GALCIT Home Page
| 2000-2001 Fluids Seminar Page |
Graduate Aeronautical Laboratories
Caltech
Abstract-
A series of exploratory boundary layer transition experiments were performed
on a
5.06 degree half-angle cone at zero angle-of-attack in the T5 Hypervelocity
Shock
Tunnel in order to test a novel hypersonic boundary layer control scheme.
Recently
performed linear stability analyses suggested that transition could be delayed
in
hypersonic boundary layers by using an ultrasonically absorptive surface that
would
damp the second mode (Mack mode). The cone used in the experiments was
constructed
with
a smooth surface on half the cone (to serve as a control) and an acoustically
absorptive
porous surface on the other half. It was instrumented with flush-mounted
thermocouples to
detect the transition location. Test gases investigated included nitrogen and
carbon
dioxide at M = 5 with specific reservoir enthalpy ranging from 1.3 MJ/kg
to 13.0 MJ/kg and reservoir pressure ranging from 9.0 MPa to 50.0 MPa.
Detailed
comparisons
were performed to insure that previous results obtained in similar boundary
layer transition experiments (on a regular smooth surface) were reproduced and
the results were extended to examine the effects of the porous surface. These
experiments indicated that the porous surface was highly effective in delaying
transition provided that the pore size was significantly smaller than the
viscous length scale.
|
GALCIT Home Page
|
|