The TTP Transonic wind tunnel Mach number uniformity analysis

The distribution of the Mach number in the test section of the Brazilian Pilot Transonic Wind Tunnel was evaluated for the subsonic, transonic and low supersonic regimes. A convergent-divergent nozzle was designed and manufactured to increase the TTP envelope up to Mach number 1.3. Static and total pressures of the airflow are input quantities for the isentropic equation used for Mach number estimation. Static pressure measurements at the test section stations are accomplished by a centreline pressure probe and by distributing pressure taps along the upper and lower walls. Data reduction includes the evaluation of the uncertainties associated with the measured quantities, as well as their propagation to the output quantity, by employing the Monte Carlo method. Least squares fitting is applied to the experimental data in order to supply Mach number calibration curves. Sources of error causing non-uniform flow for Mach number equal to 1.3 are pointed out.