Modelling navigation in muddy areas through captive model tests

Many access channels and harbours suffer from sedimentation and formation of mud layers. To keep navigation safe and economic, extensive maintenance dredging is needed. Until now, the required level of dredging has always been determined by making use of the physical characteristics of the mud layer, which does not necessarily result in efficient dredging. Ship behaviour also matters, and knowledge of ship manoeuvrability can help to redefine the level of dredging required. A mathematical model of manoeuvring for simulation purposes, based on a comprehensive series of captive model tests, is presented, along with a selection of results.     

一种基于数据挖掘的GIS及在航海中的应用

根据聚类分析方法中密度凝聚的思想，提出一种新的复合聚类分析算法，进一步将这种算法用于地理信息系统的数据挖掘，并应用于船舶航线的自动设计。     

Modelling propeller and rudder induced forces acting on deep drafted vessels in muddy navigation areas

To assess the navigability of deep drafted vessels in muddy navigation areas a mathematical model has been built that takes into account the characteristics of the mud layer. This was achieved with the introduction of a fluidization parameter which determines the corresponding hydrodynamically equivalent depth above a solid bottom. As a result, the under keel clearance dependency of a given mathematical manoeuvring model can be reformulated in such way that the effect of any realistic muddy condition is included. In this article the modelling of the propeller and rudder induced forces and the implementation possibilities of the model will be discussed. It is concluded that the mathematical model, initially formulated for a 6,000 TEU container carrier, provides reliable predictions of the behaviour of larger container carriers and even fuller deep drafted ships.     

Sensitivity of the wheel–rail contact interactions and Dang Van Fatigue Index in the rail with respect to irregularities of the track geometry

This paper investigates the effects of the track geometry irregularities on the wheel–rail dynamic interactions and the rail fatigue initiation through the application of the Dang Van criterion, that supposes an elastic shakedown of the structure. The irregularities are modelled, using experimental data, as a stochastic field which is representative of the considered railway network. The tracks thus generated are introduced as the input of a railway dynamics software to characterise the stochastic contact patch and the parameters on which it depends: contact forces and wheelset–rail relative position. A variance-based global sensitivity analysis is performed on quantities of interest representative of the dynamic behaviour of the system, with respect to the stochastic geometry irregularities and for different curve radius classes and operating conditions. The estimation of the internal stresses and the fatigue index being more time-consuming than the dynamical simulations, the sensitivity analysis is performed through a metamodel, whose input parameters are the wheel–rail relative position and velocity. The coefficient of variation of the number of fatigue cycles, when the simulations are performed with random geometry irregularities, varies between 0.13 and 0.28. In a large radius curve, the most influent irregularity is the horizontal curvature, while, in a tight curve, the gauge becomes more important.     

Prediction of the forces acting on container carriers in muddy navigation areas using a fluidization parameter

To assess the safety of navigation in muddy areas, a comprehensive captive manoeuvring model test program was executed. Based on the results of this experimental program, a four-quadrant manoeuvring model was built with a separate set of coefficients for each combination of under-keel clearance and mud layer characteristics. The disadvantage of this model is that only conditions corresponding with the experimental ones can be simulated. A more consolidated mathematical model was needed. This was achieved with the introduction of a fluidization parameter that determines the corresponding hydrodynamically equivalent depth above a solid bottom. As a result, the under-keel clearance dependency of a given mathematical manoeuvring model can be reformulated in such way that the effect of any realistic muddy condition is included. In this article, the modelling of the hull forces, the propeller thrust and torque, and the forces acting on the rudder will be discussed.     

Uncertainty quantification in vehicle dynamics

ABSTRACT

This paper presents a review of various works that highlight the importance of introducing the variability of the road-track/vehicle system into dynamic simulations as soon as this latter is meant to be predictive. The first section of the paper presents the Uncertainty Quantification, Verification and Validation method (UQ-VV). This latter proposes tools to model uncertainties, to associate a confidence to the prediction of quantities of interest and to estimate the probability of occurrence of different scenarios. The method is illustrated by various examples mainly from the rail domain but also from the road sector. The second section summarises application examples of predictive modelling, robust optimisation and calibration.