INCAS SUBSONIC WIND TUNNEL

Abstract

The INCAS Subsonic Wind Tunnel is a closed circuit, continuous, atmospheric pressure facility with a maximum speed of 110 m/s. The test section is octagonal ,of 2.5 m wide, 2.0 m high and 4 m long. The tunnel is powered by a 1200 kW, air cooled variable speed DC motor which drives a 12 blade, 3.5 m diameter fan and is equipped with a six component pyramidal type external mechanical balance with a 700 Kgf maximum lift capacity. The angle of attack range is between -45o and +45o while the yaw angle range is between -140o and +216o . The data acquisition system has been modified recently to allow the recording of all test data on a PC type computer using LABVIEW and a PXI – type chassis containing specialized data acquisition modules. The tunnel is equipped with a variable frequency electrical supply system for powered models and a 10 bar compressed air supply for pneumatic flow control applications. In the recent years the subsonic wind tunnel has been intensively used for tests within several European projects (AVERT, CESAR and others). Introduction The 2.5 m x 2.0 m Subsonic Wind Tunnel is the first aerodynamic facility at INCAS. Fig. 1 . Subsonic Wind Tunnel Its main characteristics are the following: • Prandtl type, horizontal single return • Closed test section, atmospheric • Test section size: 2.5 m wide by 2 m high • Speed range: from 7 to 110 m/s • Angle of attack range: -45o to +45o • Yaw angle range: -140o to +216o • Reynolds number (for S l 1 . 0 = ): 1x10 • Contraction area ratio: k = 10 • Turbulence factor: 1.11 The most usual tests involve forces and moments measurements using the external TEM balance, followed by pressure distributions using the existing classical and electronic scanning devices and flow visualizations using smoke, tufts and oil paints. Laser sheet visualizations have been performed recently with spectacular results. Apart from the usual measurements of aerodynamic forces, pressure distributions and visualizations on models of aircraft, missiles, cars, buildings, bridges etc., there have been many special test programs like, for instance wind turbines (tested in the large area settling chamber of the tunnel), sky divers, skiers, cyclists, flag masts etc. The whole experimental activity in the Subsonic Wind Tunnel is carried out according to the existing Manual for Quality Assurance in the Subsonic Wind Tunnel. Description of the facility The tunnel is powered by a 1200 kW, air cooled variable speed (up to 800 rpm) DC motor which drives a 12 blade, 3.5 m diameter fan. The pressure drop across the fan blades is 210 Kgf/m. The motor air cooling is done by means of a special circuit equipped with a 20 KW fan. The DC motor is fed by a thyristor controlled rectifier system connected to a 6 KV, 2 MVA transformer. The tunnel operation, air speed, model positioning and parameter measurements are controlled from an integrated control panel. 12 INCAS BULLETIN No 1/ 2009 DOI: 10.13111/2066-8201.2009.1.1.3