Sensitivity to Turbulent Boundary Layer Production Mechanisms to Turbulence Control
Final rept. 1 Oct 87-31 Mar 91,
MICHIGAN STATE UNIV EAST LANSING
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Initial experiments to explore ways to modify the key aspects of the turbulence production mechanism were made. The proposed phased momentum bursts proved too difficult for us to quantify. When applied, changes were visually observed to occur, but the changes that occurred always seemed to result in different evolutions from instant even though the same perturbation was applied, arid thus defied quantification. Therefore, we took a different approach, and determined in a statistical sense what the magnitude and the time scale of a momentum perturbation should be if we are going to precisely after the essential coherent motions. We have found these scales by constructing a complete structural model of the turbulent boundary layer Proc. Roy. Soc. Lond. A 336, 103-129, 1991, and by showing that it properly scales the intensities and Reynolds stresses. This scaling allows us to predict intensities and Reynolds stress magnitudes. From the point of view of control, it tells us, on a statistical basis, how much momentum to use in a control scheme, and for how long to apply it. for any Reynolds number arid position in the layer.
- Fluid Mechanics