Phase-resolved evolution of transition and critical loci on a lifting hydrofoil in a propeller wake

This contribution proposes details about the time and phase-averaged locations of laminar-turbulent transition, separation, and reattachment on a lifting NACA 0015 hydrofoil placed in a propeller wake following a domain decoupling approach, where pieces of information at the hydrofoil's surface, supplied by experimental investigations, are supported and justified by numerical data in the flowfield, forced by the interaction with the upstream propeller. Measurements rely on time-resolved temperature maps at the wall provided by the luminescence of a Temperature Sensitive Paint applied on the hydrofoil. The maps of standard deviation and skewness obtained as averages in the time and phase domains illustrate the spatial distribution and the temporal evolution of the transition and critical loci. Numerical data about the flow field, coming from Detached Eddy Simulation, support the connections between the critical loci dynamics on the hydrofoil's surface and the phase evolution of the pressure gradients imposed by the propeller to the incoming flow. The close connection between the time-resolved temperature maps and the skin friction exerted by the fluid on the surface allows for the detailed description of the boundary layer around the hydrofoil. Statistics of temperature's time series supply a neat, non-redundant, and valuable information on laminar-turbulent transition, separation, and reattachment within and out of the propeller's stream tube. This information appears as the natural complement of the time-resolved 3D flow maps obtained with the Detached Eddy Simulation numerical approach that, relieved of the difficulties inherent in the near-wall calculus, provides a fast and accurate description of the propeller's wake.