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The aerodynamic characteristics of separated, recirculating flows behind a two-dimensional nozzle and bluff-body combination, which modeled a lean mixture combustor, was explored by a series of cold flow tests. The detailed distributions of mean velocities, static pressures, turbulent characteristics, and the tracer gas steady-state concentration were obtained. The flow velocity observations were successfully obtained by use of a laser velocimeter, whose data reduction system was devised particularly for use in highly turbulent flow measurements. Overall features of the mean field data revealed that the nozzle blowing diminished the longitudinal extent of the recirculation zone and substantially affected the mixing of tracer gas with the surrounding airflow. The Reynolds stress data imply that a zone of opposing shear was formed near the region of coexistence between negative and positive mean axial-velocities.

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This study deals with hydrodynamics phenomena around a ram flameholder in a water channel. The Particle Image Velocimetry (PIV) method has been used to get the velocity fields around two models of flameholders. The first model is a simple V-gutter and the second has the same shape with holes through its walls. We observed the same kind of phenomena with the two models of flameholders. Some vortices are alternately shed from both edges of the flameholder and rotate in opposite directions. But in the second model, the holes through its walls.induce jets that generate swirling motions inside the flameholder zone. These vortices perturb the flow pattern in the wake of the flameholder and induce a higher level of turbulence. As a result, this should improve the mixing fuel-air inside the flameholder zone and the combustion in the ramjet engine.