| Summary: | 碩士 === 國立成功大學 === 航空太空工程學系 === 81 === The double pulsed laser holographic interferometry tech- nique
has been used to investigate the flow structure of a free
vortex type supersonic Aerodynamic Window.On comparing the flow
visualization results of three Aerodynamic Windows with
designed Mach number ratio of 1.6/2.65,1.6/3.0 and 1.6 /3.2,it
was observed that all of them can produce a very uniform
supersonic shear flow in the free vortex type shear flow
generation section.However,with the air supply total pressure
being comparatively low,on the high Mach number side of the
window the static pressure being dropped to lower than the
outside atmospheric pressure and thus the adverse pressure
gradient effect being propogated upstream through the subsonic
boundary layer causes the flow separa- tion on the wall of high
Mach number side.The radius of curvature of the jet stream is
being shift from its design condition due to the centrifugal
force of the jet stream as well as the results of the flow
separation.A diffuser was installed to overcome the change of
the curvature of the jet stream.It was found that with a
diffuser of same radius of curvature installed with its center
of curvature at same position as the Aerodynamic Window. The
jet stream from the Aerodynamic Window has the best curvature
and the low pre- ssure side of the sheared jet stream has a
very good acce- leration behavior.As the diffuser installed
with position of the center of curvature moving upward,the
curvature of the jet stream decreased and the flow separation
point on the low pressure side wall inside the Aerodynamic
Window moves upstream.For an Aerodynamic Window without
diffuser,the flow structures was observed that the jet stream
exiting from it is straight and no curvature.However,the flow
separation point on the low pressure side wall of the
Aerodynamic Window is at more downstream position comparing it
of the Aerodynamic Window with a diffuser installed 3mm away
from its original position.It shows that a proper choice
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