Investigation of turbulent flow past a yawed wavy cylinder

Low-frequency unsteadiness of vortex wakes over slender bodies at high angle of attack

“…However, the flow pattern at the after-body part far away from the fore-body will transit to Karman vortex shedding at some locations downstream if the cylinder part is sufficiently long. 6,[11][12][13] Besides the vortex shedding at an after-body, some intrinsic unsteady features also exist for the vortex system, as summarized in the review paper. 14 The unsteady characteristics of asymmetric vortices were examined in detail by Degani et al [15][16][17] They found initially unsteadiness on flow fields over slender bodies using numerical simulation, 15 thus carrying out experiments to identify these unsteady flows.…”

Passive control of flow structures around a circular cylinder by using screen

“…For the latter, heating the cylinder (Lecordier et al, 1991), rotary oscillation of the cylinder at an appropriate frequency (Lee and Lee, 2008;Naim et al, 2007), acoustics excitations (Blevins, 1985), and control of the electromagnetic force (Kim and Lee, 2001) can be remarked as the sample investigations. The passive control methods (Lam et al, 2010;Zhou et al, 2011) are still developed since there is no external energy input and no feedback sensor; furthermore they are easier to carry out than the active control methods which require actuation as well as sensing. However, many studies on the active control methods were also performed for improving efficiency of the control.…”

Numerical study of flows past airfoils with wavy surfaces

“…Sub-grid scale modeling is based on the Smagorinsky model (Smagorinsky, 1963) with a mixing length defined as l s ¼ min ky, C s D 1=3 , where k is the von Ká rmá n constant, y is the distance from the wall. The Smagorinsky constant C s is equal to 0.1 ( Lam and Lin, 2008;Lam et al, 2010;Liang and Papadakis, 2007) in the present study which is found to be a suitable value for simulation of flow around various bodies and D is the volume of the cell. The finite-volume discretization with second-order central schemes for momentum discretization is employed while a second-order implicit scheme is applied for temporal discretization.…”

“…To simulate the flow past an airfoil in such Reynolds number regime (Huang and Lin, 1995;Mueller and DeLaurier, 2003), the same LES approach on the previous wavy cylinder simulations (Lam and Lin, 2008;Lam et al, 2010) is used to solve the incompressible Navier-Stokes (N-S) equations on unstructured hexahedral grids. The filtered continuity and N-S equations are given as follows:…”

“…Recent investigations by Lin (2008, 2009) and Lam et al (2010) discovered that a circular cylinder with varying cross-section along the spanwise direction, named wavy cylinder, can reduce drag as well as minimize fluctuating lift and hence can suppress the body's vibration. Such wavy cylinders in a cross-flow would generate three-dimensional vortex sheets forming periodically repeating vortices along the spanwise direction.…”