Full-scale Measurements Research Articles

A digital twin for ship structures—R&D project in Japan

Abstract In order to clarify and visualize the real state of the structural performances of ships in operation and establish a more optimal, data-driven framework for ship design, construction and operation, an industry-academia joint R&D project on the digital twin for ship structures (DTSS) was conducted in Japan. This paper presents the major achievements of the project. The DTSS aims to grasp the stress responses over the whole ship structure in waves by data assimilation that merges hull monitoring and numerical simulation. Three data assimilation methods, namely, the wave spectrum method, Kalman filter method, and inverse finite element method were used, and their effectiveness was examined through model and full-scale ship measurements. Methods for predicting short-term extreme responses and long-term cumulative fatigue damage were developed for navigation and maintenance support using statistical approaches. In comparison with conventional approaches, response predictions were significantly improved by DTSS using real response data in encountered waves. Utilization scenarios for DTSS in the maritime industry were presented from the viewpoints of navigation support, maintenance support, rule improvement, and product value improvement, together with future research needs for implementation in the maritime industry.

The first data on the concentration and emission of methane and carbon dioxide in the underground sources of the Peshernaya beam of Lake Baskunchak

For the first time, full-scale measurements of methane and carbon dioxide emissions by the chamber method were carried out in summer for groundwater sources discharged in the valley of the creek of the Peshernaya beam, located in the north-west of Lake Baskunchak. The values of pH, temperature, concentration of basic ions and methane were determined in the water of the sources. A detailed description of the identified groundwater sources was carried out, their primary morphometric and morphological characteristics were measured, as well as the flow rate. It has been established that more than ten ascending karst groundwater sources are discharged in the Peshernaya gully, five of which were active during the research period and were mainly confined to the left branch of the gully. The active sources of the left side of the beam are characterized by a small flow rate and are sodium chloride brines with a mineralization of 93.9–107.1 g/l. The concentration of methane in the water of active sources varied between 26.3–38.4 µl/l and was on average more than 2 times higher than in the waters of the stream fed by them and an inactive source. The specific flow of methane from the water surface of active sources varied in the range of 0.6–1.5 mg/(m2·hour), which is 2 orders of magnitude lower than the specific flow of CO2, which is 46.4–106.1 mg/(m2·hour).

Геомеханические аспекты разработки пологопадающих залежей камерами с наклонными стенками

Introduction. Technologies of extraction of valuable ores with filling of the worked-out space with hardening mixtures provide the best technical and economic indicators of production. Their disadvantage is the dilution of ores by the material of laying mixtures under the influence of natural and technological stresses. Of particular relevance are the issues of use for the management of mining pressure of enrichment waste. Materials and methods. To achieve this goal, a set of studies is carried out, including generalization of experience, full-scale measurements of rock mass parameters, laboratory studies and process modeling. The priority direction of solving the problem is the differentiation of the value of the angle of inclination of the cameras on the tab array. Results. It is determined that the efficiency of the full use of the subsoil is increased by optimizing the design of the purification chambers based on the regularities of the extraction of ore reserves in the interface zone with the laying array. It is proposed to combine the rock and hardening bookmark in a single process to increase the efficiency of work, creating volumetric compression conditions in ore-containing arrays that improve its performance, including reducing the dilution of ores. It is shown that the geo-mechanical aspect of combining technologies is to create a jamming zone of rock formations with the formation of a structure capable of withstanding emerging stresses. It was found that the inclination of the walls of the cleaning chambers in contact with the laying array towards the developed space in the range of 5–25 degrees reduces compressive stresses by approximately 1.6 times. Conclusion. Taking into account geodynamic factors when choosing a technology for the development of stressed arrays opens up prospects for replacing expensive components of the filling mixture with recyclable cheap industrial waste. The research results can be used in the improvement of technologies for the extraction of valuable ores at existing enterprises and the design of new technologies for the development of ore deposits, as well as in the educational process.

Разность потенциалов в стволах березы повислой (Betula pendula ROTH): особенности процессов релаксации при изменении температуры окружающей среды

The daily dynamics of the potential difference arising in the wood of the trunk of the hanging birch (Betula pendula Roth) at ambient temperature changes makes it possible to simulate the dynamics of the processes of redistribution of salt ions in the pores. An analysis of the results of measuring the potential difference in the wood of the model tree trunk showed that its dynamics is of a relaxation nature and tends to a certain stationary value. On the basis of the data of full-scale measurements of the potential difference in the framework of classical electrodynamics, a formalized model of the dynamics of the relative potential difference was constructed, containing three parameters. As a result of a computational experiment using an optimization procedure based on the Nash-Sutcliffe criterion, the parameters of the relaxation process of formation of a stable potential difference along the birch trunk caused by a change in the ambient temperature were calculated. It was revealed that the dynamic balance of the charge redistribution flows is determined by the factors of stimulating and stabilizing processes inside the trunks of woody plants. It is shown that a competent combination of the results of monitoring the potential difference in tree trunks and a computational experiment will make it possible to form an extensive database of parameters for the processes of formation of a stable dynamic equilibrium of salt ion fluxes in them, depending on the characteristics of growth, daily and seasonal changes in ambient temperature and soil composition. The study of changes in the state of trees due to the response to the impact of various environmental factors makes it possible to expand the range of tools for predicting the occurrence of catastrophic situations in forest ecosystems.

Reducing wave impacts on high-speed catamarans through deployment of ride control: Analysis of full-scale measurements

Full-scale trials on a 98 m wave piercer catamaran were conducted in the North Sea and North Atlantic region. In order to examine, amongst other things, the effectiveness of the ride control system, the ship was deliberately operated in sea conditions likely to induce a large number of wave impact events. Primary ship motion and structural response parameters, such as angles, rates and accelerations, and strains at various locations were recorded. Slam and minor wave impact events were identified in the data records and analysed to determine the influence of wave headings, vessel speeds, sea states and ride control system activation on their occurrence rates and severity. The Empirical Mode Decomposition technique was used to remove both noise and the rigid body response from the acceleration signals. This was based on prior work by the authors and found to provide more reliable slam identification than traditional methods. A prediction of extreme slam occurrences was modelled using logistic regression. A key outcome of the study was the finding that the activation of ride control significantly reduces the probability of extreme slams occurring.

Probabilistic analysis of operational ice damage for Polar class vessels using full-scale data

To ensure the safety of maritime operations in polar waters, the IMO enforced the International Code for Ships Operating in Polar Waters (Polar Code) in 2017. To address ice navigation related risks, the Polar Code refers to a set of guidelines known as the Polar Operational Limit Assessment Risk Indexing System (POLARIS). Following POLARIS, operational limits for ice navigation are defined based on the Risk Index Outcome (RIO) value, which takes into account the prevailing ice conditions and the ice class of a ship.Recent studies indicate that the POLARIS guidelines are well-founded. However, no direct relationship between RIO values and the probability of an ice-induced hull structural damage has been established. To enable a more accurate analysis of ice navigation risks, this article addresses this issue by (i) relating measured ice-induced loads to RIO values corresponding to the ice conditions in which the loads were measured, (ii) calculating the load limits for plastic deformation and rupture of the ice belt of hull structures representing different ice classes, and (iii) defining the probability of structural damage for different load limits. The study utilizes long-term full-scale ice load measurements carried out onboard Polar Supply and Research Vessel (PSRV) S.A. Agulhas II in the Antarctic Ocean. The load limits were calculated for ice class standards, PC3, PC4, PC5, PC6, and PC7 in accordance with the Unified Requirements of the International Association of Classification Societies (IACS).On a general level, the results are consistent with earlier findings indicating that the POLARIS guidelines are well-founded. If a ship operates mainly at ‘normal operation’ level, the probability for fracture at hull are at probability levels of 10-3 and 10-4 for ice classes PC3 to PC5. The probability levels for PC6 and PC7 are higher that is possibly a result from conservative load probability distributions. When the portion of operations at ‘special consideration’ level becomes significant, the probability of fracture at the hull increases significantly. However, large ice thicknesses and the largest load magnitudes may be associated with positive RIO values. Some inconsistencies are recognized, and the uncertainty and limitations of the analysis are discussed.

Verification of simplified underwater radiated noise estimation tool using Brown's formula

In recent years, the impact of underwater radiated noise from ships on marine life has attracted considerable global attention. Therefore, various research institutions are investigating this phenomenon through research and development efforts. In this study, authors have developed an underwater radiated noise estimation tool that can be used in the early stages of ship design. This tool calculates the underwater radiated noise level by applying Brown's formula, a simple estimation formula for predicting the noise generated by ships. The parameters required for Brown's formula are estimated using HOPE Light, a ship performance estimation software developed by the National Maritime Research Institute. The extent of cavitation is estimated using Burrill's diagram, a tool for assessing the occurrence of cavitation. The accuracy of the developed tool has been verified by comparing its results with full scale measurements of underwater radiated noise levels obtained off-board hydrophone array system.

Fatigue Assessment Comparison between a Ship Motion-Based Data-Driven Model and a Direct Fatigue Calculation Method

Ocean-crossing ship structures continuously suffer from wave-induced loads when sailing at sea. The encountered wave loads cause significant variations in ship structural stresses, leading to accumulated fatigue damage. Where large inherent uncertainties still exist, it is now common to use spectral methods for direct fatigue calculation when evaluating ship fatigue. This paper investigates the use of a machine learning technique to establish a model for 2800TEU container vessel fatigue assessment. Measurement data from 3 years of cross-Atlantic sailing demonstrated and validated the machine learning model. In this investigation, the ship’s motions were used as inputs to build a machine learning model. The fatigue damage amounts predicted using a machine learning model were compared with those obtained from full-scale measurements and direct fatigue calculation. The pros and cons of the methods are compared in terms of their capability, robustness, and prediction accuracy.

Measuring Received Signal Strength of UWB Chaotic Radio Pulses for Ranging and Positioning

The use of ultra-wideband (UWB) signals for local positioning is very attractive for practice, because such signals have the potential to provide centimeter precision. In this paper, we consider wireless ranging (distance measurement) and positioning, using one of the kinds of UWB signals, i.e., chaotic radio pulses, which are noise-like signals with no constant shape. The distance measurement is based on an assessment in the receiver of the power of UWB chaotic radio pulses emitted by the transmitter. A new method for estimating their power and its experimental implementation is proposed and described. Experimental layouts of the transmitter and receiver and the principles of their operation are described. To determine the main features of this method under real signal propagation conditions, full-scale indoor measurements were carried out, and statistical estimates of the accuracy were made. We present the results of experimental testing of the proposed approach for positioning the emitter relative to a system of anchors in an office space 6 × 6.5 m2 in the mode of measuring object coordinates on a line and on a plane. The mean absolute error (MAE) of distance measurement (1D) was 25 cm, and the root mean squared error (RMSE) was 39 cm. When positioning on a plane (2D), the MAE of coordinate estimation was 34 cm and the RMSE was 42 cm. The proposed distance measurement method is intended for use in wireless UWB transceivers used in wireless sensor networks.

Damping in stay cable with damper: Practical universal damping curve and full-scale measurement

This paper includes two main parts which are the development of a universal damping curve for cables of cable-stayed bridges with dampers and a full-scale measurement of cable damping. In the first part, the universal damping curve is derived for cables with viscous dampers or High Damping Rubber (HDR) dampers. The proposed damping curve is a single curve which incorporates several cable-damper parameters like cable bending stiffness, boundary conditions at cable ends (hinged, fixed or restraint ends), damper stiffness, damper support stiffness and added negative stiffness. A numerical approach by a finite difference method (FDM) is also developed to verify the proposed universal damping curve. In addition to FDM, the accuracy of the proposed curve was confirmed with damping formulations in literature over ten different damper types. The results showed a good agreement of estimated damping between proposed damping curve and others. Additionally, a significant improvement in estimating cable damping was observed through two available full-scale tests, which compared the results between proposed curve and current curve. The second part in this study presents a full-scale measurement of cable vibration and a real application of the proposed damping curve for the identification of damping in cables of Shinminato Bridge (cable lengths from 100 to 200 m). Both HDR and viscous dampers were used for the cable vibration control of the bridge. The results of damping analysis indicated that the HDR damper effectiveness was higher than 0.7 whereas this effectiveness was smaller than 0.4 for the viscous damper.

3D numerical model for transient simulations of floor cooling capacity and thermal comfort in a thermally heterogeneous room

This study presents the development of a computational model for an analysis of the dynamic heat transfer in a room equipped with the radiant cooling floor as a full, three-dimensional, thermally heterogeneous environment. The model is validated by comparison with the results of reference models and by the full-scale experimental measurements, which prove the good accuracy of the developed model for the simulation of heat gains in a thermally heterogeneous room (mean error 0.23 °C for the air temperature), as well as for the simulation of radiant floor cooling (mean error 0.16 °C for the temperature of floor area). A set of simulations is performed for an exemplary room with solar, long-wave, and convective heat gains to investigate the effects of type and time-variability on the heat gains for the operational characteristics of the cooling floor. Different types of temperature sensors (operative and air) used in the control system with different set-points are examined. Thermal heterogeneity of the room is included in the thermal comfort analysis performed using PMV, PPD, and PD-cold floor comfort indicators. It is found that the operational characteristics of the radiant floor strongly depend on the effects of dynamic heat flow, so it should be considered on the full spatial scale and the control strategy should not be neglected. It is desirable to develop design methods and tools for cooling floors that allow precise prediction of their operational characteristics but are not too computationally complex, which is satisfied by the proposed model.

Geometric-parameter influence and orthogonal evaluation on the thermal environment for an impinging jet ventilation system inlet

Numerical simulations are conducted to illustrate the geometric-parameter influences and orthogonal evaluation of heat removal effectiveness and dimensionless buoyant jet length scale for impinging jet ventilation system, after the full-scale measurements conduced. Two geometric parameters taken into consideration are the airflow inlet length, width and height from floor. Firstly, each geometric-parameter influence is investigated individually among its varying range while maintaining the other geometric parameters. Secondly, an orthogonal analysis is performed for evaluating the importance of each geometric-parameter on the thermal environment and thermal comfort performances.

Models for thermal boundary layer in level ice growth and brash ice consolidation

It is important to understand the properties and parameters of ice growth models, to enable reliable assessment of the impact ice may have on facilities or to ship navigation. To improve the understanding of the different models, the theoretical formulations for ice growth are investigated and calculated results compared with laboratory and full-scale measurement data. The paper describes the ice growth models for level sea ice and how these are applied in brash ice consolidation modelling. In particular, analysis is made to account for modelling of snow cover in level ice growth models, and subsequently also salinity, porosity and the atmospheric boundary including wind effect in brash ice models. The paper presents an overview of laboratory tests and results for both level ice and brash ice. Also models for level ice growth for the case of snow cover are derived and compared with thetest results. Specifically, inclusion of snow thickness in the growth model presents some practical difficulties, as the thickness of snow cover is often not known a priori, and comparison between calculated level ice thickness and measurements suggests that a good assumption in predictive models is to assume the snow cover thickness to be proportional to level ice thickness. Further, it was observed that the wind influences much the heat transfer to atmosphere, which is not zero at the zero wind speed, a value for the heat transfer coefficient to atmosphere is derived based on laboratory tests. The findings from these analyses provide an improved understanding of the ice growth and consolidation process which can be incorporated into modelling techniques for marine design and operations.

Validation of a panel method with full-scale FOWT measurements and verification with engineering models

The present paper gives insights into the verification of different models of the Floatgen demonstrator by BW Ideol. This floating offshore wind turbine (FOWT) is based on a barge type-floater with moonpool. The moonpool shall dampen the platform’s motion and is challenging to model due to the increased complexity of the hydrodynamic behaviour. For the verification purposes, the results of two engineering methods (OrcaFlex, OpenFAST) equipped with frequency-dependent hydrodynamic solver and the nonlinear time-domain boundary element method panMARE are compared. The OrcaFlex model designed by BW Ideol is regarded as a reference because of a preceding calibration with measurement data. All models show fairly good agreement in most cases. Only in heave there are significant differences between engineering and the nonlinear models which is caused by different modelling of the moonpool hydrodynamics. In addition, a hybrid simulation approach with prescribed motion and constrained wind field based on motion sensors and LIDAR measurements on the Floatgen demonstrator was applied for an aerodynamic and load validation of panMARE. The validation shows good agreement based on time-domain comparison regarding the tower top loads and turbine operation.

In-air and in-water performance comparison of Passive Gamma Emission Tomography with activated Co-60 rods

A first-of-a-kind geological repository for spent nuclear fuel is being built in Finland and will soon start operations. To make sure all nuclear material stays in peaceful use, the fuel is measured with two complementary non-destructive methods to verify the integrity and the fissile content of the fuel prior to disposal. For pin-wise identification of active fuel material, a Passive Gamma Emission Tomography (PGET) device is used. Gamma radiation emitted by the fuel is assayed from 360 angles around the assembly with highly collimated CdZnTe detectors, and a 2D cross-sectional image is reconstructed from the data. At the encapsulation plant in Finland, there will be the possibility to measure in air. Since the performance of the method has only been studied in water, measurements with mock-up fuel were conducted at the Atominstitut in Vienna, Austria. Four different arrangements of activated Co-60 rods, steel rods and empty positions were investigated both in air and in water to confirm the functionality of the method. The measurement medium was not observed to affect the ability of the method to distinguish modified rod positions from filled rod positions. More extended conclusions about the method performance with real spent nuclear fuel cannot be drawn from the mock-up studies, since the gamma energies, activities, material attenuations and assembly dimensions are different, but full-scale measurements with spent nuclear fuel are planned for 2023.

Analysis of full-scale wind and pressure measurements on a low-rise frame-supported fabric expedient aircraft hangar

The use of lightweight fabric structures as a substitute for traditional building materials, such as wood, concrete, masonry, and steel has become more commonplace. Attractive selection criteria include speed of construction as well as being an economically affordable alternative for many owners. However, lightweight fabric structures come with unique engineering considerations such as the increased vulnerability to environmental loading from wind and snow when compared to more traditional and massive (i.e., heavier) building systems. This paper examines the wind-induced response of an in-service 818 SM (8,800 sf) frame-supported fabric Large-Area Maintenance Structure monitored using a suite of structural and environmental instrumentation. Analysis of such structures is missing in the published literature. The study evaluates structural performance relative to the structural design parameters and assumptions using a combination of an in-situ monitoring study, numerical modeling, and targeted material and component-level testing that characterized accurate fundamental material properties and the behavior of key connections. The study finds a high degree of uncertainty in the longitudinal load path for the Main Wind Force Resisting System (MWFRS) due to the flexibility of the structure. Additionally, irregularly shaped structures that deviate significantly from rectangular, gable-roofed structures, wind tunnel testing or other means should be used to demonstrate that the maximum wind effects are adequately enveloped. This study also demonstrates a framework for fully remote structural monitoring systems that can provide near-continuous monitoring of the structural response of in-service structures.

A comprehensive analysis of a numerical self-propulsion procedure for high-speed marine vehicles

In the context of numerical self-propulsion predictions, the literature on high-speed marine vehicles (HSMV) is still relatively scarce. Actually, extensive numerical analyses are rarely considered for these applications because of the not-so-stringent design constraints and contract requirements concerning these crafts and also thanks to the advantages of series production. On the contrary, with the growth of the market requests, in particular, in the direction of Greenhouse Gas Reduction, the exact knowledge of the vessel working point, in terms of speed and engine configuration, pushes the researchers to investigate all the factors which deeply define the propulsion condition. In the present paper, two existing vessels have been numerically studied using a robust and industrially affordable procedure based on some simplified viscous Computational Fluid Dynamic approaches to predict the self-propulsion working points. The obtained results have been then compared with available sea trials showing a very high agreement even if some uncertainties in both the experimental measurements and the CFD results still exist. The impact of these uncertainties has been further investigated to assess the reliability of the self-propulsion prediction, showing that the maximum speed can be obtained with an uncertainty of about 1 knot and 10% of the corresponding engine load. A more robust prediction can be obtained by including the uncertainty assessment in the propulsion analyses. The validity of the proposed analyses is further supported because the numerical uncertainty falls inside the uncertainty obtained from the available full-scale measurements, so defining a more robust prediction of the vessel propulsion point for design purposes.

Quantification of uncertainty in linear wave energy hydrodynamic models from experimental data

Considerable testing and modeling are required in order to fully realise, efficiently develop, and successfully industrialise the wave energy converters (WECs). Numerical modeling, full-scale measurements, and scaled prototype testing are the various methodologies that can be applied to model WECs and predict the dynamic response. Mathematical WEC models form the basis of model-based energy maximising control and directly affect the ability of model-based controllers to maximise energy capture. Linear WEC models are attractive in leading to simpler control designs, but may not cover the complete operational space. One solution is to identify a range of linear models at different operating points, which give a measure of the underlying nonlinear behaviour [1], [2]. This model set can then be used to extract a nominal model, and an associated uncertainty region, which can be used as a basis for a robust WEC controller synthesis process, such as articulated in [3].
 Recently, such an approach has been adopted using data generated from a high-fidelity numerical computational fluid dynamics (CFD) model [4]. However, numerical wave tanks (NWTs) and physical wave tanks differ significantly in terms of the range of tests which can be performed, and the contamination which can affect the measurements used to determine the data-based models e.g. measurement noise, numerical effects, wave reflections, etc [5]. As a result, the determination of nominal models and uncertainty regions in a physical wave tank may provide some advantages (and disadvantages) which need to be examined carefully. In addition, the range of post-processing techniques which could, or should, be applied to the different experimental/numerical domains, to improve the fidelity of the identified models, may differ between domains.
 In this paper, experimental testing of a WEC, by recreating a wave field similar to real-life conditions and a small-scale version of the device, is used to understand the hydrodynamic behaviour and to obtain an accurate dynamic model for WECs, which are considered to be essential towards optimal WEC design. Physical wave tank experiments, even though having their own disadvantages, overcome some difficulties of CFD-based NWT experiments, most notably huge computation time, problems in accurate representation of viscous fluids, uncertainty in the specification of an appropriate turbulence model, and propagation of incident waves [6]. 
 In this study, representative linear models of a point-absorber type WEC from a physical wave tank in the wave basin at Aalborg University are determined which give insight into the system dynamics and provide a basis for robust control of WECs. Among different stimulation techniques to excite the system dynamics in physical wave tank tests, the particular types of excitation signals covering the complete range of frequencies and amplitudes of the system dynamics, while considering limitations on the range of excitation signals or the wave tank reflections, are adopted for the determination of representative linear models. Moreover, a full investigation is carried out to ascertain the appropriate post-processing needed to optimise the signals as the basis for model identification. The model identification includes the non-parametric frequency response by means of empirical transfer function estimate (ETFE). 
 

Wind pressure on a 45° gabled roof: verifying code provisions with field measurements and wind tunnel data

The wind load provisions for gabled roofs with a slope of 27° < α < 45° in the National Building Code of Canada (NBCC) were derived from wind tunnel studies conducted in the 1970s. The coefficients have remained basically unchanged until this time. The paper presents the results of full-scale measurements and wind tunnel experiments to verify the necessity to update the current NBCC provisions. A full-scale building with a gabled roof of 45° was instrumented with pressure taps, and the wind load was monitored for 15 months. Special attention is given to the roof overhang by considering the simultaneous pressure contribution from both the upper and lower surfaces. The building and surroundings were replicated at a wind tunnel scale and investigated by Concordia University and Western University. Based on these three sources of data, the study concluded that the corner and edge provisions for both cases—a roof with and without overhang—need to be increased. It is suggested to merge the corner and edge into a single “perimeter” load provision. This code simplification would help the roofing industry to reduce misleading interpretations of the code and minimize failure due to installation errors.

Investigation of the Aerodynamic Forces on a 600-m-High Supertall Building by Field Measurements and Wind Tunnel Test

This paper investigates the aerodynamic forces on a 600-m-high supertall building based on field measurements during Super Typhoon Mangkhut and wind tunnel test on a 1∶500 scaled model of the monitored building. The local wind force coefficients and their power spectral densities obtained by the full-scale measurements and the model experiment are compared and discussed. The comparative study shows that the wind tunnel test provides conservative mean local drag coefficients and root-mean-square (RMS) local lift coefficients, whereas for the RMS local drag coefficients, the model experiment reproduces smaller predictions at higher levels than those from the onsite measurements. Moreover, to explore the deviations between the full-scale and model-scale results, the Reynolds number effects in the range of 5.5×104 to 1.8×108 on the local wind forces and the Strouhal number are investigated. It is found that the Reynolds number has evident effects on the local wind force coefficients, although its influence on the Strouhal number is negligible. This combined study of field measurements and wind tunnel test aims to enhance the understanding of the aerodynamic forces on high-rise buildings during strong windstorms and provide useful information for the wind-resistant design of supertall buildings.