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.

Bubble formation, motion and interaction in a Hele-Shaw cell

1986 ◽  
Vol 173 ◽  
pp. 95-114 ◽  
Author(s):  
T. Maxworthy
Keyword(s):  
Ad Hoc ◽  
Bubble Formation ◽  
Bubble Surface ◽  
Large Bubble ◽  
Rise Velocity ◽  
Parallel Plates ◽  
Narrow Gap ◽  
Wide Range ◽  
Bubble Characteristics ◽  
Hele Shaw Cell

We consider the motion of the flattened bubbles which form when air is injected into a viscous fluid contained in the narrow gap between two flat, parallel plates which make up a conventional Hele-Shaw cell, inclined at an angle x to the horizontal. We present a number of qualitative observations on the formation and interaction of the streams of bubbles that appear when air is injected continuously into the cell. The majority of this paper is then concerned with the shape and velocity of rise of single, isolated bubbles over a wide range of bubble size and cell inclination. We compare these results to theories by Taylor & Saffman (1959), and Tanveer (1986). It appears that the bubble characteristics found by an ad hoc speculation in Taylor & Saffman (1959) and by Tanveer (1986) only agree with the experimental results in the limit α → 0, and for large bubble widths (D). For finite values of α, it is necessary to use the measured bubble shape in order to calculate the rise velocity using the more general Taylor & Saffman (1959) formulation. Deviations from these theories for small D can be explained by considering the effects of the detailed flow close to the bubble surface.

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 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.

Exploring wall shear stress spatiotemporal heterogeneity in coronary arteries combining correlation-based analysis and complex networks with computational hemodynamics

2020 ◽  
Vol 234 (11) ◽  
pp. 1209-1222 ◽  
Author(s):  
Karol Calò ◽  
Giuseppe De Nisco ◽  
Diego Gallo ◽  
Claudio Chiastra ◽  
Ayla Hoogendoorn ◽  
...  
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Complex Networks ◽  
Coronary Arteries ◽  
Early Stage ◽  
Flow Direction ◽  
Computational Hemodynamics ◽  
Time Histories ◽  
Wall Shear

Atherosclerosis at the early stage in coronary arteries has been associated with low cycle-average wall shear stress magnitude. However, parallel to the identification of an established active role for low wall shear stress in the onset/progression of the atherosclerotic disease, a weak association between lesions localization and low/oscillatory wall shear stress has been observed. In the attempt to fully identify the wall shear stress phenotype triggering early atherosclerosis in coronary arteries, this exploratory study aims at enriching the characterization of wall shear stress emerging features combining correlation-based analysis and complex networks theory with computational hemodynamics. The final goal is the characterization of the spatiotemporal and topological heterogeneity of wall shear stress waveforms along the cardiac cycle. In detail, here time-histories of wall shear stress magnitude and wall shear stress projection along the main flow direction and orthogonal to it (a measure of wall shear stress multidirectionality) are analyzed in a representative dataset of 10 left anterior descending pig coronary artery computational hemodynamics models. Among the main findings, we report that the proposed analysis quantitatively demonstrates that the model-specific inlet flow-rate shapes wall shear stress time-histories. Moreover, it emerges that a combined effect of low wall shear stress magnitude and of the shape of the wall shear stress–based descriptors time-histories could trigger atherosclerosis at its earliest stage. The findings of this work suggest for new experiments to provide a clearer determination of the wall shear stress phenotype which is at the basis of the so-called arterial hemodynamic risk hypothesis in coronary arteries.

scholarly journals Analysis of Activation Process of Carbon Black Based on Structural Parameters Obtained by XRD Analysis

Crystals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 153
Author(s):  
Sang-Min Lee ◽  
Sang-Hye Lee ◽  
Jae-Seung Roh
Keyword(s):  
Carbon Black ◽  
Early Stage ◽  
Structural Parameters ◽  
Xrd Analysis ◽  
Activation Process ◽  
Co2 Gas ◽  
Carbon Black Surface ◽  
Black Surface ◽  
Last Stage ◽  
Pore Properties

In the present study, carbon black activated by CO2 gas was examined through XRD analysis, especially with regard to changes in its structural parameters. Based on the results, its activation process was thoroughly analyzed. The activation process was controlled by isothermally activating the carbon black inside a reaction tube through which CO2 gas flowed. With this approach, the degree of activation was varied as desired. At an early stage of the activation process, the amorphous fraction on the carbon black surface was preferentially activated, and later the less-developed crystalline carbon (LDCC) region inside the carbon black particles started to be activated. The latter process was attributable to the formation of pores inside the carbon black particles. As the activation process proceeded further, the more-developed crystalline carbon (MDCC) region started to be activated, thereby causing the pores inside the carbon black particles to grow larger. At the last stage of the activation process, La was found to be decreased to about 40 Å. This implied that the edges of the graphite crystals had been activated, thus causing the internal pores to grow and coalesce into larger pores. Activated conductive Super-P with enhanced pore properties is expected to have wide applications.

The Effect of Wall Distensibility on Flow in a Two-Dimensional End-to-Side Anastomosis

1994 ◽  
Vol 116 (3) ◽  
pp. 294-301 ◽  
Author(s):  
D. A. Steinman ◽  
C. Ross Ethier
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Intimal Hyperplasia ◽  
Bypass Graft ◽  
Numerical Approach ◽  
Flow Patterns ◽  
Temporal Variations ◽  
Model Studies ◽  
Wall Shear ◽  
Wall Distensibility

The development of intimal hyperplasia at the distal anastomosis is the major cause of long-term bypass graft failure. To evaluate the suspected role of hemodynamic factors in the pathogenesis of distal intimal hyperplasia, an understanding of anastomotic flow patterns is essential. Due to the complexity of arterial flow, model studies typically make simplifying assumptions, such as treating the artery and graft walls as rigid. In the present study this restriction is relaxed to consider the effects of vessel wall distensibility on anastomotic flow patterns. Flow was simulated in an idealized 2-D distensible end-to-side anastomosis model, using parameters appropriate for the distal circulation and assuming a purely elastic artery wall. A novel numerical approach was developed in which the wall velocities are solved simultaneously with the fluid and pressure fields, while the wall displacements are treated via an iterative update. Both the rigid and distensible cases indicated the presence of elevated temporal variations and low average magnitudes of wall shear stress at sites known to be susceptible to the development of intimal hyperplasia. At these same sites, large spatial gradients of wall shear stress were also noted. Comparison between distensible-walled and corresponding rigid-walled simulations showed moderate changes in wall shear stress at isolated locations, primarily the bed, toe and heel. For example, in the case of a distensible geometry and a physiologic pressure waveform, the heel experienced a 38 percent increase in cycle-averaged shear stress, with a corresponding 15 percent reduction in shear stress variability, both relative to the corresponding values in the rigid-walled case. However, other than at these isolated locations, only minor changes in overall wall shear stress patterns were observed. While the physiological implications of such changes in wall shear stress are not known, it is suspected that the effects of wall distensibility are less pronounced than those brought about by changes in arterial geometry and flow conditions.

Increase of the content of QP47 (a desiccation-associated nuclear protein) in embryo cells during maturation of pea seeds

1994 ◽  
Vol 4 (4) ◽  
pp. 421-429 ◽  
Author(s):  
Donato Chiatante ◽  
Paola Brusa
Keyword(s):  
Cell Proliferation ◽  
Nuclear Protein ◽  
Early Stage ◽  
Seed Maturation ◽  
Radicle Elongation ◽  
Embryo Cells ◽  
Last Stage ◽  
Pea Seeds ◽  
Metabolic Activities

AbstractA nuclear protein (QP47) is synthesized during the last stage of seed maturation when the embryo cells start to dehydrate and enter a condition of metabolic quiescence. This protein is localized in the nucleoplasm surrounding the chromosomes. The correlation existing between the synthesis of QP47 and arrest of cell proliferation, suggests that the presence of this protein in the nucleus could influence its metabolic activities. This hypothesis is supported by the fact that degradation of this protein precedes resumption of cell proliferation during the early stage of radicle elongation.

Experimental Study on Skin Friction Reduction With Micro-Blowing

Volume 4 ◽  
2004 ◽  
Author(s):  
Song Liu ◽  
Hongmin Li ◽  
Minel J. Braun
Keyword(s):  
Boundary Layer ◽  
Shear Stress ◽  
Skin Friction ◽  
Full Range ◽  
Experimental System ◽  
Main Flow ◽  
Friction Reduction ◽  
Long Distance ◽  
Full Field ◽  
Set Up

Reducing skin friction, such as friction on a car hood or a plane wing, can significantly reduce the drag force and decrease specific fuel consumption. Many techniques and methods have been tried. The Micro-blowing Technique (MBT) is an innovative way to reduce skin friction. Suggested by early research in boundary layer injection in 1950s, MBT was actually brought to effective use in 1994 by Hwang [1]. The basic idea is that by blowing fluid, same as or different from the mainstream flow, at an angle with that of the main flow, a decrease in the velocity gradient at the wall can be achieved, and thus the shear stress on the surface is reduced. Although the experimental data on boundary layer with micro blowing show a significant friction reduction, the mechanism of MBT is still not well understood and thus its full range of application is not yet established. In this paper, we further the understanding of the MBT mechanism. An experimental system is set up to visualize the flow structure on a plate with and without micro blowing in a tunnel. A long distance microscope is combined with a Full Field Flow Tracking visualization method in order to elucidate the nature of the flow interaction and mixing between the blowing flow and the main flow. The flow above the porous plates is visualized and velocities both in the blowing layer immediately adjacent to the plate and in the main flow are quantified using the PIV procedure. The flow and shear stress analysis shows that MTB has significantly different effects on a flow with a boundary layer and fully developed internal flows.

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