Observations on some transonic wind tunnel test results of a standard model with a T-tail

Abstract

As a part of a periodic health monitoring of the wind tunnel structure, instrumentation and flow quality, a series of tests of an AGARD-C calibration model was performed in the 1.5 m T-38 trisonic wind tunnel of the Military Technical Institute (VTI) in Belgrade. The tests comprised measurements of the forces and moments in the transonic Mach number range with the purpose of comparing the model's obtained aerodynamic characteristics with those from other wind tunnel laboratories, in accordance with an adopted procedure for standard models testing. Inter-facility correlations were based on test results of physically the same model in the 5ft trisonic wind tunnel of the National Research Council (later operated as National Aeronautical Establishment) of Canada, in the 1.2 m trisonic wind tunnel of the Romanian National Institute for Scientific and Technical Creation and in the T-38 wind tunnel during the commissioning period. Analysis of correlated test results confirmed a good flow quality in the T-38 test section, good condition of wind tunnel structure and instrumentation, and the correctness of the data reduction algorithm. Small differences were observed in the pitching moment coefficient data obtained in the 'normal' and 'inverted' model configurations, and it has preliminary been concluded that the effect may have been caused by a slight asymmetry of flow in the rear part of the wind tunnel test section, the AGARD-C model being known for the high sensitivity of the pitching moment to local conditions.

Keywords

• wind tunnel
• transonic flow
• aerodynamic model
• aerodynamic characteristics
• aerodynamic forces
• aerodynamic moment