4 research outputs found

    On Prediction of Wave-Induced Loads and Vibration of Ship Structures with Finite Volume Fluid Dynamic Methods

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    Rational assessment of wave loads for ultimate strength of ship structures requires appropriate numerical tools capable of dealing with physical phenomena related to severe environmental conditions. In addition to low frequency wave loads, vibration caused by wave action adds to the total wave loading of the primary hull structure. The thesis presents a numerical method for determining ship hull structural loads due to the action of waves, including the contributions from vibration of the fundamental vertical vibration modes of the hull. The proposed numerical method is based on a coupled numerical solution of the dynamics of fluid and structure. The fluid dynamics method is based on solution of the Reynolds-Averaged Navier-Stokes (RANS) equations combined with a multiphase fluid formulation, whereas the structural dynamics method relies on a simplified representation of the hull girder with a finite element beam. The fluid dynamics method is in principle well suited to capture nonlinear flow features relevant for time domain simulation of ships in severe or extreme environments due to the capability of capturing complex flows including highly disturbed free surfaces. Wave-wave interaction, wave breaking and wave impacts are implicitly accounted for. The coupled method presented here implicitly and consistently accounts for complex resonant excitation of hull girder vibrations in waves as well as impulsive vibratory excitation due to slamming. Fundamental tasks of the work documented herein are the improvement and validation of the coupled numerical method, including investigations of required computational accuracy and estimations of numerical uncertainties. Available computational procedures for obtaining statistical properties of ship loads in irregular waves are adopted to the needs of the computationally expensive numerical method, and applied in case studies

    Design decisions for a real time, alcohol craving study using physio- and psychological measures

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    The current study was a pilot for an alcohol craving monitoring study with a biosensor (E4 wristband) and ecological momentary assessment (EMA) smartphone app. The E4 wristband was evaluated on compliance rates, usability, comfort and stigmatization. Two EMA methodologies (signal- and interval-contingent design) were compared on data variability, compliance and perceived burden. Results show that both EMA methodologies captured variability of craving and compliance rates were between medium to low. The perceived burden of the designs was high, in particular for the signal-contingent design. Participants wore the wristband ranging from occasionally to often and the usability was rated good. Many participants reported frequent questioning about the bracelet, which they indicated as positive. However, addicted individuals are expected not to appreciate this attention, we therefore propose to provide them with coping strategies. Efforts should be made to increase compliance, we therefore propose the interval contingent design with micro incentives
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