Skin friction on a NACA0015 profile in the wake of a marine propeller

Kurzfassung

We report about the feasibility to experimentally characterize the interaction between a propeller and a hydrofoil model at incidence in its wake by using a temperature-sensitive paint. The experiments were conducted in a cavitation water tunnel at a freestream speed of 3.4 m/s and at a propeller rotational speed of 17 rps for two model angles of attack (4° and 8°). Time-resolved maps of the temperature evolution on both suction and pressure sides of the model obtained by means of the temperature-sensitive paint allow to take advantage of the direct link between friction velocity and celerity of propagation of temperature disturbances. By minimizing the dissimilarity between the observed propagation and that of the ideal wave suggested by the Taylor hypothesis, a quantitative estimation of the friction velocity vector field is gained. Detached eddy simulations are also conducted for the examined problem in the case of a model angle of attack of 4°, providing numerical data that are compared with the experimental results. The analysis of time-averaged results unveil the existence of laminar separation bubbles, stretched and folded according to the constructive / destructive coupling of the pressure fields induced by the hydrofoil incidence and by the propeller streamtube.