura ◽  
Shin-ichiro Uesawa ◽  
Akiko Kaneko ◽  
Yutaka Abe
Keyword(s):  
Flow Structure ◽  
High Speed ◽  
Pressure Profile ◽  
Venturi Tube ◽  
Pressure Recovery ◽  
Bubble Collapse ◽  
Bubble Behavior ◽  
Low Velocity ◽  
Breakup Mechanism ◽  
Bubble Breakup

Microbubbles are expected to be applied in various subjects such as engineering and medical fields. Thus, on-demand microbubble generation techniques with high efficiently are required. In the present study, the microbubble generator using a venturi tube (converging-diverging nozzle) is focused. Although this technique realizes generation of many tiny bubbles with less than several-hundred-micrometer diameter, there are several unsolved parts of flow structure in a venturi tube on bubble breakup behavior. The purpose of this study is to clarify the bubble breakup mechanism in a venturi tube for practical use. In the present study, using a high speed camera for detailed observation of bubble behavior, the following features were obtained. In low velocity conditions, bubbles are divided in several pieces with a jet penetrating from the top (downstream) to the bottom (upstream) part of the bubble. In high velocity conditions, bubbles collapse in countless microbubbles with a drastic bubble expansion and shrinkage. Also, in order to clarify the flow structure in a venturi tube, pressure profile is measured in detail. Under chocking condition, the pressure profile shows the tendency of supersonic flow in a Laval nozzle and sudden pressure gradient appears in the diverging section. There are strong correlations between bubble fission points and pressure recovery points. It is suggested that bubble collapse is strongly influenced with pressure recovery in the diverging section.

Experimental Visualization of Two Phase Flow Inside an Electrical Submersible Pump Stage

2009 ◽  
Author(s):  
Lissett Barrios ◽  
Mauricio Gargaglione Prado
Keyword(s):  
High Speed ◽  
Two Phase Flow ◽  
Flow Behavior ◽  
Bubble Diameter ◽  
Phase Flow ◽  
Submersible Pump ◽  
Bubble Behavior ◽  
Two Phase ◽  
Operational Conditions ◽  
Electrical Submersible Pump

Dynamic multiphase flow behavior inside a mixed flow Electrical Submersible Pump (ESP) has been studied experimentally and theoretically for the first time. The overall objectives of this study are to determine the flow patterns and bubble behavior inside the ESP and to predict the operational conditions that cause surging. An experimental facility has been designed and constructed to enable flow pattern visualization inside the second stage of a real ESP. Special high speed instrumentation was selected to acquire visual flow dynamics and bubble size measurements inside the impeller channel. Experimental data was acquired utilizing two types of tests (surging test and bubble diameter measurement test) to completely evaluate the pump behavior at different operational conditions. A similarity analysis performed for single-phase flow inside the pump concluded that viscosity effects are negligible compared to the centrifugal field effects for rotational speeds higher than 600 rpm. Therefore, the two-phase flow tests were performed for rotational speeds of 600, 900, 1200, and 1500 rpm. Results showed formation of a large gas pocket at the pump intake during surging conditions.

Bubble Behavior and Mean Diameter in Subcooled Flow Boiling

1996 ◽  
Vol 118 (1) ◽  
pp. 110-116 ◽  
Author(s):  
O. Zeitoun ◽  
M. Shoukri
Keyword(s):  
Heat Flux ◽  
Mass Flux ◽  
High Speed ◽  
Flow Boiling ◽  
Bubble Diameter ◽  
Image Processing Technique ◽  
Bubble Behavior ◽  
Subcooled Flow Boiling ◽  
Subcooled Flow ◽  
The Mean

Bubble behavior and mean bubble diameter in subcooled upward flow boiling in a vertical annular channel were investigated under low pressure and mass flux conditions. A high-speed video system was used to visualize the subcooled flow boiling phenomenon. The high-speed photographic results indicated that, contrary to the common understanding, bubbles tend to detach from the heating surface upstream of the net vapor generation point. Digital image processing technique was used to measure the mean bubble diameter along the subcooled flow boiling region. Data on the axial area-averaged void fraction distributions were also obtained using a single-beam gamma densitometer. Effects of the liquid subcooling, applied heat flux, and mass flux on the mean bubble size were investigated. A correlation for the mean bubble diameter as a function of the local subcooling, heat flux, and mass flux was obtained.

Experimental Visualization of Two-Phase Flow Inside an Electrical Submersible Pump Stage

2011 ◽  
Vol 133 (4) ◽  
Author(s):  
Lissett Barrios ◽  
Mauricio Gargaglione Prado
Keyword(s):  
High Speed ◽  
Two Phase Flow ◽  
Flow Behavior ◽  
Bubble Diameter ◽  
Phase Flow ◽  
Submersible Pump ◽  
Bubble Behavior ◽  
Two Phase ◽  
Operational Conditions ◽  
Electrical Submersible Pump

Dynamic multiphase flow behavior inside a mixed flow electrical submersible pump (ESP) has been studied experimentally and theoretically for the first time. The overall objectives of this study are to determine the flow patterns and bubble behavior inside the ESP and to predict the operational conditions that cause surging. An experimental facility has been designed and constructed to enable flow pattern visualization inside the second stage of a real ESP. Special high-speed instrumentation was selected to acquire visual flow dynamics and bubble size measurements inside the impeller channel. Experimental data were acquired utilizing two types of tests (surging test and bubble diameter measurement test) to completely evaluate the pump behavior at different operational conditions. A similarity analysis performed for single-phase flow inside the pump concluded that viscosity effects are negligible compared to the centrifugal field effects for rotational speeds higher than 600 rpm. Therefore, the two-phase flow tests were performed for a rotational speeds of 600, 900, 1200, and 1500 rpm. Results showed formation of a large gas pocket at the pump intake during surging conditions.

scholarly journals Bubble Behavior on Horizontal and Vertical Carbon Anode Surfaces in Cryolite Melt Applying a See-Through Cell

2021 ◽  
Vol 3 (1) ◽  
pp. 8
Author(s):  
Nikolina Stanic ◽  
Espen Sandnes
Keyword(s):  
Current Density ◽  
Bubble Diameter ◽  
Vertical Surface ◽  
Visual Observation ◽  
Anode Surface ◽  
Large Bubble ◽  
Carbon Anode ◽  
Gas Bubble ◽  
Bubble Behavior

Gas bubble behavior on a carbon anode in a cryolite melt has been studied by visual observation using a see-through cell. The bubble phenomena studied have included growth, coalescence, and detachment during electrolysis. Two different anode designs were tested, an anode with a horizontal facing-downwards surface and an anode with a vertical surface. At the horizontal anode, it was found that one large bubble was formed by the growth and coalescence of smaller bubbles, and finally, the large bubble detached periodically. For the vertical anode surface, many smaller bubbles were formed and detached randomly. The bubble diameter was decreasing with increasing current density for both anodes.

Theoretical Modeling and Experimental Measurements of Single Bubble Dynamics From a Submerged Orifice in a Liquid Pool

2007 ◽  
Author(s):  
S. K. Kasimsetty ◽  
A. Subramani ◽  
R. M. Manglik ◽  
M. A. Jog
Keyword(s):  
Flow Rate ◽  
High Speed ◽  
Bubble Dynamics ◽  
Bubble Diameter ◽  
Liquid Pool ◽  
Orifice Diameter ◽  
Equivalent Diameter ◽  
Bubble Behavior ◽  
Balance Of Forces ◽  
Submerged Orifice

The dynamics of a single gas bubble, emanating from a submerged orifice in stagnant water has been explored both theoretically and experimentally. The mathematical model represents a fundamental balance of forces due to buoyancy, viscosity, surface tension, liquid inertia, and gas momentum transport, and the consequent motion of the gas-liquid interface. Theoretical solutions describe the dynamic bubble behavior (incipience, growth and necking) as it grows from a tip of a sub-millimeter-scale capillary orifice in an isothermal pool of water. These results are also found to be in excellent agreement with a set of experimental data that are obtained from optical high-speed micro-scale flow visualization. Variations in bubble shape, equivalent diameter, and growth times with capillary orifice diameter and air flow rates are outlined. These parametric trends suggest a two-regime ebullient transport: (a) a constant volume regime where the bubble diameter is not affected by the flow rate, and (b) a growing bubble regime where bubble size increases with flow rate.

scholarly journals Bubble Phenomena and Bubble Properties for Horizontal and Vertical Carbon Anode Surfaces in Cryolite Melt Applying a See-Through Cell

Metals ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 965
Author(s):  
Nikolina Stanic ◽  
Ana Maria Martinez ◽  
Kristian Etienne Einarsrud ◽  
Espen Sandnes
Keyword(s):  
Current Density ◽  
Bubble Diameter ◽  
Vertical Surface ◽  
Anode Surface ◽  
Large Bubble ◽  
Carbon Anode ◽  
Bubble Behavior ◽  
Coalescence Process ◽  
The Impact ◽  
Bubble Properties

Gas bubble behavior on a carbon anode in a cryolite melt has been studied using a see-through cell. The phenomena studied have been growth, coalescence, detachment, and wetting during electrolysis. The surface orientation affects bubble behavior. Therefore, two different anode designs were tested, an anode with a horizontal downward-facing surface and an anode with a vertical surface. At the horizontal anode, it was found that one large bubble was formed by the growth and coalescence of smaller bubbles, and finally, the large bubble detached periodically. For the vertical anode surface, the detaching bubbles were smaller, and most of them had been going through a coalescence process prior to detachment. The bubbles detached randomly. The coalescence process from the initiation to the final bubble shape at the vertical surface took about 0.016–0.024 s. The current density did not affect the duration of the coalescence. The bubble diameter was decreasing with increasing current density for both anodes. The values were in the range 7.2 to 5.7 mm for the horizontal anode in the current density interval 0.2–1.0 A cm−2 and in the range 3.7 mm to 1.5 mm for the vertical anode in the current density interval 0.1–2.0 A cm−2. The wetting contact angle for the vertical anode stayed more or less constant with an increase in current density, which likely can be attributed to the decreasing bubble size rather than an increase in polarization. In addition to the bubble phenomena described and bubble properties found, the impact of the results for better design of laboratory-scale studies is discussed.

Highly aligned PAN nanofiber bundles prepared via a novel Venturi tube high-speed airflow drafting (VAD) method

2021 ◽  
pp. 130383
Author(s):  
Lei Li ◽  
Jingna Su ◽  
Yuanyuan Wang ◽  
Gang Wang ◽  
Zhichao Zhang ◽  
...  
Keyword(s):  
High Speed ◽  
Venturi Tube ◽  
Nanofiber Bundles ◽  
Pan Nanofiber

scholarly journals Bubble Dynamics in a Two-Phase Bubbly Mixture

2010 ◽  
Author(s):  
Arvind Jayaprakash ◽  
Sowmitra Singh ◽  
Georges Chahine
Keyword(s):  
Void Fraction ◽  
High Speed ◽  
Bubble Dynamics ◽  
Bubble Radius ◽  
Discharge Voltage ◽  
Large Bubble ◽  
Water Mixture ◽  
Two Phase ◽  
Mixture Density ◽  
Bubbly Medium

The dynamics of a primary relatively large bubble in a water mixture including very fine bubbles is investigated experimentally and the results are provided to several parallel on-going analytical and numerical approaches. The main/primary bubble is produced by an underwater spark discharge from two concentric electrodes placed in the bubbly medium, which is generated using electrolysis. A grid of thin perpendicular wires is used to generate bubble distributions of varying intensities. The size of the main bubble is controlled by the discharge voltage, the capacitors size, and the pressure imposed in the container. The size and concentration of the fine bubbles can be controlled by the electrolysis voltage, the length, diameter, and type of the wires, and also by the pressure imposed in the container. This enables parametric study of the factors controlling the dynamics of the primary bubble and development of relationships between the bubble characteristic quantities such as maximum bubble radius and bubble period and the characteristics of the surrounding two-phase medium: micro bubble sizes and void fraction. The dynamics of the main bubble and the mixture is observed using high speed video photography. The void fraction/density of the bubbly mixture in the fluid domain is measured as a function of time and space using image analysis of the high speed movies. The interaction between the primary bubble and the bubbly medium is analyzed using both field pressure measurements and high-speed videography. Parameters such as the primary bubble energy and the bubble mixture density (void fraction) are varied, and their effects studied. The experimental data is then compared to simple compressible equations employed for spherical bubbles including a modified Gilmore Equation. Suggestions for improvement of the modeling are then presented.

Evaluation of a Flow Measurement Probe Influence on the Flow Field in High Speed Axial Compressors

2021 ◽  
Author(s):  
Ryosuke Seki ◽  
Satoshi Yamashita ◽  
Ryosuke Mito
Keyword(s):  
Flow Field ◽  
Approximation Method ◽  
High Speed ◽  
Static Pressure ◽  
Axial Compressor ◽  
Pressure Change ◽  
Operating Point ◽  
Blade Row ◽  
Probe Insertion ◽  
Probe Geometry

Abstract The aerodynamic effects of a probe for stage performance evaluation in a high-speed axial compressor are investigated. Regarding the probe measurement accuracy and its aerodynamic effects, the upstream/downstream effects on the probe and probe insertion effects are studied by using an unsteady computational fluid dynamics (CFD) analysis and by verifying in two types of multistage high-speed axial compressor measurements. The probe traverse measurements were conducted at the stator inlet and outlet in each case to evaluate blade row performance quantitatively and its flow field. In the past study, the simple approximation method was carried out which considered only the interference of the probe effect based on the reduction of the mass flow by the probe blockage for the compressor performance, but it did not agree well with the measured results. In order to correctly and quantitatively grasp the mechanism of the flow field when the probe is inserted, the unsteady calculation including the probe geometry was carried out in the present study. Unsteady calculation was performed with a probe inserted completely between the rotor and stator of a 4-stage axial compressor. Since the probe blockage and potential flow field, which mean the pressure change region induced by the probe, change the operating point of the upstream rotor and increase the work of the rotor. Compared the measurement result with probe to a kiel probe setting in the stator leading edge, the total pressure was increased about 2,000Pa at the probe tip. In addition, the developed wake by the probe interferes with the downstream stator row and locally changes the static pressure at the stator exit. To evaluate the probe insertion effect, unsteady calculations with probe at three different immersion heights at the stator downstream in an 8-stage axial compressor are performed. The static pressure value of the probe tip was increased about 3,000Pa in the hub region compared to tip region, this increase corresponds to the measurement trend. On the other hand, the measured wall static pressure showed that there is no drastic change in the radial direction. In addition, when the probe is inserted from the tip to hub region in the measurement, the blockage induced by the probe was increased. As a result, operating point of the stator was locally changed, and the rise of static pressure of the stator increased when the stator incidence changed. These typical results show that unsteady simulations including probe geometry can accurately evaluate the aerodynamic effects of probes in the high-speed axial compressor. Therefore, since the probe will pinpointed and strong affects the practically local flow field in all rotor upstream passage and stator downstream, as for the probe measurement, it is important to pay attention to design the probe diameter, the distance from the blade row, and its relative position to the downstream stator. From the above investigations, a newly simple approximation method which includes the effect of the pressure change evaluation by the probe is proposed, and it is verified in the 4-stage compressor case as an example. In this method, the effects of the distance between the rotor trailing edge (T.E.) and the probe are considered by the theory of the incompressible two-dimensional potential flow. The probe blockage decreases the mass flow rate and changes the operating point of the compressor. The verification results conducted in real compressor indicate that the correct blockage approximation enables designer to estimate aerodynamic effects of the probe correctly.

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