Wind Tunnel Investigation of Downstream Wake Characteristics on Circular Cylinder with Various Taper Ratios

Circular cylindrical towers which are sporadically seen in engineering structures such as buildings, towers, etc are basically considered as bluff body. The flow around the circular cylindrical structures gained interest among the researchers. Since there has been lot of development in infrastructure, transport, telecommunication in the last two decades. Such cylindrical towers invite more attention, since the failure of circular cylindrical tower/ structures is not only due to the surface pressure distribution but also due to the effect of wake induced by the flow separations. Even though there are engineering challenges in circular cylindrical structures, different designs of structures such as stepped cylinders, rough cylinder and taper cylinder etc. are used in various applications. The flow field downstream is relatively less explored for the tapered circular cylinder than other cylinders. Effects of downstream wake due to such cylindrical structures are not only affecting other structures downstream but also induce vibration on itself. In this paper, circular cylinders of various taper ratios are considered for the study at various sub critical Reynolds number. Extensive wind tunnel studies were performed on various taper ratios ranging from ۰.۶ to ۱ in the increment of ۰.۱ for various x/D and h/D locations using hot wire anemometer. Various parameters like wake width, dissipation length, wind speed ratios were measured downstream for various taper ratios. The result shows that the magnitude of wake width gradually increases with increase in downstream distance along with increase in taper ratio whereas dissipation length and wind speed ratio increases with decrease in taper ratio.

Keywords:

Wind speed ratio , Dissipation length , Wake width , Velocity deficit , Tower wake