Characterization of marine propeller model near wake in the presence of external (free stream) turbulence*

High resolution, three dimensional PIV experiments were conducted in the in the US Naval Academy’s recirculating water tunnel (1.8m long test section with 0.41m x 0.41m cross sectional area) with three-bladed marine propeller model (D=13cm). Spatial coverage in the near wake was accomplished via “tiling” of individual fields of view (FIV) of nominally 12x8 cm² area covering downstream distance from the wake generator (propeller) plane up to approximately 9D downstream.Two separate set of measurements were made: phase locking, i.e. PIV image pairs were triggered at a specific blade location and “free runs” where no phase locking was performed. The resulting flow Reynolds number based on diameter is Re_D=2.6x10⁵. Two parameters of the grid generated external (free stream) turbulence are controlled: the streamwise integral length scale of the turbulence and the turbulence intensity. Results will focus on characterizing spatial distributions of ensemble averaged mean wake velocities as well as spatial distribution of wake growth rates and normal and shear turbulent stresses up to 9D downstream from the rotor plane.