SBIR-STTR Award

The time-averaged wall-shear stress is related to a number of important aerodynamic parameters such as viscous drag and flow separation, which in turn determines the performance of moving bodies such as naval and marine vehicles. Measurement of the wall shear at many points of a maneuvering vehicle provides needed data for the development of current and future designs. Existing thermal and optical shear stress sensors are not suitable for the operational environments of marine vehicles. We propose to develop an array of miniature, conformal and waterproof shear stress sensors based on a promising new Optical MEMS technology. The unique design of the proposed array of compact optical shear stress sensors allows for its application to submerged vehicles for operation in both fresh and saltwater. During the Phase I effort, a prototype array of four sensors will be manufactured for test and validation. During the phase II of the proposed effort, an integrated array of sensors will be developed and demonstrated on a captive submarine model at NSWCCD. Plans for the transition to larger scale surface ships and submarine vehicle and large-scale autonomous submarine models will be provided. These compact, robust and non-intrusive shear stress sensors will have numerous applications in both military and commercial markets. Potential applications include: 1. Wind tunnel, water tank, and flight testing in commercial and governments laboratories, 2. Monitoring skin friction as a feedback for drag reduction devices 3. Detection of reversed flow and incipient stall 4. Micro-channel devices being developed for chemical and biological applications.

The development of an array of miniature optical shear stress sensors in a conformal, waterproof package is critical to the achievements of the design of agile and maneuvering submarines and other underwater vehicles. The objective of this research project is to continue the development of optical shear stress sensors using micro-optical diffractive optic elements, which will provide accurate, in-situ measurement of the wall shear stress at a number of points over a submerged vehicle. In Phase I, feasibility of novel micro-optical shear stress sensors was demonstrated. The new sensors provide unambiguous wall shear data both for attached and reversed flows. A relatively large number of sensors can be affixed to the outside of submerged vehicles and simultaneous data can be acquired using on board data management and recording system. Phase II will pursue advanced development of fabrication of multiple sensor packages. The sensor designs will be optimized, fabricated and integrated into an array of sensors. Application of micro-machining and automated aligning procedures in Phase II options and Phase III will result in efficient and reliable fabrication of larger arrays of sensors at lower per unit cost. Benefit Commercial application of single and multiple sensor configurations has already been identified in the areas of general fluid mechanics and aerodynamic research including the on going Navy-supported drag reduction efforts. The miniature sensors have also a large potential market in the medical field. The completed device could be used for In Vivo measurement of shear stress in arteries. Keywords optical, Shear Stress, Array, diffractive optical elements