Unsteady dissipation measurements on a flat plate subject to wake passing

Boundary layer measurements were performed on a flat plate with an imposed pressure gradient typical of a high-lift low-pressure (LP) turbine blade and subject to incoming turbulent wakes shed from a moving bar wake generator. A multiple-orientation one-dimensional laser doppler anemometry (LDA) technique was used to measure the ensemble-average mean flow and Reynolds stresses. These ensemble-average measurements were used to calculate the boundary layer dissipation, thereby providing unprecedented experimental evidence of the loss-reducing mechanisms associated with wake-induced transition. The benign character of the calmed zone was confirmed and the early stages of boundary layer separation were found to have laminar levels of dissipation. A deterministic natural transition phenomenon was identified between wake passing events, highlighting the existence of natural transition phenomena in LP turbine style pressure distributions.