Abstract
The Ocean Engineering Toolbox (OET) is an open-source, Modelica™ compliant symbolic library capable of simulating the dynamic motions of floating bodies subject to polychromatic, unidirectional waves. This paper presents recent advancements in the OET: (1) the development of custom components to represent the frequency-dependent wave excitation force and (2) significant improvements in the toolbox’s computational performance. While the Modelica language can represent complex cyber-physical systems efficiently, the primary challenges with modeling wave-induced floating bodies are (1) non-compatibility with frequency-dependent variables, (2) lack of hydrodynamic components in the Modelica Standard Library (MSL), and (3) integration with the previous version of the OETv0.1. In the time-domain implementation, surface elevation profiles can now be generated for regular and irregular waves, with three spectral options for polychromatic seas: Pierson-Moskowitz (PM), Bretschneider, and Joint North Sea Wave Project (JONSWAP). Hydrodynamics coefficients are imported using a MATLAB script to process the output from Boundary Element Method (BEM) codes. A novel symbolic implementation of spectral decomposition and interpolation is presented in this work to generate the frequency-dependent excitation force in Modelica. Results from the OET are compared against data generated from WEC-Sim, validating both the wave excitation force and the corresponding system dynamic response for a floating point absorber in heave. These developments lead to superior simulation accuracy and computational performance while expanding the hydrodynamic modeling capabilities of Modelica.