E. Kufner, U. Dallmann

The option of the presented investigations is to perform studies to an optimization of the bluntness of hypersonic space planes with respect to the laminar/turbulent boundary-layer transition. Herein the bluntness effect on stability and transition is theoretically investigated by a generic simplification of the fuselage nose tip to a sharp and various circular blunt cones at zero angle of attack. The paper is dealing with the calculation of the laminar mean flow as well as with the instability analyses on the basis of primary local linear stability theory and an ideal gas assumption. Besides the effect of a variation of the nose radius on disturbance amplifications within the boundary- and entropy layer, the presented results also cover influences of wall temperature conditions On amplification rates. Within the mean flow calculation by Thin-Layer-Navier-Stokes methods a good shock resolution appears to be important for the determination of an appropriately accurate laminar mean fi.ow. Comparisons of Thin-Layer Navier-Stokes and Euler/second order Boundary Layer code solutions show a good agreement. The calculated disturbance amplification rates show clear deviations to corresponding experimental results of Stetson et al.. The general effect of wall cooling is to amplify second mode waves and to damp first mode instabilities as known from flat plate investigations. The new observations are that the wall temperature effect is more pronounced on the first mode than on the second mode and that the wave angle of maximum amplification of the first mode is increasing with cooling. The provocation of transition reversal by bluntness increasing has not been successfull. However, an unexpected vanishing of the first mode has appeared. Derived from such cases and cases of a complete damping of the first mode due to wall cooling an expansion of the double generalized inflection point criterion is proposed for finite local Reynolds numbers. For the first time two different entropy layer instability types can be introduced, which may have important effects on the aerodynamic optimization of future space planes.

9. DGLR-Fach-Symposium, Erlangen, 1994

Conference Paper

englisch

21,0 x 29,7 cm, 6 Seiten

DGLR-Bericht, 1994, 1994-04, Strömungen mit Ablösung; S.204-209; 1994; Deutsche Gesellschaft für Luft- und Raumfahrt - Lilienthal-Oberth e.V., Bonn

NA

aerodynamics, boundary layer transition, boundary layers, laminar flow, turbulent flow, hypersonic flow

Bestellbar

1994