Modelling of Aerodynamic Interaction Effects for Wind Propulsion applied in Commercial Shipping: Development of a Non-Linear Lifting Line method

Wind propulsion is a promising technology for the challenge to reduce the greenhouse gas emissions of commercial shipping. The aerodynamic interaction effects are an important secondary contributions affecting the achieved savings by applying wind propulsion. Furthermore, the operational savings depend on the used wind propulsor controls, which should be adapted to aerodynamic interactions to minimise the performance losses. It is challenging to model these effects in a computational efficient manner, because the large number of control variables and the number of wind conditions for which the calculation should be performed. For this purpose the theory of a modern non-linear lifting line method was extended and implemented for three type of wind propulsors; rigid wing sails, suction sails and rotor sails. The validity of the lifting line method is first shown for the wind propulsors in isolation using experimental and CFD results. Secondly, the predictions for a configuration of wind propulsors are compared for two in literature available test
cases, one with rigid wing sails and one with rotor sails. Using these test cases the effect of aerodynamic interaction effects on the driving force is studied and the performance increase achievable when optimising the controls is shown.