Quantifying The Impact That Coxswain Behaviour Has on Whole Body Vibration - Simulator Trial

A common risk to personnel is from Whole Body Vibration (WBV) and shock when transiting at speed in heavy seas, and much research has been done by maritime organisations to reduce this risk and the associated health impacts. It is well known that coxswain ‘driving style’ can radically affect exposure levels for a given sea state and sustained transit speed. A data-driven approach to define what makes a good coxswain from a WBV perspective is currently being developed by the Naval Design Partnering team (NDP). In phase 1, a systematic coxswain behaviour tracking methodology has been developed and demonstrated using a motion platform-based fast craft simulator at MARIN. The performance of several experienced volunteer coxswains from MOD, RNLI and KNRM has been evaluated based on a set pattern of tests. The advantages of using the simulator, over a sea trial, have been demonstrated: it is more repeatable, more controllable, accurate and more accessible. The potential disadvantages of the approach are also discussed with reference to feedback gathered from coxswains. Analysis has shown effective throttle control is much more important than steering to reduce WBV. Several interesting trends in WBV reduction potential have been shown which it is thought, with further validation, could aid mission planning, mission execution and provide data for training autonomous feedback/control algorithms. Further work is required before the findings of this study can be fully exploited. These subsequent phases, which include sea trials, aim to provide validation and further evidence to support the initial findings.

Improving Bus Route Design Using Stop Balancing and Community-level Data

Public transportation brings numerous benefits to communities when it provides people with mobility and access to opportunities. A well-designed and widely utilized system is required for regions to gain access to these benefits. Transit policies must be efficient, relevant to their specific region, and take into consideration how residents utilize public transit. In this paper, we focus on the implications of bus stop balancing and route schedule design for the Madison Metropolitan Transit in Madison, Wisconsin. We discuss where populations live and work to illustrate potential servicing barriers that limit access to employment centers. We recommend adopting standardized spacing between stops of 1000-2500 feet to increase transit speed and reliability with a particular focus on areas with low car ownership. Finally, we spotlight how transit services can be expanded to include non-traditional commuters. The adoption of these suggested improvements will lead to faster transit times with improved reliability and more equitable service within the Greater Madison Area.

Bridge Safety Analysis Based on the Function of Exceptional Vehicle Transit Speed

Background: The road management agencies often prescribe very low-speed limits for exceptional vehicles transiting on the deck. These restrictions aim to reduce the dynamic effects due to the vehicle-bridge interaction because it is assumed that these effects increase with speed. However, sometimes, a reduction in speed increases the encounter probability of two exceptional vehicles travelling in opposite directions and this could compromise the safety of the bridge when the total masses of both vehicles exceed the bridge bearing capacity (or limit mass). Objective: While the literature has investigated the encounter probability in a theoretical way and has investigated the vehicle-bridge interaction, especially in terms of dynamic load increment, to the best of our knowledge, no study has investigated the conjunction probability of encounters and of exceeding the limit mass also by using real data. This paper aims to cover this gap by proposing an integrated model that computes the “Annual Probability of Failure” of the bridge, defined as the likelihood to exceed the “Limit Mass" of the deck when two opposite exceptional vehicles encounter. Methods: According to the probability theory, the “Annual Probability of Failure” can be obtained by multiplying the likelihood that during the reference year, at least once, two exceptional vehicles, travelling in two opposite directions (ascendant and descendant), will be simultaneously on the bridge deck (“Annual probability of encounter”) with the likelihood that the sum of the single masses of two exceptional vehicles randomly extracted from the sample, including the dynamic effects, exceeds the limit mass ml (“Probability of exceeding the limit mass”). Results: The results show that the probability of encounter increases with both the exceptional vehicles flow rate and the length of the span, whereas it decreases with the passing speed. The probability of exceeding the limit mass increases with speed. Nevertheless, by combining both the probabilities, these results suggest the existence of an “Optimal Speed”, which minimizes the “Annual Probability of Failure”. Conclusion: The existence of an “Optimal Speed” should be considered when defining the exceptional vehicle transit rules on bridges as well as the speed limit.

Influence of Ice Floe Shape and Distribution on Ship Resistance

Many ice basin tests have been performed on ships to assess the ice resistance of the hull in an ice floe field. During these tests, many parameters are studied, the most important of them being the transit speed, the thickness and the concentration of ice. Given the cost and the time required to carry out these basin test campaigns, it is imperative to keep the number of tests to the strict minimum, whilst still making it possible to draw conclusions about the sizing of the vessel. Hence, the influence of ice floe shape and their distribution in the field are generally not considered. A way to achieve sensitivity studies regarding these parameters is to use numerical simulations in addition to a basin test. There are few advanced numerical design tools available in the market, especially those able to cope with any kind of structure geometry and a large variety of ice interaction & failure mechanisms. In 2012 TechnipFMC, Cervval and Bureau Veritas initiated a common development program to offer a new tool for the design of offshore structures interacting with ice combining a variety of models and approaches such as analytical, numerical and empirical. This numerical tool called Ice-MAS (www.ice-mas.com) uses a multi-agent technology and has the possibility to combine, in a common framework, multiple phenomena from various natures and heterogeneous scales (i.e. drag, friction, ice-sheet bending failure, local crushing and rubble stack up). The study presented in this paper compares the simulation results for different ice floe fields not only in terms of concentration, maximum size of floe and their distribution but also in the way to generate the ice floe and its shape.

Experimental and Numerical Study for Drillship Moonpool Gap Resonances in Stationary and Transit Conditions in Wave Flume

Experimental and numerical studies are performed to investigate drillship moonpool gap resonance in both stationary and transit conditions in a wave flume. This study contains an assessment of the influence of size and depth of the moonpool on the gap resonance phenomenon. An openfoam-based computational fluid dynamics (CFD) model was established, and the numerical data show good agreement with measurements from the model tests. Both piston and sloshing mode gap resonances are clearly observed. This study shows that the gap resonance frequency and wave elevation response amplitude operator (RAO) inside the moonpool are dependent on its dimensions, and the transit speed of the drillship and wave direction significantly influences the characteristics of gap resonances. It is noticed that the nearness of the wave flume sidewalls significantly influences the piston and sloshing wave elevation RAO at certain frequencies regardless of moonpool length and draft.

Reduction of Drillship’s Moonpool Drag during Transit

Due to unrestricted ocean operations of a drillship, the importance of its transit speed is increasing in the viewpoint of reducing the downtime of offshore operations to a minimum. The open moonpool in a drillship induces additional drag when the ship is in transit. As an unfavorable moonpool design may cause the excessive drag, various ways to reduce the drag have been studied in theoretical and experimental methods. In this paper, an efficient way to reduce the drag due to moonpool and consequently increase the transit speed has been proposed. The reduction of moonpool drag has been focused as the moonpool drag is around 30% of total resistance of the drillship. A simple and efficient shape to mitigate excessive water motion inside the moonpool during drillship's transit is developed and verified through a series of model tests at SSMB (Samsung Ship Model Basin). Based on the observation during the model tests, it is found that a remarkable drag reduction can be achieved by the devised moonpool shape. Thus, it is concluded that more economical operation of a drillship such as the lower fuel consumption and increase of working time can be expected.

Research on Cold Core Eddy Change and Phytoplankton Bloom Induced by Typhoons: Case Studies in the South China Sea

The effects of 8 typhoons which passed by coldcore eddy (CCE) areas in the South China Sea (SCS) from 1997 to 2009 were observed and evaluated. The changes in the preexisting CCE acted upon by typhoons were described by eddy kinetic energy (EKE) and eddy available gravitational potential energy (EAGPE). The mechanical energy of CCE was estimated from a two-layer reduced gravity model. Comparing with the scenario that typhoon passes by the region without CCEs, the preexisting CCE area plays an important role in the increase of chlorophyll-a (chl-a) concentration in the CCEs impacted by the typhoons. The preexisting chl-a in CCE is about 25%~45% (8%~25%) of postexisting chl-a in CCE for higher (slower) transit speed typhoons. If the EAGPE of CCE increases greatly after typhoon passing by with slow transit speed, so does the chl-a in the CCE area. The EKE (EAGPE) changes of the preexisting CCE are in the order of O(1014~1015 J). EKE and EAGPE of CCE are dominantly enhanced by typhoon with slow transit speed (<3 m/s) and the posttyphoon EAGPE is always larger than posttyphoon EKE for 8 cases. The maximum EAGPE change of the preexisting CCE reaches5.11×1015 J, which was induced by typhoon Hagibis.

Post-Tsunami Evacuation Simulation Using 3D Kinematic Digital Human Models and Experimental Verification

A post-tsunami evacuation simulation using 3D kinematic digital human models (KDHs) and its experimental verification are addressed in the present study. Methods for carrying or assisting (transporting) injured people were experimentally investigated and the results were used for KDH data calibration to increase the accuracy of the simulations. It was found that, on flat ground, both the transit speed and the amount of time spent on intermittent rests were strongly affected by the load on the transporters. During ascent of stairways, the transit speed depended on the type of carry method being used and decreased in the order saddleback carry, two-person arm carry and slightly injured walking. Several KDH evacuee motion primitives were developed for stairway ascent to a tsunami evacuation tower. The simulation results show that the evacuation time was affected by the number of evacuees and the congestion due to the transportation of injured people. The developed simulation techniques can be effectively utilized in the planning of tsunami tower evacuation and predicting related crowd behavior.

UHF-RFID solutions for logistics units management in the food supply chain

The availability of systems for automatic and simultaneous identification of several items belonging to a logistics unit during production, warehousing and delivering can improve supply chain management and speed traceability controls. Radio frequency identification (RFID) is a powerful technique that potentially permits to reach this goal, but some aspects as, for instance, food product composition (e.g. moisture content, salt or sugar content) and some peculiarities of the production environment (high moisture, high/low temperatures, metallic structures) have prevented, so far, its application in food sector. In the food industry, composition and shape of items are much less regular than in other commodities sectors. In addition, a wide variety of packaging, composed by different materials, is employed. As material, size and shape of items to which the tag should be attached strongly influence the minimum power requested for tag functioning, performance improvements can be achieved only selecting suitable RF identifier for the specific combination of food product and packaging. When dealing with logistics units, the dynamic reading of a vast number of tags originates simultaneous broadcasting of signals (tag-to-tag collisions) that could affect reading rates and the overall reliability of the identification procedure. This paper reports the results of an extensive analysis of the reading performance of UHF RFID systems for multiple dynamic electronic identification of food packed products in controlled conditions. Products were considered singularly or arranged on a logistics pallet. The effects on reading rate and reading zone of different factors, among which the type of product, the number and position of antennas, the field polarization, the reader RF power output, the interrogation protocol configuration as well as the transit speed, the number of tags and their interactions were analysed and compared.