The effects of perforated cylinders on the vortex shedding on the suppression of a circular cylinder

Abstract

Abstract. The aim of this study is the control of unsteady vortical flow occurred downstream of a circular cylinder located in shallow water flow using concentrically located outer perforated cylinder. The porosities, ȕ have been changed between 0.1 and 0.8 in the present study. The increments of porosity ȕ were taken as 0.05 in the range of 0.1 and 0.8 with a hole diameter of d=10 mm. The ratio of inner cylinder diameter to outer cylinder diameter, D i /D o was selected as 0.25, 0.3, 0.4, 0.5 and 0.6 the inner cylinder diameter is D i =50mm where the outer cylinder diameter is D d =100mm. Experiments were performed at a constant depth of the water level as h=50mm (half of the outer cylinder diameter). Free stream velocity was taken as U =100 mm/s corresponding to a Reynolds number of Re D o =10000 based on the outer cylinder diameter. It has been observed that the inner circular cylinder was highly affected by the existence of surrounding outer perforated cylinders. It is observed that the intensity of Reynolds shear stress correlating, <u´v´/U 2 > is completely attenuated in the region both downstream of concentric cylinder and between the concentric cylinders. It is determined from the experiments that porosity, ȕ=0.55 is the most effective parameter for control of flow structure that is occurred from the inner cylinder.

CFD Modelling of Wake-Induced Vibration At Low Reynolds Number

“…The induced vibration on a single isolated rigid cylinder with an incoming linear flow to the bluff body is known as VIV. Many researchers have studied VIV, such as Naseer et al, [5], Pinar et al, [6], Soti et al, [7], Zahari and Dol [8] and Atrah et al, [9]. On the other hand, vibration can also be induced on a bluff body that experiences the wake of a flow from another bluff body known as WIV.…”

Effect of Shroud Hole on the Force Characteristics of a Circular Cylinder

“…The examples of shrouds are control rods [11]- [13], wire mesh [14]- [16], flexible mesh [17] and perforated shrouds [18]- [20]. The Perforated shrouds have been extensively used in several studies placed in shallow water [21], [22] and deep water [15], [18], [19], [23], [24] with the purpose of suppressing VIV. Gozmen and Akilli [15] studied the flow around bare cylinder case, shrouded with a permeable cylinder at Reynolds number of 5000 in deep water.…”