Low-Speed Wind Tunnel Flow Quality Determination

The NPS MAE wind tunnel was reinstalled, calibrated, and its flow characteristics evaluated to determine its suitability for research and classroom demonstration. The calibration involved determining tunnel speed vs. motor speed, wall static pressure distribution, total pressures across selected planes, the uniformity of the velocity profile, using a pitot-static tube and a single component hot wire (CTA), the wall boundary layer characteristics consisting of the velocity profile, streamwise turbulence intensity, and spectral energy distributions at selected points. Incorporated instrumentation includes pressure transducers attached to a pitot-static tube, wall static pressure taps, and a pressure rake; a hotwire anemometry system, and a linear traverse system. These were integrated with a data acquisition (DAQ) processor with analog to digital conversion and digital I/O boards, and controlled using in-house developed LabVIEW software. Testing showed a maximum axial velocity of 38 m/s, which is 84% of the tunnel’s rated speed. The 2-D flow uniformity was within ±7% by pressure rake, and ±3% with a turbulence intensity ?0.11% at full speed using a CTA, affirming the tunnel’s viability as a demonstration platform. Spectral density plots in the boundary layer exhibit typical behavior of fully developed equilibrium turbulent flow with an intertial sub-range present. Future testing of a flat-plate wake for drag modification is planned.