Numerical study on propeller flow field in four quadrants

Abstract

The propeller hydrodynamic performance under different direction combinations of the uniform inflow and the propeller rate, i.e. four quadrants (Q1–Q4) conditions, is studied with CFD methods, and validated by the experimental data of a model-scale propeller. The numerical strategies including the turbulence model, the grid size, and the time step are discussed. Regarding the relative direction of the inflow and the propeller jet, RANS (Reynolds-Averaged Navier–Stokes) and DDES (Delayed Detached Eddy Simulation) are compared in resolving global and local flow quantities. RANS results show similar near-field flow fields to DDES results in Q1/Q3, while DDES gives more accurate forces and richer flow details such as vortex resolutions for cases with opposite flow directions. Then the propeller is simulated by RANS in Q1/Q3, and by DDES in Q2/Q4. In four quadrants, the propeller thrust and torque, vortex structures, and velocity and pressure distributions are presented for flow mechanism analysis. In Q1/Q3 conditions, the propeller jet evolves in the same direction as the inflow, promising a converged flow field. In Q3, the reverse rotation leads to less significant flow acceleration effects than Q1 under the same inflow velocity, and the non-uniformity of pressure distributions on the blades is strengthened. For Q2/Q4, massive flow separations occur due to the interaction of the propeller jet and counter inflow, and the recirculation zone with reversed axial velocities forms. With increased inflow velocities, the dominant role between the inflow and the propeller jet gradually shifts, and the difference in the propeller jet produced by ahead and astern rotations postpones the shift in Q2 compared with Q4. This study investigates the propeller flow field in four quadrants and can help to quantify rudder inflow variations in hull-propeller-rudder interactions for future research.