Infraestrutura Experimental
O LANT
The Low Acoustic Noise and Turbulence (LANT) wind tunnel of the Sao Carlos School of Engineering, University of Sao Paulo (USP-EESC), Brazil. The closed-loop wind tunnel features several devices to improve flow uniformity, reduce swirl, and lower the background acoustic noise and turbulence, enabling stability and aeroacoustic experiments. The design criteria was based on the best practices reported, in particular for low turbulence wind tunnels. The 3-m long closed-working section has a 1 × 1 m2 cross-section area. At 15 m/s the working section wall boundary layer is less than 100 mm thick, providing an area of at least 800 × 800 mm2 where the streamwise flow uniformity was within 1%. In the 10–30 m/s flow speed range, the turbulence intensity is about 0.04% with a low pass filter with 1Hz of cutoff frequency. The background acoustic noise level, obtained with an inflow microphone, ranged from 90 and 110 dB.
In order to accurately move and position a probe, a stepper motor’s traverse mechanism was specially
designed and built to suit the LANT test section dimensions. It is optimised for boundary layer experiments in which the model is mounted vertically in the test section centreline. The traverse positioning
system can move the probe over a course of 2,400, 830 and 720 mm in the streamwise, spanwise and
cross-stream directions, respectively. The movement resolution in the streamwise and vertical directions is 0.025 mm. A high resolution normal to the wall is very important because the boundary
layer to be measured can be very thin. In this direction, the stepper motors employed are set to 400
revolutions per step, whereas the screw shaft have 5 mm pitch, which give the nominal resolution
of 5 mm/400= 12.5 microns.
