How to Improve Full-Scale Self-Propulsion Simulations? A Case Study on a Semi-Displacement Hull

This study aims to improve Computational Fluid Dynamics (CFD) self-propulsion simulations for a semi-displacement hull with an interceptor. To enhance full-scale self-propulsion simulations, the numerical setup incorporated hull roughness based on the ITTC 78 formula and full-scale propeller open water curves following the ITTC 78 procedure. Simulations were performed using the SIEMENS PLM STAR-CCM+ CFD code for a displacement condition and for 0.638 < Fr▽ < 1.530. Comparisons were made with experimental scaled results from tests conducted at the Towing Tank of the Department of Industrial Engineering, Università degli Studi di Napoli “Federico II”. A comparison of numerical and experimental self-propulsion factors, such as wake fraction and thrust deduction coefficients, shows an average error reduction of 2.5% for wake fraction and 1.5% for thrust deduction. Additionally, a self-propulsion proportional (P) speed controller was implemented using the Ziegler-Nichols method to improve accuracy. This controller allows real-time adjustment of the propeller speed, supplying valuable insights into marine vessel performance under realistic conditions. This approach can be extended to incorporate factors like waves and wind, creating a more realistic representation of the marine environment. The implementation of a P speed controller is the first step towards developing a free-sailing approach that enhances simulations of real-world conditions for marine vessels.