Abstract

Experiments were conducted to investigate the turbulent boundary-layer skin-friction drag reductions that could be attained through the creation of boundary layers with controlled spatial and temporal scales. The goals of the experiments were to determine the magnitude of any drag reductions and to illuminate the turbulent structure of the flow. Measurements of mean and fluctuating velocities were performed, providing mean velocity profiles, turbulence intensity profiles, bursting frequency, VITA conditionally averaged velocity, and ensemble phase-averaged velocity in the synthetically generated turbulent boundary layer and a reference turbulent flow produced with a two-dimensional trip. Significant drag reductions were not found as the changes in the flow appeared to be of the form of shifts in the effective origin of the boundary-layer development. However, the outer flow in the synthetic boundary layer was altered, maintaining some of the periodicity of the generation.

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