High pitch sweep rates in supersonic wind tunnel tests

• Published in: Materials today : proceedings 2023, Vol.93, p.712-718
• Main Authors: Damljanović, Dijana, Vuković, Djordje, Ilić, Biljana, Ocokoljić, Goran, Isaković, Jovan, Miloš, Marko
• Format: Article
• Language: English
• Subjects: Base pressure; Forces and moments; Pitch rate; Supersonics; Sweep; Wind tunnel
• ISSN: 2214-7853; 2214-7853
• DOI: 10.1016/j.matpr.2023.05.504

A typical test in a high-Reynolds-number blowdown wind tunnel, such as the VTI T-38 facility in Belgrade, involves a model sweep in a range of angles of attack. Increasing pitch sweep rates can bring two-fold benefit. The angle-of-attack range can be extended in tests at high stagnation pressures with limited run time, or test time can be shortened for the desired angle-of-attack range in other tests, in both cases bringing significant energy savings. The potential effect of the increased pitch rates on measurement data in the VTI T-38 wind tunnel was investigated in a recent supersonic wind tunnel test campaign of a hypervelocity standard model. The Mach 2 tests were performed at pitch rates of 2, 3, 4, 8 and 12° per second. While the wind tunnel balance measurement data were not seemed to be affected, the base pressure data revealed a high dependency on changing pitch sweep rates. It was found that the high lag in pressure piping affected the measured base pressure and, consequently, the forebody axial force, which is an important fact to know when dealing with ‘base drag corrected’ supersonic data. The conclusions derived from the Mach 2 tests have been verified in the additional Mach 4 tests. The verification tests confirmed that, for the currently employed base pressure measurement system, reliable measurement results can be obtained in wind tunnel tests by applying pitch rates up to 3° per second. The recommendations for modifications of the base pressure measurement system have been given.