Large Water Tank Research Articles

Prediction of Bubble Generation Based on Acoustic Emission

The noise associated with gas discharged from a submerged nozzle is of great interest to many industries because of its important applications. For example, it can be used to size bubbles and to detect gas flow rate. However, the physics associated with the acoustic emission due to bubble formation is complex, particularly when a large number of bubbles are involved, and has not been fully understood. In this study, the dynamics of the bubble formation from a submerged nozzle has been studied experimentally using the Particle Droplet Image Analysis technique. An improved model for prediction of the bubble generation rate and size distribution based on acoustic emission is presented. The experimental study is carried out in a large water tank, of dimensions 10 m \(\times \) 10 m \(\times \) 6 m, using multiple hydrophones. The water tank is carefully calibrated in order to provide free-field measurements. The predicted bubble generation rate and size distribution have been compared with the experimental data. It has been found that the predicted results are in good agreement with the experimental measurement, implying that an accurate prediction of acoustic emission associated with a bubbling plume from a submerged nozzle can be achieved by using the model.

An Incorporate Ultrasonic Coupling Device for Long-Focal- Zone Photoacoustic Imaging System

An incorporate ultrasonic coupling device for extended focal zone focused photoacoustic imaging was designed. Phantom experimental imaging was carried out. The results show that, with the incorporate ultrasonic coupling device,accurate imaging position of absorber in the sample can be achieved. And it is worth mentioning that without the large water tank,the photoacoustic imaging experimental system become simple. Our work has a potential application in the noninvasive photoacoustic imaging of bio-tissue.

A passive decay heat removal strategy of the integrated passive safety system (IPSS) for SBO combined with LOCA

An integrated passive safety system (IPSS), to be achieved by the use of a large water tank placed at high elevation outside the containment, was proposed to achieve various passive functions. These include decay heat removal, safety injection, containment cooling, in-vessel retention through external reactor vessel cooling, and containment filtered venting. The purpose of the passive decay heat removal (PDHR) strategy using the IPSS is to cope with SBO and SBO-combined accidents under the assumption that existing engineered safety features have failed. In this paper, a PDHR strategy was developed based on the design and accident management strategy of Korean representative PWR, the OPR1000. The functions of a steam generator gravity injection and a passive safety injection system in the IPSS with safety depressurization systems were included in the PDHR strategy. Because the inadvertent opening of pressurizer valves and seal water leakage from RCPs could cause a loss of coolant in an SBO, LOCAs during a SBO were simulated to verify the performance of the strategy. The failure of active safety injection in LOCAs could also be covered by this strategy. Although LOCAs have generally been categorized according to their equivalent break diameters, the RCS pressure is used to classify the LOCAs during SBOs. The criteria values for categorization were determined from the proposed systems, which could maintain a reactor in a safe state by removing the decay heat for the SBO coping time of 8h. The accidents were simulated by MARS code considering several specific processes characterized from LOCA and SBO. For a high-pressure LOCA, water in an IPST could be injected into a steam generator using gravity after depressurization of the secondary circuit caused by opening atmospheric dump valves. For a low-pressure LOCA, the pressure in the RCS naturally decreased due to coolant loss. Additional depressurization was needed during LOCAs for which RCS criteria pressures at the time of estimation were in the range between high-pressure LOCA and low-pressure LOCA. This is referred to as medium-pressure LOCA, according to the range of the RCS pressure. The procedures of the PDHR strategy can be implemented after failure of the steps in emergency operating procedures, before entering the condition for the severe accident management. Even when external conditions make a given site extremely inaccessible, the PDHR strategy can allow for cooling the core in an EDMG by installing an IPSS beside each nuclear power plant. The proposed PDHR strategy can be applied in both current and future nuclear power plants by considering modifications for enhancing their safety.

Experimental study of vortex-induced vibrations of flexibly mounted cylinder in circulating water tunnel

This paper presents the experimental results concerning the vortex-induced vibration phenomena of a flexibly mounted enclosed smooth rigid pipe. The experiment was newly designed and fabricated, utilizing the circulating water tunnel concept. New results on the dynamic response of the vibrating system are shown. The stream flow was generated by using a large displacement volume submersible water tank, controlled through the ABB inverter. The rotation frequency controlled based was implemented in the ABB inverter, and the measurement of stream flow was taken by using a flow rate sensor at the respective pump rotation frequency. The Reynolds number of the experiments ranges from \({\sim4900}\) to \({\sim15,000}\), and its corresponding reduced velocities, based on the natural frequency in still water, vary up to \({\sim7}\). The riser modeled pipe was positioned in vertical direction, and it is flexibly mounted at both ends. The system has low mass ratio and damping coefficient, with the values 1.184 and 0.08, respectively. The mass–damping ratio \({({m}^{*}\zeta)}\) is 0.09472. The results for the bare pipe cylinder in this experimental setup are in good agreementwith othermeasurements found in the literature.

Liquefaction mitigation using secant piles wall under a large water tank

Two-dimensional and three-dimensional numerical models were developed to evaluate the effectiveness of a foundation perimeter wall on the mitigation of the effects of liquefaction in a 64m diameter, reinforced-concrete water tank. The seismic response of the tank was evaluated in terms of differential settlements induced by an actual earthquake recording by comparing the situations with and without a mitigation strategy consisting of 20m-long, 1m-diameter secant piles wall. Although the mitigation strategy did not significantly reduce the liquefaction-induced settlements, it enforced a relatively homogeneous distribution of these settlements, leading to less structural damage.

Thermochromic phantom for therapeutic ultrasound daily quality assurance

Errors in power output ranging from −100% to +210% have been reported in a multitude of physiotherapy transducers.[1] Differences in power output can arise even after careful calibration on an annual or bi-annual schedule, which can either result in harm to the patient or non-effective treatment. Therefore, easy implementation of daily quality assurance is of great importance. We propose a simple, easy to use DQA phantom which allows the user to assess the power output of the focused ultrasound transducer, and determine if it has changed significantly after calibration. The basis of this phantom is the use of a highly attenuating ultrasound absorber with a surface layer of thermochromic liquid crystals (TLC). The use of thermochromic materials as a technique for use in ultrasound phantoms has been an ongoing area of interest. Many of these techniques require complicated set-ups, with large water tanks and imaging systems to produce very accurate data.[2,3] Simpler phantoms have been developed for use in benchtop settings, but still with a large emphasis on complicated image analysis.[4] Our proposed phantom will be a product where the end-user can visually assess the size of the lesion formed as a function of power output, without resorting to complicated image analysis.

Calculation of skid resistance from texture measurements

Abstract There is a wide range of routine skid resistance measurement devices on the market. All of them are measuring the friction force between a rubber wheel and the wetted road surface. Common to all of them is that they are relatively complex and costly because generally a truck carrying a large water tank is needed to wet the surface with a defined water layer. Because of the limited amount of water they can carry they are limited in range. Besides that the measurement is depending on factors like water film thickness, temperature, measurement speed, rubber aging, rubber wear and even road evenness and curviness. All of these factors will affect the skid resistance and are difficult to control. We present a concept of contactless skid resistance measurement which is based on optical texture measurement and consists of two components: measurement of the pavement texture by means of an optical measuring system and calculation of the skid resistance based on the measured texture by means of a rubber friction model. The basic assumptions underlying the theoretical approach and the model itself based on the theory of Persson are presented. The concept is applied to a laboratory device called Wehner/Schulze (W/S) machine to prove the theoretical approach. The results are very promising. A strong indication could be provided that skid resistance could be measured without contact in the future.

Improved dengue fever prevention through innovative intervention methods in the city of Salto, Uruguay.

BackgroundUruguay is located at the southern border of Aedes aegypti distribution on the South American sub-continent. The reported dengue cases in the country are all imported from surrounding countries. One of the cities at higher risk of local dengue transmission is Salto, a border city with heavy traffic from dengue endemic areas.MethodsWe completed an intervention study using a cluster randomized trial design in 20 randomly selected ‘clusters’ in Salto. The clusters were located in neighborhoods of differing geography and economic, cultural and social aspects.ResultsEntomological surveys were carried out to measure the impact of the intervention on vector densities. Through participatory processes of all stakeholders, an appropriate ecosystem management intervention was defined. Residents collected the abundant small water holding containers and the Ministry of Public Health and the Municipality of Salto were responsible for collecting and eliminating them. Additional vector breeding places were large water tanks; they were either altered so that they could not hold water any more or covered so that oviposition by mosquitoes could not take place.ConclusionsThe response from the community and national programme managers was encouraging. The intervention evidenced opportunities for cost savings and reducing dengue vector densities (although not to statistically significant levels). The observed low vector density limits the potential reduction due to the intervention. A larger sample size is needed to obtain a statistically significant difference.

A preliminary study of continuous discharge flow from horizontal drains using 3-dimensional resistivity model

A massive slope failure occurred on the 22nd March 2007 after 3 days of continuous rainfall at Precinct 9, Putrajaya, Malaysia. Back analysis carried out identified that the main cause of failure is due to the existing high groundwater level within the cut slope. It is also observed that the continuous discharge from the horizontal drains yield approximately 100 ml/s even during dry season. Thus, it is suspected that the main contribution to the high groundwater level is due to the leakage from the large water tank constructed on the crest of the slope. Electrical resistivity survey was adopted to facilitate the investigation for the source of high groundwater level within the slope. A 3-dimensional resistivity model was developed using the Inverse Distance Weighting (IDW) interpolation method. The 3D resistivity model shows that the high water content zone is not caused by the leakage of water tank but is originated from an unknown source at the south-east side of the slope.

Topographically induced internal solitary waves in a pycnocline: Ultrasonic probes and stereo-correlation measurements

Internal solitary waves (ISWs) are large amplitude stable waves propagating in regions of high density gradients such as the ocean pycnocline. Their dynamics has often been investigated in two-dimensional approaches, however, their three-dimensional evolution is still poorly known. Experiments have been conducted in the large stratified water tank of CNRM-GAME to study the generation of ISWs in two academic configurations inspired by oceanic regimes. First, ultrasonic probes are used to measure the interfacial displacement in the two configurations. In the primary generation case for which the two layers are of constant density, the generation of ISWs is investigated in two series of experiments with varying amplitude and forcing frequency. In the secondary generation case for which the lower layer is stratified, the generation of ISWs from the impact of an internal wave beam on the pycnocline and their subsequent dynamics is studied. The dynamics of ISWs in these two regimes accords well with analytical approaches and numerical simulations performed in analogous configurations. Then, recent developments of a stereo correlation technique are used to describe the three-dimensional structure of propagating ISWs. In the primary generation configuration, small transverse effects are observed in the course of the ISW propagation. In the secondary generation configuration, larger transverse structures are observed in the interfacial waves dynamics. The interaction between interfacial troughs and internal waves propagating in the lower stratified layer are a possible cause for the generation of these structures. The magnitude of these transverse structures is quantified with a nondimensional parameter in the two configurations. They are twice as large in the secondary generation case as in the primary generation case.

Attenuation of standing waves in a large water tank using arrays of large tethered encapsulated bubbles.

The use of bubble resonance effects to attenuate low-frequency underwater sound was investigated experimentally in a large water tank. A compact electromechanical sound source was used to excite standing wave fields at frequencies ranging between 50 and 200 Hz in the tank. The source was then surrounded by a stationary array of tethered encapsulated air bubbles, and reduction in standing wave amplitude by as much as 26 dB was observed. The bubbles consisted of either thin-shelled latex balloons with approximately 5 cm radii or thicker-shelled vinyl boat fenders with 6.9 cm radii. The effects of changing the material and thickness of the bubble shells were found to be in qualitative agreement with predictions from Church's model for sound propagation in a liquid containing encapsulated bubbles [J. Acoust. Soc. Am. 97, 1510-1521 (1995)]. Although demonstrated here for low frequency noise abatement within a tank, which is useful for quieting acoustic test facilities and large tanks used for marine life husbandry, the eventual aim of this work is to use stationary arrays of large tethered encapsulated bubbles to abate low frequency underwater noise from anthropogenic sources in the marine environment.

EURECA Conceptual Design Report

Abstract The EURECA (European Underground Rare Event Calorimeter Array) project is aimed at searching for dark matter particles using cryogenic bolometers. The proponents of the present project have decided to pool their strengths and expertise to build a facility to house up to 1000 kg of detectors, EURECA, consisting in the first instance of germanium and CaWO4 crystals. The shielding will be provided through a large water tank in which the cryostat with detectors will be immersed. The EURECA infrastructure will be an essential tool for the community interested in using cryogenic detectors for dark matter searches. Beyond European detectors, it will be designed to host other types of similar cryogenic detectors, requiring millikelvin operating temperatures. In particular, this includes the germanium detectors currently in use by the SuperCDMS team, following the current collaborative work performed by the EURECA and SuperCDMS collaborations. EURECA will have two stages. The first phase aims at a sensitivity of 3 . 10−10 pb and will involve building the infrastructure, cryostat and shielding, and operating 150 kg of detectors. The second phase will be completed with 850 kg of additional detectors, the relative weight between the different detectors being decided by the collaboration according to the physics reach. A sensitivity of 2 . 10−11 pb is aimed for at the second stage. EURECA will ideally benefit from the planned extension of the deepest underground laboratory in Europe – LSM. With a site-independent design, it can also be hosted in other locations at similar or deeper sites such as SNOLAB.

EXPERIMENTAL STUDY OF GROUND EFFECT ON THREE-DIMENSIONAL INSECT-LIKE FLAPPING MOTION

This paper focuses on an experimental investigation aimed at evaluating the aerodynamics force characteristics of three-dimensional (3D) insect-like flapping motion in the vicinity of ground. The purpose is to establish whether flapping wing insects can derive aerodynamic benefit from ground effect similar to that experienced by a fixed wing aircraft. To evaluate this, force measurements were conducted in a large water tank using a 3D flapping mechanism capable of executing various insect flapping motions. Here, we focus on three types of flapping motions, namely simple harmonic flapping motion, hawkmoth-like hovering motion and fruitfly-like hovering motion, and two types of wing planforms (i.e. hawkmoth-like wing and fruitfly-like wing). Results show that hawkmoth-like wing executing simple harmonic flapping motion produces average lift to drag ratio [Formula: see text] similar to that of fruitfly wing executing the same motion. In both cases, they are relatively independent of the wing distance from the ground. On the other hand, a hawkmoth wing executing hawkmoth flapping motion produces [Formula: see text] characteristic different from that of fruitfly wing executing fruitfly motion. While the [Formula: see text] value of the former is a function of the wing distance from the ground, the latter is minimally affected by ground effect. Unlike fixed wing aerodynamics, all the flapping wing cases considered here do not show a monotonic increase in [Formula: see text] with decreasing wing distance from the ground.

Dynamics of domestic water supply and consumption in a semi-urban Nigerian city

A survey of water supply and consumption status in Nsukka Metropolis was done using questionnaires, interviews, observations and secondary data obtained from other sources. Water consumption was estimated using water balance principle. The water consumption per capita was found to be 34.9 L per day. At a cost of N̿0.81/L, this value represents 7% of average monthly income of residents. The price of water fluctuates from N̿0.45/L to N̿0.9/L during the rainy season and N̿0.9/L to N̿1.5/L in dry season, depending mostly on size of container. Those who own large water tanks ranging from 2273 L (500 gallons) upwards pay less than those who trek or drive long distance to fetch water in smaller containers. While more than 98% of the residents attain the average daily water need for survival (2.5 lpcd), only 27% attain the basic water need of 50 lpcd. The distribution of drinking water sources was as follows: boreholes (64%), sachet water (23%), rainwater (7%), tap water (3%) and bottled water (2%). It was further found that most people would prefer to drink bottled water but for its expensive cost of N̿106/L. About 55% of residents rely on rainwater for domestic use during the rainy season. However, as rain recedes, 78% rely almost exclusively on water vendors (tankers) for water supply.Key: $1.00 = N̿157.00.

HAWC: A next-generation all-sky gamma-ray telescope

The High-Altitude Water Cherenkov (HAWC) Gamma-Ray Observatory is currently under construction 4100m above sea level on the slope of Pico de Orizaba in Mexico. HAWC is a high-duty cycle, large field-of-view instrument capable of monitoring the gamma-ray sky between roughly 50GeV and 100TeV. The detector will be used to record both steady and transient gamma-ray sources and to provide an unbiased survey of the northern sky with 2π sr daily coverage. Upon completion in 2014, HAWC will comprise 300 large light-tight water tanks arrayed over an area of 20,000m2. Each tank will be instrumented with four photomultipliers to detect particles from extensive air showers produced by gamma rays and cosmic rays. With 15 times the sensitivity of its predecessor experiment Milagro, the HAWC Observatory will enable significant detection of Crab-like fluxes each day at a median energy of 1TeV. We present the scientific case for HAWC and describe its design and sensitivity.

커터헤드 형태에 따른 준설효율에 관한 실험적 연구

본 연구에서는 준설용 커터헤드의 형태에 따른 준설효율 특성을 분석하기 위하여 개방형 및 폐쇄형으로 나누어 수리실험을 수행하였다. 준설효율에 관한 실험을 수행하기 위하여 <TEX>$4.9m(L){\times}2.2m(W){\times}1.5m(H)$</TEX> 크기의 대형수조를 제작한 후 준설 운영에 필요한 여러 장치를 제작하였다. 준설효율 실험에서는 커터헤드의 준설깊이, 회전속도, 흡입속도 등에 관한 운영조건을 달리하여 실험을 수행하였다. 준설효율에 관한 실험 결과를 살펴보면 개방형의 경우보다 폐쇄형의 경우에 상당히 높은 준설효율을 유지하였다. 동일한 커터헤드의 형태에서는 커터헤드의 회전속도가 준설효율 결과에 가장 큰 영향을 미쳤으며, 보다 높은 준설효율을 위해서는 적정수준의 흡입속도가 필요한 것으로 나타났다. In this study, the hydraulic experiments were conducted for the dredging efficiency of the cutter head type, which includes the open type and the close type cutter head. The dredging experimental instrument was installed in the large water tank which has the dimension of <TEX>$4.9m(L){\times}2.2m(W){\times}1.5m(H)$</TEX>. The dredging experiments were performed for the various conditions of dredging depth, rotating speed, and suction speed of the cutter head. As the results, the dredging efficiency of the close-type cutter head is much higher than that of the open-type cutter head. The dredging efficiency of the same cutter head type was mainly influenced by the rotating speed of cutter head. Also the adequate suction speed of the cutter head is needed for more effective dredging.

First Report on Invasion of Yellow Fever Mosquito, Aedes aegypti, at Narita International Airport, Japan in August 2012

The invasion of the yellow fever mosquito Aedes aegypti at Narita International Airport, Japan was detected for the first time. During the course of routine vector surveillance at Narita International Airport, 27 Ae. aegypti adults emerged from larvae and pupae collected from a single larvitrap placed near No. 88 spot at passenger terminal 2 on August 8, 2012. After the appearance of Ae. aegypti in the larvitrap, we defined a 400-m buffer zone and started an intensive vector survey using an additional 34 larvitraps and 15 CO2 traps. International aircraft and passenger terminal 2 were also inspected, and one Ae. aegypti male was collected from the cargo space of an international aircraft from Darwin via Manila on August 28, 2012. Larvicide treatment with 1.5% fenitrothion was conducted in 64 catch basins and one ditch in the 400-m buffer zone. Twenty-four large water tanks were also treated at least once with 0.5% pyriproxyfen, an insect growth regulator. No Ae. aegypti eggs or adults were found during the 1-month intensive vector survey after finding larvae and pupae in the larvitrap. We concluded that Ae. aegypti had failed to establish a population at Narita International Airport.

Removal of unwanted fluid

This work is concerned with the removal of unwanted fluid through the source-sink pair. The source consists of fluid issuing out of a nozzle in the form of a jet and the sink is a pipe that is kept some distance from the source pipe. Of concern is the percentage of source fluid sucked through the sink. The experiments have been carried in a large glass water tank. The source nozzle diameter is 6Â mm and the sink pipe diameter is either 10 or 20Â mm. The horizontal and vertical separations and angles between these source and sink pipes are adjustable. The flow was visualized using KMnO 4 dye, planer laser induced fluorescence and particle streak photographs. To obtain the effectiveness (that is percentage of source fluid entering the sink pipe), titration method is used. The velocity profiles with and without the sink were obtained using particle image velocimetry. The sink flow rate to obtain a certain effectiveness increase dramatically with lateral separation. The sink diameter and the angle between source and the sink axes don't influence effectiveness as much as the lateral separation.

Formation of Turbulent Vortex Breakdown: Intermittency, Criticality, and Global Instability

This study provides quantitative insight into the formation of vortex breakdown and the onset of global instability in a turbulent swirling jet. A water jet is guided through a rotating honeycomb that imparts the rotational motion, passed through a contraction, and discharged into a large water tank. The flow states evolving at increasing swirl are mapped out via time-resolved particle image velocimetry. The experimental results scale properly with the swirl number based on the axial momentum flux when the commonly used boundary-layer approximations are omitted. The instantaneous velocity field reveals that vortex breakdown occurs intermittently at a wide range of swirl numbers before it appears in the mean flow. At this intermittent state, the evolving breakdown bubble oscillates heavily between two streamwise locations where the vortex core is subcritical. Upon further increasing the swirl, the breakdown oscillations decay and a region of reversed flow appears in the mean flowfield. The formation of this socalled axisymmetric breakdown state is accompanied by a supercritical-to-subcritical transition of the inflowing vortex core. The reversed flow region is found to grow linearly with increasing swirl until the flow undergoes a supercritical Hopf bifurcation to a global single-helical mode, and vortex breakdown adopts a spiral shape. The global mode shape is extracted from the particle image velocimetry snapshots by means of proper orthogonal decomposition and Fourier analysis. The present experiment reveals that, at gradually increasing swirl, the jet first transitions to an axisymmetric breakdown state that remains globally stable until a critical swirl number is exceeded. This sequence of flow states agrees well with the transient formation of vortex breakdown observed in laminar flows.

On the sensitivity of the HAWC observatory to gamma-ray bursts

We present the sensitivity of HAWC to gamma ray bursts (GRBs). HAWC is a very high-energy gamma-ray observatory currently under construction in Mexico at an altitude of 4100m. It will observe atmospheric air showers via the water Cherenkov method. HAWC will consist of 300 large water tanks instrumented with 4 photomultipliers each. HAWC has two data acquisition (DAQ) systems. The main DAQ system reads out coincident signals in the tanks and reconstructs the direction and energy of individual atmospheric showers. The scaler DAQ counts the hits in each photomultiplier tube (PMT) in the detector and searches for a statistical excess over the noise of all PMTs. We show that HAWC has a realistic opportunity to observe the high-energy power law components of GRBs that extend at least up to 30GeV, as it has been observed by Fermi LAT. The two DAQ systems have an energy threshold that is low enough to observe events similar to GRB 090510 and GRB 090902b with the characteristics observed by Fermi LAT. HAWC will provide information about the high-energy spectra of GRBs which in turn could help to understanding about e-pair attenuation in GRB jets, extragalactic background light absorption, as well as establishing the highest energy to which GRBs accelerate particles.