Rim-driven pumpjet design by optimization

Abstract

Abstract This paper presents a numerical study based on a Simulation-Based Design Optimization (SBDO) framework for the design of a marine rim-driven pumpjet propulsion system at a prescribed operating condition. The main objective is to compare the hydrodynamic performance of rim-driven pumpjets with that of a conventional ducted propeller designed for the same functioning point. In addition, the influence of stator blades on the performance of rim-driven configurations is investigated. Three independent optimization campaigns are performed, corresponding to three configurations: rim-driven pumpjet with post-swirl stator (RDPJ R/S), rim-driven pumpjet with pre-swirl stator (RDPJ S/R), and rim driven without stator (RD). Each geometry is defined by a set of design variables and automatically converted into a CFD-ready model. The optimization process is then carried out via Reynolds Average Navier Stokes (RANS) simulations coupled with the MOGA-II algorithm in ModeFrontier. The primary objectives are to maximize open-water efficiency and minimize cavitation inception. The optimization outcomes are used to derive design guidelines and insights into the key parameters governing the performance of rim-driven pumpjet propulsion systems. These results enable a complete comparison among the three configurations, highlighting the effects of stator placement and identifying optimal designs for the selected operating condition. The best-performing geometry of each configuration is further analyzed using unsteady and cavitating RANS for validation and comparison with reference ducted propeller in both design and off-design working conditions.