DOI: 10.1615/TSFP4
STRUCTURE OF OSCILLATING VORTEX GENERATOR JETS
Краткое описание
The suction side boundary layer of an airfoil passage was studied experimentally. The pressure gradient along the airfoil was typical of a low pressure turbine environment, and the Reynolds number, based on suction surface length and exit velocity, was 25,000. A row of oscillating vortex generator jets (VGJs), located at the pressure minimum on the suction side was used for flow control. The jets had no net mass flow and a dimensionless oscillation frequency, F+, of 0.65. Velocity profiles were acquired with single and cross sensor hot-wire probes at multiple streamwise and spanwise positions downstream of the VGJs. Time averaged results showed that with the VGJs active, the boundary remained attached and essentially laminar, and was spanwise uniform. Without the VGJs the boundary layer separated and did not reattach. Phase averaged results showed that instantaneously the boundary layer was very non-uniform across the span. The outpulse of the jets generated turbulence and produced streamwise vortices, which brought high speed fluid into the near wall region and helped to keep the boundary layer attached. The vortices persisted to the trailing edge. A calmed region followed the jet pulsing events, and the calmed flow was characterized by a thin, spanwise uniform boundary layer that was resistant to separation. Phase averaged mean velocity, Reynolds stresses, and integral quantities are presented to illustrated the structure of the unsteady boundary layer.