Route optimization in dynamic flow fields

avigation system for the North Sea and Wadden Sea

Master thesis (2019)

Authors

J.P. van Halem Civil Engineering & Geosciences

Contributors

J.D. Pietrzak Environmental Fluid Mechanics - CEG (supervisor 1)
G.J. de Boer Environmental Fluid Mechanics - CEG (supervisor 1)
M. Verlaan Mathematical Physics - EEMCS (supervisor 1)
M. van Koningsveld Rivers, Ports, Waterways and Dredging Engineering - CEG (supervisor 1)
F. Baart Rivers, Ports, Waterways and Dredging Engineering - CEG (supervisor 1)
Firmijn Zijl Deltares (supervisor 1)
Faculty
Civil Engineering & Geosciences
Copyright: © 2019 Pieter van Halem
Simulation Graph theory Route planning Logistics Dredging Operations research Route optimisation Digital-Twin
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Published Date

03-10-2019

Language

English

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Faculty

Civil Engineering & Geosciences

Abstract

This thesis introduces a new algorithm for optimising shipping routes within a dredging project. Highly dynamic and time-dependent hydrodynamic features influence shipping routes. Due to the complex interactions between the horizontal tide, vertical tide, stratifying forces, wind-driven forces, and limited water-depth, shipping routes were previously only optimised for large scale routes (order of 1000 km). This study presents an algorithm that can optimise shipping routes that are influenced by these small scales (order of 10 km) hydrodynamic features. This algorithm uses graph theory to solve for the time-dependent fastest path between start and destination. Graph theory searches for the optimal path through a set of nodes that are connected with edges. This study uses the time-dependent shortest path algorithm which accounts for the FIFO-criteria (Waiting criteria) and can solve the non-convex nature of the problem

The input of this algorithm is a hydrodynamic model. These models are Computational Fluid Dynamic (CFD) models that calculate currents and water levels in a specific domain. The domain is discretised into cells and nodes to calculate these hydrodynamic features. This study uses the nodes of this hydrodynamic model as the vertices of the graph. However, for some cases, the hydrodynamic model has too many nodes for the shortest path algorithm. This study presents a method for reducing the number of nodes without reducing the spatial resolution. The nodes are reduced based on a combination of the vorticity and the magnitude of the flow.

This algorithm is implemented in a python software package named Hydrodynamic Algorithm for Logistic enhancement Module (HALEM). HALEM can determine the optimal shipping route for a given hydrodynamic model. Defining different cost functions results in different optimisation purposes. This thesis presents cost functions for the fastest route, shortest route, cheapest route and least polluting route. This software is then implemented in the OpenCLSim software so that this combination of software can optimise routes of entire projects. A case study simulates a beach-nourishment at Schouwen Westkop Noord to demonstrate the practical use of HALEM and OpenCLSim. For this project, 425,500 m3 sand should be dredged offshore and pumped onto the beach. Due to the narrow gullies and tidal changes in hydrodynamic features, the routes were hard to predict. The simulation with HALEM and OpenCLSim shows an increase in the production with 21 % compared to the simulation with just OpenCLSim.