Flow Tank Research Articles

Inverted sand dollars actively orient themselves in flow to increase likelihood of righting

AbstractThe fact that sand dollars are often dislodged and inverted is an inescapable consequence of living at or slightly below the sediment–water interface. Once inverted, however, how do sand dollars effectively right themselves, given their small spines and stiff internal skeletons? Here, we examined the possibility that individuals of Mellita quinquiesperforata and Dendraster excentricus may take advantage of the interaction of their morphology and flow to increase the likelihood of righting. Based on flow tank observations, the critical velocity required to flip an inverted sand dollar varies with orientation and increases with test size. For both species, the critical velocity was lower when inverted sand dollars were oriented with the posterior margin facing directly downstream, compared with when the posterior margin was positioned in an upstream orientation. To test whether inverted sand dollars would actively rotate into a more advantageous position for flipping, we exposed inverted animals in three starting orientations – with their posterior edge directed upstream (the least favored position for flipping), perpendicular, and downstream to flow – to the minimum flow expected to induce flipping and compared their responses. Time‐lapse photography showed that regardless of initial orientation, within one hour, a majority of individuals of both species rotated into positions that were not statistically different from the downstream orientation (the most favored position for flipping). These results for D. excentricus were further confirmed in a field experiment. Taken together, these data suggest that inverted sand dollars are able to recognize flow direction and respond by modifying their orientation to maximize lift and drag for righting.

Flow velocity underpins microhabitat selection by gobies of the Australian Wet Tropics

Summary1. Water flow is a critical driver of aquatic ecosystem health and function. Amid rising concerns over changing flow regimes, there is an urgent need to understand the functional mechanisms by which flow influences patterns of freshwater biodiversity.2. We explored the functional link between flow velocity and microhabitat specialisation in a speciose group of freshwater gobies (comprising over half the total fish species richness) within insular streams of the Australian Wet Tropics under base flow conditions. We addressed two particular questions: (i) What is the relative selectivity of species towards streambed composition and water flow velocity? and (ii) Can patterns of microhabitat occupation be explained by differences in intrinsic flow performance among species? To answer these questions, we combined visual field observations of microhabitat use with flow tank assessments of flow speed performance.3. Tropical freshwater gobies displayed strong specificity towards flow velocities, while being relatively non‐selective towards streambed composition. At opposite extremes of the spectrum, we found Sicyopterus lagocephalus occupying high‐flow (>1.0 ms−1) microhabitats while Redigobius bikolanus selected slower‐flow (<0.05 ms−1) areas. These patterns of microhabitat flow specificity were largely explained by the different abilities of species to swim and/or cling to the substratum under these different flow settings.4. Our findings confirm suggestions that predictable base flows in tropical streams support habitat specialists, which include one species capable of occupying areas of extremely high flow that very few other fishes can withstand.5. The functional link between flow and gobioid fish distribution patterns could occur throughout tropical streams of the Indo‐Pacific and Caribbean as a widespread phenomenon that may help inform stream flow management guidelines to maintain this substantial component of tropical freshwater biodiversity around the globe.

On the Potential Application of Uniformity Tests in Circular Statistics to Chemical Processes

Three methods of circular statistics: Rao’s spacing test, Kuiper’s V-test, and Rayleigh’s test based on the mean resultant length are applied to examine the hypothesis of uniform data distribution (i) in a hypothetical study of decaying effectiveness of electrocatalysis, and (ii) in a tank flow reactor with excessive local temperatures (“hot spots”). Numerical illustrations involve test results indicating rejection, or failure of rejection, for the null hypothesis of population uniformity. The results confirm the power of Rao’s method demonstrated in pertinent literature.

Developed hydraulic simulation model for water pipeline networks

A numerical method that uses linear graph theory is presented for both steady state, and extended period simulation in a pipe network including its hydraulic components (pumps, valves, junctions, etc.). The developed model is based on the Extended Linear Graph Theory (ELGT) technique. This technique is modified to include new network components such as flow control valves and tanks. The technique also expanded for extended period simulation (EPS). A newly modified method for the calculation of updated flows improving the convergence rate is being introduced. Both benchmarks, ad Actual networks are analyzed to check the reliability of the proposed method. The results reveal the finer performance of the proposed method.

熱画像から溶質分散長を評価する試み

The solute dispersivity is one of the most important factors to evaluate solute transport in groundwater environment. In this study, the non-destructive method to evaluate solute dispersivity by the thermal image of the thermal tracer test was proposed. Heated sodium chloride was used as tracer injected into the flow tank packed glass beads. Electrical conductivity and temperature change were observed at the 5 points of the downstream. According to the results of this experiment, thermal diffusivity of this system was evaluated. The thermal images were photographed at the tracer experiment under the same conditions. The method to evaluate solute dispersivity from this thermal image was examined. As a result of this study, it is possible to investigate solute dispersivity from the thermal image, if the thermal diffusivity of the medium is evaluated accurately.

Experimental investigations on the performance of an air heated humidification–dehumidification desalination system

Experiments on a single- and two-stage air-heated humidification–dehumidification desalination system (HDD) driven by solar energy are conducted. The system is built on the seashore of Dhahran, Eastern Province of the Kingdom of Saudi Arabia. In this harsh climate, natural water sources are absent. Currently, Saudi Arabia uses desalination to augment its water supply. It is ranked the first worldwide in water desalination. However, the current large-scale desalination plants are fossil-fuel-driven and consume large amount of energy. Since there is abundance of solar energy in the region, attempts are made to utilize the solar energy to produce fresh water on a small scale for remote areas. The HDD systems have received considerable attention as an effective way to produce fresh water in remote areas where receiving water through pipelines is a challenge. The system used in this study is a solar air heated, closed-water closed-air cycle that can be adjusted to operate in a single-stage or two-stage mode. In this system, evacuated tube solar heaters are used to heat the air. The heated air is humidified by passing it over a spray of seawater in a countercurrent direction inside a humidifier. Additional heating and humidification processes follow in case of operating the two-stage system mode. The humidified air is then dehumidified inside a water-cooled dehumidifier (condenser). Air leaving the dehumidifier is circulated again to the solar heaters. Due to the relatively elevated temperature of incoming water to the dehumidifier, the water cycle is divided into two. In the first cycle, water leaving the cooling water tank flows to the condenser and then returns back to a tank. In the other one, water leaves a small tank and is then distributed to the humidifiers where it is sprayed. The rejected brine returns to the tank. The reason for using a small tank is to keep the water in the cycle warm due to its interaction with hot air in the humidifiers. A make-up tank is connected to this tank through a float valve to compensate for the evaporated water. Measuring sensors are connected to various locations within the system to measure dry- and wet-bulb temperatures, flow rates, and solar radiation flux. Data acquisition system is used to record the reading every 10 min. Results show the effect of the main controlling parameters on the system performance in terms of produced distillate.

ため池決壊に伴う洪水流出過程に関する研究

Recently, many hazardous flooding cases caused by an irrigation tank overflow under concentrated downpour have been reported. Using a hydrograph to predict the overflow is an important countermeasure against hazardous flooding in the downstream area. Many preceding studies have considered only peak flow discharge without timescale for the hydrograph in the prediction of runoff characteristics due to irrigation tank flow. The present paper deals with the importance of the runoff characteristics and proposes a new index for the hydrograph to evaluate flooding risks in the downstream area, using numerical simulation. The proposed index includes both peak flow discharge and timescale for the hydrograph. Next, the applicability of the two-dimensional numerical simulation model is examined comparing the examples of damage with the in situ experimental results, which were carried out in a narrow channel located in a mountainous site.

Release characteristics of molasses from a well-type barrier system in groundwater: a large test tank study for nitrate removal

A pilot-scale study was conducted to characterize the performance of molasses' release from a well-type barrier system harboring solidifying molasses named slowly released molasses (SRM) as a reactive medium to promote indigenous denitrifying activity. A SRM rod was made by mixing molasses with paraffin wax, cellulose, and silica sands in a cylindrical mold. Two SRM systems harboring 30 and 60 SRM rods, referred to as Systems A and B, respectively, were constructed in a large flow tank (L × W × D = 8 m × 4 m × 2 m) filled with natural sands. These two systems continuously delivered molasses with groundwater flow over 96 days, with decreasing molasses' concentrations ranging from 763 to 95 and 1,150 to 183 mg L−1 as chemical oxygen demand values (COD) for Systems A and B, respectively. From simulation results with an aid of the upscaled mass transfer function (MTF) model, the molasses' mass flux was slowly decreased with time, exhibiting 57, 11, and 3 mg COD day−1 in 10, 100, and 365 days in System A, and 138, 25, and 6 mg COD day−1 in System B, respectively; 90, 70, and 50 % of total molasses' mass remained after 12, 63, and 267 days in System A and 12, 65, and 291 days in System B, respectively. This study demonstrates that SRM system can provide a remedial alternative for long-term in situ treatment of nitrate-contaminated groundwater.

CRABS SMELL FEAR THROUGH ANTENNULES

Even if you're armed with a fierce pair of pincers, life can be risky. There's always going to be a larger crab that might decide to dine on you. So, crabs tend to give the odour produced by injured crabs a wide berth, treating it as a warning that a larger predator may be lurking nearby. ‘The environment is filled with threats,’ says Marc Weissburg from the Georgia Institute of Technology, USA, although it is also full of the scents of enticing tasty treats. ‘Unless you are immune to eating, then you are always going to have to confront the conflict between aversive and attractive odours’, Weissburg says. Intrigued by how crabs successfully negotiate this conflict, Weissburg and a team of undergraduate student researchers set out to discover which course blue crabs (Callinectes sapidus) steer when presented with a whiff of lunch spiced with danger (p. 4175).Collecting crabs from the ocean off Savannah, Georgia, Weissburg returned with them to the lab where he and Kimberly Berkenkamp started to test their reactions to plumes of different odours in a flow tank. Sure enough, when the animals were downstream of luscious shrimp aroma they practically galloped toward the origin. However, when the water smelled of injured crab, the animals became evasive and some even buried themselves to avoid the stench.But, how would they react when the two odours were flowing in parallel in close proximity? This time, the crabs were much more cautious. Although they continued to pursue the attractive scent, the crabs actively avoided the side of the tunnel that smelled of injured crab. Discriminating between the plumes and following the attractive odour to its source, the crabs were able to successfully home in on the food despite the close proximity of the warning signal.However, when the duo disrupted the flow by introducing a cylinder into the water, to generate turbulence and mix the plumes, Weissburg says, ‘The animals were no longer willing to track to the attractive source and they reacted as if there was only an aversive source’. Thoroughly mixing the two odours had altered the crab's perception of the tasty prawn aroma sufficiently for it to no longer appear attractive. Weissburg decided to find out which of their many olfactory organs the crabs use to distinguish between the attractive and aversive odours.‘In blue crabs, the control over orientation toward an attractive substance is split between the antennules, which are the small structures between the eyes on the head, and chemosensors on the tips of the walking legs’, explains Weissburg. So, together with Lauren Atkins and Danielle Mankin, he tested the animals' reactions to the merged plume when one or other of the ‘nostrils’ were effectively plugged.Desensitizing the scent receptors on a crab's legs by immersing them in fresh water, Weissburg then released the animal into the blended plume: the animal tried to take cover. However, after gently removing the scent receptors from another crabs' antennules and positioning it in the plume mixture, the animal bounded toward the source of the attractive aroma of food as if it was uncontaminated. The crab was no longer repelled by the aversive odour. ‘We had knocked out the input [from the antennules] that suppresses navigation. The behaviour of the animals to track the attractive cue in the presence of the aversive cue was rescued’, explains Weissburg.

Processes controlling 220Rn concentrations in the gas and water phases of porous media

To study why 220Rn is commonly ubiquitous in soil gas but, in contrast to 222Rn, not detectable in groundwater, we conducted targeted laboratory experiments. In these experiments, we used a special 220Rn productive sand and analyzed the behavior of 220Rn in the gas and water phases of the sand under unsaturated and saturated conditions. To simulate changing water contents of soils under unsaturated conditions, we slowly flooded and drained a box filled with the sand and analyzed the resulting dynamics of 220Rn in the gas phase. Under saturated conditions, we analyzed the dependence of 220Rn concentrations in the water phase on water flow by extracting water at different pumping rates from the saturated sandbox and a flow tank filled with the same saturated sand. The results revealed that under unsaturated conditions the migration of 220Rn through the pore space is limited by water menisci between the grains, acting as barriers for 220Rn. Under saturated conditions, the observed dependency of 220Rn concentrations in water on the induced water flow velocity implies that fast flowing water in porous media is able to disturb commonly immobile water layers around the grains and, therefore, stimulate the emanation of 220Rn to the flowing water phase. Extrapolating the findings to common natural conditions, the results explain why 220Rn can be detected in unsaturated soil but not in groundwater. In addition, general conclusions to small scale dynamics of soil gas and groundwater are drawn from the dynamics of 220Rn in subsurface fluids.

Effect of dosing regime on nitrification in a subsurface vertical flow treatment wetland system

In this study, the effect of dosing regime on nitrification in a subsurface vertical flow treatment wetland system was investigated. The experimental unit was composed of four circular concrete tanks (1 m diameter and 80 cm deep), filled with gravel (1-2 cm) and planted with Cyperus alternifolius L. Synthetic wastewater with average chemical oxygen demand (COD) and ammonia nitrogen of 1,151 and 339 mg/L was fed into each tank. Different feeding and resting periods were applied: continuous flow (tank 1), 4 hrs on and 4 hrs off (tank 2), 1 hr on and 3 hrs off (tank 3) and 15 minutes on and 3 hrs 45 minutes off (tank 4). All four tanks were under the same hydraulic loading rate of 5 cm/day. After 165 days the reduction of total Kjeldahl nitrogen and ammonia nitrogen and the increase of nitrate nitrogen were greatest in tank 4, which had the shortest feeding period, while the continuous flow produced the lowest results. Effluent tanks 2 and 3 experienced similar levels of nitrification, both higher than that of tank 1. Thus supporting the idea that rapid dosing periods provide better aerobic conditions resulting in enhanced nitrification within the bed. Tank 4 had the highest removal rates for COD, and the continuous flow had the lowest. Tank 2 also exhibited a higher COD removal rate than tank 3, demonstrating that short dosing periods provide better within-bed oxidation and therefore offer higher removal efficiency.

Effect of diffusive transport limitations on UO2 dissolution

The effects of diffusive transport limitations on the dissolution of UO2 were investigated using an artificial groundwater prepared to simulate the conditions at the Old Rifle aquifer site in Colorado, USA. Controlled batch, continuously-stirred tank (CSTR), and plug flow reactors were used to study UO2 dissolution in the absence and presence of diffusive limitations exerted by permeable sample cells. The net rate of uranium release following oxidative UO2 dissolution obtained from diffusion-limited batch experiments was ten times lower than that obtained for UO2 dissolution with no permeable sample cells. The release rate of uranium to bulk solution from UO2 contained in permeable sample cells under advective flow conditions was more than 100 times lower than that obtained from CSTR experiments without diffusive limitations. A 1-dimensional transport model was developed that could successfully simulate diffusion-limited release of U following oxidative UO2 dissolution with the dominant rate-limiting process being the transport of U(VI) out of the cells. Scanning electron microscopy, X-ray diffraction, and extended X-ray absorption fine structure spectroscopy (EXAFS) characterization of the UO2 solids recovered from batch experiments suggest that oxidative dissolution was more evident in the absence of diffusive limitations. Ca-EXAFS spectra indicate the presence of Ca in the reacted UO2 solids with a coordination environment similar to that of a Ca–O–Si mineral. The findings from this study advance our overall understanding of the coupling of geochemical and transport processes that can lead to differences in dissolution rates measured in the field and in laboratory experiments.

Performance of stormwater detention tanks for urban drainage systems in northern Italy

The performance of stormwater detention tanks with alternative design configurations (insertion in the storm sewer network; volume per impervious hectare) and operating conditions (continuous and intermittent emptying rules) have been evaluated according to an integrated approach. Various performance indices have been adopted to describe the mitigation of the pollution impact to the natural environment, the reduction of the management and maintenance charges for the urban drainage system, the preservation of the normal purification efficiency, and the limitation of the costs at the treatment plant. The US EPA Storm Water Management Model has been used to simulate the rainfall-runoff process and the pollutant dynamics on theoretical catchments and storm sewer networks for an individual event, as well as for a continuous run of events and inter event periods of one year recorded at the rain gauge of Cascina Scala (Pavia, northern Italy). Also the influence of the main characteristics of the urban catchment and the drainage system (area of the catchment and slope of the network) on the performance of alternative design and operating solutions has been examined. Stormwater detention tanks combined with flow regulators demonstrated good performance with respect to environmental pollution: satisfactory performance indicators can be obtained with fairly low flow rates of flow regulators (0.5-1L/s per hectare of impervious area) and tank volumes of about 35-50m(3) per impervious hectare. Continuous emptying guaranteed the lowest number and duration of overflows, while an intermittent operation minimised the volume sent for purification reducing the costs and the risks of impairment in the normal treatment efficiency of the plant. Overall, simulation outcomes revealed that the performance indexes are scarcely affected by the area of the catchment and the slope of the drainage network. Theresult of this study represents a key issue for the implementation of environmental policies in large urban areas.

Dialysate Purification After Introduction of Automated Hot Water Disinfection System to Central Dialysis Fluid Delivery System

Most dialysis clinics in Japan have mainly adopted the central dialysis fluid delivery system (CDDS) to provide constant treatment to many patients. Chemical disinfection is the major maintenance method of the CDDS. Our clinic introduced an automated hot water disinfection system that used the heat conduction effect to disinfect a reverse osmosis (RO) device and dialysis fluid supply equipment. Endotoxin level and the amount of viable bacteria often showed abnormal values before introduction of this system. After its introduction, weekly disinfection resulted in endotoxin levels and the amount of viable bacteria lower than measurement sensitivity. In hot water disinfection, water heated to 90°C in the RO tank flows into the dialysis fluid supply equipment. The maximum temperature inside the tank of the supply equipment is 86.3°C. (We confirmed that the temperature was maintained at 80°C or more for 10 minutes or more during the monitoring.) Dialysate purification was maintained even after introduction of the automated hot water disinfection system and the dialysate could be supplied stably by the CDDS. Therefore, this disinfection system might be very useful in terms of both cost and safety, and can be used for dialysis treatment of multiple patients.

Visualization of Stirring Rods and Stirred Tank Flow by Digital In-line Holography

Visualization of Stirring Rods and Stirred Tank Flow by Digital In-line Holography

정화조의 효율적인 운영을 위한 실험적 고찰

A septic tank is a purification treatment system where night soil and other waste matter is converted into harmless material by the activities of bacteria. Effluent from the septic tank flows into the sewer pipe, and then this effluent affects the quality of water environment and makes foul smell. In this study, through the proper maintenance of septic tank it was tried to minimize the impact of sewer pipe on water quality and fouling smell. BOD removal rate from the septic tank`s effluent which exceeded legal cleaning period was investigated for the proper maintenance. BOD Removal rate of the twelve septic tank`s effluent is -62.5% to 43.9%. According to the result of BOD removal rate, septic tank cleaning should be done at least once a year. And the pathogenic coliform bacillus in the twelve septic tank`s effluent is average 768,000 (MPN/). The chlorine disinfection is needed to remove the pathogenic coliform bacillus in septic tank effluent.

Dynamic Multiobjective Global Optimization of a Waste Water Treatment Plant for Nitrogen Removal

AbstractThis paper deals with the dynamic optimization of a wastewater treatment plant model for nitrogen removal. Two process variables (i.e., aeration factor in a tank and internal recycle flow rate) are selected as control variables and their time profiles are approximated using the control vector parameterization (CVP) technique. Two conflicting objectives have been considered to formulate a multiobjective optimization problem, namely the quality of the effluent and the plant economy. To solve the multiobjective problem and find the Pareto front the epsilon-constraint technique has been considered. In order to solve this complex problem and to prove its multimodality, a multistart procedure and the scatter search metaheuristic have been applied, showing that the problem is indeed multimodal. Results reveal that this approach is successful to find optimal operation policies in this type of plants.

The Review of the Interior Corner Flow Research in Microgravity

In this paper the theoretical research of vane-type surface tension tank and the study of the interior corner flow are reviewed. Firstly, the conception of interior corner flow and its application in the research of vane-type surface tension tank are introduced. Then the development of analytical solutions about the interior corner flow is expounded, besides some important numerical solutions and experiments in microgravity condition. Up to now, a great deal researches of interior corner flow are carried out overseas, including many drop tower experiments and some space experiments. This paper will provide valuable references for the surface tension tank and interior corner flow research.

数値計算による不飽和浸透水槽における分散長の評価

It is important to apply proper dispersivity in unsaturated condition when solute transport near the soil surface is assessed. However data on unsaturated dispersivity are limited because dispersion in unsaturated condition is more complicated than in saturated condition. In the previous study, we tried to evaluate unsaturated-dispersivity by tracer experiment in the laboratory seepage tank. However, it was difficult to investigate clear results because observed values were scattered. In this study, numerical tracer simulation was conducted under unsaturated water flow condition. The numerical tracer simulation results were confirmed that longitudinal and transverse dispersivities have dependency on soil water content. When the water content is lowered, dispersivity becomes larger. The ratio of transverse dispersivity to longitudinal dispersivity was in the range of 1/1000-1/6000. Numerical results showed that longitudinal dispersivity may have almost constant value in the small scale as seepage flow tank used in this study.

Model of inactivation of Campylobacter jejuni in poultry scalding

The purpose of this study was to develop a model of inactivation of Campylobacter jejuni in industrial scalding of chickens. Models can be used as a guide for broiler slaughterhouse operations for reducing levels of C. jejuni contamination on broiler carcasses. Mean concentrations of C. jejuni in terms of colony forming units (CFU) in scald tank water and in carcass rinse solution after scalding were 2.90 ± 0.07 and 3.86 ± 0.11 LogCFU/mL, respectively. Scald tank water temperature, flow rate, pH, and total solids in scalding process water were 54.15 ± 0.2 °C, 172.0 ± 8.4 L/min, 8.0 ± 0.01, and 2565 ± 114.3 mg/L, respectively. Inactivation models were developed by using mass balances and literature data for inactivation kinetics, of Campylobacter and the Arrhenius equation. Results of the inactivation models of scalding process indicate that high temperature and short time (less than 2 min) of scalding process were effective in reducing the number of viable cells. For this experimental data more than 50% of the Campylobacter are inactivated on surfaces of the chickens. The model fits the experimental data well and the values of the estimated parameters provide insight for this process. The model can be used for process design and potential process modifications.