Abstract:
The effects of leading edge bluntness and sweep angle on the three
dimensional glancing shock wave - boundary layer interaction have been
investigated. A large number of hemi-cylindrically blunted fins with
leading edge diameter ranging from 0 to l.Oin, with leading
edge sweep angles between 0° and 75° were tested. The incidence
angle was varied from 0° to 21°. The shock wave from each configuration
interacted with a fully developed turbulent boundary layer growing along
the tunnel side wall. The free stream Mach number in the 9in x 9in
continuous flow supersonic wind tunnel was 2.4 and the Reynolds number
based on boundary layer thickness was 5 x 10^. Experimental investigations
included oil smear tests, surface pressure surveys, schlieren pictures
of the inviscid shock envelopes and shock structure in the plane of
symmetry.
The study highlighted the significant effects of bluntness and sweep
on the scale and character of the interaction. While bluntness intensified
the interaction, sweep alleviated its intensity. The most dramatic effect
of sweep angle was observed when the leading edge was swept from 0° to 30°.
Sufficiently outboard of the plane of symmetry, the features of blunt
and sharp fins became similar. The boundary between the inner "bluntness
dominated" and the outer "viscous dominated" regions shifted inboard
at the higher incidence and sweep angles.
The characteristic surface oil flow patterns showed little change for
sweep angles up to A = 60°. Leading edge bluntness increased the scale of
the interaction almost linearly while leaving its character unchanged.
The multiplicity of the separation and attachment lines on the side wall
and the fin surface, suggested a system of vortices in the interaction
region. Flow field models have been proposed over the range of sweep
angles considered in the present study. The number and strength of the
vortices is seen to depend on the leading edge bluntness, sweep
and the incidence angle.
The important parameters governing the primary separation distance
and the peak pressure in the plane of symmetry have been identified.
Correlation formulae suggest a strong interdependence of the various
parameters concerned.
