CFD analysis of NACA 4415 marine propeller ducts for managing flow separation

This investigation aims to explore the potential of reducing drag on marine propeller ducts by managing flow separation. The use of traditional propellers to reduce fuel consumption and carbon emissions in the shipping sector has become increasingly difficult. As a result, unconventional methods of ship propulsion have been proposed. One such method is the ducted propeller, which is a hydrodynamically engineered duct that better controls water flow. This nozzle form reduces cavitation and noise while increasing efficiency, making it a popular choice for marine propellers. Despite significant efforts to increase ship propulsion efficiency in recent years, there is a lack of experimental and computational studies on flow separation control over hydrofoils. The duct section of NACA (National Advisory Committee for Aeronautics, now known as National Aeronautics and Space Administration NASA) hydrofoils is less studied, but interest in this field of research has remained over time. This investigation analyzes the hydrofoil NACA4415 for the practical use of decelerating duct design. We install vortex generators and dimpled surfaces upstream of the separation point to control flow separation and energize the boundary layer. The investigation uses computational fluid dynamics (CFD) analysis to examine how “dimpled” surfaces and vortex generators affect the ducts’ hydrodynamic properties. We performed all transient simulations using Ansys-Fluent and the k-SST turbulence model. We evaluate the performance of NACA4415 for lift, drag, pressure coefficient, vortex shedding, and Strouhal number at a 5-degree duct angle and different flow conditions. During the present investigation, it is found that the NACA4415 hydrofoil under consideration for a decelerating duct configuration has a lower drag coefficient when it has a dimpled surface. For decelerating ducts, the NACA4415 hydrofoil section exhibited better efficiency for thrust augmentation. The optimum duct angle is between 3° and 5° for all ranges of Reynolds numbers considered here.