Control of Lagrangian Coherent Structures at Stagnation and Separation Locations on Airfoils
Technical Report,30 Sep 2016,29 Sep 2019
UNIVERSITY OF SOUTHERN CALIFORNIA Los Angeles United States
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A combined numerical, theoretical and experimental program was performed towards a rational control strategy for transitioning andor separated flows. The model platform was the NACA 651-412, a commonly used turbine blade section. Investigations were made for the basic flows and their stability, in experiment and computations. Studies were conducted in 2D and in 3D. Lagrangian flow descriptors in terms of Finite Time Lyapunov Exponent FTLE fields were made in 2D and in 3D, for the first time. The numerical data for pulse actuation of the base flow was used to determine optimal actuator placement, using a frequency-space formulation of a controllability Gramian to determine the most sensitive control regime. The optimal location for separation point and separation streamline angle control were different, as confirmed in the simulations. The separation control can be more closely linked with structures in an LCS-based reduced order model of surface information. DMD modes confirm that those for the two strategies differ in spatial arrangement. Significant computational and theoretical progress was made in examining spike formation in wall-bounded flows. We believe an exciting baseline has been established for explicit LCD-based mode control.
- Fluid Mechanics