Affiliations: Dept. of Aerospace Engineering, Indian Institute of
Science, Bangalore-560 012, India. Tel: +91-80-309-2522; Fax: +91-80-360-0134;
E-mail: jaggie@aero.iisc.ernet.in | Shock Wave Research Center, Institute of Fluid
Science, Tohoku University, Sendai-980-8577, Japan
Abstract: The presence of an adverse pressure gradient, shock/shock
interaction and shock wave/boundary layer interaction often induces flow
separation around bodies. However, the effect of dissociated flow on separated
flow characteristics, especially at hypersonic speeds, is still not clear, and
considerable differences are observed between experiments and numerical
simulations. In this investigation, the unsteady separated flow features around
double cones are visualized in the Shock Wave Research Center (SWRC)
free-piston driven shock tunnel at a nominal Mach Number of 6.99 using multiple
optical techniques. The time resolved shock structure oscillations in the flow
field around double cones (first cone, semi-apex angle = 25°; second cone,
semi-apex angles=50°, 65°, 68° and 70°) have been visualized
using a high-speed image converter camera (IMACON) at a nominal stagnation
enthalpy of 4.8 MJ/kg. In addition, flow visualization studies around the
double cone is also carried out using Schlieren and double exposure holographic
interferometry in order to precisely locate the separation point and measure
the separation length. The presence of a triple shock structure in front of the
second cone and a non-linear unsteady shock structure oscillation in the flow
field are the significant results from visualization studies on the
25°/65°, 25°/68° and 25°/70° double cones. On the other
hand, the flow field around 25°/50° is relatively steady and Type V
shock/shock interaction is observed. Illustrative numerical simulation studies
are carried out by solving N-S equations to complement the experiments. The
simulated flow features around a double cone agree well qualitatively with
experiments.
