Analysis on the Dynamic Load in a Water Pool During Air Discharge From Submerged Sparger

2004 ◽  
Author(s):  
Ken Uchida ◽  
Takeshi Shimizu ◽  
Mitsuo Komuro ◽  
Masatomo Kuroda ◽  
Seijiro Suzuki
Keyword(s):  
Dynamic Load ◽  
Early Stage ◽  
Bubble Formation ◽  
Time History ◽  
Entropy Change ◽  
Water Pool ◽  
Two Phase ◽  
Pressure Time ◽  
Small Bubbles ◽  
Air Discharge

This paper presents a study of the applicability of the VOF (Volume of Fluid) method to estimation of dynamic load in a water pool induced by oscillation of bubbles that are ejected through sparger holes. We choose the VOF method to simulate this phenomenon, and the pressure of a bubble is given by entropy change in order to consider the compressible effect of the bubble and the effect of gas coming into the bubble. In calculation of air flow rate passing through the holes, the effect of two-phase pressure drop is incorporated. In order to investigate applicability of this method, a simplified blowdown test is carried out. According to the numerical results, the pressure-time history inside the sparger and that in a water pool are both generally reproduced well with analysis except that the magnitude of first peak pressure in a water pool is overestimated. The most likely reason is that the bubble cloud has especially low void fraction at the early stage of bubble formation, and small bubbles around a major bubble work as a buffer, which is discussed in detail in this paper.

Analysis on the Dynamic Load in a Water Pool during Air Discharge from Submerged Sparger

2005 ◽  
Vol 127 (4) ◽  
pp. 495-501 ◽  
Author(s):  
Ken Uchida ◽  
Takeshi Shimizu ◽  
Mitsuo Komuro
Keyword(s):  
Dynamic Load ◽  
Early Stage ◽  
Bubble Formation ◽  
Time History ◽  
Entropy Change ◽  
Airflow Rate ◽  
Water Pool ◽  
Two Phase ◽  
Pressure Time ◽  
Small Bubbles

This paper presents a study of the applicability of the VOF (volume of fluid) method to estimation of dynamic load in a water pool induced by oscillation of bubbles that are ejected through sparger holes. We choose the VOF method to simulate this phenomenon, and the pressure of a bubble is given by entropy change in order to consider the compressible effect of the bubble and the effect of gas coming into the bubble. In calculation of the airflow rate passing through the holes, the effect of two-phase pressure drop is incorporated. In order to investigate applicability of this method, a simplified blowdown test is carried out. According to the numerical results, the pressure-time history inside the sparger and that in a water pool are both generally reproduced well with analysis, except that the magnitude of first peak pressure in a water pool is overestimated. The most likely reason is that the bubble cloud has especially low void fraction at the early stage of bubble formation, and small bubbles around a major bubble work as a buffer, which is discussed, in detail, in this paper.

Analysis of Liquid Slug Motion in a Voided Line

1998 ◽  
Vol 120 (1) ◽  
pp. 74-80 ◽  
Author(s):  
J. Yang ◽  
D. C. Wiggert
Keyword(s):  
Momentum Transfer ◽  
High Speed ◽  
Time History ◽  
Air Entrainment ◽  
Phase Flow ◽  
Liquid Slug ◽  
Two Phase ◽  
Pressure Time ◽  
History Of ◽  
Good Agreement

A quasi-two-dimensional two-phase flow cylindrical model of slug motion in a voided line is developed that can reasonably predict the change of flow pattern of the slug, air entrainment, “holdup” and the distribution of axial velocity. However, when using the theory of incompressible momentum transfer to estimate the pressure-time history of slug at the elbow, the calculated results are not in good agreement with those of the experiments. Further analysis of the experimental results indicate that an acoustic, or waterhammerlike response may occur immediately upon impact of the high-speed slug with the elbow, and subsequently, the waveform exhibits momentum transfer due to the acceleration of the slug at the elbow.

The Pseudo-Shakedown of Beams and Plates When Subjected to Repeated Dynamic Loads

1992 ◽  
Vol 59 (1) ◽  
pp. 168-175 ◽  
Author(s):  
Wei Qin Shen ◽  
Norman Jones
Keyword(s):  
Static Analysis ◽  
Pulse Duration ◽  
Dynamic Load ◽  
Dynamic Problem ◽  
Time History ◽  
Dynamic Loads ◽  
Perfectly Plastic ◽  
Transverse Loads ◽  
Pressure Time ◽  
Finite Displacements

A conjecture is derived in this paper for the pseudo-shakedown phenomenon of beams and plates which strengthen with finite displacements when subjected to repeated dynamic transverse loads causing material plastic flow and permanent deflections. This behavior is illustrated for a fully clamped, rigid, perfectly plastic beam which is subjected to a repeatedly applied, rectangular-shaped pressure-time history at the midspan. It transpires that a curve divides the dynamic load magnitude-pulse duration time area into two regions where pseudo-shakedown may or may not occur. Another curve in the region where pseudo-shakedown does not occur identifies when the dynamic problem may be studied with a static analysis.

Intermittent Noises Due to Bubbles Sucked Into a Siphon Pipe

2003 ◽  
Author(s):  
Hiroshi Shigefuji ◽  
Osamu Mochizuki
Keyword(s):  
Shear Stress ◽  
Early Stage ◽  
Bubble Formation ◽  
Flow Patterns ◽  
Bubble Surface ◽  
Main Flow ◽  
Large Bubble ◽  
Last Stage ◽  
Small Bubbles

Intermittent noises arising from a siphon pipe attached to a toilet bowl are investigated experimentally. The see-through model of a drained system is used to study the relation between noises and flow patterns near the entrance of the siphon pipe. We observed the different manner of the formation of large bubbles for different values of sucking velocity in the siphon pipe. The overall value of the noise in the sucking period increases with increasing the draining velocity. When the draining velocity is constant, the largest noise is generated at completion of the large bubble attached on the wall. The intermittent noises in the early stage of the period are found to be caused by small bubbles separated from the tail of the large bubble. The small bubbles are torn off because of shear stress of the main flow acting on the bubble surface. Another intermittent noises arising in the last stage is caused by periodic formation of the large bubble near the entrance. The detailed process of the bubble formation in the siphon pipe and the noises are discussed in this paper.

scholarly journals Dynamic Load on a Pipe Caused by Acetylene Detonations – Experiments and Theoretical Approaches

1999 ◽  
Vol 6 (1) ◽  
pp. 29-43 ◽  
Author(s):  
Axel Sperber ◽  
Hans-Peter Schildberg ◽  
Steven Schlehlein
Keyword(s):  
Dynamic Load ◽  
Pipe Wall ◽  
Time History ◽  
Load Factor ◽  
Transverse Waves ◽  
Theoretical Approaches ◽  
Pressure Time ◽  
Predicted Values ◽  
Modelling Methods ◽  
Dynamic Load Factor

The load acting on the wall of a pipe by a detonation, which is travelling through, is not yet well characterized. The main reasons are the limited amount of sufficiently accurate pressure time history data and the requirement of considering the dynamics of the system. Laser vibrometry measurements were performed to determine the dynamic response of the pipe wall on a detonation. Different modelling approaches were used to quantify, theoretically, the radial displacements of the pipe wall. There is good agreement between measured and predicted values of vibration frequencies and the propagation velocities of transverse waves. Discrepancies mainly due to wave propagation effects were found in the amplitudes of the radial velocities. They might be overcome by the use of a dynamic load factor or improved modelling methods.

scholarly journals Detonation effects of shallow buried explosive in sandy soil on target plate acceleration in a small-scale blast test

2018 ◽  
Vol 192 ◽  
pp. 02028
Author(s):  
Hassan Zulkifli Abu ◽  
Ibrahim Aniza ◽  
Mohamad Nor Norazman
Keyword(s):  
Sandy Soil ◽  
High Speed ◽  
Early Stage ◽  
Time History ◽  
Video Camera ◽  
Small Scale ◽  
Target Plate ◽  
Air Blast ◽  
High Speed Video Camera ◽  
The Impact

Small-scale blast tests were carried out to observe and measure the influence of sandy soil towards explosive blast intensity. The tests were to simulate blast impact imparted by anti-vehicular landmine to a lightweight armoured vehicle (LAV). Time of occurrence of the three phases of detonation phase in soil with respect to upward translation time of the test apparatus were recorded using high-speed video camera. At the same time the target plate acceleration was measured using shock accelerometer. It was observed that target plate deformation took place at early stage of the detonation phase before the apparatus moved vertically upwards. Previous data of acceleration-time history and velocity-time history from air blast detonation were compared. It was observed that effects of soil funnelling on blast wave together with the impact from soil ejecta may have contributed to higher blast intensity that characterized detonation in soil, where detonation in soil demonstrated higher plate velocity compared to what occurred in air blast detonation.

Second Paper: Deep Drawing and Free Forming Using a Water Hammer Technique

1964 ◽  
Vol 179 (1) ◽  
pp. 222-233 ◽  
Author(s):  
A. P. Vafiadakis ◽  
W. Johnson ◽  
I. S. Donaldson
Keyword(s):  
Deep Drawing ◽  
Time History ◽  
Water Hammer ◽  
High Rate ◽  
Pressure Time ◽  
Order Of Magnitude ◽  
History Of ◽  
Overall Efficiency ◽  
Initial Movement ◽  
Better Than

Earlier work on a water-hammer technique for high-rate forming of sheet metal has been extended to include work on deep drawing using lead plugs. A study of the pressure-time history of a deforming blank during its initial movement is reported. An assessment of the overall efficiency of the process has been made and is found to be about 50 per cent; this is an order of magnitude better than that found with comparable electro-hydraulic and explosive methods.

A Study on the Hydrodynamic Load in a Water Pool When Discharged Air Forms a Bubble Cloud

2006 ◽  
Author(s):  
Ken Uchida ◽  
Seijiro Suzuki
Keyword(s):  
Void Fraction ◽  
Pressure Oscillation ◽  
Numerical Results ◽  
Numerical Dissipation ◽  
Hydrodynamic Load ◽  
Water Pool ◽  
Two Phase ◽  
Bubble Cloud ◽  
Water Region ◽  
Media Layer

This paper presents a numerical and qualitative study on the expected hydrodynamic load-reducing effect of bubbly media near a volumetrically oscillating bubble. In this study, the bubble or bubble cloud is assumed to be spherically symmetric, and its motion is analyzed as a one-dimensional compressible two-phase flow in the radial direction in spherical coordinates. We adopted the CCUP (CIP-Combined Unified Procedure) method, which is a unified analysis method for both compressible and incompressible fluids proposed by Yabe et al. (1991) in order to treat interaction among gas, liquid, and two-phase media, and to avoid large numerical dissipation at density discontinuities. To verify the analysis program we developed, we analyzed free oscillations of a bubble with a unity void fraction and of a bubble cloud with an initial void fraction of 0.5, and found that the natural frequency from numerical results are well reproduced with an error of 0.9% for the bubble and 5% for the bubble cloud as compared to those obtained on a theoretical basis. Using this method, we analyzed the free oscillation of a bubble cloud in which a bubble with a unity void fraction is covered by a bubbly media layer with an initial void fraction of 0.5. Numerical results show that the amplitude of pressure oscillation inside the bubble is about halved, and that a higher mode of oscillation appears when a bubbly media layer covers the bubble. The measured results from a blowdown test we previously reported also shows a similar higher mode of oscillation. The amplitude of pressure oscillation in the water region was apparently reduced when a thick bubbly media layer covers the bubble. Thus, if the bubbly media is ejected from sparger holes prior to the ejection of a high-pressure bubble, the bubbly media might reduce the hydrodynamic load induced in a water pool made by volumetric oscillation of the bubble.

Mixing Characteristics of a Two-Phase Flow (Gas-Liquid) Microchannel Mixer

2011 ◽  
Author(s):  
Tarek Abdel-Salam ◽  
Srikanth Pidugu
Keyword(s):  
Reynolds Number ◽  
Two Phase Flow ◽  
Bubble Formation ◽  
Width Ratio ◽  
Phase Flow ◽  
Two Phase ◽  
Bubble Generation ◽  
Air Bubble ◽  
And Performance ◽  
Actual Shape

Multiphase phase flows occur in many engineering and bio-medical applications. Bubble formation in microchannels can be beneficial or harmful depending upon their influence on the operation and performance of microfludic devices. Potential uses of bubble generation found in many applications such as microreactors, micropump, and micromixers. In the present work the flow and mixing process in a passive microchannel mixer were numerically investigated. Effects of velocity, and inlet width ratio (Dgas/Dliquid) on the two phase flow were studied. Numerical results are obtained for 2-dimensional and 3-dimesional cases with a finite volume CFD code and using structured grids. Different liquid-gas Reynolds number ratios (Reliquid/Regas) were used ranging from 4 to 42. In addition, three values of the inlet width ratio (Dgas/Dliquid) were used. Results for the 3-D cases capture the actual shape of the air bubble with the thin film between the bubble and the walls. Also, increasing Reliquid increases the rate of the development of the air bubble. The bubble length increases with the increase of Dgas/Dliquid. For the same values of Re, the rate of growth of the bubble increases with the increase of Dgas/Dliquid. Finally, a correlation is provided to predict the length of the bubble with liquid-gas Reynolds number ratio (Reliquid/Regas) and tube width.

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