Design and validation of a nanoscale cross-wire probe (X-NSTAP)

Abstract: A nano-sized crossed thermal anemometer (X-NSTAP) was developed and validated for measurements of two-components of velocity at high Reynolds numbers. The new sensor design is based on the single-component nanoscale thermal anemometry probe (NSTAP) previously used to acquire streamwise velocity measurements at high Reynolds numbers. The new sensor can, simultaneously, measure two components of velocity with a spatial resolution of 42×42×50μm, an order of magnitude smaller in each dimension than conventional cross-wires. The new X-NSTAP design features several structural and manufacturing modifications to improve the aerodynamic performance of the sensor compared to previous nanoscale cross-wire designs. The effects of different manufacturing modifications were evaluated using dye visualizations over scale models of the sensor tip. The pitch sensitivity of the final sensor design was evaluated in an open-loop wind-tunnel and was comparable to the single-component NSTAP design. The X-NSTAP was then deployed in the Princeton Superpipe to acquire axial and radial velocity measurements up to friction Reynolds numbers, Re_τ= 24 , 000 with good agreement to existing studies. Graphical abstract: [Figure not available: see fulltext.].