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Item type:Publication, Access status: with files , Scouring induced by a confined propeller jet nearby a vertical quay structure : scale model tests(Norwegian University of Science and Technology, Department of Marine Technology, 2024-04-04); ; The turbulent jet generated by a ship propeller may cause damages to sediment beds due to its erosive potential. When local erosion or scour appears nearby harbour infrastructure like berthing quay walls, the risk of failure increases. To further develop approaches for the determination of the scour depth and geometry at quay walls as a function of time, scale-model experiments were carried out in a flume using different boundary conditions. The temporal development of the scour geometry was obtained by scanning the bed at predefined time-steps using an array of 16 ultrasonic sensors. These measurements were supplemented by additional measurements using a Vectrino Profiler and the Structurefrom-Motion-Photogrammetry technique. The results from the tests show consistent relations between the measured maximum scour depth and the wall and bed clearance distances, respectively, as well as the rotational speed of the propeller. Contrary to the expectations according to published equations to estimate scour depths, the results obtained in this study show a direct linear dependency between the maximum scour depth and the wall clearance distances for all the tested boundary conditions. Moreover, the data also reveal a consistent functional relationship between the main scour hole dimensions and the eroded volume.Publicationtype: Conference Paper57 93 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Numerical study of propeller slipstream characteristics during berthing and unberthing maneuvers of a RORO vessel(Norwegian University of Science and Technology, Department of Marine Technology, 2024-04-04); ; ; ; For the investigation of the impact of the propeller slipstream on the port facilities, detailed analyses are carried out using a Reynolds-Averaged Navier-Stokes (RANS) method. The characteristics of the propeller flow field were studied, taking into account operating conditions during berthing and unberthing, interactions with the ship hull, quay wall and harbor bed. To obtain the necessary maneuvering data, information was extracted from the voyage data recorder (VDR) of a twin-screw RORO vessel during berthing and unberthing in the Port of Lubeck- ¨ Travemunde. Automatic identification system (AIS) and ¨ VDR data sets were collected and analyzed to identify conditions of interest for the numerical investigations. The vessel is equipped with two flap rudders and two bow thrusters. RANS simulations were performed for different rudder angles and number of revolutions of the main propellers (MPs) and transverse thrusters (TTs). The simulation results include unsteady velocity and pressure distributions in the flow field near the quay walls and harbor bed, considering different positions and orientations of the ship relative to the quay walls. The calculated maximum axial induced velocities are compared with those obtained using the semi-empirical formulae. In addition, the proper orthogonal decomposition (POD) on the harbor bed was used to evaluate the wall shear stress (WSS) and turbulent kinetic energy (TKE) to identify locations of maximum scour potential. The numerical results were thoroughly evaluated and analyzed to provide a robust basis for future extensions of the semi-empirical formulae.Publicationtype: Conference Paper114 119 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Volkswagen Group Logistics applies operations research to optimize supplier developmentVolkswagen Group Logistics (VWGL) is responsible for the logistics and supply processes of the automotive brands of the Volkswagen Group. In this context, supplier development is vital for efficient and reliable material flows between the process partners. In recent years, VWGL implemented a collaborative approach for supplier development in logistics wherein it is crucial to identify disrupting suppliers and apply improvement measures to increase their logistics performance. Against this background, VWGL initiated a project to examine how supplier development measures can be implemented efficiently to improve the overall logistics performance of VWGL’s supply base. This paper presents the developed operations research approach, which integrates Monte Carlo simulation and a knapsack model on the specific problem of supplier development. The approach consists of three stages: (1) data preparation, (2) measure evaluation, and (3) measure allocation. The approach is validated based on 18 existing less-than-truckload networks of VWGL. We find that, on average, considerable cost savings of 31% can be achieved throughout the networks compared with VWGL’s previous procedure. A new workflow facilitates our approach to lift its potential in practical application sustainably.Publicationtype: Journal Article166