Advancements in measuring the wall-normal velocity fluctuations in a turbulent boundary layer

A novel velocity sensor has been developed and characterized for use in turbulent flows. The new strain-based sensor uses a freestanding nano-ribbon exposed to the flow, which results in a geometrically determined sensitivity to a single velocity component. A nano-ribbon deflects under the action of fluid forcing, causing an internal strain which can be calibrated to the fluid velocity. An anisotropic sensitivity to forcing enables measurements of turbulent fluctuations orthogonal to the free-stream flow using only one sensing element. The sensor is deployed in a turbulent boundary layer, with sensitivity to fluctuations in the wall-normal direction. Operation of the sensor is simple and, in contrast to constant temperature hot-wire anemometry, does not require a feedback circuit. The predicted frequency response is O(10⁵)Hz, making the sensor an interesting alternative for turbulence measurements.