Mean Flow Structure of Swept Impinging Oblique Shock Boundary Layer Interactions
PublisherThe University of Arizona.
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AbstractAn experimental investigation has been conducted to assess the e↵ect of sweep on the mean flow structure of impinging oblique Shock/Boundary Layer Interactions (SBLIs), specifically focused surface flow visualization and mean wall pressures. Four shock generators are utilized with x-y plane deflection of ✓ = 12.5!, and x-z plane sweep angles of 15.0!, 22.5!, 30.0!, and 40.0!. The swept oblique shocks impinge upon the naturally turbulent Mach 2.3 boundary layer along the tunnel floor (Re✓ ⇡ 5000). The resultant SBLIs all exhibit significant separation, with a structure that grows in the spanwise direction. Surface flow visualization shows a quasi-infinite region of separation that is limited by corner e↵ects at the root and tip of the interaction. The rise in mean pressure near separation scales locally with cylindrical similarity suggesting the three-dimensional separation along the span obeys Free Interaction Concept. Local reattachment behavior is only mildly dependent upon span. Convention from literature states that when the flow features, such as separation and reattachment lines are parallel, the interaction scales cylindricalyly. Conversely, when these flow features diverge from each other, the interaction scales conically. Divergence of separation and reattachment lines indicated that the global shock structure scales cylindrically for shock generator sweep angles less than 22.5! and conically above this angle. Another wind tunnel configuration suggests that the incoming boundary layer can influence this behavior. Similar trends to compression ramp observations (Settles and Teng, 1984) are seen for the asymptotic behavior of the inception length near the root of the SBLI. This suggests a cylindrical/conical boundary similar to that found from the divergence of separation and reattachment lines. The root behavior was further investigated using a delta shock generator producing an inviscid shock similar to the shock generator with an x-z plane sweep angle of 22.5!. Surface flow visualization shows good agreement between the two shock generators at the separation line. The pressure at separation also appears to align between the two, but the delta span, which is limited by tunnel size, is not sufficient to generate a quasi-infinite region.
Degree ProgramGraduate College