Water Tank Experiments Research Articles

Shadowgraph Visualization of the Scattering of Focused Ultrasonic Waves at Bone-like Constructs

Background: Despite a wealth of literature on medical high-intensity focused ultrasound (HIFU), there are knowledge gaps related to therapeutic ultrasound in the presence of bone obstructions. In particular, the literature on detailed imaging of ultrasonic wave-scattering at bones to validate numerical models is still sparse. Objective: Experimentally investigate the ultrasonic energy deposition in areas surrounding flat and curved bone-like obstructions. Methods: Imaging from a diffraction-based shadowgraph method is used to visualize ultrasound wave propagation in laboratory water tank experiments. The experiments are performed with no obstruction, varying partial obstruction, and with complete obstruction by bone-like constructs. In addition, hydrophone measurements and numerical simulations are performed for similar bone obstruction configurations, and the results are compared. Results: The shadowgraph technique produces high-resolution images of the wave transmission through and reflection from bone-like constructs. There is generally good agreement between experimental findings and numerical results. In particular, hydrophone measurements match closely with simulation data for both obstructed and unobstructed cases. Also, shadowgraph images qualitatively confirm simulation and hydrophone measurements. Conclusions: Overall, the results of this work demonstrate the utility of shadowgraph imaging in the development and evaluation of novel treatments in the field of therapeutic ultrasound.

In-situ remotely controllable ocean radiation monitoring system

Prompt in-situ monitoring of sea radiation contamination is crucial to prevent the sea from spreading radioactive materials to other parts of the world and the hazard of internal exposures in marine life and the human through food chain. In this paper, we evaluated the performance of a new ocean radiation monitoring robotic boat prototype system. The system featured real-time and on-site gamma spectroscopy with a portable detector of a CsI(Tl) crystal and a PIN diode carried by an unmanned surface vehicle. The system performed good energy linearity and energy resolution (21% at 662 keV). The efficiency and the minimum detectable activity (24 h acquisition) for underwater 137Cs detection were 1.334 × 10−5 and 2.5 Bq/kg, respectively. We conducted a Monte Carlo simulation to estimate the detection performance with uniform and point source distributions. In the water tank experiments, we measured the count rates with differing depths of a 137Cs point source. The maximum detectable distance was 50 cm according to both experiment and simulation results. Additionally, on-site experiment was conducted to test the operability of the system in a real sea. The overall study showed the feasibility of the system for in-situ ocean radiation monitoring.

Conditions for transition from a plume to a dome above a heated horizontal area

Natural convection flow above a heated horizontal area plays a major role in energy utilisation, indoor/outdoor thermal environment, city ventilation and pollutant dispersion. Such natural convection can present different flow patterns, and identifying the type of flow pattern is crucial for determining the bulk heat transfer coefficient. Water tank experiments were carried out to study two different forms of convection flow above a large area with different levels of background inversion. Two major flow patterns, i.e., plume-like and dome-like, were observed. The critical Froude number (Frc = 0.08) for the transition from plume-like to dome-like was identified. Plume flow developed when Fr > Frc and dome flow developed when Fr < Frc. The heat transfer coefficients in a stable environment were significantly lower than those in a neutral environment. The Nusselt number, which is a function of both the Rayleigh number Ra and buoyancy frequency N in a stable environment, was calculated and analysed. Natural convection develops over the built-up area due to the urban heat island effect. The diameter Dc of the critical built-up area was found to be 2.3 km under typical atmospheric background conditions for the transition from the plume-shape natural convective flow to the dome-shape. When atmospheric conditions are met, villages and small towns with diameters less than 2.3 km will probably present plume-like structures, whereas cities and megacities with larger diameters are most likely to form heat domes. Our findings may also have implications for city- and regional-scale urban planning.

Underwater acoustic positioning with a single beacon and a varied baseline for a multi‐jointed AUV in the deep ocean

The multi-jointed autonomous underwater vehicle (AUV) has higher manoeuvrability and a smaller turning radius in comparison with an AUV with a rigid body. It is able to implement spatially denser sample collection in three-dimensional space in the deep ocean for scientific expeditions. As conventional positioning approaches, such as ultra-short-baseline and long-baseline, cannot be employed to obtain the coordinates of a multi-jointed AUV, because they only work with constant baselines, a novel underwater acoustic positioning system with a single beacon and a varied baseline is proposed. The coordinate transformation based on the angles of rotating joints and the geometry of the multi-jointed AUV is mathematically modelled. Generalised cross-correlation is applied to measure the time delays of sound signals between the beacon and the hydrophones on the AUV. Numerical simulations and experiments in an anechoic water tank were carried out, and the impacts of parameters on the accuracy of the estimated coordinates of the multi-jointed AUV are examined. Accuracies of 0.86% in simulation and 0.2 m (at a range of 30 m) in experiments are demonstrated.

Preliminary study on the detection efficiency and estimation of minimum detectable activity for a NaI(Tl)-based seawater monitoring system

To monitor radioactivity levels in seawater Korea Institute of Nuclear Safety has installed and been operating 18 NaI(Tl)-based gamma detectors around the Korean peninsula. This study was conducted to estimate the detector efficiency and MDA of 137Cs in seawater for measurement situations. For this purpose, experiments in the air and a water tank, and Monte Carlo simulations were performed using a seawater radioactivity monitor system with 3 in. × 3 in. NaI(Tl) scintillation detector.In the geometry reliability assessment using certified reference materials in a disc source, the validity of simulations was obtained by comparing measurement and Monte Carlo simulation results. The FWHM of the seawater radioactivity monitor were obtained from the results of the water tank measurement for applying a Gaussian Energy Broadening (GEB) option to Monte Carlo N-Particle (MCNP) radiation transport code. In addition, the detection efficiency of 40K in the water tank was measured and compared with the Monte Carlo simulation results in order to estimate the MDA and the detection efficiency of the seawater radioactivity monitoring system. For the based condition of water tank, 40K concentration in water tank was controlled to 10.13±0.18 Bq/L, similar to that of real marine.In laboratory water tank experiments, the detection efficiency of the radioactivity monitor for 40K was measured at 0.184±0.005 cps/(Bq/L), the Monte Carlo simulations showed the similar result of 0.182±0.002 cps/(Bq/L), and the detection efficiency of 137Cs was estimated to be 0.224±0.009 cps/(Bq/L) from the simulations. For 3h measurement in the water tank based condition, the MDA of 137Cs was estimated to be 0.077±0.003 Bq/L. Future research will include detailed studies for detector sizes and seawater salinities.

Comprehensive Zebrafish Water Tank Experiment for Metabolic Studies of Testolactone.

Testolactone is a potent steroid aromatase (CYP19A1) inhibitor, and its main effect is a reduction in estradiol and estrone and an increase in testosterone and androstenedione levels. In this work, we evaluated a zebrafish water tank (ZWT) as a model to investigate testolactone biotransformation and the possibility to increase knowledge regarding the applicability of the ZWT on steroid hormone elimination research, as well as on the impact of steroid hormones on the endogenous metabolism of zebrafish. High-resolution mass spectrometry combined with SIEVE software was used to discriminate the peaks of interest based on significant changes in the relative signal intensity of the m/z values between different ZWT experiments. The metabolites, 4,5-dihydrotestolactone and 1,2,4,5-tetrahydrotestolactone, the same metabolites as those described in humans, were detected in ZWT, both in quite similar proportions. The presence of testolactone in the ZWT caused a rise in testosterone and androstenedione in the water tank, similar to that in human serum. These data suggest that, while the concentration of testolactone was high enough to inhibit the aromatase enzyme, an accumulation of androgens in the water occurred, indicating that the ZWT can be considered a model to investigate the impact of steroids on live organisms.

Application of PIV-based Pressure Field Estimation for Wind Tunnel and Water Tank Experiments

Application of PIV-based Pressure Field Estimation for Wind Tunnel and Water Tank Experiments

Effect of substrate type on burrowing behaviors of yellow-phase Japanese eels in water tank experiments

Effect of substrate type on burrowing behaviors of yellow-phase Japanese eels in water tank experiments

Design of Experiments Teaching on Inversion Layer Turbulent Movement Simulation in Glass Water Tank

The glass water tank experiment is using water as the medium to simulate the temperature fields’ structure characteristics and development process of the convection boundary layer in the laboratory. This experiment uses a fast-responding temperature sensor to measure vertical profile of temperature and temperature differences at different height. In this experiment, parameters such as tropospheric boundary thickness and stability are obtained. The experimental results show that the indoor water tank convection system can simulate the formation, development and extinction of inversion layer in boundary layer. This experiment is suitable as a professional experiment for atmospheric fluid dynamic course. Meanwhile, students’ understanding of meteorological concepts and basic principles is more profound and excellent teaching effect is achieved, and thus the designed experiments have certain promotion value.

A deep neural network approach to acoustic source localization in a shallow water tank experiment.

In this paper, an acoustic source localization method using the emerging technology of the deep neural network (DNN) is proposed. After the construction and training of the DNN, the capability of the DNN for source localization through a set of numerical simulations is verified. Next, experimental studies and demonstrations in a very shallow water tank with acoustic reflective walls are prepared, which enable the quick acquisition of a huge amount of experimental data for the training of a one-dimensional DNN-based source localization model. The development of the DNN-based source localization method and the corresponding numerical and experimental demonstration constitute the main contribution of this work. The associated performance is then evaluated at various frequencies. In particular, the localization results of the DNN are compared with readily available model-based localization methods, such as the conventional matched field processing method and the normal-mode based multiple signal classification method. The comparison shows that the proposed DNN approach is able to produce satisfactory accuracy in this reflective shallow water tank environment, for which a forward acoustic propagating model is not required. Last but not least, the generality of the proposed DNN approach from one-dimensional localization to progressively more complicated two-dimensional tasks is also considered.

Stimulation by gutweed to increase the abundance of insect larvae as food for shrimp aquaculture in Thailand

Naturally occurring insect larvae are a good dietary source of protein for shrimps. The role of gutweed (Ulva intestinalis) to stimulate the occurrence of insect larvae to support the growth of juvenile shrimps has been evaluated in water tank experiments. Larvae of chironomid and mosquito occurred and increased in raked tanks in which different amounts (0, 28, and 56 g/m2) of gutweed were planted but no shrimps were present. Most chironomid larvae (90%) were associated with the gutweed planted. The number of chiromonid larvae showed a higher correlation to the gutweed biomass than did mosquito larvae. When post-larvae (initial weight 0.013 g/individual) of black tiger shrimp (Penaeus monodon) were cultured for 5 weeks with commercial pellets, with neither pellets nor gutweed, or without pellets but with gutweed (56 g/m2) planted, there was no significant difference in shrimp growth between tanks with pellets and those without pellets but with gutweed planted. Gutweed stimulated the abundance of insect larvae, in particular the abundance of chironomid larvae. Planting gutweed in shrimp ponds is an efficient way to support the growth of juvenile shrimps and will reduce the amount of pellet feed that needs to be given in shrimp aquaculture.

Observations of Island Wakes at High Rossby Numbers: Evolution of Submesoscale Vortices and Free Shear Layers

AbstractOceanic vortex evolution on the lee side of Taiwan’s Green Island (~7 km in diameter), where the Kuroshio flows at a speed of 1–1.5 m s−1, is observationally examined and compared to theories and the preceding results of laboratory experiments. In the near wake, recirculation occurs with a relative vorticity of ζ ~ 20f (where f is the planetary vorticity) and subsequently sheds at a combination of periods resulting from the tidal oscillations and the intrinsic time scale of eddy evolution. The tidal oscillations are the predominant processes. Our analysis suggests that an island positioned in the Kuroshio with periodic and cross-stream tidal excursions is analogous to a cross-stream oscillating cylinder. Consequently, the shedding period of the vortex is synchronized to a tidal period occurring close to the intrinsic period. The free shear layer, which is characterized by an ~30f relative vorticity band (2 km wide) and a wavy thermal front, develops between the Kuroshio and recirculation. The frontal wave occurring over a time period of 0.5–2 h resembles Kelvin–Helmholtz instability corresponding to high Re values. For the far wake, repeated cross-wake surveys suggest that cyclonic and anticyclonic vortices are alternatively present at a period close to the period of M2 tides in agreement with near-wake measurements. Repeated along-wake surveys reveal a cyclonic eddy shedding downstream at a speed of 0.35 m s−1, 1/3 of the upstream current speed, from the near wake. In comparing our observations with the results of previous water tank experiments, an Re value of O(103) for the submesoscale wake regime is expected.

Acoustic camera modeling and compensation technique based on SONAR equation

Acoustic camera is a type of ultrasonic equipment used to detect or classify nearby objects located in water. The distortion of SONAR images acquired from conventional acoustic camera equipment inevitably occurs depending on the platform speed and operating frequency. This has not been huge concern because the platform speeds were low. However, more recently, a high accuracy of acoustic camera images has become essential in accordance with the development of unmanned autonomous systems. Additionally, a high speed of operating platform is also required. Therefore, there is a need for the study of image correction to reduce the distortion of SONAR images acquired from the equipment. In this study, we simulate virtual acoustic camera SONAR images by performing numerical modeling based on the SONAR equation to improve the accuracy of acoustic camera images. To verify the validity of the simulated images, we use the literature data and water-tank experiment data. Finally, we conduct the image compensation both in the direction of motion relative to the platform speed, and in the transverse direction relative to the platform speed and operating frequency.Acoustic camera is a type of ultrasonic equipment used to detect or classify nearby objects located in water. The distortion of SONAR images acquired from conventional acoustic camera equipment inevitably occurs depending on the platform speed and operating frequency. This has not been huge concern because the platform speeds were low. However, more recently, a high accuracy of acoustic camera images has become essential in accordance with the development of unmanned autonomous systems. Additionally, a high speed of operating platform is also required. Therefore, there is a need for the study of image correction to reduce the distortion of SONAR images acquired from the equipment. In this study, we simulate virtual acoustic camera SONAR images by performing numerical modeling based on the SONAR equation to improve the accuracy of acoustic camera images. To verify the validity of the simulated images, we use the literature data and water-tank experiment data. Finally, we conduct the image compensation both...

Water tank modelling of variations in inversion breakup over a circular city

Air pollution and extreme heat waves are among the major environmental challenges faced by modern cities. Stable stratification and temperature inversion help to trap urban airborne pollutants and produce a strong urban heat island intensity. Such adverse effects can disappear when the buoyancy flows introduced by the city heat is sufficiently strong to break up the inversion. This paper investigates the possible mechanisms of the inversion breakup process and their effects. A lack of time-saving and cost-effective techniques with high temporal and spatial resolution in the field study has been the main limiting factor to a systematic investigation of the physical process of inversion breakup. In this study, water tank experiments were conducted to study the characteristics of the mean and turbulent flow structures of the inversion breakup process. Four cases with different background density profiles are simulated. Three stages of inversion breakup were identified, the two-dome stage, the wing-shrinking stage and the perforative-plume stage. During the two-dome stage, shear instability and buoyancy instability (Fig. 3d) are both important for heat and mass transfer between the lower-level dome in the stable layer near the surface and the upper-level dome in the neutral residual layer aloft. The vertical dimension of the lower-level dome begins to grow, whilst the horizontal extent shrinks at the wing-shrinking stage. Finally, in the perforative-plume stage, the stable layer is destroyed, and the plume extends from the surface to the top of the residual layer. The pollutants and heat dispersion are both enhanced significantly during this stage.

Use of frequency-difference beamforming for scatterer localization

Acoustic fields interacting with discontinuities or environmental variations lead to secondary scattered fields superimposed onto incident fields. As a result, the signal measured at a remote receiving array will be modified by the scatterer’s presence. Prior work has shown that the effects of strong random scattering are reduced using frequency-difference beamforming to downshift the analysis to a below-band frequency known to be less impacted by scattering. In some applications, information about a scatterer is desired, such as location, shape, or composition. However, a relatively weak scattered field from a single scatterer is difficult to detect when the incident field dominates the measurements, as both conventional and frequency-difference beamforming ambiguity surfaces primarily provide the incident field’s source information. Here, a subtraction-based algorithm is implemented with frequency-difference beamforming to locate the position of a single scatterer near a source. Simulations and water tank experiments with a 110 kHz center frequency signal are considered for incident and scattered fields with a 4 cm diameter spherical scatterer, where the scattered field’s received energy is roughly 2% that of the incident field. The ability to downshift the frequency demonstrates a more robust implementation of subtraction-based algorithms for locating weak scatterers without prior location knowledge. [Work supported by ONR.]

Target strength measurements of spherical and wobbly bubbles

Methane gas bubbles released from the seafloor transport gas upwards through the water column and in some cases even to the atmosphere. Researchers exploit the large acoustic impedance contrast between the gas within the bubble and the surrounding water to acoustically estimate the flux of methane in the ocean. Flux estimation employs the use of analytical acoustic scattering models to convert acoustic backscatter measurements of gas bubbles to size estimates. However, these models assume that bubbles are both spherical and that their radius is much smaller than the acoustic wavelength (ka « 1). Typically, bubbles in the ocean range from 1 to 5 mm in radius are non-spherical in shape and are observed for ka values that are greater than 0.1. A controlled shallow water tank (<6 m) experiment was conducted to assess the uncertainty associated with using analytical models that assume bubbles are spherical and that ka values are much smaller than one. Small, spherical and large, wobbly gas bubbles (radii ranging from 0.7 to 4.5 mm) were ensonified over a broad range of frequencies (10–250 kHz) in order to observe ka values from 0.1 to 5.

Probabilistic Monitoring of Sensors in State-Space With Variational Bayesian Inference

Measurements quality is important for process systems engineering. In this paper, an estimation scheme is proposed in the state-space form to monitor the degree of accuracy of measurements within a predefined horizon. Under the assumption that all the sensors are uncorrelated with each other, the distribution of measurement noise covariance as well as the distribution of state vector are estimated simultaneously. The key technique is to approximate the true posterior distribution by two independent proposal distributions using the variational Bayesian inference. It is shown that the proposed algorithm provides not only a complete picture of the working status of each sensor, but also satisfied estimates of the hidden states in the presence of faulty signals. Numerical examples with a moving target tracking model and a quadrate water tank experiment are conducted to demonstrate that the proposed method exhibits better performance than the existing methods, and even a small fluctuation of sensors can be accurately captured by the proposed algorithm.

Remote sensing estimation of the biomass of floating Ulva prolifera and analysis of the main factors driving the interannual variability of the biomass in the Yellow Sea

Since 2007, green tide blooms with Ulva prolifera as the dominant species have occurred every summer in the Yellow Sea. Biomass is a critical parameter used to describe the severity of green tide blooms. In this study, we analyzed the relationships between several indices (normalized difference vegetation index (NDVI), floating algae index (FAI), ratio vegetation index (RVI), enhanced vegetation index (EVI), ocean surface algal bloom index (OSABI), Korea Ocean Satellite Center (KOSC) approach) and the biomass per unit area of Ulva prolifera by using the in situ measurements from a water tank experiment. EVI, NDVI, and FAI showed strong exponential relationships with Ulva prolifera biomass per unit area. In order to apply the relationships to satellite remote sensing data, the impacts of the atmosphere (different aerosol optical depth at 550 nm) and mixed pixels to the relationships were analyzed. The results show that atmosphere has little effect on the relationship between EVI and Ulva prolifera biomass per unit area with R2 = 0.94 and APD (the average percentage deviation) = 19.55% when EVI is calculated from Rrc (Rayleigh-corrected reflectance), and R2 = 0.95 and APD = 17.53% when EVI is calculated from Rtoa (top-of-atmosphere reflectance). Due to the low sensitivity to the atmosphere, the EVI relationship can be directly utilized in the top-of-atmosphere (TOA) reflectance without atmospheric correction. In addition, the EVI was slightly affected by mixed pixels with the APD only increased by ~10%. The EVI relationship was then applied to a long MODIS image time series to obtain the maximal total biomass of floating Ulva prolifera in the Yellow Sea from 2007 to 2016. The results showed that the maximum and minimum total biomass occurred in 2016 (~1.17 million tons) and 2012 (~0.074 million tons), respectively. The main factors that caused the inter-annual biomass variability were analyzed. The total amount of nutrients from Sheyang River which was the largest river on the northern coast of Jiangsu Province, and Porphyra cultivation in the Radial Sand Ridges of Jiangsu Province had both strong correlation with Ulva prolifera total biomass.

A Lagrangian dispersion model with a stochastic equation for the temperature fluctuations

A new plume rise scheme for the Lagrangian stochastic model SPRAYWEB is developed and tested. The plume rise scheme is based on a stochastic differential equation for the potential temperature fluctuations coupled with the equations for the wind velocity fluctuation components. The new approach is tested against measured data from a water tank experiment (Weil et al., 2002). The results are discussed in terms of statistical indices and scatter plots. For the sake of comparison, the new scheme's performance is compared with the algorithm used in SPRAYWEB formerly proposed by Anfossi et al. (1993) which doesn't account for the temperature fluctuations. The results obtained with the novel plume rise scheme are generally satisfactory. A better agreement is found for the vertical standard deviation with respect to the results given by the Anfossi et al. (1993) scheme.

Three-dimensional Pulmonary Monitoring Using Focused Electrical Impedance Measurements.

Lung pathologies such as edema, atelectasis or pneumonia are potentially life threatening conditions. Especially in critically ill and mechanically ventilated patients, an early diagnosis and treatment is crucial to prevent an Acute Respiratory Distress Syndrome [1]. Thus, continuous monitoring tool for the lung condition available at the bedside would be highly appreciated. One concept for this is Electrical Impedance Tomography (EIT). In EIT, an electrode belt of typically 16 or 32 electrodes is attached at the body surface and multiple impedance measurements are performed. From this, the conductivity change inside the body is reconstructed in a two-dimensional image. In various studies, EIT proved to be a useful tool for quantifying recruitment maneuvers, the assessment of the ventilation homogeneity, the detection of lung edema or perfusion monitoring [2, 3, 4, 5]. Nevertheless, the main problem of EIT is the low spatial resolution (compared to CT) and the limitation to two dimensional images. In this paper, we try to address the latter issue: Instead of projecting conductivity changes onto a two-dimensional image, we adjust electrode positions to focus single tetrapolar measurements to specific, three-dimensional regions of interest. In earlier work, we defined guidelines to achieve this focusing [6, 7]. In this paper, we demonstrate in simulations and in a water tank experiment that applying these guidelines can help to detect pathologies in specific lung regions.