Artificial Intelligence Machine Learning in Marine Hydrodynamics

Artificial Intelligence (AI) Support Vector Machine (SVM) learning algorithms have enjoyed rapid growth in recent years with applications in a wide range of disciplines often with impressive results. The present paper introduces this machine learning technology to the field of marine hydrodynamics for the study of complex potential and viscous flow problems. Examples considered include the forecasting of the seastate elevations and vessel responses using their past time records as "explanatory variables" or "features" and the development of a nonlinear model for the roll restoring, added moment of inertia and viscous damping using the vessel response kinematics from free decay tests as "features". A key innovation of AI-SVM kernel algorithms is that the nonlinear dependence of the dependent variable on the "features" is embedded into the SVM kernel and its selection plays a key role in the performance of the algorithms. The kernel selection is discussed and its relation to the physics of the marine hydrodynamic flows considered in the present paper is addressed.United States. Office of Naval Research (Grant N00014-17-1-2985

Multi-Factor Model of Correlated Commodity - Forward Curves for Crude Oil and Shipping Markets

An arbitrage free multi-factor model is developed of the correlated forward curves of the crude oil, gasoline, heating oil and tanker shipping markets. Futures contracts trading on public exchanges are used as the primary underlying securities for the development of a multi-factor Gaussian Heath-Jarrow-Morton (HJM) model for the dynamic evolution of the correlated forward curves. An intra- and inter-commodity Principal Component Analysis (PCA) is carried out in order to isolate seasonality and identify a small number of independent factors driving each commodity market. The cross-commodity correlation of the factors is estimated by a two step PCA. The factor volatilities and cross-commodity factor correlations are studied in order to identify stable parametric models, heteroskedasticity and seasonality in the factor volatilities and correlations. The model leads to explicit stochastic differential equations governing the short term and long term factors driving the price of the spot commodity under the risk neutral measure. Risk premia are absent, consistently with HJM arbitrage free framework, as they are imbedded in the factor volatilities and correlations estimated by the PCA. The use of the model is described for the pricing of derivatives written on inter- and intra-commodity futures spreads, Asian options, the valuation and hedging of energy and shipping assets, the fuel efficient navigation of shipping fleets and use in corporate risk management.Massachusetts Institute of Technology. Center for Energy and Environmental Policy Researc

VELOS : a VR platform for ship-evacuation analysis

Virtual Environment for Life On Ships (VELOS) is a multi-user Virtual Reality (VR) system that aims to support designers to assess (early in the design process) passenger and crew activities on a ship for both normal and hectic conditions of operations and to improve ship design accordingly. This article focuses on presenting the novel features of VELOS related to both its VR and evacuation-specific functionalities. These features include: (i) capability of multiple users’ immersion and active participation in the evacuation process, (ii) real-time interactivity and capability for making on-the-fly alterations of environment events and crowd-behavior parameters, (iii) capability of agents and avatars to move continuously on decks, (iv) integrated framework for both the simplified and advanced method of analysis according to the IMO/MSC 1033 Circular, (v) enrichment of the ship geometrical model with a topological model suitable for evacuation analysis, (vi) efficient interfaces for the dynamic specification and handling of the required heterogeneous input data, and (vii) post-processing of the calculated agent trajectories for extracting useful information for the evacuation process. VELOS evacuation functionality is illustrated using three evacuation test cases for a ro–ro passenger ship

Computation of Nonlinear Hydrodynamic Loads on Floating Wind Turbines Using Fluid-Impulse Theory

A hydrodynamics computer module was developed to evaluate the linear and nonlinear loads on floating wind turbines using a new fluid-impulse formulation for coupling with the FAST program. The new formulation allows linear and nonlinear loads on floating bodies to be computed in the time domain. It also avoids the computationally intensive evaluation of temporal and spatial gradients of the velocity potential in the Bernoulli equation and the discretization of the nonlinear free surface. The new hydrodynamics module computes linear and nonlinear loads — including hydrostatic, Froude-Krylov, radiation and diffraction, as well as nonlinear effects known to cause ringing, springing, and slow-drift loads — directly in the time domain. The time-domain Green function is used to solve the linear and nonlinear free-surface problems and efficient methods are derived for its computation. The body instantaneous wetted surface is approximated by a panel mesh and the discretization of the free surface is circumvented by using the Green function. The evaluation of the nonlinear loads is based on explicit expressions derived by the fluid-impulse theory, which can be computed efficiently. Computations are presented of the linear and nonlinear loads on the MIT/NREL tension-leg platform. Comparisons were carried out with frequency-domain linear and second-order methods. Emphasis was placed on modeling accuracy of the magnitude of nonlinear low- and high-frequency wave loads in a sea state. Although fluid-impulse theory is applied to floating wind turbines in this paper, the theory is applicable to other offshore platforms as well.United States. Department of Energy (National Renewable Energy Laboratory. Contract DE-AC36-08GO28308)United States. Department of Energy. Office of Energy Efficiency and Renewable Energy. Wind and Water Power Technologies OfficeMassachusetts Clean Energy Cente

Karhunen-Loeve representation of stochastic ocean waves

A new stochastic representation of a seastate is developed based on the Karhunen–Loeve spectral decomposition of stochastic signals and the use of Slepian prolate spheroidal wave functions with a tunable bandwidth parameter. The new representation allows the description of stochastic ocean waves in terms of a few independent sources of uncertainty when the traditional representation of a seastate in terms of Fourier series requires an order of magnitude more independent components. The new representation leads to parsimonious stochastic models of the ambient wave kinematics and of the nonlinear loads and responses of ships and offshore platforms. The use of the new representation is discussed for the derivation of critical wave episodes, the derivation of up-crossing rates of nonlinear loads and responses and the joint stochastic representation of correlated wave and wind profiles for use in the design of fixed or floating offshore wind turbines. The forecasting is also discussed of wave elevation records and vessel responses for use in energy yield enhancement of compliant floating wind turbines.ALSTOM (Firm)Ente nazionale per l'energia elettricab_TE

Coupled Dynamic Modeling of Floating Wind Turbine Systems: Preprint

This article presents a collaborative research program that the Massachusetts Institute of Technology (MIT) and the National Renewable Energy Laboratory (NREL) have undertaken to develop innovative and cost-effective floating and mooring systems for offshore wind turbines in water depths of 10-200 m. Methods for the coupled structural, hydrodynamic, and aerodynamic analysis of floating wind turbine systems are presented in the frequency domain. This analysis was conducted by coupling the aerodynamics and structural dynamics code FAST [4] developed at NREL with the wave load and response simulation code WAMIT (Wave Analysis at MIT) [15] developed at MIT. Analysis tools were developed to consider coupled interactions between the wind turbine and the floating system. These include the gyroscopic loads of the wind turbine rotor on the tower and floater, the aerodynamic damping introduced by the wind turbine rotor, the hydrodynamic damping introduced by wave-body interactions, and the hydrodynamic forces caused by wave excitation. Analyses were conducted for two floater concepts coupled with the NREL 5-MW Offshore Baseline wind turbine in water depths of 10-200 m: the MIT/NREL Shallow Drafted Barge (SDB) and the MIT/NREL Tension Leg Platform (TLP). These concepts were chosen to represent two different methods of achieving stability to identify differences in performance and cost of the different stability methods. The static and dynamic analyses of these structures evaluate the systems' responses to wave excitation at a range of frequencies, the systems' natural frequencies, and the standard deviations of the systems' motions in each degree of freedom in various wind and wave environments. This article in various wind and wave environments. This article explores the effects of coupling the wind turbine with the floating platform, the effects of water depth, and the effects of wind speed on the systems' performance. An economic feasibility analysis of the two concepts was also performed. Key cost components included the material and construction costs of the buoy; material and installation costs of the tethers, mooring lines, and anchor technologies; costs of transporting and installing the system at the chosen site; and the cost of mounting the wind turbine to the platform. The two systems were evaluated based on their static and dynamic performance and the total system installed cost. Both systems demonstrated acceptable motions, and have estimated costs of $1.4-$1.8 million, not including the cost of the wind turbine, the power electronics, or the electrical transmission

Surface Waves and their Interaction With Floating Bodies

Introduces the physics and mathematical modeling of linear and nonlinear surface wave interactions with floating bodies, e.g., ships and offshore platforms. Surface wave theory, including linear and nonlinear effects in a deterministic and random environment. Ship Kelvin wave pattern and wave resistance. Theory of linear surface wave interactions with floating bodies. Drift forces. Forward speed effects. Ship motions and wave-induced structural loads

Study of the greek strains of Cucumber mosaic virus: cucumber mosaic virus (CMV)

The biodiversity of cucumber mosaic virus (CMV) has been thoroughly investigated but some information, as the phylogenetic relationship among its isolates or natural population is still missing. So the application of different techniques for isolates differentiation and characterization on a wide range of isolates in combination with dendrogrms from bibliographic data can provide useful information for research, diagnosisi, plant breeding and epidemology. Here we established the most appropriate fuidelines for detecting and typing CMV isolates according to the new phylogenetic relationship, which is I_a, I_b, II. The same study we have done with CMV satellites. The conclusions obtained from the above work were used for typing national CMV and satellite populations on field surveys in Southern Greece. The results of this survey, we used to make secisions to the selection of propper "vacines' for the bioconrol of CMV epidemics in Greece. The results were promising for commercialization of this biocontrol technology in Greece. The last part of our study targeted to the genetic microeterogeneaty of CMV isolates that means differences in one or a few nucleotides in relation to their biological properties. The results showed that a single nucleotide change in the CMV genome (CP) may affect. the bilogical exression of an isolate dramatically. The criteria by which someone could detect this kind of biodiversity are discussed.Η βιοπαραλλακτικότητα του ιού του μωσαϊκού της αγγουριάς (Cucumber mosaic virus, CMV) έχει μελετηθεί εκτενώς τα προηγούμενα χρόνια. Ωστόσο τα νέα δεδομένα καθώς και η εξέλιξη των τεχνικών δείχνουν οτι ακόμα υπάρχουν κενά. Στην εργασία αυτή ορίζουμε μια κατευθυντήρια γραμμή για την μελέτη της βιοπαραλλακτικότητας των απομονώσεων του ιού χρησιμοποιώντας κατάλληλες τεχνικές και δενδρογράμματα. Ετχι ορίστηκε σαφώς η νέα φυλογεννετική σχέση των απομονώσεων του ιού Ι_α,Ι_β, ΙΙ καθώς και οι τεχνκές με τις οποίες μπορούμε να ομαδοποιήσουμε ως προς αυτή τις απομονώσεις του ιού. Τα συμπεράσματα από αυτή την εργασία χρησιμοποιήθηκαν για να ομαδοποιηθουν οι φυσικοί πληθυσμοί του ιού κατά την διάρκεια μιας επισκοπήσεως αγρών στην Νότιο Ελλάδα. Παρόμοια κινηθήκαμε για να ομαδοποιήσουμε τις παραλλαγές του δορυφόρου του ιού. Ακολούθως τα δεδομένα από αυτή την επισκόπηση χρησιμοποιήθηκαν για να επιλέξουμε το εμβόλιο με τα καταλληλότερα χαρακτηριστικά το οποίο θα εξασφάλιζε την καλύτερη απατελεσματικότητα για την καταπολέμηση των νόσων που προκαλούνται από τον ιό με την μέθοδο του προεμβολιασμού. Τα αποτελέσματα από την εφαρμογή της μεθόδου κρίθηκαν ικανοποιητικά ακκόμα και για την εμπορευματοποίηση αυτή. Στο τελευταίο κεφάλαιο μελετάται η μικροετερογένεια του γενώματος του ιού η οποία οφεόλεται σε μια ή λίγες αλλαγές βάσεων σε συσχέτιση με τις βιολογικές ιδιότητες του ιού. Τα αποτελέσματα έδειξαν οτι μιά αλλαγή νουκλεοτιδίου στο γόνο της καψιδιακής πρωτείνης μπορεί να επηρεάσει δραματικά την βιολογική έκφραση μιας απομονώσεως. Εξετάστηκαν τα κριτήρια με τα οποία κάποιος μπορεί να ανιχνεύσει τέτοιες μικροδιαφορές βιοπαραλλακτικότητας