Abstract
In this present work, the effects of surrounding outer porous cylinder on vortex structure downstream of a circular inner cylinder are investigated experimentally in deep water flow. The porosity of outer cylinder were selected as β = 0.4, 0.5, 0.6, 0.65, 0.7, 0.75, 0.8 and 0.85. Porosity is defined as the ratio of the gap area on the body to the whole body surface area. The ratio of outer cylinder diameter to inner cylinder diameter, Do /Di was selected as 2.0, i.e. the inner cylinder diameter is Di = 30 mm where the outer cylinder diameter is Do = 60 mm. All experiments were carried out above a platform. The water height between the base of the platform and the free surface was adjusted as 340 mm. Free stream velocity is U = 156 mm/s, which corresponds to the Reynolds number of Rei = 5,000 based on the inner cylinder diameter. It has been observed that the outer porous cylinders have influence on the attenuation of vortex shedding in the wake region for all porosities. The turbulent intensity of the flow is reduced at least 45% by the presence of outer porous cylinder compared to the bare cylinder case. The porosities β = 0.4 and 0.5 are most suitable cases to control the flow downstream of the circular cylinder.
Highlights
They carried out experiments by Digital Particle Image Velocimetry (DPIV) for Reynolds Numbers of 200, 400 and 750, based on the circular cylinder diameter D
Hu and Zhou [12] measured the wake of asymmetric bluff bodies using particle image velocimetry, laser Doppler anemometry (LDA), load cell, hotwire, and flow visualization techniques at Re = 2,6008,500 based on the freestream velocity
To explain the flow structure, the instantaneous dye image, normalized Reynolds stress contours and dimensionless turbulent kinetic energy (TKE) contours are shown as seen in figure 3
Summary
Stappenbelt [10] investigated the proposed utility of splitter-plate wake stabilization as a passive control mechanism for vortex-induced vibration (VIV) mitigation for low aspect ratio cylinders. His experiments of Stationary cylinder show the effectiveness of splitter plates in reducing lift and drag coefficients for a cylinder in uniform flow. Hu and Zhou [12] measured the wake of asymmetric bluff bodies using particle image velocimetry, laser Doppler anemometry (LDA), load cell, hotwire, and flow visualization techniques at Re = 2,6008,500 based on the freestream velocity They revealed that with increasing corner radius, the flow reversal region is expanded and the vortex formation length is prolonged. The porous wrapper reduces the pressure drop and skin friction which leads to a reduction in drag compared with a solid cylinder of equal radius
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
