| Autor: |
Wagner, Justin L., DeMauro, Edward P., Casper, Katya M., Beresh, Steven J., Lynch, Kyle P., Pruett, Brian O. |
| Zdroj: |
Experiments in Fluids; Jun2018, Vol. 59 Issue 6, p1-1, 1p |
| Abstrakt: |
The impulsive start of a circular cylinder in a shock tube was characterized with time-resolved particle image velocimetry measurements (TR-PIV) at 50 kHz using a pulse-burst laser. Three Reynolds numbers Re of 1.07, 1.63 and 2.46 × 105 were studied adding insight into the transient process near the drag crisis. In all cases, vorticity was maximum in the first pair of vortices formed. In a fashion analogous to previous studies at Re ≤ 104, a single symmetric vortex pair was first shed from the cylinder at Re = 1.07 × 105 prior to the eventual transition to a von Kármán vortex street. In contrast, at Re ≥ 1.63 × 105, two or more symmetric vortex pairs were first shed. The non-dimensional time for the wake to begin to exhibit asymmetry was also found to be lower at the two higher Re. The time required to reach a fully antisymmetric wake (peak von Kármán shedding) was roughly five times the asymmetric onset time. Altogether, the study indicates a transformation in the impulsive wake structure and associated time scales to occur at Re near 1.6 × 105. [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
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