Water Tank Test Research Articles

Experimental and numerical study on the flow and heat transfer of ring-ribbed tank in deep-sea manned submersible

The ring-ribbed tank is the key equipment of cooling system of deep-sea manned submersible. The heat transfer characteristics of the outer wall and the heat transfer and flow characteristics of the inner flow channel of the ring-ribbed tank for different inlet and outlet temperatures and flow rates were studied through a water tank test. The results indicate that Nusselt number for the inner flow channel correlates with Reynolds and Prandtl numbers, while for the outer wall, it correlates with Grashof and Prandtl numbers with an overall error within 5%. A numerical study using the Realizable k-ε turbulence model and Boussinesq approximation of the flow-solid conjugate heat transfer is conducted, which can accurately determine the heat exchange capacity and the import and export differential pressure with an average relative error of 1.98% for hot water temperature and 7.73% for shell wall temperature. Additional simulations for determining the heat transfer capacity and flow resistance characteristics of the ring-ribbed tank in open water results demonstrate that the differential pressure and its coefficient are basically consistent with model test results. The cooling system can achieve a heat transfer rate of up to 17 kW with an external seawater flow velocity of approximately 2 knots.

Research on the inflation process of underwater parachute by numerical simulation and model test

In order to meet the application requirements of the underwater parachute, the underwater inflation performance of a drag parachute is investigated based on numerical simulation and water tank test. A method for simulating the inflation process of underwater parachute based on Arbitrary Lagrangian Eulerian (ALE) method is proposed. The variation of axial force in the numerical simulation exhibits a similar trend to that observed in the model test, and the discrepancy of value between them is relatively insignificant. The purpose of this paper is to provide a basis for the evaluation and design of underwater parachutes for underwater applications. The effects of parameters such as permeability and flow velocity on the inflation performance are discussed in detail, and the analysis is carried out for parameters such as axial force and structural deformation. The results show that the high-stress zone and high-pressure intensity zone of the underwater parachute were found to be mainly concentrated in the center of the canopy and the joint. It can be observed both in model test and numerical simulation that, during the inflation process, vortexes are generated inside and outside the canopy. After the inflation shape of the canopy has stabilized under steady flow, lateral forces are generated on the parachute due to asymmetric vortex shedding, which cause the parachute to rotate around the axis.

Large-scale laboratory investigation of the performance of a novel isolation particle layer for offshore final disposal sites

The complex seabed conditions and ocean environment pose significant challenges to the material selection and construction of bottom liners for offshore final disposal sites. To overcome the challenges, this study proposed a novel isolation particle layer for offshore final disposal sites. The isolation particle was composed by salt-resistant bentonite coating material and cement core material (D10 was 10 mm in core diameter and 2 mm in coating thickness; D20 was 20 mm and 4 mm). Upon immersion in artificial seawater, the isolation particles underwent expansion, leading to the formation of the novel isolation particle layers with low hydraulic conductivity less than 1 × 10-7 cm/s and adsorption of heavy metals in bentonite interlayers. Large column tests showed that both D10 and D20 isolation particle layers exhibited remarkable swelling capacity and low hydraulic conductivity (4.3 × 10-9 cm/s and 2.6 × 10-8 cm/s) under 3 m seawater pressure. During one year of observation, water tank test demonstrated that both isolation particle layers displayed remarkable stability and low hydraulic conductivity of 2.73 × 10-10 cm/s and 8.36 × 10-10 cm/s with load. The maximum adsorption capacities of salt-resistant bentonite were 123.55 mg/g for Pb2+, 60.29 mg/g for Cd2+ and 54.22 mg/g for Cu2+. Both isolation particle layers exhibited a high removal rate of over 95 % for heavy metals in water tank tests. The large-scale laboratory tests indicated the significant potential of the novel isolation particle layer for offshore final disposal sites. Subsequently, a testing ocean site will be selected to further investigate its practical engineering performance.

Numerical investigation of a Wave-Powered Vertical Profiler

The wave-power vertical profiler harvests surface wave energy through a buoy, and the converts the wave energy into a kinetic energy of a vehicle (underwater vehicle with sensors for profiling) via a mooring cable. The vehicle is aided by a unidirectional motion mechanism to submerge and surface in water. In this paper, a numerical simulation method is proposed to analyze the motion characteristics of the wave-power vertical profiler and reconstruct the entire moving process.Firstly, numerical work is conducted using Ansys Fluent software to investigate the response of the buoy to Stokes waves of different heights. Secondly, the relationship between the underwater vehicle's motion velocity and fluid resistance are studied. Finally, the numerical simulation results are combined using Matlab software to reconstruct the motion process and draw corresponding curves. Compared with the results from the water tank tests, our method can effectively reconstruct the vehicle's motion, with an accuracy rate of 96.5% in simulating the velocity values during the surfacing phase and a good match with the experimental results under natural sea conditions. We found that wave height is the determining factor for the vehicle's sinking time; the weight of the counterweight affects the vehicle's maximum sinking speed; the vehicle's net buoyancy and drag coefficient determine its surfacing speed, while the weight of the buoy can be ignored. Based on these conclusions, we recommend a counterweight weight of 100 N when the wave height is less than 0.6 m and an increase in weight when it exceeds 0.6 m. The recommended net buoyancy value for the vehicle is between 10 and 40 N, and the recommended buoy weight is 65 kg. We hope that these findings will be helpful for the design of wave energy buoys.

Numerical study of hydrodynamic forces and dynamic response for barge type floating platform by computational fluid dynamics and engineering model

The hydrodynamic coefficients are evaluated by fully nonlinear Navier-Stokes forced oscillation simulations using the volume of fluid method. Richardson extrapolation is employed to obtain the grid-independent solution. The predicted hydrodynamic coefficients are validated by the water tank tests. The applicability of the drag coefficient models as the function of Keulegan-Carpenter numbers in the surge and heave directions are investigated for the barge-type floater by comparing with the numerically predicted drag coefficients. The dynamic response analyses are then conducted using the engineering model with the validated drag coefficient models. The predicted mean values of surge and mooring tension without considering drag forces underestimate the measurements in the high wave height condition, where those with considering drag forces show good agreement, which is analytically explained by the mean drag force being inversely proportional to the square of wave period and proportional to the cube of wave height. Dynamic responses of floater predicted without considering drag forces cause overestimation at the natural frequencies in the heave and pitch directions, while those considering drag forces show good agreement with the measurements.

Study on reconstruction and analytical method of seawater radioactive gamma spectrum

Gamma detector detection technology based on NaI(Tl) scintillation crystal has become a popular research topic and has been applied in the field of marine radioactive environment automatic monitoring because of its advantages of low power consumption, low cost and strong environmental adaptability. However, insufficient energy resolution of the NaI(Tl) detector and great Compton scattering in the low-energy region caused by the abundance of natural radionuclides in seawater hinder the automatic analysis of radionuclides in seawater. This study adopts the combination of theoretical derivation, simulation experiment, water tank test and seawater field test, establishing an effective and feasible spectrum reconstruction method. The measured spectrum in seawater is regarded as the output signal formed by the convolution of the incident spectrum and the detector response function. The acceleration factor p is introduced to construct the Boosted-WNNLS deconvolution algorithm, which is used to iteratively reconstruct the spectrum. The analysis results of the simulation test, water tank test and field test meet the radionuclide analysis speed and accuracy requirements for the in-situ automatic monitoring of seawater radioactivity. The spectrum reconstruction method in this study converts the physical problem of insufficient detection accuracy of spectrometer in the practical application into a mathematical problem of deconvolution solution, restores the original radiation information in seawater, and improves the resolution of the seawater gamma spectrum.

A single-tube-braided stent for various airway structures.

Background: Airway stent has been widely used in airway procedures. However, the metallic and silicone tubular stents are not customized designed for individual patients and cannot adapt to complicated obstruction structures. Other customized stents could not adapt to complex airway structures with easy and standardized manufacturing methods. Object: This study aimed to design a series of novel stents with different shapes which can adapt to various airway structures, such as the "Y" shape structure at the tracheal carina, and to propose a standardized fabrication method to manufacture these customized stents in the same way. Methods: We proposed a design strategy for the stents with different shapes and introduced a braiding method to prototype six types of single-tube-braided stents. Theoretical model was established to investigate the radial stiffness of the stents and deformation upon compression. We also characterized their mechanical properties by conducting compression tests and water tank tests. Finally, a series of benchtop experiments and ex vivo experiments were conducted to evaluate the functions of the stents. Results: The theoretical model predicted similar results to the experimental results, and the proposed stents could bear a compression force of 5.79N. The results of water tank tests showed the stent was still functioning even if suffering from continuous water pressure at body temperature for a period of 30days. The phantoms and ex-vivo experiments demonstrated that the proposed stents adapt well to different airway structures. Conclusion: Our study offers a new perspective on the design of customized, adaptive, and easy-to-fabricate stents for airway stents which could meet the requirements of various airway illnesses.

Maternal separation increased memory function and anxiety without effects of environmental enrichment in male rats

Maternal separation is a detrimental postnatal influence, whereas environmental enrichment is a therapeutic and protective agent. It is unclear if long-term environmental enrichment can compensate for the effects of maternal separation stress on memory-related alterations. This study examined how environmental enrichment affected memory functions, anxiety level, Grin2a, Grin2b, BDNF, and cFos expressions in the maternally separated rats. There are seven groups in this study: control (C), maternal separation+standard cage (MS), maternal separation + enriched cage (MSE), enriched cage (E), the maternal separation that decapitated at postnatal 21 (MS21) and standard cage that decapitated at PN21 (C21) for hormone and gene expression analysis. The maternal separation procedure consisted of postnatal 21 days. Learning and memory performance were determined with the Morris water tank test; anxiety and locomotor activity were examined with the open field and elevated plus-maze test. The expression levels of genes were measured by the RT-PCR method. Blood corticosterone level was evaluated by the ELISA method. Results showed that MS increased memory performance, locomotor activity, and anxiety, but it did not change gene expression levels. An enriched environment did not change the memory performance, locomotor activity, and related gene expression levels. MSE group increased their memory performance, but the anxiety, locomotor activity, and gene expression level did not change. Grin2a, Grin2b, and BDNF gene expression and corticosterone levels increased in the MS21 group. Maternal separation increased memory performance, but it also increased anxiety. Environmental enrichment alone was insufficient to cause alterations in the memory performance.

An adaptive parametric level-set method for lung health monitoring with smartphone-based electrical impedance tomography

In this paper, an adaptive parametric level-set method is presented for lung health monitoring with smartphone-based electrical impedance tomography (EIT). Firstly, assuming that the conductivity distribution to be reconstructed is piecewise constant, the shape of lung-like targets is represented by a PLS function using a Gaussian radial basis function. Secondly, the unknown parameters (e.g. centers, widths, and weights) are computed adaptively without a prior information about targets. Thirdly, rectified Adam is proposed to adaptively adjust the learning rate during the iterative process. The proposed method is evaluated quantitatively by simulated lung imaging, water tank tests, and human breathing data. In addition, the robustness of the proposed method is performed by considering different gradient descent methods and different number of RBF centers. The reconstruction results show that the proposed method not only overcomes some problems associated with the traditional level-set method (e.g. reinitialization and use of signed distance function), but also avoids empirical parameter selections in the PLS method, resulting in faster imaging speed and better imaging quality with an average image correlation coefficient greater than 0.90. It is found that the one-second rate of the proposed method is closer to the true value with an average error of no more than 2% when the forced vital capacity tests are repeatedly performed on five volunteers with healthy lungs. The proposed method is promising in providing the reliable assessment of lung health monitoring with smartphone-based EIT.

Bidirectional Impulse Turbine With Spiral Flow Collector for Tidal Energy Conversion

Abstract In order to make use of ocean renewable energy, a combination system of a bidirectional impulse turbine and a bidirectional flow collector for tidal current energy conversion is investigated in this paper. It is the advantage that this turbine system does not need an operation of orientation change according to the reversal of regular tidal orientation when fixed on the seabed. The experimental investigations by using both a circulating water tank and a towing tank showed that the turbine power output could be increased by adopting the flow collector proposed in this study. Then the flow collector with a fixed spiral vane named spiral flow collector was investigated by both a circulating water tank test and computational fluid dynamics (CFD) analysis. The experimental result of the spiral flow collector showed that the performance improvement was found on the increase of axial velocity in the turbine which contributed to the increase of the turbine power output. The results of CFD analysis showed that 180 deg of the skew angle of the fixed spiral vane was suitable in view of the angular moment at the turbine inlet in this case.

Sensor Placement with Two-Dimensional Equal Arc Length Non-Uniform Sampling for Underwater Terrain Deformation Monitoring

Sensor placement plays an important role in terrain deformation monitoring systems and has an essential effect on data collection. The difficulty of sensor placement entails obtaining the most adequate and reliable information with the fewest number of sensors. Most sensor placement schemes are currently based on randomized non-uniform sampling and probability statistics, such as structural modality and optimization methods, which are difficult to directly apply due to the randomness and spatial heterogeneity of terrain deformation. In this study, the placement conditions of two-dimensional non-uniform sampling with equal arc length were deduced for underwater terrain deformation monitoring based on the MEMS accelerometer network. In order to completely reconstruct the underwater terrain, the arc length interval of the sensors should be less than 12Ω (Ω is the maximum frequency of the detected terrain). The maximum MRE and maximum RMSE were both less than seven percent in a terrain deformation monitoring experiment and a water tank test. The research results help technicians apply contact sensor arrays for underwater terrain monitoring.

Investigating the utilization of polyethylene pipe for automated hauling system in set net fishery

The use of an automated net-hauling system using four polyethylene (PE) pipes is proposed in this study to increase the efficiency of set net fishery. In this system, the pipes are installed on the seabed beneath a box chamber net. Compressed air is injected into the first pipe at the slope net and then into the other pipes in succession. In this system, the fish are cornered between the fourth pipe and the end of the box chamber net. The performance of the system from the second to the fourth pipe is evaluated using numerical analysis, water tank tests, and field experiments. In addition, a static numerical model for the deformation of the PE pipes is developed using the theory of finite deformation and is validated by the results of the water tank and coastal sea experiments. The results show that the maximal bending stress of the full-scale pipe is about 10 MPa, which is within the allowable range of 23 MPa, indicating that the risk of pipe breakage in the automated net-hauling system is considerably low. Therefore, the automated net-hauling system developed in this study has high application value and development potential in set net fishery.

Topiramate and darbepoetin alpha ameliorate bilirubin-induced neuronal cell damage.

The aim of this study was to determine whether prophylactic darbepoetin alpha and/or topiramate administration could prevent bilirubin neurotoxicity (BNTx) in experimental model of kernicterus. A total of 60 Wistar albino rat puppies with experimental kernicterus model were included in the study. The Kernicterus was established administering a bilirubin injection via a cisterna magna puncture 30 minutes after ip drug injection. The puppies were divided into five groups with 12 in each group as shown below: a control group, bilirubin group, darbepoetin alpha group, topiramate group and darbepoetin alpha+ topiramate group. Darbepoetin alpha and/or topiramate were administered on day 5 intraperitoneally (ip). At the 6th and 24th hours, bilirubin induced neurological dysfunction (BIND) score was used to assess behavioral changes. Hearing functions were evaluated on days 10 and 28. On day 30, the Water Maze water tank test was implemented to evaluate spatial memory. The rats were sacrificed on days 6 and 34 and apoptosis in the globus pallidus and hippocampus was examined. The BIND score was improved following darbepoetin alpha treatment. Neither darbepoetin alpha nor topiramate therapy ameliorate spatial memory. There were no significant differences between groups in terms of the auditory brainstem response (ABR). The combined use of darbepoetin alpha and topiramate lead to slight decrease in apoptosis. Darbepoetin alpha or topiramate administration ameliorates bilirubin induced neurological dysfunction in experimental model of kernicterus.

Dose-dependent effects of prenatal exposure of pioglitazone, the PPARγ agonist, on the hippocampus development and learning and memory performance of rat offspring

It is known that pioglitazone, defined as a PPARγ agonist, has neuron-protective properties in nervous system disorders. The aim of this study is to investigate the effects of pioglitazone administration at different doses during prenatal period on the neurons, glial cells and learning-memory levels in the hippocampus of rat offspring.Pregnant rats were divided into three groups; Low-Dose Pioglitazone (LDP), High-Dose Pioglitazone (HDP) and control (C) (n = 3). Pregnant rats in the HDP and LDP groups were given pioglitazone at 30 mg/kg and 5 mg/kg doses, respectively, by gavage once a day during their pregnancy. No procedure was applied to the rats in the control group. Morris water tank test was applied to offspring obtained from postnatal 24th to 28th day. The offspring were sacrificed on the 29th postal day and their brain tissues removed. Stereological, histopathological and immunohistochemical techniques were used to analyze brain tissues.As a result of the analysis, it was observed that there were delays in learning and memory, the number of pyramidal neurons decreased, and the density of cells stained with glial fibrillar acidic protein (GFAP) positive increased in the HDP group compared to the other groups (p < 0.05). No significant difference was found between the LDP and control groups in terms of these parameters (p > 0.05).Our results showed that pioglitazone administered in the prenatal period had an effect on the hippocampus development and learning and memory performance of rats, depending on the dose.

Experimental on the protective performance of column bridge pier anti-scouring device

Because of the problem of local scour caused by the change of the flow structure caused by the water-resistance of the column bridge pier, the theoretical analysis, and indoor water tank test were used to study the effect of installing a new anti-scouring device in front of the bridge pier on the local scour reduction effect; the influence of the main design parameters such as the height of the protective device, the angle of the protective device and the distance from the protective device to the bridge pier on the local scour of the bridge pier was selected, and the optimal parameter design combination was selected. The test results show that: under the same water flow conditions, the maximum scour depth reduction rate of the measuring point under the protection of the protective device is 48.4% to 74.2% compared with the unprotected scour; the reduction rate of the bridge pier is relative to the relative height of the device and the device equivalent. The angle and the distance between the device and the bridge pier are related, and the shock reduction rate decreases with the increase of the flow intensity. In the test range, the ratio of the device height to the water depth is 2/3, the device angle is 60 °, and the distance from the bridge pier is 3. When the diameter of the pier is doubled, the effect of reducing the impact on the pier is the best.

Water tank test of the dynamic response of spar type offshore floating platform with 10MW wind turbine

Water tank test of the dynamic response of spar type offshore floating platform with 10MW wind turbine

Numerical Study on Sectional Loads and Structural Optimization of an Elastic Semi-Submersible Floating Platform

This study investigates the sectional loads on an elastic semi-submersible platform for a 2 MW FOWT (floating offshore wind turbine) used in the Fukushima demonstration project. A water tank test is firstly carried out with an elastic model to study the dynamic responses and sectional loads of the platform in regular and irregular waves. Numerical simulations are then performed using multiple hydrodynamic bodies connected by elastic beams. The dynamic responses of the elastic model are compared to those of a rigid model to clarify the influence of the structural stiffness on the platform motion and mooring tension. The predicted sectional loads on the deck, brace and pontoon by the proposed nonlinear hydrodynamic models show good agreement with the experimental data obtained from the water tank test and a simplified formula is proposed to evaluate the distribution of the moments on the platform. Finally, the structural optimization of the elastic semi-submersible platform is conducted. The sectional moments and fatigue loadings on the pontoons are significantly reduced using the strut between the pontoons since the horizontal wave loads on the side column are dominant and the vertical wave loads acting on the platform are relatively small due to the deep draft.

Dynamic Response Analysis of a Semi-Submersible Floating Wind Turbine in Combined Wave and Current Conditions Using Advanced Hydrodynamic Models

In this study, advanced hydrodynamic models are proposed to predict dynamic response of a floating offshore wind turbine (FOWT) in combined wave and current conditions and validated by laboratory and full-scale semi-submersible platforms. Firstly, hydrodynamic coefficient models are introduced to evaluate the added mass and drag coefficients in a wide range of Reynolds numbers. An advanced hydrodynamic model is then proposed to calculate the drag force of cylinder in combined wave and current conditions. The proposed model is validated by the water tank tests in the current-only, wave-only and current-wave conditions and is used to investigate the effect of current on the dynamic response of FOWT. Finally, the full-scale semi-submersible platform used in the Fukushima demonstration project is investigated. It is found that the predicted dynamic responses of platform by the proposed hydrodynamic models are improved by the directional spreading function of the sea wave spectrum and show favorable agreement with the field measurement.

Characterization and verification of a two-body wave energy converter with a novel power take-off

The lack of high efficient, predictable, and reliable power take-off (PTO) systems limits developments of ocean wave energy technology. In this paper, a two-body self-reacting wave energy converter (WEC) with a novel PTO is designed, modelled and implemented for efficiency enhancement. A novel mechanical motion rectifier (MMR) using a ball screw mechanism and an enclosed gear set is integrated to improve the energy harvesting efficiency and reliability by rectifying the oscillatory wave motion into unidirectional rotation of the generator. Detailed design and dynamic modelling for the proposed WEC are presented. A prototype of the PTO is tested in a dry lab to characterize and refine the dynamic modelling. The characterized PTO model is combined with the WEC model to create an overall system model. A water tank test is conducted to verify the overall system dynamics, which proves the accuracy of the model and shows the advantages of the proposed WEC on efficiency and predictability. Following the method of how the WEC system is characterized, performance prediction of the proposed WEC with MMR PTO can be achieved with high accuracy.

Testing Method and Application for Impulse- Dispersed Current Around Earthing Devices in Power Transmission Networks

Dispersing current under lightning impulse has a significant influence on the safety of creature and equipment. In field application, there is a lack of a direct and effective measurement method of impulse-dispersed current around earthing devices in power transmission networks. To solve this problem, this article presents a calculation method of the current density and makes a sensor for measuring impulse-dispersed current in the soil. The sensor device is made using the flat-type electric field structure, and a water tank test platform is set to determine the optimal sensor device size, and the absolute measurement error of the sensor is not to exceed 8 A/ $\text{m}^{2}$ . Then, in order to verify the effectiveness of the sensor, impact simulation and test based on a hemispherical sand pool are developed, and the absolute error between measured data and simulated data is within 6 A/ $\text{m}^{2}$ . Finally, the impulse current density sensor has been utilized in the field project; and the measurement results could guide the site selection and renovation in tower construction.