Introduction

Open source Transport Network Simulation

OpenTNSim is a python package for the investigation of traffic behaviour on networks. It can be used to investigate how water transport chains interact with the waterway network and its infrastructure. Simulations can be used to compare the consequences of traffic scenarios and network configurations.

Book overview

For the design and optimization of port water areas and inland waterways, simulation can be a helpful tool. While simulations are not the same as real life data, they still can save time and money as they allow us to explore the unknown. You can simulate unseen events (incidents, low/high water extremes) and variants of the real world (possible changes to the waterway and/or its infrastructure).

OpenTNSim simulates vessels navigating (existing or planned) waterway networks. Useful features are visualisation of sailed paths (route selection, traffic intensities, transport capacity), analysis of the behaviour and interaction of (random) generated vessels, integration of real-world data (water levels, currents) and estimation of energy consumption, fuel use and emissions of vessels. With the increasing demand for sea-going and inland shipping and societal changes related to digitalisation, sustainability, and climate change, OpenTNSim can help researchers and practitioners to investigate the complexity of water transport networks and support decision making under conditions of uncertainty.

This book provides an introduction to the use and application of the OpenTNSim package. The goal of this book is to introduce the basics of the package by explaining how to setup your first simulation. The book will guide you through the use of real-life data and the simulation of more complex systems by explaining the use of shape files, multiple vessel generators and the visualization of sailed paths. Finally, it addresses how to estimate energy consumption, fuel use and emissions from the simulations.

This book intends to serve researchers, engineers and students that want to simulate vessel traffic on marine and inland waterways. OpenTNSim has grown into a community effort to collect algorithms that can represent sailing strategies, engines choices/setting, and structures (e.g. locks). Using discrete event simulations (schematized using an event log, using queuing and asynchronous tasks), the model is well suited to be integrated into the logistical chain of ports and waterways. Due to its open-source nature, OpenTNSim facilitates an environment where connections with external data, models and tools can be made, such as digital twins.

Goals

The learning goals of this book are: 1. Learn the basics of OpenTNSim 2. Learn how to apply real-life data in OpenTNSim 3. Learn how to make more advanced simulations 4. Learn how to retrieve emissions and energy usage data

Context / OpenCLSim

OpenTNSim is an open-source Python package which is an adaptation of the OpenCLSim package. OpenCLSim was developed by the Ports and Waterways (P&W) department of TU Delft, Van Oord and Deltares. The development of the tool was started by the P&W department for the analysis of maritime transport. Van Oord, Deltares and P&W joined efforts to increase the adaptability and workability of the tool.

Simulation of real-world processes requires a representation of the real-world system and a way to represent the different processes in such a system. More importantly, the simulation of real-world processes requires a way to incorporate congestion and delay as these are unavoidable in in real life. OpenCLSim (and OpenTNSim) utilises the SimPy package for this kind of event simulation. SimPy revolves around the passing fixed periods of time that represent different processes [ref Team Simpy]. The outcome of a such a process can be either a triggered event or a non-triggered event. When an event is triggered and completed, the process can be a success or a failure. The failure can be inherent (caused by the process itself) or caused by the interruption of a different process [ref OpenCLSim article]. In SimPy it is possible to create interdependencies between different processes and thus create a schematisation of a real-world chain of events.

OpenCLSim builds on SimPy by the addition of maritime-specific activities: e.g. loading and unloading of items and the moving and storing of items. Furthermore, the addition of components such as, ports, terminals, storage, quays, cranes and vessels, allow for a real-world maritime system to be simulated. To increase the usability of these maritime components and activities, OpenCLSim utilises so-called mixin classes. These mixins represent a certain set of parameters that apply to a type of activity or component. This makes it easier to configure complex supply chains. An example of such a mixin is the mixin Processor. This class has loading and unloading functions and can be used to represent a crane. Other mixin classes, with different properties, can be used to represent other components in the system. Combining different mixins can then be used to represent a port, or a container vessel [ref OpenCLSim article].

It is expected that OpenCLSim and OpenTNSim will grow in the future with the growing importance of emissions reduction and with the development of maritime transport.