Passive acoustic determination of wave breaking dissipation rate across the spectrum

2021 ◽  
Author(s):  
Xiaochen Zou ◽  
Alexander Babanin
Keyword(s):  
Bubble Size ◽  
Wave Breaking ◽  
Dissipation Rate ◽  
Acoustic Pulse ◽  
Pulse Amplitude ◽  
Dominant Factor ◽  
The Mean ◽  
Bubble Sizes ◽  
Passive Acoustic ◽  
Lake George

<p>The ambient sound near the ocean surface is controlled by many processes, while wave breaking becomes the dominant factor once it occurs. Laboratory experiment shows that a severer breaker will result in a higher sound level and a larger mean bubble size. This relationship indicates a potential to extract information about wave breaking from acoustic records. Based on both laboratory and field experiments, a passive acoustic method has been developed to determine the wave breaking dissipation rate across the spectrum which had been extremely difficult to obtain in the open sea. The laboratory experiments were carried out in a flume at the University of Adelaide. Waves of different amplitudes and periods were generated and triggered to break by an underwater obstacle. The wave profiles before and after breaking were measured by two capacitance probes to calculate their breaking severities. The acoustic noise emitted by bubbles was recorded by a hydrophone located right under the breaking zone and the mean bubble sizes were computed on the basis of the relationship between bubble radius and acoustic frequency. A non-dimensional empirical formula between breaking severity and mean bubble size was established then applied to acoustic measurements in Lake George, New South Wales, Australia. Acoustic pulse amplitude, power spectral density of acoustic spectrum and the ratio between acoustic pulse amplitude and period were analyzed to identify the acoustic pulses truly produced by bubbles. The mean bubble sizes of each breaker were deduced from the acoustic records and further converted into their breaking severities. Combined with the wave scale information extracted from wave surface records, the spectral dissipation rates in Lake George were finally obtained. The acoustic based results are compared with various kinds of whitecapping dissipation source terms of WAVEWATCH III® and their differences are discussed.</p>

Passive Acoustic Determination of Wave-Breaking Events and Their Severity across the Spectrum

2006 ◽  
Vol 23 (4) ◽  
pp. 599-618 ◽  
Author(s):  
Richard Manasseh ◽  
Alexander V. Babanin ◽  
Cameron Forbes ◽  
Kate Rickards ◽  
Irena Bobevski ◽  
...  
Keyword(s):  
Probability Distribution ◽  
Bubble Size ◽  
Wave Breaking ◽  
Bubble Formation ◽  
Acoustic Method ◽  
Breaking Waves ◽  
Sound Level ◽  
Real Field ◽  
Video Record ◽  
Passive Acoustic

Abstract A passive acoustic method of detecting breaking waves of different scales has been developed. The method also showed promise for measuring breaking severity. Sounds were measured by a subsurface hydrophone in various wind and wave states. A video record of the surface was made simultaneously. Individual sound pulses corresponding to the many individual bubble formations during wave-breaking events typically last only a few tens of milliseconds. Each time a sound-level threshold was exceeded, the acoustic signal was captured over a brief window typical of a bubble formation pulse, registering one count. Each pulse was also analyzed to determine the likely bubble size generating the pulse. Using the time series of counts and visual observations of the video record, the sound-level threshold that detected bubble formations at a rate optimally discriminating between breaking and nonbreaking waves was determined by a classification-accuracy analysis. This diagnosis of breaking waves was found to be approximately 70%–75% accurate once the optimum threshold had been determined. The method was then used for detailed analysis of wave-breaking properties across the spectrum. When applied to real field data, a breaking probability distribution could be obtained. This is the rate of occurrence of wave-breaking events at different wave scales. With support from a separate, laboratory experiment, the estimated bubble size is argued to be dependent on the severity of wave breaking and thus to provide information on the energy loss due to the breaking at the measured spectral frequencies. A combination of the breaking probability distribution and the bubble size could lead to direct estimates of spectral distribution of wave dissipation.

Numerical and Experimental Investigation Into the Effects of Nanoparticle Mass Fraction and Bubble Size on Boiling Heat Transfer of TiO2–Water Nanofluid

2016 ◽  
Vol 138 (8) ◽  
Author(s):  
Cong Qi ◽  
Yongliang Wan ◽  
Lin Liang ◽  
Zhonghao Rao ◽  
Yimin Li
Keyword(s):  
Heat Transfer ◽  
Bubble Size ◽  
Boiling Heat Transfer ◽  
Mass Fraction ◽  
Experimental Methods ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Mass Fractions ◽  
Boiling Heat Transfer Coefficient ◽  
Bubble Sizes

Considering mass transfer and energy transfer between liquid phase and vapor phase, a mixture model for boiling heat transfer of nanofluid is established. In addition, an experimental installation of boiling heat transfer is built. The boiling heat transfer of TiO2–water nanofluid is investigated by numerical and experimental methods, respectively. Thermal conductivity, viscosity, and boiling bubble size of TiO2–water nanofluid are experimentally investigated, and the effects of different nanoparticle mass fractions, bubble sizes and superheat on boiling heat transfer are also discussed. It is found that the boiling bubble size in TiO2–water nanofluid is only one-third of that in de-ionized water. It is also found that there is a critical nanoparticle mass fraction (wt.% = 2%) between enhancement and degradation for TiO2–water nanofluid. Compared with water, nanofluid enhances the boiling heat transfer coefficient by 77.7% when the nanoparticle mass fraction is lower than 2%, while it reduces the boiling heat transfer by 30.3% when the nanoparticle mass fraction is higher than 2%. The boiling heat transfer coefficients increase with the superheat for water and nanofluid. A mathematic correlation between heat flux and superheat is obtained in this paper.

Light, Nutrients, and Water Temperature as Determinants of Phytoplankton Production in Two Saline, Prairie Lakes with High Sulphate Concentrations

1992 ◽  
Vol 49 (11) ◽  
pp. 2281-2290 ◽  
Author(s):  
Richard D. Robarts ◽  
Marlene S. Evans ◽  
Michael T. Arts
Keyword(s):  
Water Temperature ◽  
Photosynthetic Capacity ◽  
Chlorophyll Concentration ◽  
Euphotic Zone ◽  
Dominant Factor ◽  
Phytoplankton Production ◽  
Dissolved Phosphorus ◽  
Prairie Lakes ◽  
The Mean ◽  
Algal Productivity

Our data support empirical models indicating that algal productivity is low relative to total phosphorus (TP) levels in prairie lakes with high sulphate concentrations. Mean chlorophyll accounted for 91.1% of the variance in euphotic zone primary production (ΣA) in Humboldt Lake (total dissolved solids (TDS) = 3.3 g∙L−1; Zmax = 6 m), while TP, total dissolved phosphorus, and water temperature accounted for 82.7% of ΣA variance in Redberry Lake (TDS = 20.9 g∙L−1; Zmax = 17 m). The relative importance of these variables to ΣA resulted from biological, chemical, and physical differences of these lakes. Light usually penetrated to the bottom of Redberry Lake due to a mean euphotic zone (Zeu) chlorophyll of 1.7 mg∙m−3, while Humboldt Lake's mean Zeu was 3.4 m with a mean chlorophyll concentration of 62.6 mg∙m−3. Chlorophyll was the dominant factor correlated with light penetration in Humboldt Lake (r2 = 0.65) but not in Redberry Lake. Photosynthetic capacity was correlated (r2 = 0.72) with water temperature only in Redberry Lake. The mean ΣA was 57.1 and 230.2 mg C∙m−2∙h−1 for Redberry and Humboldt lakes, respectively.

Changes in ocular pulse amplitude and choroidal thickness in childhood obesity patients with and without insulin resistance

2021 ◽  
pp. 112067212110393
Author(s):  
Gözde Aksoy Aydemir ◽  
Emre Aydemir ◽  
Abdulvahit Asik ◽  
Semih Bolu
Keyword(s):  
Insulin Resistance ◽  
Childhood Obesity ◽  
Choroidal Thickness ◽  
Pulse Amplitude ◽  
Enhanced Depth Imaging ◽  
Control Group ◽  
Healthy Children ◽  
Ocular Pulse Amplitude ◽  
The Mean ◽  
Ocular Pulse

Purpose: To compare choroidal thickness (CT) and ocular pulse amplitude (OPA) in childhood obesity with insulin resistance (IR) and without IR. Methods: Seventy-three childhood obesity and 62 healthy children, who were both age-matched and gender-matched, comprised the study population in this prospective study. Obesity was determined as having a body mass index (BMI) – standard deviation (SD) score that was > 2 SD. Intraocular pressure (IOP) and OPA were measured using a dynamic contour tonometer. The CT measurements were performed using enhanced depth imaging optical coherence tomography at three locations, comprising at the fovea, at a position 500 µm nasal, and also at a position 500 µm temporal to the fovea. Results: Mean BMI value was 28.72 ± 4.85 in the patients with childhood obesity and 21.47 ± 1.14 in the control group. The mean IOP and OPA values were determined 15.90 ± 2.30 and 14.10 ± 2.16 mm Hg, 1.50 ± 0.28 and 1.74 ± 0.32 mm Hg in the patients with childhood obesity and the control group, respectively ( p < 0.001, p < 0.001). The mean subfoveal CT value was 350.50 ± 81.51 μm in the eyes with childhood obesity and 390.02 ± 71.50 μm in those of the control group ( p = 0.003). When the patient groups with and without IR were compared, no significant difference was found between CT, OPA and IOP values ( p > 0.005). Conclusions: Our results showed that both OPA and CT values were significantly decreased in childhood obesity patients. We suggest further studies to verify longitudinal changes in OPA and CT, as also the evaluation of these parameters in other populations.

scholarly journals Development of Bubble Characteristics on Chute Spillway Bottom

Water ◽  
2018 ◽  
Vol 10 (9) ◽  
pp. 1129
Author(s):  
Ruidi Bai ◽  
Chang Liu ◽  
Bingyang Feng ◽  
Shanjun Liu ◽  
Faxing Zhang
Keyword(s):  
Size Distribution ◽  
Bubble Size ◽  
Dissipation Rate ◽  
Bubble Diameter ◽  
Bubble Size Distribution ◽  
Impact Zone ◽  
Air Bubble ◽  
Air Supply ◽  
Bubble Characteristics ◽  
The Impact

Chute aerators introduce a large air discharge through air supply ducts to prevent cavitation erosion on spillways. There is not much information on the microcosmic air bubble characteristics near the chute bottom. This study was focused on examining the bottom air-water flow properties by performing a series of model tests that eliminated the upper aeration and illustrated the potential for bubble variation processes on the chute bottom. In comparison with the strong air detrainment in the impact zone, the bottom air bubble frequency decreased slightly. Observations showed that range of probability of the bubble chord length tended to decrease sharply in the impact zone and by a lesser extent in the equilibrium zone. A distinct mechanism to control the bubble size distribution, depending on bubble diameter, was proposed. For bubbles larger than about 1–2 mm, the bubble size distribution followed a—5/3 power-law scaling with diameter. Using the relationship between the local dissipation rate and bubble size, the bottom dissipation rate was found to increase along the chute bottom, and the corresponding Hinze scale showed a good agreement with the observations.

scholarly journals Electroflotation of cassiterite fines using a hydrophobic bacterium strain

2013 ◽  
Vol 66 (4) ◽  
pp. 507-512 ◽  
Author(s):  
Lorgio Gilberto Valdiviezo Gonzales ◽  
Gabriela Alejandra Huamán Pino ◽  
Maurício Leonardo Torem
Keyword(s):  
Current Density ◽  
Bubble Size ◽  
Mean Value ◽  
Contact Angles ◽  
Rhodococcus Opacus ◽  
Bacterial Concentration ◽  
Electrophoretic Mobilities ◽  
Potential Contact ◽  
Bacterium Strain ◽  
The Mean

In this work, the electroflotation of cassiterite fine ranges using Rhodococcus opacus (R. opacus) as bioreagent has been carried out. The interaction between R. opacus and mineral surface was valued through the zeta potential, contact angles measurements and adsorption studies. Furthermore, studies were attempted to check the effect of current density and microorganism concentration on mean bubble size (Sauter). After the interaction, the resulting particles exhibited hydrophobic characters, as verified by the increase of the contact angle. Also, the electrophoretic mobilities of cassiterite particles showed a mean value close to zero after interaction with R. opacus. The measurement of bubble size by laser diffraction showed a mean bubble size of 26µm. Current density and bacterial concentration seem to be the main parameters affecting the mean diameter of the bubbles. An electroflotation test reported recovery of around 64.5% at pH 5, concentration of 2.87x10¹² cells/ml (50 mg/L) and current density of 51.4 mA/cm².

scholarly journals Acoustic Measurement in a Rectangular Bubble Column to Determine Bubble Size and Interfacial Area for Aqueous Solutions of Ethylene Glycol

2019 ◽  
Vol 8 (2) ◽  
pp. 994-998
Keyword(s):  
Ethylene Glycol ◽  
Bubble Size ◽  
Bubble Column ◽  
Bubble Diameter ◽  
Water System ◽  
Interfacial Area ◽  
Bed Height ◽  
Specific Interfacial Area ◽  
Bubble Sizes ◽  
Distributor Plate

Bubble sizes in bubble column affect the bubble induced mixing of phases, interfacial area and transfer processes. Acoustic technique is used to measure bubble size distribution in a rectangular bubble column of cross section 0.2m x 0.02m for air sparged into water and aqueous solutions of ethylene glycol. Five condenser mikes at intermediate distance of 0.05 m measured above the distributor plate were used to find out the variation of bubble size as the bubbles move up. Sauter-mean bubble diameter and specific interfacial area were estimated from bubble size distribution at several superficial air velocity, static bed height, distance above the distributor plate and ethylene glycol concentration. The BSD exhibited mono-modal distribution and indicated non-uniform homogeneous bubbling regime. Sauter-mean bubble diameter is independent of superficial gas velocity, static bed height and concentration of EG, although, the values were higher than that for air-water system. Sauter-mean bubble diameter decreases as the bubbles move up indicating bubble breakup to take place once the bubbles leave the sparger. The value of interfacial area increases as the static bed height decreases and distance above the distributor plate increases. For air-ethylene glycol solution the values of specific interfacial area are about 200% higher than that observed in case of air-water system. The acoustic technique may be used to measure local values of bubble sizes and specific interfacial area.

Effects of light and food on plasma leptin concentrations in ewes

2000 ◽  
Vol 71 (2) ◽  
pp. 235-242 ◽  
Author(s):  
T. Tokuda ◽  
T. Matsui ◽  
H. Yano
Keyword(s):  
Diurnal Rhythm ◽  
Energy Requirement ◽  
Pulse Length ◽  
Pulse Amplitude ◽  
Pulse Frequency ◽  
Pulse Plasma ◽  
Dark Cycle ◽  
Blood Samples ◽  
The Mean ◽  
Plasma Leptin

AbstractPlasma leptin concentration shows pulsatility and diurnal rhythm in humans. However, there are few reports concerning the 24-h profile of circulating leptin levels in ruminants. Five crossbred ewes were housed in metabolism cages under a 1-h light-dark cycle. The ewes were offered alfalfa hay daily to meet their energy requirement. Blood samples were collected at 15-min intervals for 24 h. Plasma leptin concentrations were determined using a radioimmunoassay and the profile of plasma leptin levels was analysed by the PULSAR algorithmic program for detecting pulse. Plasma leptin concentration changed in a pulsatile fashion. The mean leptin concentration was 2·93 ng/ml. The mean pulse frequency was 4·8 pulses per day and the mean pulse amplitude was 0·67 ng/ml with an average pulse length of 1:13 h. Plasma leptin level was not affected by feeding or lighting cycle. These results indicate that plasma leptin level in sheep shows pulsatility but diurnal rhythm is not exhibited.

Gas dispersion in the oxygen delignification process

TAPPI Journal ◽  
2021 ◽  
Vol 20 (5) ◽  
pp. 311-318
Author(s):  
JARI KAYHKO ◽  
HEIKKI MUTIKAINEN ◽  
KARI PELTONEN ◽  
RIKU KOPRA ◽  
MARKUS HONKANEN
Keyword(s):  
Bubble Size ◽  
Oxygen Delignification ◽  
Noticeable Effect ◽  
Gas Dispersion ◽  
New Information ◽  
Oxygen Bubble ◽  
The Mean ◽  
Mixer Rotation ◽  
Reactor Pressure

There has been very little knowledge about the state of gas dispersion in the oxygen delignification process, even though this has a major impact on the performance of the reactor. This paper presents a new continu-ous inline method for measuring oxygen bubble size distribution in the reactor, as well as results from studies con-ducted in softwood and hardwood lines. This new measurement worked well, and new information about oxygen bubble size, as well as how different reactor conditions affected the distribution, was obtained. For example: • In the softwood line, the mean volume-weighted bubble size was about 0.1 mm, whereas in the hardwood line, this size was almost 10 times higher. For both lines, there was considerable variation in the measured bubble size over the long term. • For both lines, an increase in mixer rotation speed caused a discernible decrease in the bubble size, and an increase in oxygen charge caused a discernible increase in the bubble size. • In the softwood line, no coalescence of the bubbles in the reactor was observed, but in the hardwood line, some coalescence of the larger bubbles occurred. • In the test conducted in the hardwood line, the use of brownstock washer defoamer caused a discernible increase in oxygen bubble size. • In the hardwood line, reactor pressure had a noticeable effect on the amount of delignification, which indicated that improving mass transfer of oxygen (e.g., by decreasing the oxygen bubble size, in this case) should also have an increasing effect on the delignification.

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