Innovative Solid-State All-Weather Shear Stress Transducers

Nielsen Engineering & Research (NEAR) is proposing to investigate the feasibility of two innovative solid-state concepts for MEMS-based turbulent wall shear-stress transducers. The first design, which relies on the variation in acoustic convection velocity through the boundary layer, employs established MEMS transducers. The second concept, which directly measures the shear force on the wall, is produced using an emerging MEMS fabrication technique. Neither of the proposed designs incorporate any moving parts or are sensitive to airborne contaminants such as dust and rain. During the Phase I program, NEAR will determine the feasibility of each of the proposed designs in terms of their environmental robustness, manufacturability, frequency response, and accuracy. Both theoretical analysis and wind tunnel experimentation will be used to investigate the influence of design parameters and flow conditions. Relatively large scale (non-MEMS) prototypes will be used during the wind tunnel tests to evaluate feasibility. During the Phase II effort, NEAR will use the Phase I results to refine the system design and will fabricate operational transducers using MEMS production techniques. An evaluation study will be conducted to assess the design's ability to handle harsh operating conditions and to evaluate the final system's performance in real-world operational conditions. BENEFITS: These all-weather shear stress sensors will have numerous applications in military and commercial markets. Potential applications include 1) wind tunnel, water tank, flight, and track testing in commercial and government research laboratories, 2) monitoring for increased skin friction on aircraft employing laminar flow wings and drag reduction devices, and 3) detecting reversed flow and incipient stall on wings.