Annular impinging jets and an active control of hysteretic effects

0563923 - ÚT 2023 RIV CZ eng V - Research Report
Devani, Yogendrasasidhar - Antošová, Zuzana - Trávníček, Zdeněk
Annular impinging jets and an active control of hysteretic effects.
Praha: Ústav termomechaniky AV ČR, v. v. i., 2022. 64 s.
R&D Projects: GA ČR(CZ) GC21-26232J
Institutional support: RVO:61388998
Keywords : annular jet * impinging jet * bistability * hysteresis
OECD category: Thermodynamics

An annular air jet with and without flow control was studied experimentally using flow visualization and measurements of the wall pressure and flow velocity by the Pitot and Prandtl probes and the hot-wire anemometer. To investigate flow control swirling effects, eight synthetic jets were generated from the annular nozzle center body.The experiments cover Reynolds numbers 4000–10000 (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 and 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 of separated flow bridges entire nozzle-to-wall distance. For higher Re > 9000, the bistability and hysteresis were not found.Flow control swirling effects causes suppression of the hysteresis. Moreover, weak flow control causes that the entire annular jet is forced into a precessing motion.
Permanent Link: https://hdl.handle.net/11104/0336270