SHAPE Project: CFD calculations for side-by-side (SBS) propulsion

Water depths become forbiddingly shallow to allow ship traffic in connection rivers. Propellers can damage by interacting with the riverbed under low water conditions because they are designed with the largest possible diameter for efficiency reasons. Two propellers can replace a single propeller to reduce the penetration depth of the propulsion system, with the same propeller disk area delivering similar amounts of thrust. The optimal configuration of such twin-propeller propulsion systems arranged side-by-side is investigated by computational methods simulating the flow in this project. A numerical methodology that can handle the turbulent and multiphase nature of the flow around propellers has been established. Tight side-by-side  arrangements are needed to enable possible compensation of the efficiency losses due to the propeller diameter reductions by flow structure interactions. The small gaps between propellers enforced the application of the overset approach to handle rotating geometries. The accuracy of this approach is governed by the careful mesh design in the interpolation region. The application of a shell/nozzle enclosing the side-by-side propellers has been investigated. The flow interaction between the propellers shall be steered such that part of the swirling flow energy is redirected in the heading direction and generates thrust. Thereby, the performed simulations could deepen the knowledge of nozzle design for twin-propeller configurations.