Tank Facility Research Articles

Experimental study on kinetic energy conversion of horizontal axis tidal stream turbine

The present study aims to understand the energy conversion mechanism of a 100 kW horizontal axis tidal stream turbine by analyzing thrust, torque, and wake flow measurements. The scale ratio of the turbine model was 1/20 and model tests for power and wake measurements were conducted in a towing tank facility. Wake fields were measured by a towed underwater stereoscopic particle image velocimetry (SPIV) system. The chord-length based Reynolds number at 40% of the radius of the turbine ranged from 53,000 to 63,000 in the test conditions. The turbine model showed the highest power coefficient at a tip speed ratio (TSR) of 3.5, and the magnitude of power coefficient was 0.278. Three TSR conditions were selected for SPIV measurement after power measurement tests, representing heavy loading, highest efficiency, and light loading, respectively. In the wake field measurement results, conversion of kinetic energy of the turbine wake was investigated, decomposing it into effectively extracted work, loss due to the drag on the turbine system, kinetic energy of the time-mean axial flow, local flow structures, turbulence, and secondary flow loss. In high TSR conditions with a small angle of attack onto the turbine blade, the secondary flow loss was minimized.

Wave energy conversion through a point pivoted absorber: Numerical and experimental tests on a scaled model

This paper presents numerical and experimental tests on an innovative wave energy conversion (WEC) system for extracting electrical power from waves. It consists of a point pivoted floater which oscillates due to waves. Linked to the buoyant body, an electromechanical generator based on ball-bearing screw converts floating movements into electrical power. At first, an analytical description of the system arrangement is presented. Then, experimental tests on a scaled model have been performed in wave/towing tank facility and data from tests were used for comparison with data from numerical simulations: both potential flow and Unsteady Reynolds Averaged Navier–Stokes (URANS) numerical simulations were performed. These simulations have been performed in order to identify critical parameters for further WEC developments.

URANS prediction of roll damping for a ship hull section at shallow draft

It is analytically difficult to calculate roll damping of ships due to the effects of viscosity. Therefore, computational fluid dynamics (CFD) has become a powerful tool in predicting roll damping recently. The unsteady flow around a forced rolling hull section with bilge keels can be calculated using a commercial URANS code which includes the viscous effects. In this study, two-dimensional (2D) roll damping calculations for a S60 midsection with bilge keels including free surface effects are performed for shallow draft case. The first objective of the study is to show whether the URANS code can be used to predict roll damping coefficient correctly. The second one is to show why Ikeda’s estimation method is insufficient at shallow draft case. Sinusoidal forced roll motion calculation method of roll damping moment with the help of a sliding interface and a fixed roll axis is successfully applied to predict roll damping coefficient. The calculations are carried out for different roll motion periods and amplitudes to validate the accuracy of the URANS code for different cases. Numerical results are compared with experiments, which were carried out at the towing tank facility of Osaka Prefecture University (OPU), and Ikeda’s estimation method. The results show that the URANS code is capable of predicting roll damping coefficients in a good agreement with experimental results and can be used further to develop a better model for prediction of roll damping.

Optimal Design of Pumped Water Distribution Networks with Storage Under Uncertain Hydraulic Constraints

This paper discusses research on the optimal design of looped water distribution networks with complex layouts. It focuses on incorporating uncertain hydraulic constraints in the optimal design of networks which includes tanks and pumping facilities. The Fuzzy Decision System is utilized to define the hydraulic constraints uncertainty. Using Fuzzy Genetic Algorithm, the genetic algorithm selects the cost efficient network, while fuzzy reasoning evaluates the water delivery quality of each potential solution. This paper includes an overview of the selection of design variables to determine siting and sizing of tanks and pumps, define initial water level and daily operational schedules for tanks; and define the total number of parallel pumps and their operational schedule. This is followed by a new method to optimally design a water distribution network in two stages of consumption and tank filling periods. The performance of the proposed algorithm is evaluated using Anytown network, which includes pumps and tank facilities. It is concluded that the Fuzzy Genetic Algorithm is able to optimally design water distribution networks under multi uncertain hydraulic constraints. Moreover, conducting the optimal design procedure in two stages (consumption and filling period) would substantially decrease the computational costs and improve the performance of the designed network.

Vortex-induced vibrations of elastically mounted circular cylinder at Re of the O(105)

In the field of fluid structure interaction and offshore engineering, vortex induced vibrations (VIV) have been a highly researched topic over a last few decades. There is a continuous need to understand the magnitude of peak oscillations and force–phase relationship, possible under all forcing conditions. Considering this fact, and bearing in mind that in practical situations, cylindrical structures are subjected to water currents corresponding to high Re. Present study is focused on the VIV in regimes of high Re beyond 105. Measurements were made in a towing tank facility, for mass ratio m⁎=0.87–2.52; damping ratio ζ=0.058–0.066; and m⁎ζ=0.05–0.166. Displacement measurements together with force coefficients in the transverse direction and the phase relationship between force and displacement were also investigated. An attempt has been made to capture hysteresis as part of the main objective of the study. The present investigation sheds new light in the VIV response of the cylinder in terms of its dependence on reduced velocity (Ur) and hysteretic response. There is a need to include the effects of high Re in predictive relationships for maximum amplitude response (Ymax). A new equation is proposed for Ymax including the effects of α=[(m⁎+CA)ζ] and Re which appears to be better than the only other available approach in the literature.

Determining the discharge rate from a submerged oil leak jet using ROV video

With expanded deep sea drilling in the Gulf of Mexico, and possibly the Arctic, it is imperative to have a technology available to quickly and accurately measure the discharge rate from a submerged oil leak jet. This paper describes an approach to measure the discharge rate using video from a Remotely Operated Vehicle (ROV). ROV video can be used to measure the velocity of visible features (turbulent eddies, vortices, entrained particles) on the boundary of an oil leak jet, from which the discharge rate can be estimated. This approach was first developed by the Flow Rate Technical Group (FRTG) Plume Team, of which the authors Savaş and Shaffer were members, during the response to the Deepwater Horizon (DWH) oil leak. Manual tracking of visible features produced the first accurate government estimates of the oil discharge rate from the DWH. However, for this approach to be practical as a routine response tool, software is required that automatically measures the velocity of visible features. To further develop this approach, experiments were conducted to simulate a submerged oil leak jet using a dye-colored water jet in the U.C. Berkeley Tow Tank facility. Jet exit diameters were 10.2cm and 20.3cm. With flow rates up to 11gal/s, Reynolds numbers in the range of the DWH oil leak jets (up to 500,000) were achieved. The dye-colored water jets were recorded with high speed video and radial profiles of velocity were mapped with Laser Doppler Anemometry (LDA). Particle Image Velocimetry (PIV) software was applied to measure the velocity of visible features. The velocities measured with PIV software were in good agreement with the LDA measurements. Finally, the PIV software was applied to ROV video of the DWH oil leak jet. The measured velocities were 10–50% lower than manual measurements of velocity. More research is required to determine the reasons why PIV software produced much lower velocities than manual tracking for the DWH oil leak jet.

Statistical Analysis of Compartment Permeability Influence on Damaged Ship Motions

The study shows the changes in heave and pitch motions when a ship hull is damaged with varying compartment permeability values using wave statistics. It is an experimental investigation into obtaining motion measurements of an intact and damaged frigate model in waves. Experiments were carried out using the Southampton Solent University towing tank facility and a 1/43.62 scale segmented frigate model of the Leander Class Frigates Hull. During the experiment wave length/wave height was kept constant whilst wave frequencies were varied from 3.173 to 6.276 rad/s. The tests were carried out with the model stationary and in motion with a forward speed of 1.4ms-1. Results of the tests indicated that compartment permeability has a non-linear effect on heave and pitch motions of a damaged ship.

1702 回転場中の気泡プルームによって駆動される対流パターンの実験的研究

Influence of background rotation on the behavior of a bubble plume in a tank is investigated experimentally, purposing a flow control for large LNG container subject to the Earth rotation. We used the rotating tank facility in University of Warwick, and found a single air-chimney stabilized in the case of point-source of air injection. In contrast, the line-source bubble injection resists to the chimney formation and keeps planer curtain like structure. We also found eccentric oscillation of bubble plume in the disk-source type of injection.

Prospects of virtual or computational towing tank facility for the shipbuilding industry of Bangladesh

Shipbuilding is on the verge of blooming into the major foreign revenue-earning industry in Bangladesh. A number of export-oriented shipyards are developed to deliver different kinds of ships for local and international clients. For designing a ship, model testing facilities are required not only to predict power requirements but also to evaluate its performance in actual sea operation. At present, Bangladesh does not have this facility. Also carrying out model testing is very expensive and time consuming. Therefore, now-a-days most of the shipyards all over the world are using virtual or computational towing tank facility. Due to improvement of solution algorithm for handling non-linear problem and computational infrastructure, computational or virtual towing tank can be used as a replacement of physical towing tank experiments. In the present study, a numerical or computational towing tank technique named WISDAM which is developed at The University of Tokyo, Japan is described with its applicability in perspective of Bangladesh shipbuilding industries.DOI: http://dx.doi.org/10.3329/jname.v11i1.15619

SUBMERSIBLE OPTICAL SENSORS EXPOSED TO CHEMICALLY-DISPERSED CRUDE OIL: WAVE TANK SIMULATIONS FOR IMPROVED OIL SPILL MONITORING

In situ fluorometers were deployed during the Deepwater Horizon (DWH) Gulf of Mexico oil spill to provide critical measurements for tracking the subsea oil plume. In the wake of the spill, uncertainties regarding instrument specifications, capabilities and reliability necessitated performance testing of sensors (commonly used during spill response) exposed to simulated, dispersed oil plumes. Moreover, concerns on the applicability of laboratory calibrations (at high concentrations and insufficient mixing energies) to field conditions and on sensor reliability to detect dispersed oil persist. To address these uncertainties the performance of select commercially-available sensors (from Chelsea Technologies Group, Satlantic, Turner Designs, WetLabs Inc) was evaluated using a wave tank facility at the Bedford Institute of Oceanography in Halifax, Nova Scotia. Breaking waves were generated within the tank to simulate mixing energies and achieve dispersant effectiveness observed in the field. Presented here are the results of the sensors exposed to chemically-dispersed MC252 crude oil using Corexit 9500, DOR=1:20. Stepwise additions of dispersed oil (0.3 – 12 ppm) to the tank were used to establish linearity. Model 1 linear least squares regressions were calculated and applied to sensor data during validation experiments to simulate dilution of an oil plume. Dynamic ranges of the sensors, exposed to fresh and artificially weathered crude oil, were determined. Sensors were standardized against known oil volumes and measured Total Petroleum Hydrocarbons (TPH) and Benzene-Toluene-Ethylbenzene-Xylene (BTEX) values – both collected during spills, providing oil estimates during dilution experiments. Results were validated against particle size data (Sequoia LISST). All sensors estimated oil concentrations down to 300 ppb oil, refuting previous reports. Low percent differences and absolute errors between chemistry and sensor results were metrics to evaluate performance. Discussed will be the application of this vicarious calibration approach as a means to calibrate the DWH fine-scale fluorescence data into oil concentrations. This allows for filling in coarse-scale field chemistry data, improved assessment of DWH spill measurements mined from the NOAA NODC, and understanding the fate and transport of the DWH oil plume.

Study on Propulsive Performance of Two Geometrically Similar Podded Propulsors

This paper presents the outcome of a research to evaluate the effect of size on the propulsive performance of podded propulsors in cavitating and non-cavitating open water conditions. Two cases are examined, namely: propeller-only case and pod-unit case. In the propeller-only case, a commercial propeller dynamometer is used to measure the thrust and torque of two propellers of different size at the four quadrants of propellers with varied shaft and flow speeds. Also, both propellers are tested at different tunnel pressure to study and compare the behaviour under similar cavitation conditions. In the pod-unit case, two geometrically similar but different sized pod-units are tested using two separate custom-made pod dynamometer systems in two towing tank facilities in straight-ahead and static azimuthing conditions. The study showed that the performance characteristics stabilize at lower Reynolds Number for the smaller propeller than the larger propeller. The propulsive performance of the two propellers was comparable in the four-quadrant experiments. Also, the experiments at the cavitating conditions showed that the cavitation characteristics of the two propellers were consistent at corresponding operating conditions. The experiment results of the two pod-units were also comparable for forces and moments in the three coordinate directions in the straight-ahead and static azimuthing conditions. A brief discussion on the uncertainty assessments for each of the measurements is also presented.

The influence of surface gravity waves on marine current turbine performance

Surface gravity waves can significantly impact operating conditions for a marine current turbine, imparting unsteady velocities several orders of magnitude larger than the ambient turbulence. The influence of surface waves on the performance characteristics of a two-bladed horizontal axis marine current turbine was investigated experimentally in a large towing tank facility at the United States Naval Academy. The turbine model had a 0.8m diameter (D) rotor with a NACA 63-618 cross section, which is Reynolds number independent with respect to lift coefficient in the operating range of Rec≈4×105. The torque, thrust and rotational speed were measured at a range of tip speed ratios (TSR) from 5<TSR<11. Tests were performed at two rotor depths (1.3D and 2.25D) with and without waves. The average turbine performance characteristics were largely unchanged by depth or the presence of waves. However, tests with waves indicate large variations in thrust, rotational speed, and torque occurred with the passage of the wave. These results demonstrate the impact of surface gravity waves on power production and structural loading and suggest that turbines should be positioned vertically within the water column at a depth which maximizes power output while minimizing material fatigue.

Acoustic radiation force. Part I: Finite element modeling for elastic objects

The study of the acoustic radiation force produced by acoustic beams has been the topic of active research in the last few years mainly due to its ability for particle trapping and non-contact manipulations. However, efforts in modeling the radiation force have mainly focused on analytic solutions and thus have been limited to spherical objects, where the acoustic radiation force has been calculated for a plane wave as well as various types of beams. But up until recently, even those efforts were limited to using on-axis beams, where the incident beam is along an axis that goes through the center of the sphere and thus reduces the problem to an axially symmetric one. In this work we use the finite element technique to compute the acoustic radiation force for an arbitrary elastic object and for an arbitrary incident beam. One of the main objectives of this work is to understand and interpret the data we collected at a recent experiment we conducted at the Washington State University test tank facility, where a 2.5-in. PMMA sphere was ensonified by an intense amplitude-modulated ultrasound beam focused at its surface.

Quantifying wave and yaw effects on a scale tidal stream turbine

The behaviour of Tidal Stream Turbines (TST) in the dynamic flow field caused by waves and rotor misalignment to the incoming flow (yaw) is currently unclear. The dynamic loading applied to the turbine could drive the structural design of the power capture and support subsystems, device size and its proximity to the water surface and sea bed. In addition, the strongly bi-directional nature of the flow encountered at many tidal energy sites may lead to devices omitting yaw drives; accepting the additional dynamic loading associated with rotor misalignment and reduced power production in return for a reduction in device capital cost. Therefore it is imperative to quantify potential unsteady rotor loads so that the TST device design accommodates the inflow conditions and avoids an unacceptable increase in maintenance action or, more seriously, suffers sudden structural failure.The experiments presented in this paper were conducted using a 1:20th scale 3-bladed horizontal axis TST at a large towing tank facility. The turbine had the capability to measure rotor thrust and torque whilst one blade was instrumented to acquire blade root strain, azimuthal position and rotational speed all at high frequency. The maximum out-of-plane bending moment was found to be as much as 9.5 times the in-plane bending moment. A maximum loading range of 175% of the median out-of-plane bending moment and 100% of the median in-plane bending moment was observed for a turbine test case with zero rotor yaw, scaled wave height of 2 m and intrinsic wave period of 12.8 s.A new tidal turbine-specific Blade-Element Momentum (BEM) numerical model has been developed to account for wave motion and yawed flow effects. This model includes a new dynamic inflow correction which is shown to be in close agreement with the measured experimental loads. The gravitational component was significant to the experimental in-plane blade bending moment and was also included in the BEM model. Steady loading on an individual blade at positive yaw angles was found to be negligible in comparison to wave loading (for the range of experiments conducted), but becomes important for the turbine rotor as a whole, reducing power capture and rotor thrust. The inclusion of steady yaw effects (using the often-applied skewed axial inflow correction) in a BEM model should be neglected when waves are present or will result in poor load prediction reflected by increased loading amplitude in the 1P (once per revolution) phase.

Concomitant vortex-induced vibration experiments: a cantilevered flexible cylinder and a rigid cylinder mounted on a leaf-spring apparatus

This paper presents experimental results of vortex-induced vibrations (VIV), concomitantly carried out in water with a flexible cylinder, rigidly fixed, and with a ‘rigid’ cylinder, mounted on an elastic apparatus. The experiments were run at IPT towing tank facility, in a side-by-side arrangement. The flexible cylinder is simply fixed at the upper end. For the flexible cylinder, two degrees of freedom (2DOF) are implied for each vibration mode: crosswise and aligned with respect to the incident flow. The elastic support to which the ‘rigid’ cylinder is mounted is made of two vertical leaf-springs, fixed to two thick horizontal plates, conferring to the cylinder a single degree of freedom (SDOF) to oscillate transversally with respect to the incident flow. The mass ratios of the cylinders are almost the same, around 1.2 and 1.4, respectively, very low values, typical of long ocean pipe structures, as risers and pipelines. The structural damping ratio is also typically low and such as to guarantee high-amplitude responses. Besides usual spectral and statistical analysis, the Hilbert–Huang spectral analysis technique is applied, as, strictly, VIV is a non-stationary oscillation emerged from a nonlinear dynamic system. A discussion is made on the distinct VIV behaviors of the SDOF and the 2DOF systems.

ENSURING INDUSTRIAL SAFETY AT REPLACEMENTOF TECHNOLOGICAL CONTAINERS PRODUCTION ISOBUTANE

Industrial safety depends not only on the normal operation of buildings and structures, but also on the proper functioning of the technological equipment and the foundations on which it is located. The proper technical condition of tank facilities helps to avoid premature wear designs, ensuring industrial and environmental safety.Due to the ongoing reconstruction, to be replaced existing tanks to horizontal, but with a greater capacity, which imposes additional requirements for safe operation of a pedestal, consisting of three frame supports. Were held visual and instrumental examination, during which revealed damage of object elements, analyzed the technical documentation, calculations of load capacity and proposed strengthening for ensuring industrial safety at hazardous production facilities.

Excitation of rogue waves in a variable medium: An experimental study on the interaction of water waves and currents

We show experimentally that a stable wave propagating into a region characterized by an opposite current may become modulationally unstable. Experiments have been performed in two independent wave tank facilities; both of them are equipped with a wavemaker and a pump for generating a current propagating in the opposite direction with respect to the waves. The experimental results support a recent conjecture based on a current-modified nonlinear Schrödinger equation which establishes that rogue waves can be triggered by a nonhomogeneous current characterized by a negative horizontal velocity gradient.

Investigation of an explosion in a gasoline purification plant

An explosion in an atmospheric storage tank initiated additional tank explosions and a pool fire at a tank facility in Norway. The tank farm had been operated as a purification plant for a petroleum product called coker gasoline. The process entailed extraction of malodorous sulfur containing components, in particular thiols (mercaptans). After several tanker loads of coker gasoline had been treated with a solution of sodium hydroxide and water, the efficiency of the sweetening process declined as precipitated waste accumulated in the tanks and the alkaline solution became increasingly saturated with impurities. The approach adopted for handling the accumulated waste included the addition of hydrochloric acid to neutralize the spent caustic. The explosion occurred when about 80% of the scheduled amount of acid had been added to the solution in the tank. There were no fatalities in the accident, but at least two people received medical treatment for injuries sustained during the course of events. The investigation concluded that the accident was caused by a chemical explosion in the tank. Several factors point toward thiols as the predominant constituents in the fuel–air mixture, but vapors from other volatile substances may also have played a decisive role. The ignition source was most likely a hot surface, resulting from adsorption of volatile organic compounds on activated carbon in the air filter and subsequent self‐heating and glowing combustion in the carbon bed. The article summarizes the main results from the accident investigation and lists various measures that can be taken to prevent similar accidents in the future. © 2013 American Institute of Chemical Engineers Process Saf Prog 32: 268–276, 2013

The effect of surface waves on the performance characteristics of a model tidal turbine

Scale model tests were conducted on a three bladed horizontal axis tidal turbine in a large tow tank facility at the United States Naval Academy. Performance characteristics are presented for a turbine towed at a constant carriage speed for cases with and without surface waves. Intermediate waves were modeled that are representative of swells typically found on the continental shelf of the United States eastern seaboard. The oscillatory wave velocity present in the water column results in significant variations in measured turbine torque and rotational speed as a function of wave phase. This in turn produces cyclic variations in tip speed ratio and power coefficient. The power coefficient over the entire wave phase did not show a difference from the experiments without waves for a range of tip speed ratios, as reported in previous studies. The waves limited the lower range of tip speed ratios at which the turbine could operate. These results highlight the impact of surface waves on turbine design and performance, and the importance of understanding the site-specific wave conditions.

On the flow generated on the leeward face of a rotating flat plate

We experimentally investigate the flow generated on the leeward face of a rotating trapezoidal flat plate of low-aspect-ratio; the motion is an advancing stroke from rest at 90° angle of attack with Reynolds numbers of O(103). The objectives are to characterize the fluid velocity near the tip of the plate for different plate kinematics. The experiments are conducted in a water tank facility, and digital particle image velocimetry is performed to obtain planar velocity measurements. The flow in the region near the tip is relatively insensitive to Reynolds number over the range studied. The component normal to the plate is unaffected by total rotational amplitude, while the tangential component has dependence on this angle. Also, an estimate of the first tip vortex pinch-off time is obtained from the near-tip velocity data and agrees very well with values estimated using circulation. The angle of incidence of the bulk root-to-tip flow relative to the plate normal becomes more oblique with increasing rotational amplitude. Accordingly, the peak magnitude of the tangential velocity is also increased and as a result advects fluid momentum away from the plate at a higher rate. The more oblique impingement of the root-to-tip flow for increasing rotational amplitude is shown to have a distinct effect on the associated fluid dynamic force normal to the plate. For impulsive plate deceleration the time that a nonnegligible force exists decreases, while for nonimpulsive plate deceleration both this time and the relative force magnitude decrease for larger rotational amplitudes.