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Annular Impinging Jets and an Active Control of Hysteretic Effects
Devani, Yogendrasasidhar ; Antošová, Zuzana ; Trávníček, Zdeněk
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 higher Re>9000, the hysteresis were not found.
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Annular impinging jets and an active control of hysteretic effects
Devani, Yogendrasasidhar ; Antošová, Zuzana ; Trávníček, Zdeněk
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.
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Annular Jets and Annular Impinging Jets
Turek, Tomáš ; Trávníček, Zdeněk ; Šafařík, Pavel ; Tesař, Václav
A near field of annular jets and annular impinging jets is experimentally investigated at three inner/outer diameter ratios 0.84, 0.90 and 0.95. Time-mean velocity profiles are evaluated, and three main flow field zones are distinguished – in agreement with the literature, namely the initial merging zone, the intermediate one, and the fully merged one. A distribution of the pressure on the impingement wall is measured for various nozzle-to-wall distances. Two basic annular impinging jet regimes are clearly distinguished, with either small or large recirculation bubbles. Moreover, a hysteretic behavior has been identified under specific parameters.
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