A formerly developed vortex lattice method (VLM) is coupled with Renolds Averaged Navier Stokes based Computational Fluid Dynamics (CFD) tools, in order to predict the hydro-dynamic performance of ducted propulsion systems. The analysis of the performance for ducted propellers subject to steady and unsteady cavitating inflow is via applying a hybrid numerical method which couples a vortex lattice method (MPUF-3A) with RANS solvers for analyzing the viscous flow around the propulsor and the drag force on the hub and duct surfaces. The presence of the propeller is represented through distributed pressure gradients, or in other words, body forces. The body forces can be obtained from the potential flow method, and re-associated to the fluid domain revolved by the propeller blades. The propeller force distributions are considered as source terms (body forces) in the momentum equations of RANS solver. The effects of viscosity on the effective wake and on the performance of the propeller blade, as well as on the predicted hub and duct forces, can be assessed.
The demand of high-speed marine vehicles for commercial has increased drastically in recent decades. Therefore, marine propulsors are designed with more complex geometries to satisfy various requirements, such as high efficiency, less noise and vibration, better course stability, lower vessel resistance and economic operation, etc. Following this trend, ducted propellers have become more and more popular in the contemporary design. The complexity of the geometric characteristics of the propulsion systems introduces complicated flow fields around the propulsors and thus creates a lot of challenges to the design and computational analysis. Using numerical methods to solve ducted propulsion systems is much more challenging than those of open propellers because of the complicate geometric configurations and the interactions among the components. The primary problems and challenges are caused by hydrodynamic cavitation and viscosity.
