Experiments were conducted to study the jet dynamics of unconfined and
confined coaxial high-speed flows from radially lobed nozzles. The sh
ear-layer growth rate of the lobed nozzles was found to be considerabl
y higher than that of a conical nozzle, Pressure profiles indicated in
creased radial uniformity and transport of properties between flows. I
ncreases in lobe height and number of lobes were associated with enhan
ced mixing and larger total pressure drops. The thrust loss observed w
as due primarily to divergent nozzle flow and duct friction losses. Us
e of a confining duct forced interaction of the Bows and enhanced mixi
ng. Compression of the primary flow produced intense compression-expan
sion regions in the flowfield. Another advance over earlier studies is
the visualization of the axial vortices generated by lobed nozzles. T
hese vortices can be linked to the observed cross-plane transport of p
roperties.