RANSEs Simulation of the Flow past a Marine Propeller under Design and Off-design Conditions

In the present work the results of a preliminary computational fluid dynamics (CFD) simulation of the flow past a marine propeller are presented. The principal aim of the study is to verify the ability of a CFD method, solving the Reynolds-Averaged Navier-Stokes Equations (RANSEs), to predict the performances of a marine propeller. The complexity in the mesh generation is one of the main obstacles for CFD. Following an hybrid mesh generation approach, prisms have been generated in the boundary layer, where viscous phenomena are dominant, and tetrahedra in the remaining regions. A parallel RANS solver has been used, employing a cell-centered, finite-volume method that allows the use of computational cells of arbitrary polyhedral shape. Boundary conditions were given to simulate the flow past a rotating propeller in open water conditions. The equations have been written in a moving reference frame fixed on the propeller blades. The steady-rotating reference frame source terms, i.e., the centrifugal and Coriolis force terms, therefore, are added to the RANS equations derived in the inertial frame. The k-w model has been employed for turbulence closure. Different values of advance ratios are considered, at design and off-design conditions. Computational results have been obtained for all the four-quadrant operational conditions: forward, backing, crashback and crashahead, considering also non-positif values for the advance ratio J. The thrust and torque coefficients, k_T and k_Q, have been selected as global quantities and compared with available experimental data. Pressure and velocity distributions and turbulent quantities were also used to analyze the computed flow field. The results show a good qualitative agreement with the experimental data. Important issues need to be addressed like an extensively improvement in the mesh generation techniques and in turbulence modeling.