Study of buzz phenomenon using visualization of external shock structure

Abstract

An experimental study was carried out on an axisymmetric supersonic inlet with external compression in order to investigate the buzz phenomenon at different angles of attack and mass flow rates. The model was equipped with accurate and high-frequency pressure sensors, and the tests were conducted at Mach numbers varying from 1.8 to 2.5, for various angles of attack. Shadowgraph visualization technique, together with a high-speed camera, was used to provide the visual description of the shock structure in front of the inlet and to study the characteristics of buzz. Furthermore, pressure distribution over the spike surface was measured using several pressure sensors. Frequency of the buzz and shock displacement were measured by inspection of visualization pictures in each test. The obtained data from shadowgraphs were compared with those obtained from pressure measurements, and good agreement was found between them. The results revealed that for a moderate value of mass flow rate, the frequency of shock oscillation decreases as Mach number increases. Further, by increasing angle of attack, the shock displacement of oscillation will increase. At non-zero angles of attack, the displacement and frequency of shock motion show different behaviors on the leeward and windward sides of the body.

Aerodynamic Instabilities in High-Speed Air Intakes and Their Role in Propulsion System Integration

“…Soltani et al [36] extensively investigated buzz instability under a range of freestream conditions, M ∞ = 1.8-2.5, using an axisymmetric external compression intake. The study clearly shows that the Mach number affects the position of the normal shock, and depending on the freestream Mach number, the buzz may occur at higher values of the mass flow rate [89].…”

“…As mentioned before, the effect of the angle of attack with a varying mass flow rate exhibits different characteristics. More specifically, Farahani and Jaberi [89] observed that for a Mach number M ∞ = 2.0, within the AOA range of 0-3 • and 6-10 • , the buzz frequency displays a similar decreasing pattern. However, between the angles of 3 • and 6 • , and at a mass flow ratio of 0.26, strangely, the buzz frequency exhibits a large jump (see Figure 9 of Ref.…”

“…However, between the angles of 3 • and 6 • , and at a mass flow ratio of 0.26, strangely, the buzz frequency exhibits a large jump (see Figure 9 of Ref. [89]). This behavior is not observed in other values of mass flow rate or other Mach number cases.…”

“…The study demonstrates that the location of the normal shock shifts upstream with an increasing angle of attack, but the shock movement on the leeward side is larger, with a greater separation size compared to the windward side, causing the buzz to become asymmetric. In addition, the leeward and windward sides experience different shock displacement and buzz frequency for non-zero angles of attack [89].…”

“…Soltani and Farahani [62,89,99] looked more closely into the effects of the angle of attack on the buzz initiation and characteristics, and reported that for a constant Mach number of 2, increasing the angle of attack decreases the intake performance and the stability margin, causing an earlier initiation of the intake buzz. The combination of the angle of attack and mass flow rate seemed important since different characteristics were observed.…”