Effect of spherical roughness on hypersonic boundary-layer transition.

Abstract

Tests were conducted in the Arnold Engineering Development Center (AEDC) C Tunnel at a Mach number of 10 on a sharp slender cone and on the frustum, with three alternate spherical bluntness noses to determine the size of spherical roughness required to effectively trip to a turbulent boundary layer. The spherical roughnesses were placed on the surface of the sharp cone and at several flow-inclination angles on the spherical noses. Data are correlated in terms of k/d* and a trip-diameter Reynolds number that accounts for changes of local Reynolds number profile over the trip height. A definite effect of tripping effectiveness was noted as wall temperature changed. Laminar and turbulent heat-transfer results were in good agreement with the Eckert reference enthalpy method. Angle of attack affected transition by causing it to occur earlier on the leeward side for a smooth cone, but where transition was induced by roughness, it occurred earlier on the windward side. The results of the investigation may be utilized to determine allowable size of ablation roughness or spacing and position of roughness required for artificially inducing turbulence on cones and sphere cones for turbulent heating experiments in wind tunnels and flight. NomenclatureCp = specific heat at constant pressure, Btu/lb °R Cv = specific heat at constant volume, Btu/lb °R g = 32.2 ft/sec 2 = gravitational const h = enthalpy, Btu/lb H = q/T Q -T w = heat-transfer coeff, Btu/ft 2 sec°R J = 778 ft-lb/Btu = Joule's const k = trip diam, ft K = thermal conductivity, Btu/ft sec°R L = characteristic length, ft M = Mach number p = pressure, psf p r = (C P /K}n = Prandtl number q = heating rate, Btu/ft 2 sec RN = nose radius, in. RB = base radius, in. Rek = pkUkk/nk = trip Reynolds number Re x = peVeX/Ve = Reynolds number based on length Red* = peHeS*/v e = Reynolds number based on displacement thickness Rexk = In I P~^ V x = Reynolds number based on integrated J 0 \ fJLe / flow and length to the trip condition <s = wetted length, ft t = time, sec T = temperature (°R) u = velocity, fps x = longitudinal distance from stagnation point or leading edge, ft y =• radial distance from centerline, ft a = angle of attack, deg 7 -Cp/Cv d = velocity thickness, ft 8* = displacement thickness, ft = dimensionless velocity thickness '2 -= dimensionless displacement thickness Presented as Preprint 66-26 at the AIAA 3rd Aerospace *FP = 0 = momentum thickness, ft fj, = dynamic viscosity, Ib/ft sec p = density, Ib/ft 3 Subscripts c = convective e = edge of boundary layer FP = flat plate k = trip diam L = laminar N = nose o = stagnation r = recovery (adiabatic wall) T = turbulent w = wall oo = freestream Superscript * = reference (based on Eckert's reference enthalpy)

Unit Reynolds number, Mach number and pressure gradient effects on laminar–turbulent transition in two-dimensional boundary layers

“…The unit Reynolds number effect has been observed in various hypersonic facilities (Stainback 1967;Stainback et al 1974;McCauley et al 1966;Softley et al 1969) and was carefully investigated by Stetson et al (1986). However, it has never been investigated in a large subsonic flow regime before, which is most relevant for commercial aircraft today.…”

Effects of Roughness on Hypersonic Boundary-Layer Transition

“…Bishop reviewed roughness-induced transition on supersonic blunt bodies [34,35] [36]. The effect of nose tip roughness on frustum transition for blunt sphere cones was reviewed in [5] (see also [37]). Transition on capsules and planetary probes was previously reviewed by the present author, without special attention to roughness effects [38].…”

“…It should be noted that in Fig. 20, Klebanoff et al 1955 is apparently [16], Van Driest and Blumer is from [14] and an unavailable North American Aviation report [68] (for which the data may be available elsewhere), Korkegi 1956 is from [69], where these data are actually from sidewall contamination rather than a roughness element, Potter [72] (see also [37]), and the Morrisette 1969 data was generated for [64].…”

Development of a time-resolved quantitative surface-temperature measurement technique and its application in short-duration wind tunnel testing

“…The unit Reynolds number effect has been observed in various hypersonic facilities (McCauley et al, 1966;Softley et al, 1969;Stainback, 1967;Stainback et al, 1974) and was carefully investigated by Stetson et al (1986). However, it has never been investigated in a large subsonic flow regime before, which is most relevant for commercial aircraft today.…”