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Completed TRL 6 (started at 4, targeting 6)
Supersonic propulsion systems include internal ducts, and therefore, the flow often includes shock waves, shear layers, vortices, and separated flows. Passive flow control devices such as micro-vortex generators and micro-ramps have been proposed to improve vehicle performance. The ability to measure surface quantities such as skin friction and unsteady pressure on the inlet model would provide insight into the complex flow characteristics that govern inlet performance. Unfortunately, nonintrusive sensors require optical access that has been difficult to obtain. Optical sensors for measurements of pressure (Fast Pressure-Sensitive Paint) and skin friction (Surface Stress Sensitive Films) offer non-intrusive measurements on surfaces, exactly the capability that is needed. To date, the size of the hardware such as camera and illumination devices have precluded application of these technologies in regions like an internal duct. During the past several years, camera and LED technology has advanced resulting in small packages for both imaging and illumination. Combining this new hardware with state-of-the-art optical technology such as fast responding PSP and S3F will result in a pair of sensors that can be miniaturized and utilized for non-intrusive measurements in traditionally inaccessible regions of the model. These measurements include continuous distributions of skin friction and unsteady pressure.
Surface Stress Sensitive Films are being investigation for a variety of applications in aerodynamics, hydrodynamics, and biomedical research. Skin friction is a quantity of interest in many aerodynamics applications such as validation of CFD, and investigation of supersonic/hypersonic inlets. Biomedical applications include ongoing research with the Cleveland Clinic for identification and correlation of shear on the foot of diabetics. The formation of bed sores is believed to be related to shear stress, and therefore this would be a similar application of the technology. Other biomedical applications include shear stress on surfaces of artificial implants such as stints, hearts, valves, and assist pumps. Finally, ISSI has recently begun investigating S3F as a tactile sensor for artificial limbs and robotic touch sensors. This technology may be of interests for unmanned planetary probes.
Surface Stress Sensitive Films, is under investigation for a variety of applications in aerodynamics, hydrodynamics, and biomedical research. Traditional interest exists in skin friction for CFD validation and drag reduction on supersonic/hypersonic air vehicles and hydrodynamic drag reduction. A miniature point version of the sensor has been produced by ISSI that will sense 2-components of skin friction and provide real time feedback for closed loop flow control. This sensor is of interest for using in Navy applications, and may have applications in MAV's. Biomedical applications include ongoing research with the Cleveland Clinic for identification and correlation of shear on the foot of diabetics. Other biomedical applications include shear stress on surfaces of artificial implants such as stints, hearts, valves, and assist pumps. The S3F sensor has recently been used to detect shear forces on tires and a means of using the system for predictive maintenance of fleet vehicles is underway.
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