Tower Tests Research Articles

Investigation of the distribution of transuranic radionuclides in marine sediment at the Montebello Islands, Western Australia

Three nuclear weapons tests were conducted in the 1950s at the Montebello Islands, Western Australia. The detonations were of different yields and configurations (two tower tests, one ship test), and led to substantial radionuclide contamination within the surrounding terrestrial and marine ecosystems. The region possesses great ecological and recreational significance, particularly within the marine environment. However, studies conducted so far have largely neglected the marine ecosystem which makes up the majority of the Montebello Island Marine Park and in which most test fallout would have deposited. Here we investigated the distribution of the transuranic radionuclides 238Pu, 239,240Pu and 241Am in marine sediment from the Montebello Islands. Marine sediment samples near Operation Mosaic G2 and Operation Hurricane were collected and analysed by gamma and alpha spectrometry. Activity concentrations of 239,240Pu across both series ranged from 45 to 2900 Bq kg−1, while 241Am levels ranged from 2.8 to 70 Bq kg−1. Higher activity concentrations were observed in sediment near the land-based, higher yield Mosaic G2 test, compared with the ship-based, lower yield Hurricane test. Sediment samples located closer to the detonation site were also observed to have higher activity concentrations. Radioactive particles of 0.94 mm and 1.5 mm in diameter were identified by analysis of size-fractioned sediment via investigation of 152Eu levels, photostimulated autoradiography and point gamma spectroscopy. Particles were confirmed to have transuranic radionuclide interiors, with surface coatings which were dominated by vitrified CaCO3. Their long-term resistance to weathering and subsequent persistence in the marine environment can therefore be attributed to their coated structural form. Our study confirms the persistence of transuranic radionuclides in Montebello Island marine sediment and highlights the need for additional studies to improve our understanding of the nuclear legacy in this region.

Estimation of Passive Drag in Swimming via Experimental and Computational Means

Discussed is a comparison of computational and experimental evaluations of passive drag during human swimming. Experimentally, ten trials were conducted per athlete at five chosen velocities, using a commercial resistance trainer to record the tension force in a rope during a streamline position tow test. The resistive force recorded was assumed equal to the passive drag force and an average value of passive drag was found across each tow test. Mean passive drag values measured during the tow test were agreed well with existing experimental data across the range of velocities used, varying between 20 N at 1 ms−1 up to 100 N at 2 ms−1. Computationally, using the immersed boundary method in OpenFOAM, basic geometry validation cases and streamline passive drag cases were simulated. Validation cases were completed on 2D cylinders and 3D spheres with the drag coefficient found at low and high Reynolds numbers, using the simpleFoam solver within OpenFOAM. Results tended to be slightly over predictive when compared with existing simulation and experimental data in literature. The accuracy of results could potentially be improved using a finer mesh and better quality geometries. The passive drag was also computed using OpenFOAM over a range of velocities, similar to the experiments, varying from 30 N at 1 ms−1 to 120 N at 2 ms−1. Drag forces computed using simpleFoam were over predictive when compared to existing literature and the completed experiments, likely due to the inaccuracy of the geometry used in the simulations. When results were compared to existing literature for swimmers not in a perfect streamline position, more similar to the geometry used in this study, results were in better agreement. The accuracy of the results could be improved using a better quality geometry in the correct position.

Computational Study on Influence Factors and Vortical Structures in Static Drift Tests

This paper conducted a computational study on the KCS benchmark model at static drift conditions. At the first instance, the roles played by the grid size, turbulence model, and time step are qualitatively and quantitatively analyzed with the orthogonal experimental method (OEM). After the verification of simulated results compared with experimental data in a Static Oblique Towing Test (OTT), hydrodynamic performance is obtained with the employment of the SST κ-ω turbulence model. The grid size is set as 0.07 m while the time step as 0.01 s. The characteristics of the wake field are illustrated in different forms, such as contours of the free surface, distribution of pressure and hydrodynamic forces, variation of turbulent kinetic energy (TKE), and so on. For a deep insight into the physical mechanisms of the asymmetrical flow field, the Detached Eddy Simulation (DES) method is also utilized to capture vortical structures occurring around the hull, in comparison with results obtained through the Reynolds Averaged Navier Stokes (RANS) model. With the aim of a hydrodynamic derivative estimation or detailed flow characteristics analysis, corresponding selections of the computational method are disparate.

Simulative investigation of the required level of geometrical individualization of the lumbar spines to predict fractures.

Injury mechanisms of the lumbar spine under dynamic loading are dependent on spine curvature and anatomical variation. Impact simulation with finite element (FE) models can assist the reconstruction and prediction of injuries. The objective of this study was to determine which level of individualization of a baseline FE lumbar spine model is necessary to replicate experimental responses and fracture locations in a dynamic experiment.Experimental X-rays from 26 dynamic drop tower tests were used to create three configurations of a lumbar spine model (T12 to L5): baseline, with aligned vertebrae (positioned), and with aligned and morphed vertebrae (morphed). Each model was simulated with the corresponding loading and boundary conditions from dynamic lumbar spine experiments. Force, moment, and kinematic responses were compared to the experimental data. Cosine similarity was computed to assess how well simulation responses match the experimental data. The pressure distribution within the vertebrae was used to compare fracture risk and fracture location between the different models.The positioned models replicated the injured spinal level and the fracture patterns quite well, though the morphed models provided slightly more accuracy. However, for impact reconstruction or injury prediction, the authors recommend pure positioning for whole-body models, as the gain in accuracy was relatively small, while the morphing modifications of the model require considerably higher efforts. These results improve the understanding of the application of human body models to investigate lumbar injury mechanisms with FE models.

A horizontal vibration prediction method of high-speed elevator based on transferred-digital twin model

The vibrations of high-speed-elevators (HSEs) significantly impact the comfort of elevator rides, with horizontal vibrations (HV) being the most sensitive to bodies. Customized elevator products are characterized by high-speed capabilities, customization options, and complex operational conditions. These characteristics often lead to challenges such as difficulties in predicting HV, low prediction accuracy, and limited reusability of prediction models and data. In order to mitigate HV in elevators, its crucial to implement HV prediction during the design phase. To address this need, this paper proposes a method for predicting HSEHV based on a Transferred Digital Twin (TLDT) model. The HSE’s design is physically extracted, and an elevator Digital Twin (DT) model with a digital layer is constructed. This model includes product geometry models, dynamics models, and simulation models. A transfer learning (TL) model is developed to integrate simulation data generated by the digital layer with measurement data acquired from the data interface layer, resulting in high-capacity and high-fidelity DT data. Using the support vector regression (SVR) method, a high-dimensional nonlinear HSEHV prediction model is established, and is trained and optimized using DT data to achieve data-driven HSEHV prediction. The validity of this approach is confirmed using measured data from an elevator test tower. Results indicate that the SVR-based TLDT model achieves the highest accuracy and the lowest absolute error values for both peak-to-peak and A95 vibration acceleration when compared to other models such as NN, KNN, decision tree, and lasso models. Furthermore, by incorporating DT data, the model accuracies improve by 16.9%, 14.5%, 8.6%, 14.1%, and 8.6%, and 12.3%, 12.4%, 19.7%, 7.6%, and 8.7%, respectively, for the mentioned models. Finally, the HV of KLK2 elevator car system is predicted. When compared with simulation analysis and the conventional SVR prediction model, obtained results through the proposed method closely align with the measured values.

Impact Characteristics and Repair Approaches of Distinct Bio-Based Matrix Composites: A Comparative Analysis

Increasing global concerns regarding environmental issues have driven significant advancements in the development of bio-based fiber reinforced polymer composites. Despite extensive research on bio-composites, there remains a noticeable gap in studies specifically addressing the challenges of repairing bio-composites for circular economy adoption. Traditional repair techniques for impacted composites, such as patching or scarf methods, are not only time-consuming but also require highly skilled personnel. This paper aims to highlight cost-effective repair strategies for the restoration of damaged composites, featuring flax fiber as the primary reinforcement material and distinct matrix systems, namely bio-based epoxy and bio-based vitrimer matrix. Glass fiber was used as a secondary material to validate the bio-based vitrimer matrix. The damage caused specifically by low impact is detrimental to the structural integrity of the composites. Therefore, the impact resistance of the two composite materials is evaluated using instrumented drop tower tests at various energy levels, while thermography observations are employed to assess damage evolution. Two distinct repair approaches were studied: the resin infiltration repair method, employing bio-based epoxy, and the reconsolidation (self-healing) repair method, utilizing the bio-based vitrimer matrix. The efficiency of these repair methods was assessed through active thermography and compression after impact tests. The repair outcomes demonstrate successful restoration and the maintenance of ultimate strength at an efficiency of 90% for the re-infiltration repair method and 92% for the reconsolidation repair method.

The interactive force between fat, oil, and grease (FOG) deposits and the effect of food waste disposers on kitchen drainage systems

Food waste disposers (FWDs) streamline kitchen waste management and facilitate waste classification, whether they would increase the potential of blockage in kitchen drainage system is still unknown. This study conducted a theoretical analysis of the interactive forces between fat, oil, and grease (FOG) deposits and their aggregation on pipe walls. The study involved grading food waste particles processed by FWDs using sieving and weighing techniques to determine the mean weight diameter (MWD) of various aggregations. A full-scale experimental system, implemented in a 60-m high test tower, simulated blockages in horizontal pipes of high-rise buildings. The effect of pipeline materials and particle sizes on blockage were examined by measuring the adhesion of deposits on horizontal pipes. Energy dispersive spectrometer (EDS) analysis suggested that liquid bridge force is a primary factor in aggregate formation. Hand-cut particles formed aggregates with the highest MWD value. Particle size analysis revealed that sizes ranging from 2.36 to 4.75 mm, 1.18–2.36 mm, and 0.60–1.18 mm constituted over 80 % of particles ground by FWDs, with an average size of 2.16 mm. Results of full-scale experiment indicate particle diameters, friction coefficients and lipophilic coefficient significantly affected the propensity of these aggregates to adhere to pipes. Notably, particles processed by FWDs tended to cause blockages more frequently than hand-cut particles. These findings elucidate the deposition mechanism of FOG deposits and offer strategies to reduce blockages in kitchen drainage systems, such as reducing current grinding particle size by 18 % to 1.77 mm or selecting pipes like cast iron and high-density polyethylene.

A Comparative Study on Lattice Tower Angle Member Capacities as Per Indian, American, and BSEN Standards

The transmission lines and Telecommunication networks are normally supported by lattice towers. Therefore, the reliability of these essentials depends much on the reliability of the towers and their foundations. In Both telecom and power transmission line sectors, the towers are mass-produced and generally based on optimized tower weight and foundation volumes. The weight of a tower is influenced to a great extent by the selection of tower configuration, choice of bracing patterns, choice of steel grade, and profile type. The towers in general are lattice types consisting of main legs, diagonals, horizontals, cross-arm members, and peak members. The telecommunication and power transmission line tower members are generally made of steel equal-angle sections. These tower members are modeled and analyzed as pin-jointed 3-dimensional space truss models and the members are subjected to axial forces, either axial compression or axial tension in nature. Estimation of member compression capacity is the most vital parameter in design as per respective local standards and proving those estimations during full-scale model tower testing if carried out. This paper presents the differences in axial compression capacity of angle members as per Indian, American, and European standards viz., IS: 802 (Part 1/Sec 2)-2016, IS 800-2007, ASCE 10-15 and BS EN 1993-3-1:2006.

Numerical Study of a Model and Full-Scale Container Ship Sailing in Regular Head Waves

In the present study, the added resistance, heave, and pitch of the KRISO Container Ship (KCS) in waves, at both model scale and full scale, are predicted numerically in regular head waves, for four wavelengths and three wave heights. The ISIS-CFD viscous flow solver, implemented in the Fidelity Fine Marine software provided by CADENCE, was employed for the numerical simulations. The spatial discretization was based on the finite volume method using an unstructured grid. The unsteady Reynolds-averaged Navier–Stokes (RANS) equations were solved numerically, with the turbulence modeled by shear stress transport (k-ω) (SST). The free-surface capturing was based on the volume-of-fluid method. The computed solutions were validated through comparisons with towing test data available in the public domain. To predict the uncertainties in the numerical solution, a systematic grid convergence study based on the Richardson extrapolation method was performed for a single wave case on three different grid resolutions. Specific attention was given to the free-surface and wake flow in the propeller plane. The purpose was to compare the numerical results from the model- and full-scale tests to examine the scale’s effect on the ship’s performance in regular head waves. The comparison between the model scale and full scale showed obvious differences, less accentuated for the free-surface topology and clearly observed in terms of boundary layer formation in the propeller’s vicinity.

Uncertainty Assessment of the Remaining Volume of an Offshore Gravity Fish Cage

The volume of a gravity cage is greatly reduced under a current due to the flexible structure, which affects the growth and health of the fish. Thus, an accurate assessment of cage volume is essential to determine the number of fishes in the cage. In this study, firstly, a numerical model was built to study the cage volume reduction of gravity cages due to the flexible net deformation when subjected to uniform flow. The remaining volume was calculated and compared with earlier experiments. Even though the flow velocity reductions were considered according to the data from previous experiments, the differences between the results from the numerical calculation and the towing tests are still significant. The physical model tests were treated as the reference value to investigate the uncertainty of the model results. Both the velocity-independent model error and velocity-dependent model error were calculated. With the help of the error models, the uncertainty of the remaining volume can be predicted. In addition, the velocity-dependent model error performs better in evaluating the uncertainty of the numerical calculation of the remaining culturing volume. Overall, the results show that the numerical model assisted by the model errors can calculate the cage volume accurately.

Numerical Assessment of the Hydrodynamic Loads for a Manta Type Unmanned Underwater Vehicle: Oblique Towing Test

Numerical Assessment of the Hydrodynamic Loads for a Manta Type Unmanned Underwater Vehicle: Oblique Towing Test

Experimental study of the resistance of a hydrofoil supported watercraft (hysuwac)

A possible alternative to reduce fuel consumption on a ship is through energy efficiency. For this purpose, a hydrofoil supported watercraft (hysuwac) utilizes two hydrofoils, one installed near the bow and the other near the stern of the catamaran, to reduce the vessel’s resistance. To investigate the effectiveness of the hydrofoils, CFD calculations were conducted in an earlier study. The purpose of this study is to provide experimental data to validate the CFD calculation results reported earlier for which towing tests were conducted at the Laboratory of Ship Hydrodynamics, ITS Surabaya, Indonesia. The ship model was made by using a three-dimensional print, which is then assembled into a ship model that meets the test requirements. The hydrofoil used has a NACA 641-212 section with an angle of attack of 4°. Twelve variations of towing tests were carried out with six variations of speed and two conditions, namely catamaran without and with foil system. A comparison between the CFD and experimental results shows that the CFD results are consistent with the experimental data. The minimum magnitude of percentage difference between the CFD results and experimental data is 1.14%, while the maximum magnitude of this is 16.79%. The observed difference is ascribed mainly to scale effects.

A Method for Forcing a Number of Motions or Rotations in 6 Degrees of Freedom Ship Simulators

In this paper, a method is introduced which enables the forcing of any degrees of freedom in 6 DoFs ship simulator. It is based on the introduction of an extra force in the equation of motion of the ship and on the forcing of the second derivatives of the forced degrees of freedom rather than the forced degrees of freedom themselves. The method is explicit which makes it easy to implement in existing software. Examples of its application to oblique towing tests and forced heading in wind and waves are presented.

Dynamic Oblique Towing Test (DOTT) to calculate the ship's hull maneuvering derivatives

An accurate and time-efficient numerical method is developed to find the hydrodynamic maneuvering derivatives with only a single simulation by computational fluid dynamics. The method is based on the oblique towing test by introducing an oscillatory variation to the model ship drift angle as time progress. The fluid flow velocity and direction are fixed during the simulation but the orientation of the model ship is changing sinusoidally with respect to the fluid flow with a certain amplitude and frequency. The velocity and acceleration of the model ship are calculated using the kinematic relationships and the forces and moment on the model ship are computed in a time period while the model ship drift angle is changing. The method is named dynamic oblique towing test (DOTT) and is applied to a container model ship and a surface combat model. The hydrodynamic maneuvering derivatives are obtained by an optimized curve fitting using Genetic Algorithms. The results of the computation in coefficient derivation and maneuver simulation indicate the accuracy and time efficiency of the method.

Estimating Active Drag Based on Full and Semi-Tethered Swimming Tests.

During full tethered swimming no hydrodynamic resistance is generated (since v = 0) and all the swimmer's propulsive force (FP) is utilized to exert force on the tether (FT = FP). During semi-tethered swimming FP can be made useful to one of two ends: exerting force on the tether (FST) or overcoming drag in the water (active drag: Da). At constant stroke rate, the mean propulsive force (FP) is constant and the quantity FP - FST (the "residual thrust") corresponds to Da. In this study we explored the possibility to estimate Da based on this method ("residual thrust method") and we compared these values with passive drag values (Dp) and with values of active drag estimated by means of the "planimetric method". Based on data obtained from resisted swimming (full and semi-tethered tests at 100% and 35, 50, 60, 75, 85% of the individual FT), active drag was calculated as: DaST = kaST.vST2 = FP - FST ("residual thrust method"). Passive drag (Dp) was calculated based on data obtained from passive towing tests and active drag ("planimetric method") was estimated as: DaPL = Dp.1.5. Speed-specific drag (k = D/v2) in passive conditions (kp) was )25 kg.m-1 and in active conditions (ka) )38 kg.m-1 (with either method); thus, DaST > Dp and DaST > DaPL. In human swimming active drag is, thus, about 1.5 times larger than passive drag. These experiments can be conducted in an ecological setting (in the swimming pool) by using basic instrumentation and a simple set of calculations.

Investigation of water resistance of semi-submersible floating cranes of various designs

The paper considers the effect on water resistance of the movement of a semi-submersible floating crane model on quiet deep water in working and transport positions and different heading angles. The research was conducted in the experimental pool of Sevastopol State University. The performed towing tests of the model made it possible to plot the dependence of the coefficient of impedance on the Froude number. Each of the presented graphs refers to a certain horizontal clearance and heading angle, as well as the number of intermediate stabilization columns. According to the obtained graphs, it is possible to estimate the power of the power plant, mainline and shunting engines of a semi-submersible floating crane of the selected design scheme at the initial stages of design. In the future, it is planned to carry out research to determine the coefficient of additional resistance from the excitement of the considered cases of the hull shape.

Experimental study on the sound of water flowing through a storm drain

In buildings where storm drains are installed indoors, the sound of running water radiated from the surface of storm drains during rainfall may raise the noise level in rooms near the drain. To take appropriate measures against such sound according to the required quietness for the room, quantitative data on the sound of running water from storm drains is necessary, but few studies have dealt with this kind of sound. Therefore, the authors conducted experiments in an existing building, a drainage test tower, and a reverberation room to understand the characteristics of the sound produced by storm drains. Based on the results obtained through these experiments, this paper presents the effects of flow rate, pipe diameter, pipe material, and horizontal piping on the sound of running water from storm drains. The paper also discusses the differences between the sound generated by storm drains and the sound generated by sanitary sewers.

Effects of strut cover and lower vertical fin in podded propulsion units on ship maneuverability

To investigate the effects of a strut cover and lower vertical fin in podded propulsion units (POD units) on the maneuverability of a POD-driven ship, free-running model tests (turning test, spiral/revers spiral test, and zig-zag maneuver test) were conducted for three different profiles of the POD units: only a vertical strut without the strut cover or fin (F0), smaller strut cover and smaller fin (FS), and larger strut cover and larger fin (FL). The profile area increases in the order of F0, FS, and FL. The tests were conducted using two propeller positions: one with a propeller equipped in front of the POD units (PULL position) and another with the propeller equipped behind the POD units (PUSH position). The steady turning performance at a steering angle of 35° in the PULL position deteriorated in the order of F0, FS, and FL. In contrast, in the case of the PUSH position, the turning performance improved in the order of F0, FS, and FL. Thus, the PULL and PUSH positions demonstrated different tendencies. The non-dimensional steady yaw rate exceeded 1.0 in all cases, which indicates that the present ship has an excellent turning performance. Furthermore, captive model tests (the POD steering force test in straight towing, oblique towing test, and circular motion test) were conducted to determine the effects of the strut cover and lower vertical fin on the lateral force and yaw moment acting on the ship model. It was found that the large strut cover and fin increase the steering force and improves the course stability of the ship in both the PULL and PUSH positions.

Determination of Hydrodynamic Coefficients of Atmospheric Diving Suit

Atmospheric Diving Suit (ADS) is commonly featured with complex configurations and great difficulty in accurate control. To achieve a satisfying control effect, it is necessary to establish a hydrodynamic formula for ADS. This paper employs the model test method to obtain the ADS hydrodynamic coefficients, providing the foundation for ADS hydrodynamic formula. A 1:1 scale hydrodynamic test model of ADS is designed and machined, and then the hydrodynamic test is carried out. The hydrodynamic coefficients correlated with vertical motion are obtained through a vertical towing test, revealing the hydrodynamic characteristics of the ADS.

A study of the towing characteristics of a semi-submersible floating offshore wind platform

A robust pipeline of floating wind energy has emerged with a general trend of projects becoming larger, further from shore, and placed in increasingly energetic seas. The installation process for these farms involves the pre-assembly of components onshore or in sheltered waters before towing the platform to the operational location using tugs. It can be expected that such marine operations will be repeated in reverse at the time of decommissioning. The cost and safety of these operations will be influenced by the tugs used, towing speed, the local metocean conditions, the platform/turbine characteristics and other factors. This paper investigates the hydrodynamic characteristics of a large semi-submersible floating offshore wind turbine (FOWT) under tow. The motions of the FOWT are analysed using a numerical tool and validated using a towing test. A framework is proposed for the assessment of FOWT towing operations. Various limiting factors have been identified and the hydrodynamic performance of the system has been evaluated using the framework.