Micro-Optical Sensor Use in Boundary Layer Flows with Polymers and Bubbles

Recent advancements in the design and development of small optical sensors have made it possible to investigate complex flows. These include flows with bubbles and polymers at high Reynolds numbers which are present in drag reduction experiments. We have developed optical sensors for use in scaled and full-scale experiments, both in laboratory and at sea conditions. These sensors have been tested in water tunnels and at sea, with and without polymer injection. The presence of polymers and/or bubbles in the flow did not degrade their performance. The sensors also performed well in full-scale at-sea tests. Recently, we have fabricated a total of 37 optical sensors packaged for installation on the surface of a lifting body hydrofoil of a full-scale, vessel and scheduled to be tested soon. This paper describes the individual sensors and sensor suites that have demonstrated their capability to provide reliable flow velocity data throughout the boundary layer under a variety of flow conditions. These non-intrusive sensors are appropriate for single-phase and multi-phase flows present in drag reduction related experiments. They do not require on-site calibration, and are not affected by environmental parameters such as pressure, density, temperature, salinity, or index of refraction.