Characterization of the transitional boundary layer flow on a marine propeller blade through Under-resolved Direct Numerical Simulation.

In this paper, the full boundary layer flow on a C-series marine propeller is investigated through Under-resolved Direct Numerical Simulation (U-DNS). The simulated Reynolds number of 600,000 corresponds to experimental conditions for which a lab-scale propeller was designed and tested at MARIN's towing tank in the late 1970s. The operating conditions of the simulations are set by matching the experimental advance ratio of 0.73. The simulation uses the high-order spectral element code Nek5000 to solve the boundary layer flow accurately. A specific computational domain is set to simulate the flow in the near-wall region of one of the propeller blades. The results are validated using experimental data on the propeller's performances and the boundary layer regimes obtained from previous paint test measurements. The detailed boundary layer flow analysis provides new insights into understanding the transition mechanisms on both sides of the blade. Results suggest that centrifugal instabilities occur at the blade's surface, inducing laminar-to-turbulent transition. A new flow map of the boundary layer regime is then discussed. The laminar cross-flow vortice inception and breakdown are studied in detail to characterize the transition dynamics. • DNS of a complete boundary layer transition around a marine propeller blade. • The boundary layer flow at the suction side is close to experimental observations. • The pressure side experiences transition through centrifugal instabilities. • Experiments predict early transition due to streak inception raising wall friction. [ABSTRACT FROM AUTHOR]