Interactive Control of Wall Structures by MEMS-Based Transducers
In turbulent boundary layers, the near-wall streamwise vortices contribute to a significant part of the turbulence production. Successful control of the streamwise vortices can lead to the desirable skin-friction drag reduction. In the past, passive devices such as longitudinal riblets were used to achieve a 6% reduction (Bruse et al. 1993). Recent numerical simulations (Choi et al. 1994) indicate that an active control scheme based on surface shear-stress measurements can increase the drag reduction to almost 30%. We are currently developing a large-scale integrated systems of micromachined sensors, micromachined actuators, and neural network VLSI circuits for interactive control of the wall structures. The newly developed MEMS technology allows us to, for the first time, fabricate micro sensors and actuators that can match both the temporal and spatial resolutions of the wall structures (Ho and Tai 1994). Individual components of the integrated system have been developed and tested. The following is a discussion of their design and capabilities.
KeywordsDrag Reduction Streamwise Vortex Surface Shear Stress CMOS VLSI Active Control Scheme
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