Influence of Tubercle Modifications on the Performance of Marine Vertical Axis Propellers

Abstract

Even though past efforts in computational fluid dynamics (CFD) simulations have shown great progress in the implementation of tubercles into aero-foils and turbines blades, incorporating these tubercles into marine vertical axis propellers is still comparatively less well understood. In general, the performance of marine propellers is highly related to the pressure and velocity distributions over the propeller blades. Since the presence of tubercles’ serrations in the blade leading edge can vary these distributions over the blade, the performance of the propellers can be enhanced. In this article, tubercle modifications are investigated in marine vertical axis propellers through the use of CFD simulation. To achieve this purpose, a complete procedure of CFD simulation using ANSYS FLUENT 16 is proposed. Obtained CFD results are validated using direct comparison with the previous analytical studies. Obtained performance characteristics of the modified vertical axis propeller are assessed against the available characteristics of the baseline one. The CFD results are found in a good agreement with the analytical ones. Moreover, the results demonstrate the improvement of the obtained performance of the modified vertical axis propeller compared to the baseline one in terms of increased thrust coefficient and higher efficiency over the considered range of advance ratio. Shallow waters, rivers, and seas; the presence of obstacles; the complexity of water routes; and the territorial orography require the availability of effective maneuverability to enhance marine propulsion compared to the traditional rudder-propeller system (Pasetto1 2013). In this context, the vertical axis propellers (VAP) can be a real and valid alternative to the rudder-propeller system (Chen 2007), allowing the ships to navigate in an effective way also in the difficult routing and in shallow water conditions (Carlton 2007). The VAP provides the ability to sail vessels in all sea conditions effectively. It maintains the ability to direct the thrust to 360° and, consequently, provides a better performance in terms of maneuverability, stop and crash maneuvers and higher efficiency. It is therefore necessary for all kinds of vessels requiring high level of maneuverability in congested waterways to be equipped with VAPs for ease, safety, and immediate response.