In this paper a dye experiment was implemented to investigate the vertex shedding patterns of flow around 8 circular cylinder, Cell structures were observed clearly and the cell lengths were measured at several separated Reynolds numbers (2700, 6660, 7900). Meanwhile dynamic pressure measurement was carried out with 10 semiconductor pressure transducers. Spectral analysis. phase analysis and correlation analysis of the 10 pressure signals were done to investigate characteristics in the spanwise. Furthermore PIV was also applied to detection of 3-D characteristics of flow around 8 circular cylinder by mains of the bi- laser sheet illuminating method Finally a theoretical model was proposed based on 3-D N-S equation in cylindrical coordinate frame. The model successfully interpreted the cell pattern of vortex shedding and expected the relationship between cell length and Reynolds number. This relationship agrees very well with the results of previous experiments published in some paper and the results from the dye and PIV experiments carried out by author. Therefore this model may describe the intrinsic features of the flow around a circular cylinder in the spanwise.
There has been a vast amount of literature published on subjects related to vortex shedding from a circular cylinder. (King(l977), Lienhard (1966), el Baraudi (1960), Grelach (1970), Sarpkaya (1981,1989), Phillips 417 (966). Gerrard 0968, 1963, 1966. 1978). Hama (1967). Humphreys (1960), Graham (1966), Bruun and Davies (1975») Although the basic mechanisms of the vortex shedding ∼process have been known for some time, (the early work being done by Strouhal. Reyleigh and Von Karmman) recent advances in instrumentation and measurement technology have opened up new areas of investigation. Of these. the understanding of the 3-D characteristics of vortel shedding poses the most challenging problem whether from the experimental or theoretical standpoint.