3-DIMENSIONAL HYPERSONIC LAMINAR BOUNDARY-LAYER COMPUTATIONS FOR TRANSITION EXPERIMENT DESIGN

The stability of boundary layers on sharp-nosed cones with elliptical cross sections is assessed using Linear stability theory and crossflow correlations. The objective is to identify a configuration for wind-t unnel testing that exhibits significant crossflow but also possesses a sufficient laminar region for boundary-layer stability probing. Parab olized Navier-Stokes computer codes were used to calculate the mean fl ow about cones with eccentricities of 1.5:1, 2.0:1, and 4.0:1 at a fre estream Mach number of 7.95 and freestream unit Reynolds number of 3.3 x 10(6) m(-1). Correlations indicated that transition was possible on each configuration at the above conditions. All three configurations showed unstable, inflectional velocity profiles and boundary-layer thi ckening along the centerline (minor axis) due to the influx of low-mom entum fluid. Crossflow separation was observed on the 2.0:1 configurat ion. Linear stability theory was used to calculate stationary crossflo w N factors on all three configurations, and to calculate traveling-wa ve N factors on the 1.5:1 and 2.0:1 configurations. All three configur ations showed crossflow instability, with the 4.0:1 configuration atta ining the highest N factors. The 1.5:1 and 2.0:1 configurations were u nstable to a broad spectrum of traveling waves, with the highest N fac tors attained on centerline, due to the unstable profiles there.