Evolution Of The Experimental Study Of Flow Around Two Cylinders Of Space Based On Scale Extraction

This study put emphasis on the spatial evolution of flow around two side-by-side circular cylinders and the experimental instruments that realized the simultaneous measurements of velocity fluctuations in the wake and the pressure fluctuations on the cylinder's walls, particularly on the direct measurement of the pressure fluctuations by the strain-patches. Base on the simultaneous measurements, the experimental researches could be separated into two parts corresponding to the two values of the diameter of the cylinder with 28 mm and 7 mm, termed as the thick-cylinder's experiment and the thin-cylinder's experiment respectively.As the signals of the pressure fluctuations were often contaminated by the 50Hz electrical signal with its harmonics, a kind of method based on the EMD (i.e. empirical mode decomposition put forward by N.E.Huang) was adopted to wide off the non-intrinsic disturbances. However, we didn't achieve the desired results, subsequently the analysis about the press-velocity phase relations can not be carried our due to the severe electrical disturbances.It is well known that there exist some kinds of large-scale vertical structures accompanying with some kinds of small-scale structures if it is possible. A kind of scale-identification based on EMD was put forward, and some novel results differ from general FFT was attained through this method. This scale-identification method as we thought can also be adopted to other flow researches. On the other hand, through the HHT based on the EMD of the velocity fluctuations, it was discovered that the instant-frequency of some scales can converging energy continuously. Related these scales to certain kinds of vortical structures in the flow field, the declined flow character of the wake of side-by-side circular-cylinders was further certified.