Annular Impinging Jets and an Active Control of Hysteretic Effects

Abstract

An annular impinging air jet with and without flow control was studied experimentally using measurements of the wall pressure and flow velocity by the Pitot probe. To investigate flow control swirling effects, eight synthetic jets were generated from the nozzle center body. The experiments cover Reynolds numbers 4000–10,000 (evaluated from the outer exit diameter of the annular nozzle). For Re<9000, the bistability and hysteresis were identified and two different flow field patterns (A, B) were found under the same boundary conditions. For A pattern, a small recirculation area (bubble) of separated flow is attached to the nozzle center body. For B pattern, a large recirculation area bridges entire nozzle-to-wall distance. For higher Re>9000, the hysteresis were not found.