01. Experimental/Computational Fluid Dynamics

The turbulent wake behind a long circular cylinder is characterized by coherent structure, which is large-scale organized motions, particularly in the near-wake subregion. There exist limits in the velocity measurements no matter using the intrusive diagnostics such as hot-wire anemometry (HWA) or the non-intrusive diagnostics such as the particle image velocimetry (PIV), which are employed in this study. HWA is a point-wise measurement tool and can sense correctly the incoming flow direction within ± 45o. In addition, the intrusion of HWA may interfere with the flow field and result in measurement accuracy. PIV is a planar but indirect measurement tool. It needs input of seedings and takes the seedings’ velocities as the velocities of the surrounding fluid flows. Numerical simulation can overcome the restrictions mentioned for the above measurements. However, the theoretical approach for simulation of the turbulent near-wake flow is heavily dependent on the employed turbulence model. The SST k-ω IDDES formalism on the triple-decomposition-like basis, which is supposed to be capable of better capture of the coherent structure in the near-wake and good predicting capabilities for the near-wall flow behaviors is employed in this study. Mutual verifications of the results obtained with these three different approaches and discussions for pros and cons of each approach are presented for the near wake at Reynolds number of 3860.