An experimental study was conducted to investigate the near wake structure and instability characteristics related to the mechanism of vortex shedding behind a V-gutter in a simulated augmentor. The shedding mechanism is generally believed to be closely associated to the combustion instability and flame stabilization problems in augmentors. Experiments were performed in a simulated augmentor with a V-gutter of 5/12 blockage ratio and operated at a Reynolds number of 630. From flow visualization, the flow structure in the near wake can be divided into four distinctive regions: the dead zone, the vortex roll-up region, the buffet zone, and the reversed flow zone. Vortex shedding is identified as a result of splitting of the shear layer vortex after impingement of the upper and lower shear layers in the buffet zone. A feedback loop consisting of the path along the shear layer and the reversed flow zone with a 8π phase-matching is identified. This phase-matching characterizes the global resonance in a limit-cycle oscillation (self-sustained oscillation). Absolute instability regions in the near wake are identified in most areas of the reversed-flow zone. The shedding frequency is identified to be the one possessing maximal energy amplitude of the transverse velocity fluctuation at the end of the self-sustained resonance region, also called the direct resonance region.
|Number of pages||11|
|Journal||Journal of the Chinese Society of Mechanical Engineers, Transactions of the Chinese Institute of Engineers, Series C/Chung-Kuo Chi Hsueh Kung Ch'eng Hsuebo Pao|
|Publication status||Published - 1997 Dec|
All Science Journal Classification (ASJC) codes
- Mechanical Engineering