A new rock cutting and splitting method for hard-rock excavation: methodology, scaled model test and numerical modelling, and field validation

Experimental and numerical study of dynamic responses of a new combined TLP type floating wind turbine and a wave energy converter under operational conditions

Validation of a TLP wind turbine numerical model against model-scale tests under regular and irregular waves

An attempt to evaluate the impact noise due to rail joints was carried out by using the scale model tests. The derivation of law of similarity related to wheel/rail noise was made and actual phenomena can be estimated by the scale model tests. Through the measurement with an impact hammer, the vibratory characteristics of track and wheel are estimated in the scale model test with the law of similarity and they are compared with that of the actual track and wheel. It is found that overall trends are well-estimated. In the running test it is shown that the acoustic power of the impact noise is proportional to the power of 2.3 of wheel speed and it is possible that impact noise due to rail joints is simulated by the scale model test. To investigate a potential for impact noise reduction, the relation between impact noise and track parameters, e.g. a soft rail pad, is examined in the scale model test. It is indicated that soft rail pad leads to the reduction of the impact noise and sleeper vibration, though rail vibration is increased. The scale model test may also evaluate the properties associated with rolling noise. And in the vibration of the rail and sleeper the results obtained in the scale model test show a good agreement with those in the field test.

Experimental and numerical study of hydrodynamic responses of a new combined monopile wind turbine and a heave-type wave energy converter under typical operational conditions

A man-computer system for simulating upending motions of offshore platforms has been used to study one of the largest tower structures designed by the industry to date, and the analytical results have been verified by scale model tests. The man-computer system combines the man's insight and experience with a highly interactive computer's accuracy and speed, permitting synthetic yet adequate understanding of complicated hydrodynamic phenomena. Scale model tests have demonstrated that the man computer approach to understanding upending motion is valid, and have substantiated the concept that an interactive analytical system based on rudimentary physical principles can contribute significantly to planning a far-reaching scale model test program. 1. INTRODUCTION 1.1 Tower Upending Studies The development of petroleum reserves in the far offshore has brought new demands on the designs of the fixed platform structure that supports offshore activities. Greater water depths, more severe environmental conditions and increased operating deck loads demanded by the economics of development and production have combined to make the platform structure not only taller and wider, but far heavier than once envisoned or considered practical. The erection of the larger platform has acquired a new complexion as well. Because of its size, no longer can the structure be hoisted at its top by a' barge crane and allowed to sink to vertical. Rather, a ballasting scheme must be developedand carefully tested to effect a controlled upending motion that will jeopardize neither the tower nor the support vessels attending the erection operation. Thus, from a structural configuration with sufficient integral buoyancy to float the tower, a scale model is usually used to test in a tank a predefined erection operation, the model performance generally being accepted as representing how the prototype will respond. If the original design was good, the dual requirements of a structurally sound configuration and a hydrostatically stable and controllable body will have been simultaneously achieved. This good fortune, however, is sometimes not the case: while a design might satisfy all in place structural requirements, the upending operation might be hazardous or not possible at all. Thus, a new design cycle might be necessary. Analytical studies of upending motion by computer have become more common throughout the industry, both to assist in designing a configuration with adequate integral buoyancy, and to predict an upending trajectory and floating stability. Analytical studies provide the structural engineer and naval architect an opportunity to experiment with different structural configurations, to test in a preliminary way whether the structure can be upended, and to specify that a scale model of only a feasible structure be built. The naval architect especially benefits from analytical studies in that a broader based model testing program can be planned in advance; that is, he can determine what should and what should not be studied in the model test program. With a comprehensive program planned, he can perform only those tests that yield important information about upending not revealed by the analytical investigation.

The state-of-the-art deepwater offshore basin is presently under construction at Shanghai Jiao Tong University. Its current generation system is considered as one of the most challenging and crucial equipments in the basin. Hydraulic performances of the current generation system in the new deepwater offshore basin are investigated using both CFD and experimental methods. 3D numerical models are applied and calculated. Besides a 1:10 scaled model test is also carried out to validate the numerical simulation. Uniformities of the flow field in the basin, including horizontal and vertical current profiles with various mean values are studied in detail. In addition turbulence levels are also analyzed. Satisfactory agreements can be achieved between numerical calculation and model test. It is concluded that hydraulic performances of current generation system in the new basin can satisfy the requirements of model tests in deepwater. Uniform and constant current field can be obtained in measuring area. Besides various typical vertical current profiles in deep water, including uniform profiles and sheared profiles etc. can be modeled. And suggestions are also presented which will be helpful instructions for the design and operation of the new deepwater offshore basin.

Over the past 6 years, the University of Maine (UMaine) has been an active contributor in research and scale-model testing of floating offshore wind turbines (FOWTs). This paper serves to share the evolution of UMaine’s scale-model testing pedigree by exploring the various test campaigns at a high level, culminating with the design validation of the VolturnUS floating platform. These model test campaigns have each provided key insights into the behavior of FOWT platforms as well as improving the ability to perform model tests of FOWTs. In 2011, the UMaine-led DeepCwind Consortium carried out 1/50-scale model tests of a generic tension leg platform (TLP), a semi-submersible (semi), and a spar-buoy (spar) floating platform at the Maritime Research Institute Netherlands (MARIN) test facility. The designs were Froude-scaled and supported a scaled version of the 5-MW National Renewable Energy Laboratory (NREL) offshore research turbine. Data from these tests has been used extensively for numerical simulation validation efforts using NREL’s computer-aided engineering software FAST and laid the foundation for UMaine’s design efforts on VolturnUS. In 2013, UMaine conducted another test campaign at MARIN using the original semi-submersible from 2011 with an improved turbine as well as a 1:50-scale model of the VolturnUS concrete semi-submersible design. The improved DeepCwind semi-submersible data is currently being utilized in the validation of a large number of other analysis codes as part of the International Energy Agency’s OC5 project. In 2015, UMaine opened its own Wind/Wave test facility, the Alfond Wind/Wave Ocean Engineering Laboratory (W2). Utilizing this new facility, UMaine tested the 1:50-scale model DeepCwind semi-submersible, repeating the tests from MARIN, to validate the experimental equipment and procedures as well as demonstrate the capability of the W2. In 2016 UMaine carried out testing of a 1:52-scale model of the 100% design of the VolturnUS with a 6-MW topside as a final design validation to support the US Department of Energy-supported, full-scale Aqua Ventus demonstration project scheduled to be connected to the grid in 2019. A newly designed 6-MW scale model turbine was used in this test and the performance-matched turbine design methodology is described. Selected results from the test campaign and preliminary numerical comparisons are discussed as well as key lessons learned from the model test campaigns are presented.

A geosynthetic-reinforced pile-supported (GRPS) embankment that consists of embankment fill, geosynthetic, piles, and foundation soils is a complex soil–structure system. Its key load transfer mechanisms include soil arching and tensioned membrane effects and subsoil resistance. Type of embankment fill (cohesive or cohesionless) and type of pile (end-bearing or floating) are expected to affect these load transfer mechanisms; however, their influence has not been well investigated. Six scaled model tests were conducted in this study to investigate the influence of the embankment fill properties, the clear spacing of pile caps, and the pile type on soil arching and tensioned membrane effects. This study used cohesive and cohesionless embankment fills and end-bearing and floating piles. The test results show that the cohesive embankment fill strengthened the soil-arching effect, increased the pile efficacy, and reduced the settlements of the subsoil between pile caps and the embankment crest under the same load as compared with the cohesionless embankment fill. The soil arching-effect was inversely proportional to the clear spacing of pile caps. Soil arching initiated at a low ratio of the embankment height to the clear spacing of pile caps (i.e. 0.5 to 0.7) and became stable at a higher ratio (i.e. 1.1 to 1.5). The embankment height when the soil arching becomes stable is also referred to as the critical height, at which full soil arching is formed. The measured vertical earth pressures at the edges of the pile caps were higher than those in the middle of the pile caps in all six model tests. When the end-bearing or floating piles were used, the loads on the piles (i.e. the pile efficacy) increased during the construction of the embankment. However, when the floating piles started to penetrate into the underlying soil under a higher load; the pile efficacy decreased with the embankment and the surcharge load. Floating piles resulted in less soil arching and larger settlement.

This paper presents experimental results of WindFloat 1 platform and comparisons with the numerical model developed by Principle Power. The WindFloat platform is designed to support multi-megawatt wind turbines. A full-scale prototype was installed offshore Portugal from 2011 to 2016, and produced 17GWh into the Portuguese grid. An extensive monitoring system was installed, including a wave rider buoy, 6-degrees of freedom measurement devices, anemometers, strain gauges, turbine monitoring instruments. Important results obtained during the measurement campaign are described in this paper. These include power predictions, turbine and tower loads, and platform motions. Comparison with numerical simulations are also provided. The numerical analysis methodology includes fully coupled simulations, based on Orcaflex, a commercially available state-of-the-art software to compute the hydrodynamic response of floating systems, combined in the time-domain with FAST, a well-established numerical tool for the design of wind turbines. Results of these comparisons show that the numerical tools are fit for purpose, and were used to calibrate some hydrodynamic coefficients that cannot be obtained accurately with numerical analysis or scaled model tests.

The assessment of liquid flow patterns forming due to a submerged pump intake, and its associated gas entrainment phenomena, need to be reliable and accurate for a number of design applications. The use of conservative correlations can lead to gross over-design or, inaccurate predictions in certain complex suction arrangements. Scale model testing often has scale effects which leads engineers to rely on other analysis methods. Simplified analyses can fail to correctly predict the vortical features near the suction intakes and associated gas entrainment, which may lead many applications to use Computational Fluid Dynamics (CFD) as a method for intake flow predictions. However, reliable assessment of gas entraining into a suction intake with high Reynolds number internal flow, involves several physical modeling and numerical challenges. An accurate assessment requires, (1) a transient model, (2) proper resolution in the wall boundary layers near the intakes, (3) resolution of the swirl in the vortical structures, and (4) modeling of the laminar-to-turbulent transitional effects in the vicinity of the intake. This paper addresses and evaluates the performance of several turbulence model options and modifications within a CFD code for the assessment of intake flow. The results presented in this paper, are compared against published experimental data on vortical flow patterns at intakes, to identify physical and numerical modeling needs for such assessments. The results show that while, adequately resolved meshes, and low Reynolds number RANS (Reynolds Averaged Navier Stokes) turbulence models can capture the location and relative strength of vortices, the results for flow details inside the vortical structures identified need to be interpreted carefully, considering the relevant flow physics and modeling limitations. The turbulence model modifications proposed involve curvature correction and scale adaptiveness.

As part of the process of deploying new floating offshore wind turbines, scale model testing is carried out to de-risk and verify the design of novel foundation concepts. This paper describes the testing of a 1:43 Froude-scaled model of the TetraSpar Demo floating wind turbine prototype that shall be installed at the Metcentre test facility, Norway. The TetraSpar floating foundation concept consists of a floater tetrahedral structure comprising of braces connected together through pinned connections, and a triangular keel structure suspended below the floater by six suspension lines. A description of the experimental setup and program at the Alfond W2 Ocean Engineering Lab at University of Maine is given. The objective of the test campaign was to validate the initial design, and contribute to the development of the final demonstrator design and numerical models. The nonlinear hydrodynamic characteristics of the design are illustrated experimentally and the keel suspension system is shown to satisfy design criteria.

Seismic isolation system can be an effective alternative to protect the NPPs (Nuclear Power Plants) against to the strong seismic events. Therefore, some research activities to adopt the seismic isolation concept to the design of the next generation NPPs have been progressed for last few years in Korea. Nuclear structures, secondary systems and components must remain undamaged during and after the SSE (Safe Shutdown Earthquake) event. The seismic events will cause the high seismic response in the stiff structural systems and extremely high demands of deformation on the safety-related secondary systems like piping components. If seismic isolation devices are installed in nuclear power plant for seismic stability, safety against seismic load of power plant may be improved. But in some equipment, seismic risk may increase because displacement may become greater than before installation of seismic isolation device. Therefore, it is necessary to select the equipment in which seismic risk increases due to increase in displacement by the installation of seismic isolation device, and perform a research on seismic performance evaluation of equipment. In this study, one of the typical Korean NPPs assuming the application of seismic isolation devices, and one of the interface piping systems which introduced this NPP was used for seismic analysis. The numerical models include representations of seismic isolation devices. In order to validation of numerical piping system model and defining failure mode & limit states, quasi-static loading tests were conducted on the scale-modeled piping components before the analysis procedures. The fragility analysis was performed by using results of inelastic seismic response analysis. Inelastic seismic response analysis was carried out by using shell finite element model of piping system considering internal pressure. The implicit method was used for the direct integration time history analysis. Generally, PGA (Peak Ground Acceleration) was used for seismic intensity of fragility curve. However, in the case of the displacement sensitive system, lateral displacement could be an useful alternative measure for estimation of probability of failure. Thus in this paper, fragility curves were plotted based on maximum relative displacement.

Deepwater offshore structures such as semi-submersible platforms suffer powerful ocean waves due to their location and site condition. The long distance away from the shore also brings many difficulties to energy supply for the platform operation. How to reduce the response of the platform and convert the wave energy into electrical power is a meaningful topic. In this paper, a tuned heave plate system (THP) is presented and designed to be employed on a semi-submersible platform for heave motion suppression and energy harvesting. This THP system is composed of spring supports, a power take-off system (PTO), and a heave plate. The PTO system is a permanent magnet linear generator (PMLG), which could directly convert the kinetic energy of the heave plate into electronic power. The stiffness of the spring supports is designed based on the principle of the tuned mass damper (TMD). The numerical model of the platform and the THP system is established according to the hydrodynamic analysis results of the platform. The model is tested and modified by scale model tests on the platform in the wave tank. A parameter study, including the size, tuned period, and damping ratio of the THP system, is conducted systematically based on the numerical model. The optimal parameters of the THP are selected due to the maximum heave motion reduction under severe wave conditions in South China Sea. The performance of the semi-submersible with and without the THP system under different wave conditions is analyzed. It is demonstrated that this novel tuned heave plate system could reduce the heave motion of the semi-submersible platform significantly and generate considerable power, which makes the THP system have a broad prospect for development.

The stability of rock pillars between twin tunnels is a critical aspect of tunnel design and construction. To ensure the stability of rock pillars between twin tunnels, this study employ numerical modeling to assess pillar stability based on excavation method, tunnel geometry, determine pillar length based on rock mass quality, and quantify deformation, stress, and zone of influence of twin tunnels. To explore the role of rock mass quality in influencing pillar stability, the study considers factors such as rock strength, intactness, and discontinuity characteristics. Numerical modeling simulates the excavation process, considering the effects of rock mass properties, in situ stress conditions, and excavation methods. The results of the numerical simulations provide valuable insights for optimizing rock pillar design and construction practices for twin tunnels.

Environmental impact of electricity production has come under increasing international scrutiny over the last few decades. In particular, fossil fuel-fired power plants constitute a significant portion of the world’s carbon dioxide emissions. One of the main internal energy-consuming components in a thermal power plant is the main boiler feedwater pump, and its efficiency is a contributor to overall plant efficiency. This paper reports the design optimization of a 30 MW multistage, double-case, volute pump in order to increase overall efficiency by at least three percentage points. The six stage barrel pump produces 3865 m (12680 ft) of head at a capacity of 2750 m3/hr (12100 USGPM) at a speed of 4665 RPM. The machine is installed at the coal-fired supercritical Nuon Hemweg 8 power station in Amsterdam, the Netherlands, as the main boiler feedwater pump. The design study employed Computational Fluid Dynamics (CFD) to identify energy losses and evaluate design iterations. This paper describes the optimization of several individual components, including volutes, short and long crossovers, suction box and final discharge. Scaled model tests were conducted on series stages to validate the CFD results. Additional design constraint that had to be taken into account was that new hardware had to be installed within the limits of the existing pressure boundary components, sealing device and bearing design, which confines the design space considerably. Hardware has, at the time of writing this paper, entered production and is planned to be installed during a May 2013 plant outage.