CFD Investigation of Wind-powered Ships under Extreme Condition: Simulations on the NACA-0015 Foil under Deep Stall Condition

Abstract

This thesis is dedicated to study the loading condition of the rigid wingsails on a ship with wind-assisted propulsion using CFD methods. OpenFOAM is used for the CFD simulations. 2D simulation cases are performed for both low angles of attack and 90 degrees angle of attack conditions. Simulations on a uniform 3D foil with 90 degrees angle of attack conditions are also performed. Unsteady RANS and DES simulations are carried out to predict the loading condition on a NACA-0015 foil. Under the conditions of low angles of attack, the k − ! SST model and the k − ! SST DDES model are used in the simulation. For 90 degrees angle of attack simulation cases, the k − ! SST model and the k − ! SST IDDES model are used. The simulation results are compared with experimental data. These simulation cases provide the loading condition on foils and characters of the flow field. The possible causes of error, especially the overestimation of the force coefficients for 90 degrees angle of attack, are discussed. For the cases of 90 degrees angle of attack, the influence of mesh factors on the simulation results is analyzed, which includes the refinement of profile mesh, structured and unstructured downstream fields, and the ratio between the chord length and the longitudinal length. A rough prediction of the interaction between two foils is presented as well. Experiences on performing deep stall simulation, and suggestions on wind propulsion from an engineering perspective are also provided.