# In Fig along the upper shear layer the frills

At each grid point over the entire flow domain, an average of three PSD yields the ensemble-averaged spectral amplitudes at each ACT 335827 frequency.

3. Results and discussions

3.1. Frequency responses and flow structures for D/d = 1.0

Fig. 2(a) demonstrates the relation between the Strouhal numbers (Stn and Stw) and the gap ratio for side-by-side cylinders of equal diameter. In Fig. 2(b) and (c), the point Q is near the location where the vortices A and B are formed and the point P is at downstream location where the shear layers roll up into a vortex D or cluster of vortices A, B and C. Depending on the flow structures at the gap ratios and Reynolds numbers studied, the streamwise locations of the points P and Q may vary; but their elevations are along the free stream sides of both shear layers to have good signal quality and correctly demonstrate the characteristic frequencies of the wide and the narrow wakes.

Fig. 2. Frequency responses of the wide and narrow wakes and typical flow structures. Note steroids depending on the Reynolds numbers and the gap ratio, the streamwise locations of the measuring points P and Q shown in (b) and (c) may change. They are situated on the free stream sides of the shear layer to monitor the characteristic frequencies of the wide and the narrow wakes.Figure optionsDownload full-size imageDownload as PowerPoint slide