Tank Experiments Research Articles

Modeling Dissolution of Soluble Compounds from Multi-Component NAPL Using a Desorption Approximation.

Groundwater professionals require methods to estimate the potential time required to achieve remedial goals, including locations within and downgradient of zones containing non-aqueous phase liquids (NAPLs). NAPLs have long been recognized as persistent contaminant sources to groundwater. Dissolution of multi-component NAPLs is particularly complex, and numerical models that explicitly simulate it are not widely available. This study introduces an equilibrium partitioning approximation to simulate the dissolution of the most soluble chemical components from multi-component NAPL containing a significant fraction of relatively insoluble mass. The effective distribution coefficient that describes depletion of a specific compound from NAPL is estimated based on the properties of the NAPL and the porous medium. This study also presents numerical modeling results that support the utility of the method, with verification using published empirical data collected during dissolution of residual coal tar in a controlled laboratory sand tank experiment. The numerical modeling method uses equilibrium partitioning as an approximation and matched the concentrations of the two most soluble NAPL components in and downgradient of the NAPL zone with reasonable accuracy. The results suggest that the method should be useful for screening level assessments and can be adapted to compare relative groundwater restoration timeframes of select NAPL components for various remedial alternatives.

Real-time PCR assay for detection of Environmental DNA from <i>Chironex yamaguchii</i>

The box jellyfish Chironex yamaguchii is a highly venomous cubomedusa, also known as “habu-kurage” in Japan. It is a significant threat to marine activities in Okinawa in southern Japan. Annually, envenomation of the species causes nearly 100 to 200 injuries in the Okinawa Prefecture. The present study developed a species-specific real-time PCR assay to analyze environmental DNA (eDNA) for rapid detection of jellyfish in water samples. Primers and probe were designed based on the sequences of the mitochondrial cytochrome c oxidase subunit I region using tissue samples of nine specimens obtained from the Okinawa Prefecture. The specificity of the real-time PCR assay was confirmed by amplifying the DNA samples of 10 different box jellyfish species. A practical assay for eDNA detection was successful on water samples obtained from the natural habitat of C. yamaguchii. In addition, the degradation rate of eDNA in the tank experiment was 65% of the initial concentration at 1 h, 22% at 12 h, and 3% at 48 h.

Circadian rhythm of preferred temperature in fish: Behavioural thermoregulation linked to daily photocycles in zebrafish and Nile tilapia

Ectothermic vertebrates, e.g. fish, maintain their body temperature within a specific physiological range mainly through behavioural thermoregulation. Here, we characterise the presence of daily rhythms of thermal preference in two phylogenetically distant and well-studied fish species: the zebrafish (Danio rerio), an experimental model, and the Nile tilapia (Oreochromis niloticus), an aquaculture species. We created a non-continuous temperature gradient using multichambered tanks according to the natural environmental range for each species. Each species was allowed to freely choose their preferred temperature during the 24h cycle over a long-term period. Both species displayed strikingly consistent temporal daily rhythms of thermal preference with higher temperatures being selected during the second half of the light phase and lower temperatures at the end of the dark phase, with mean acrophases at Zeitgeber Time (ZT) 5.37 h (zebrafish) and ZT 12.5 h (tilapia). Interestingly, when moved to the experimental tank, only tilapia displayed consistent preference for higher temperatures and took longer time to establish the thermal rhythms. Our findings highlight the importance of integrating both light-driven daily rhythm and thermal choice to refine our understanding of fish biology and improve the management and welfare of the diversity of fish species used in research and food production.

Transcranial 3D ultrasound localization microscopy using a large element matrix array with a multi-lens diffracting layer: an in vitro study

Objective. Early diagnosis and acute knowledge of cerebral disease require to map the microflows of the whole brain. Recently, ultrasound localization microscopy (ULM) was applied to map and quantify blood microflows in 2D in the brain of adult patients down to the micron scale. Whole brain 3D clinical ULM remains challenging due to the transcranial energy loss which reduces significantly the imaging sensitivity. Approach. Large aperture probes with a large surface can increase both the field of view and sensitivity. However, a large active surface implies thousands of acoustic elements, which limits clinical translation. In a previous simulation study, we developed a new probe concept combining a limited number of elements and a large aperture. It is based on large elements, to increase sensitivity, and a multi-lens diffracting layer to improve the focusing quality. In this study, a 16 elements prototype, driven at 1 MHz frequency, was made and in vitro experiments were performed to validate the imaging capabilities of this new probe concept. Main results. First, pressure fields emitted from a large single transducer element without and with diverging lens were compared. Low directivity was measured for the large element with the diverging lens while maintaining high transmit pressure. The focusing quality of 4 × 3cm matrix arrays of 16 elements without/with lenses were compared. In vitro experiments in a water tank and through a human skull were achieved to localize and track microbubbles in tubes. Significance. ULM was achieved demonstrating the strong potential of multi-lens diffracting layer to enable microcirculation assessment over a large field of view through the bones.

Sperm Quality Assessment of White Shrimp (Litopenaeus Vannamei) Broodstock using Comet Assay

The quality of sperms is considered one of the factors determining fertilization success of white shrimp, Litopenaeus vannamei. Generally, conventional methods such as sperm count and viability are used for determining sperm quality. Occasionally, the fertilization rate does not correlate with what conventional parameters indicate. Presently, it has become increasingly evident that sperm DNA damage is a potential cause of an unexplained fertilization incompetence of the sperm. Therefore, the present study aimed to determine the feasible application of the comet assay for measuring sperm quality from different male broodstock and to analyze the correlation between sperm DNA integrity and fertilization efficacy of the shrimp. Male and female shrimp sampled from 4 different broodstock ponds were mated in experimental tanks (n = 5). Sperm were collected and subjected to alkaline comet assay. Sperm count, sperm viability, and Gonadosomatic index(GSI) were analyzed for comparison. Viability of the obtained nauplii were recorded and used as larvae production efficiency. The results revealed that nauplius numbers were significantly different among treatments (6.78±1.61×104, 12.18±1.17×104, 16.76±0.97×104 and 21.38±1.14×104 cells/spawn in treatment 1, 2, 3 and 4, respectively), indicating the different fertilization rate between treatments. The average body weights, lengths, and GSIs of broodstock were not significantly different, indicating that the morphological factors were not major causes of the different nauplii production among treatments. The results of comet measurements clearly showed that the levels of comet parameters correlated with the numbers of nauplii obtained from each treatment while the conventional sperm analyses were unable to detect the different quality of the sperm among treatments. This indicates that the degree of sperm DNA damage correlates with the fertilization rate of the shrimp and can be used as a sensitive indicator for determining sperm quality of broodstock shrimp. HIGHLIGHTS Sperm DNA damage is one of the potential causes of low fertilization rate in L. vannamei captive breeding Comet assay is used to assess the degree of DNA damage in a single cell such as shrimp sperm cell using electrophoresis technique Comet assay is more sensitive to detect the sperm integrity among individual L. vannamei broodstock when compared to morphological methods Sperm DNA damage can be used as a sensitive indicator for determining the sperm quality of L. Vannamei GRAPHICAL ABSTRACT

Self-cleaning performance of three bottom drain modes in circular culture tank: Experimental and numerical study

This work investigated the self-cleaning performance of three drain modes in circular bottom drain water tanks with tangential inlet. Removal experiments in center, eccentric and center-eccentric combined (dual) drain modes were carried out in a miniature tank with a diameter of 0.44 m and a depth of 0.215 m for a hydraulic retention time of 30 min using two artificial bio-wastes mimicking fish fecal and uneaten feed matters. The experiments were simulated by using the Eulerian model of FLUENT. The correlations between the numerical solutions and the experimental data confirm the adequate reproduction of the bio-waste removal behavior. It was confirmed that the self-cleaning performance of the center drain is four times greater than that of the eccentric drain under the same water supply condition. Since the water drainage speeds of the dual-drain were less than those of the other two drains under the same water supply condition, the order of precedence for self-cleaning performance was the center drain, dual-drain, and eccentric drain. According to numerical experiments in the full-size tank with a diameter of 9.15 m and a depth of 1.83 m for hydraulic retention times of 30 and 55 min, the above order was kept constant, but the self-cleaning performance of the center drain was reduced by 1.04 times of that in the eccentric drain. The numerical experiments of all possible dual, triple and quadruple bottom drain modes in the full-size tank with one center drain and three eccentric drains showed that an increase of the eccentric drains causes a decrease of the drainage speed and thus does not lead to a noticeable improvement in self-cleaning performance. Numerical experiments in a medium-size tank showed that the above order was also kept constant. The reason why the self-cleaning performance of the center-eccentric combined drain is lower than that of the center drain is that its reduced drainage speed does not have kinetic energy enough to push the bio-wastes up to the height of the outlet. The center drain has the best self-cleaning performance in the circular tanks with tangential inlet and if the drainage speed is not sufficiently increased, the multiple drain system might have negative effect on self-cleaning performance.

An experimental investigation of the influence of inter-turbine spacing on the loads and performance of a co-planar tidal turbine fence

Multi-rotor tidal turbine systems offer engineering benefits through shared infrastructure and improved opportunities for maintenance. Additionally, the ability to specify accurately the inter-turbine spacing in co-planar arrays allows rotors to be designed and deployed to benefit from the constructive interference effects available from neighbouring rotors. In this work we consider the effect of inter-turbine spacing and control of this spacing for a fence of turbines in low overall levels of global blockage (4.5%). We conduct experiments in a towing tank using two tidal turbine models that were previously designed to benefit from constructive interference effects at high local blockage, i.e. close inter-turbine spacing. The turbines were towed in a side-by-side configuration by suspending them from above. By making use of the tank’s side wall to act as a symmetry plane we were able to emulate a fence of four laterally arrayed turbines. As indicated by theory, decreasing inter-turbine spacing is shown to have a positive effect on fence performance. By reducing the inter-turbine spacing from one diameter to a quarter of a diameter, we observe an overall 1.4% performance increase, which is driven by a 2.8% increase in the inboard turbine’s power coefficient. This research is a first attempt to quantify constructive interference effects for a four turbine fence; the methods and results will be used to instruct further studies to aid the development of such multi-rotor tidal turbine systems.

Toxicity Assessment of the Ethanolic Stem Bark Extracts of Ackee, Blighia sapida on the African Catfish, Clarias gariepinus

Acute toxicity effects of ethanolic stem bark extract of ackee, Blighia sapida was tested on catfish fingerlings over a 96hr exposure period as a potent organic piscicide. A static toxicity bioassay was conducted after a preliminary trial tests were carried out to determine effective extract concentrations to be used. A 300 number catfish fingerlings were randomly selected and distributed in triplicate concentrations of stem bark extracts of ackee. The test fish were treated with concentrations of 0.00, 1.60, 3.20, 6.40 and 12.8g/l stem bark extracts. At the end of the exposure period, plant toxicant caused visible behavioral changes on test fish which included aggression, erratic swimming, stunned posture, opercula movement, air gulping, settlement at the bottom and eventual death. The LC50 lethal concentration of 8.394g/l was recorded while the safe concentration was established to be 1.281g/l. There were significant changes in water quality parameters of the experimental tanks. It could be inferred from the results of this study that treated fish were irritated by the plant toxicant such that unstable behavioral changes were exhibited in all treated groups. Therefore, the use of stem bark of ackee in fish harvesting should be regulated.

Characteristics of Sound Attenuation by Individual and Multiple Fishes

Fish biomass and stock assessment are estimated from acoustic volume backscattering strengths (Sv) obtained from various hydroacoustic equipment. Although sound attenuation due to fish schools and water influences the Sv value, only attenuation from water is considered during the acoustic data process. For these reasons, it is necessary to understand the characteristics of sound attenuation by fish. Unfortunately, little is known about sound attenuation from fish. In the present study, the attenuation from one to four fish specimens was precisely measured during ex situ experiments in a water tank. The scientific echo sounder of a split-beam 200 kHz transducer and a miniature hydrophone were used for the attenuation measurements. Results show that the maximum attenuation coefficient (α) was approximately 25 dB/cm when the 4 multiple fishes had high fish heights. The relationship between the attenuation coefficient (α200kHz) and the total fish height (Htotal) was approximately α200kHz=0.54∗Htotal ± 0.06 (r2=0.72). This work describes the sound attenuation characteristics to provide basic information for the compensation of Sv from fish schools or layers.

Experimental investigation on flow approach profile for comparison of surface velocity at the inlet of the vertical ultra-low head hydro turbine using a non-rotating model

This article reports the need for an inlet approach profile in front of the turbine system for the newly developed vertical ultra-low head turbine applicable on channel flow section without dropped bed level. The fixed wall available in the conceptualization stage was found to act as a barrier to a certain level disturbing the flow towards the turbine that need to rectify with the addition of a suitable profile. The four-simple geometry for inlet approach profiles as vertical, inclined, curved, and a combination of inclined and curved profiles were selected for testing in pair with the alternation of a two-dimensional non-rotating model of the turbine having 150, 180, and 22.50 orifice opening on it. With the review of the literature, a different experimental methodology has been explained. The tests were conducted on an experimental setup tank of the length of 10 m developed for the vertical ultra-low head hydro turbine with input variables such as flow rate, inlet profile, and non-rotating models. The experimental analysis is presented about the vertical profile with the concern of flow surface velocity and upstream height possessed by different combinations. The comparisons made for upstream height and surface velocity with different flow rates, upstream height with surface velocity, maximum surface velocity, and upstream height with orifice opening of non-rotating models are discussed and selected the most suitable one among the tested. The conclusion is made for the necessity of an inlet approach profile with suitable geometry to minimize the loss at turbine inlet mentioning the future task is desired for optimization.

Sound properties produced by white-edged rockfish (Sebastes taczanowskii) in relation to body and swim bladder size

The sound properties produced by the white-edged rockfish (Sebastes taczanowskii Steindachner, 1880) were compared with the body size. We conducted a tank experiment to compare the sound properties with body length, which ranged from 12.4 to 19.8 cm. Sound production was composed of pulses with a duration of 0.010-0.022 s and a peak frequency of 400-1000 Hz. Peak frequency decreased with fish and swim bladder size and pulse duration. The relationship between sound properties and body size may be useful for estimating the body length of the target species by using passive acoustic monitoring.

Drag reduction on a blunt body by self-adaption of rear flexibly hinged flaps

We study the aerodynamics of a blunt-based body with rear flexibly-hinged rigid flaps, subject to a turbulent flow of Reynolds number Re=12000, under aligned and cross flow conditions with yaw angle β=0° and β=4°. To that aim, different values of the equivalent torsional stiffness are considered, to cover the range of reduced velocity U∗=(0,3.48] in water tank experiments. The effect of the angular deflection of plates on the drag and near wake flow is analyzed, experimentally and numerically. The results show that, in the range of U∗ herein considered, the plates undergo an inwards quasi-static, self-adaptive deflection, which is symmetric for yaw angles β=0° and asymmetric for β=4°. In particular, the plates feature small mean deformation angles for values of U∗<1, whereas a sharp and monotonic increase of such deflection occurs for U∗>1, i.e. for lower values of the hinge’s stiffness, with an asymptotic trend towards the larger values of U∗. A critical value of reduced velocity of U∗≃0.96 is obtained as the instability threshold above which plates depart from their initial equilibrium position. The progressive streamlining of the trailing edge translates into significant reductions of the associated mean drag coefficients. Thus, reductions close to 19% with respect to reference static plates configurations are obtained for the most flexible case of U∗=3.48 for both β=0° and β=4°. A close inspection of the near wake reveals that the inwards progressive mean displacement of the plates yields a reduction in the recirculation bubble size. A symmetric evolution of the recirculating bubble is observed for β=0°, whereas the bubble becomes asymmetric for β=4°, with a larger leeward clockwise vortex. In both cases, the drag coefficient is shown to vary linearly with the global aspect ratio of the recirculating bubble. The analysis of the numerical results shows that the reduced extension of the recirculating bubble significantly alters the formation length and intensity of the eddies size and associated pressure. It is observed that despite the local pressure decrease in the vortices shed from the trailing edges, the plates self adaption reduces their size and prevents the eddies from entering the cavity, thus, creating a dead flow region with a consequent pressure increase at the body base.

Retention effect and mode of capillary zone on the migration process of LNAPL pollutants based on experimental exploration

Two-dimensional sand tank experiments were designed to investigate the retention process of the capillary zone during the migration of light non-aqueous phase liquid (LNAPL) pollutants. The fine sand and silt media experiments simulated the LNAPL migration process given a shallow point source leakage scenario. The results indicate that the LNAPL was retained in the capillary zone. A retention factor, based on the ratio of the change in the vertical migration velocity of the LNAPL front with time, was proposed to quantitatively characterize the retention effect. The retention factor and time satisfied the function of σ=A×exp(−kt). And the retention factor increased gradually with time, indicating the enhanced retention effect of capillary zone on the vertical migration of LNAPL. The concentration change rate was then used to investigate the LANPL redistribution process, which had a relationship with time of νc=B×ln(t)+C. The capillary zone could be divided from top to bottom into a weak retention zone (B > 0, vc < 0), a strong retention zone (B < 0), and a barrier zone (B > 0, vc > 0). The retention effect of capillary zone on LNAPL migration gradually strengthened during the vertical migration of LNAPL. In addition, the coefficient B had a relationship with the environmental factors (i.e., EC, pH, and ORP) of B=a×sin(b×α×β×γ)c and the fitting coefficient R2 of the function was above 0.913 for both media, indicating a strong correlation between the LNAPL redistribution process and the key environmental factors.

Parent-child underwater robot-based manipulation system for underwater structure maintenance

This study proposes a parent–child robot-based underwater manipulation system for underwater structure maintenance comprising two underwater vehicles with split roles. The larger autonomous underwater vehicle (AUV) acts as the base to transport and control a tethered child robot that is deployed to perform actual manipulation tasks. Conventional AUVs face several challenges when performing manipulation missions because of their large and massive body and the complexity of dynamic control with a rigid arm manipulator in the precise hovering state. To address this problem, we proposed an underwater manipulation system that uses a large parent AUV with high-performance sensors to navigate to the desired location and a child robot with high mobility to perform manipulation tasks. In this study, a parent–child robot-based manipulation system was developed and mathematically modeled considering hydrodynamics. Based on the system model, a nonlinear time delay (TD) controller was applied to the child robot to ensure robustness of the movement, and complementary sensing methods were proposed according to the observation distance. Subsequently, we detailed the mission process such that the manipulation tasks could be performed autonomously. To implement and verify the proposed method, we conducted three-dimensional (3D) simulations, water tank experiments, and sea trials. In the 3D simulation and water tank experiments, we evaluated the position control using a TD controller during a specific disturbance and performed an operational evaluation of the parent–child system. In the water tank, we performed the operation of the child robot with the tether length adjustment of the winch system and the manipulation task. In the sea trial, the predefined mission was successfully completed, which demonstrated the feasibility of properly operating both the robots. The results of the experiments demonstrated the high potential and capabilities of the proposed manipulation system.

Experimental Investigation on Ignition Effects of Fuel Tank Impacted by Bi2O3-Reinforced PTFE/Al Reactive Material Projectile

A series of impact fuel tank experiments are carried out through the ballistic impact method. The ignition abilities of Bi2O3-reinforced PTFE/Al reactive material, metal aluminum, and inert metal steel are compared and analyzed, and the ignition mode of kerosene is explored when PTFE/Al/Bi2O3 impacts the fuel tank at different velocities. The results offer that PTFE/Al/Bi2O3 reactive material has outstanding ignition ability, and the order for ignition ability is PTFE/Al/Bi2O3 reactive material, metal aluminum, and inert metal steel. The kerosene content of the fuel tank has a significant impact on the ignition effect. The ignition effect of PTFE/Al/Bi2O3 reactive material impacting the fuel tank filled with 50% kerosene is weaker than that impacting the full tank. Under different impact velocities, PTFE/Al/Bi2O3 reactive materials display diverse ignition modes for kerosene: kerosene is directly ignited by the flame in the reverse reaction zone under low-velocity conditions, while high-temperature-activated reactive fragments are the ignition heat source of high-velocity conditions.

Thermal-Imaging-Based PCA Method for Monitoring Process Temperature

To overcome the shortage of traditional temperature sensors, this paper adopts infrared thermal imaging technology for temperature measurement. To avoid the spatial information loss issue during the image data vectorization process, this paper adopted the spatial relationship between pixels in principal component analysis (PCA) model training, which is called spatial information-based PCA (SIPCA). Then, spatial information is also used in the fault localization method to enhance the fault location performance. Tested by an experimental tank system, the proposed method achieves better performance than the traditional PCA approach, and it can detect heat leakage faults on the surface of the equipment.

Data from laboratory tank experiment of Dalian University of Technology

Data from laboratory tank experiment of Dalian University of Technology

Numerical Analysis on Added Resistance of a Crew Boat with Variation of Wave Period

Crew boat is a type of vessels used for the mobility of offshore workers and logistical supply needed for the offshore platform. Crew boat KCT-1901 is categorized as a planning boat with hard chine body. KCT-1901 requires an added power when it is sailing through a seaway. The reason behind this is because when a ship sails through a seaway, the ships experienced a heave and pitch motion resulted in added resistance and hence added power. The goal of the investigation is to estimate added resistance and added power of the crew boat using computational fluid dynamic (CFD) method and tested in calm water and in waves with several Froude numbers (Fr) and wave periods. A method developed by Savitsky is used for verification at high-speed mode. The largest total resistance using CFD in calm water is 38.98 kN and using Savitsky method is 39.00 kN obtained at Fr 0.72. Both are in good agreement and the discrepancy is less than 0.1%. Comparative study was carried out against experimental test in a towing tank. The drag forces tested at Fr 0.12 and 0.24, between the two approaches, showed a discrepancy of about 4%. Further CFD test was conducted on wave pattern analysis, which demonstrated that as the Fr increases the becomes clearer and stronger and tests in waves condition at lower wave period showed that the transverse wave becomes more apparent. Therefore, overall can be said that the CFD simulation showed such a good agreement with empirical Savitsky method and experimental tank test.

Juvenile American Alligators (Alligator mississippiensis) Use Behavioral Thermoregulation to Cope with Dehydration and Salt-Loading when Chronically Exposed to 12 ‰ Saltwater

American alligators (Alligator mississippiensis) are native to freshwater habitats in the Southeastern United States. These areas are susceptible to salinity increases due to extreme weather events (e.g., hurricanes) and climate change. The goal of this study was to investigate behaviors in juvenile alligators exposed to 12‰ saltwater for five weeks. Sixteen alligators were maintained in an experimental tank with 90 L of water and a heat lamp overhanging a basking plate. Observations were conducted in freshwater (prior to exposure to saltwater) and over the course of 5 weeks in 12‰ saltwater. This allowed for comparison of behaviors in freshwater and in saltwater in the same group of animals. Behaviors related to thermoregulation (basking and staying in the water) and feeding were recorded via instantaneous sampling, in which sampling intervals of 1 min occurred throughout a 20 min observation period. Saltwater-exposed alligators reduced foraging and feeding within the first week of saltwater exposure and spent significantly less time basking compared with freshwater observations. Furthermore, significantly fewer animals chose to bask over the course of 5 weeks in saltwater. A novel behavior, never seen in freshwater, was the closing of the outer eyelids when alligators were in the saltwater. Collectively, the present study demonstrates that chronic saltwater exposure has significant impact on the thermoregulatory behavior in juvenile alligators concomitantly exposed to dehydration and salt-loading without access to freshwater. As alligator hatchlings emerge during peak hurricane season, the survivability of hatchlings may be compromised if access to freshwater is unattainable.

Virtual laboratory experiments on the interaction of a vortex with small-scale topography

This study presents numerical analogs of laboratory experiments designed to explore the interaction of broad geophysical flows with irregular small-scale bathymetry. The previously reported “sandpaper” theory offered a succinct description of the cumulative effect of small-scale topographic features on large-scale flow patterns. However, initial investigations have been conducted using numerical models with simplified quasi-geostrophic equations that may inadequately represent the dynamics realized in the world’s oceans. This investigation advances previous efforts by using a fully nonlinear Navier–Stokes model configured for rotating tank experiments to (i) validate the theory and (ii) offer guidance for future physical experiments that will confirm theoretical ideas.