Heat transfer reduction in manipulated turbulent boundary layers

Turbulent boundary layers over a mildly heated plate were successfully manipulated by a set of large-eddy breakup devices in tandem. Significant skin friction and heat transfer reduction were achieved with a single pair of manipulators, and larger and longer lasting effects were attained with doubly stacked LEBUs. The results were very sensitive to the angle of attack of the manipulators, with small negative values yielding substantial skin friction and heat transfer increase. The manipulators were slightly more effective at modifying momentum transfer than heat transfer, suggesting different transport mechanisms with different relaxation lengths.