Bluff-Body Flow
The flow past a square cylinder was chosen to investigate the vortex shedding. An overview of the flow is given in Fig. 2. The Reynolds number based on cylinder diameter and mean velocity is 22 000. The RANS calculation were 2D, whereas the LES grid was expanded in spanwise direction, which leads to 30 times more cells compared to the RANS grid.
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Fig. 2 instantaneous u-velocity
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Fig. 3 phase averaged streamline
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Fig. 3 displays the strong influence of the model used in the RANS calculation.
The EASM reveals the same topological features as the LES, but differs in the extent of the recirculation zones.
The Wilcox model predicts, however, a considerably different flow field: the recirculation zone becomes larger and the wake is much more stretched.
This can also be concluded from table 1, where the global parameters are listed.
The Wilcox model cannot capture the transient dynamics of the flow, as both rms values are nearly zero.
The EASM predicts fluctuations in the range of the LES and almost the same drag coefficient.
However, slight differences appear in the predicted Strouhal number.
Tab. 1 global parameters
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Last modified: Fri Dec 17 10:40:59 CET 1999
