This paper analyses a set of velocity time histories which were obtained at fixed point in the bottom boundary layer tidal stream, 5 m from seabed, and where mean flow reached 2.5 s −1 . Considering two complete cycles near spring tide, streamwise turbulence intensity during non-slack was found to be approximately 12–13%, varying slightly between flood ebb tides. The ratio that transverse vertical intensities is typically 1 : 0.75 0.56, respectively. Velocity autospectra computed maximum...

An improved characterisation of the hydrodynamic blade loads due to onset turbulence is essential in order mitigate premature failures, reduce excessive levels conservativeness and ultimately ensure commercial viability tidal turbines. The literature focussing on fast flowing streams unsteady that are subsequently imparted rotors has previously been very limited. However, increased activity energy community led new investigations insights which reported this paper. It found through use...

An improved characterisation of the unsteady hydrodynamic loads on tidal turbine blades is necessary to enable more reliable predictions their fatigue life and avoid premature failures. To this end, paper presents a set blade-root bending moment responses for scale-model subjected an planar forcing in towing tank. In cases where boundary layer was believed be attached outer sections blade, out-of-plane amplitude flow up 15% greater than corresponding load measured steady exhibited phase-lead...

Accurate predictions of surface waves and subsequent wave-induced vessel motion have the potential to improve safety efficiency for a wide range offshore operations, such as active control wave energy converters floating wind turbines. In this paper, an Auto-Regressive model is proposed predict motions based on measured time sequences at particular location. Based numerically synthesized data, it shown that band-pass filtering with single cut-off frequency can accuracy predictions. These...

Accurate surface wave predictions have the potential to greatly enhance safety and efficiency of many offshore applications, such as active control energy converters floating wind turbines. However, real-time prediction becomes increasingly challenging when large directional spreading is considered. To address this challenge, present study introduces a machine learning model that utilizes an Artificial Neural Network (ANN) for predicting moderate waves. Linear, short-crested time histories...

Surface wave predictions for several periods in advance are crucial optimizing a wide range of offshore applications. This work focuses on the potential application active control energy converters (WECs), which can dramatically enhance efficiency power generation. Field tests were conducted Southern Ocean Albany, Western Australia. We compared two prediction models: physics-based algebraic model and machine learning-based Artificial Neural Network (ANN) model. Although standard ANN is found...

The wave-induced resonant flow in a narrow gap between stationary hull and vertical wall is studied experimentally numerically. Vortex shedding from the sharp bilge edge of gives rise to quadratically damped free surface response gap, where damping coefficient approximately independent wave steepness frequency. Particle image velocimetry direct numerical simulations were used characterise dynamics explore influence discretisation measurements computations. Secondary separation was identified...

The structure of turbulence in a rapid tidal flow is characterized through new observations fundamental statistical properties at site the UK which has simple geometry and sedate surface wave action. mean Sound Islay exceeded 2.5 m s-1 turbulent boundary layer occupied majority water column, with an approximately logarithmic velocity profile identifiable close to seabed. anisotropic ratios, spectral scales higher-order statistics generally agree well values reported for two-dimensional open...

Abstract A hull-pendulum system is introduced to investigate the roll damping of a hull through decay. Compared conventional decay tests, this method can reduce KC number (roll amplitude) and more conveniently allows for range oscillatory frequencies be investigated. Further, setup experiments with low mechanical friction at cost. The study primarily focuses on flow separation vortex shedding. Two types sharp bilges were investigated: square bilge round equipped keel. results demonstrate...

Wind tunnel measurements of the incident turbulent velocity fields and axial forces on a horizontal axis turbine porous disc analogues are reported. The models were tested in both simulated atmospheric boundary layer (ABL) grid turbulence, allowing for range turbulence length scale to rotor diameter ratios be considered. A theoretical framework account combined effect distortion potential flow blocking induction zone is presented. In case very large length-scale ratios, where effects...

The application of computational fluid dynamics (CFD) and overset meshing, to predict the roll response ships is significant interest ocean engineering. Despite its growing popularity, it remains essential validate efficacy computations using meshing for modelling strong vortex flows, particularly in complex geometric scenarios involving relative motion narrow gaps, deriving damping coefficients. This study presents a new series results which solvers methods open-source CFD code, OpenFOAM,...

Phase-resolved predictions of surface waves can be used to optimize a wide variety marine applications. In this paper, we compare obtained using two independent methods for field data, with horizons sufficient control wave energy converters. The first method is physics-based prediction. method, set optimal representative angles, an optimization algorithm given time histories buoy motion in 3D, are forward propagation based on linear theory. second machine learning Artificial Neural Network...

The changes in spectra and intensities of the streamwise component turbulent velocity are calculated inflow a turbine rotor. flow is initially limit when turbulence small scale compared with rotor diameter. Rapid distortion theory (RDT), Batchelor & Proudman ( Q. J. Mech. Appl. Maths , vol. 7 (1), 1954, pp. 83–103) (BP), for small-scale combined effect fluctuating potential field on caused by direct interaction incident as sheet resistance. A second computation then carried out larger...

Abstract In recent years, floating wind has been attracting increasing attention due to its ability be deployed in greater water depths, which are usually associated with higher energy. At present, technology is more expensive than fixed offshore wind, cost being driven by challenges such as the extended length of mooring lines, installation anchors deep etc. For become competitive it will necessary devise methods that able bring down overall addressing areas these. This paper presents a...