Development of a Nano-Scale Thermal Anemometry Probe (NSTAP)
NSTAP is being developed for high Reynolds number turbulence measurements to capture ultra small-scale velocity fluctuations. We believe that it is the first micro-scale velocity sensor free of end- or substrate-conduction, which has been fabricated and successfully tested in a turbulent flow. Fabrication of NSTAP is done by using several semiconductor techniques and recently, novel MEMS (Micro Electro-Mechanical System) techniques have been successfully implemented. NSTAPs have working principles similar to conventional hot-wire anemometry technique and are able to provide greatly improved spatial and temporal resolution. The sensing elements of NSTAPs are nano-scale wires, with dimensions of 100 nm × 2 µm × 60 µm or 100 nm × 300 nm × 30 µm. In figure 1, a Scanning Electron Microscope picture of the most recent design of NSTAP is shown. Experiments with NSTAP in grid-turbulence show good agreement with conventional hot-wire sensors. It demonstrated faster temporal response and improved spatial resolution. Currently, NSTAPs are being used in Princeton/ONR Superpipe and High Reynolds Number Test Facility (HRTF) to study highly resolved very high Reynolds number turbulent flow.
· Bailey, S., Hultmark, M., Meyer, K., Hill, J., Kunkel, G. and Arnold, C. & Smits, A. (2008) Nano-scale thermal anemometry probe. APS Meeting Abstracts pp. A5+.
· Bailey, S.C.C., Kunkel, G.J., Hultmark, M., Vallikivi, M., Hill, J.P., Meyer, K.A., Tsay, C., Arnold, C.B. and Smits, A.J. (2010) Development of NSTAP: a nano-scale thermal anemometry probe. J. Fluid Mech (accepted).
· Vallikivi, M. Turbulence measurements with a nano-scale thermal anemometry probe. (2010) Master thesis. Chalmers University.