Turbulent boundary-layer characteristics over a flat-plate/wedge configuration at Mach 6

Abstract

Nomenclature PO= stagnation pressure P t = local pitot pressure P s = static pressure PI -surface pressure at a given xy location P ref = undisturbed reference surface pressure acquired at x = -6.469 cm Presented as Paper 90-3028 at the Re =unit Reynolds number/meter T 0 = stagnation temperature T t = local total temperature T s = static temperature U = local mean velocity C/ inf = freestream velocity x t y, z = streamwise, lateral (along the plate's width), and perpendicular to plate distance <5 = boundary-layer thickness d T = thermal boundary-layer thickness (where T t is 1% of the freestream) IntroductionA RECENT review of aerothermodynamic problems surrounding hypersonic flight and its associated research by Holden 1 demonstrates our present lack of predictive capability. Holden states that the intense research programs of the 1960s and early 1970s were superseded by hypersonic flow investigations that were limited to supporting specific missions such as the Space Shuttle, the Jovian entry vehicle, and ballistic re-entry vehicles. The results of this review vividly point out the scarcity of previous research encompassing turbulent boundary-layer separation and hypersonic flows.Many earlier studies 2 ' 7 on turbulent boundary-layer separation were preformed on smooth surfaces in supersonichypersonic flow regimes. These studies investigated incipient separation using compression corners to simulate flow over aerodynamic flaps or ailerons. Because high-speed flight vehicles employ various external control devices that can produce large areas of flow separation, a program was initiated to examine such effects. Model and Experimental FacilityA smooth flat-plate/22 deg wedge configuration extending approximately 45.7 cm in streamwise length and 35.6 cm in lateral extent was machined to a no. 32 surface finish. A sharp 10-deg asymmetric leading edge was also machined into the model. Approximately 39.4 cm downstream from this leading edge was the intersection point of the instrumental wedge.The model was then mounted downstream of a 30.5-cm open jet, high-Reynolds-number, Mach 6 blowdown wind tunnel. By adjusting the total pressure and stagnation temperature, unit Reynolds numbers ranging from approximately 33 to 98 x 10 6 /m were obtained.Model instrumentation consists of 46 surface pressure points and seven type-K (chromel/alumel) thermocouples. These ports were spaced streamwise in the x direction along the plate at its center (y = 0) and ±9.5 mm off the center through the interaction region. Boundary-Layer CharacteristicsDistribution of both the total pressure and total temperature in the boundary layer were obtained using a pitot pressure probe and a Winkler-type temperature probe. To allow for high-resolution, near-wall total pressure measurements, the tip of the pressure probe was flattened resulting in an overall height of 0.51 mm. For the same reasoning, a miniature Winkler probe was fabricated measuring 1.52 mm in diameter. The recovery factor for this probe was determined to be 0.984 and the uncertainty i...