The effect of flow perturbations on the near wake characteristics of a circular cylinder

2003 ◽  
Vol 18 (3-4) ◽  
pp. 367-386 ◽  
Author(s):  
E. Konstantinidis ◽  
S. Balabani ◽  
M. Yianneskis
Keyword(s):  
Circular Cylinder ◽  
Near Wake ◽  
Wake Characteristics

Numerical investigation of near-wake characteristics of cavitating flow over a circular cylinder

2016 ◽  
Vol 790 ◽  
pp. 453-491 ◽  
Author(s):  
Aswin Gnanaskandan ◽  
Krishnan Mahesh
Keyword(s):  
Circular Cylinder ◽  
Single Phase ◽  
Three Dimensional ◽  
Low Frequency ◽  
Reynolds Numbers ◽  
Cavitating Flow ◽  
Cylinder Surface ◽  
Near Wake ◽  
Eddy Simulation ◽  
Wake Characteristics

A homogeneous mixture model is used to study cavitation over a circular cylinder at two different Reynolds numbers ($Re=200$ and 3900) and four different cavitation numbers (${\it\sigma}=2.0$, 1.0, 0.7 and 0.5). It is observed that the simulated cases fall into two different cavitation regimes: cyclic and transitional. Cavitation is seen to significantly influence the evolution of pressure, boundary layer and loads on the cylinder surface. The cavitated shear layer rolls up into vortices, which are then shed from the cylinder, similar to a single-phase flow. However, the Strouhal number corresponding to vortex shedding decreases as the flow cavitates, and vorticity dilatation is found to play an important role in this reduction. At lower cavitation numbers, the entire vapour cavity detaches from the cylinder, leaving the wake cavitation-free for a small period of time. This low-frequency cavity detachment is found to occur due to a propagating condensation front and is discussed in detail. The effect of initial void fraction is assessed. The speed of sound in the free stream is altered as a result and the associated changes in the wake characteristics are discussed in detail. Finally, a large-eddy simulation of cavitating flow at $Re=3900$ and ${\it\sigma}=1.0$ is studied and a higher mean cavity length is obtained when compared to the cavitating flow at $Re=200$ and ${\it\sigma}=1.0$. The wake characteristics are compared to the single-phase results at the same Reynolds number and it is observed that cavitation suppresses turbulence in the near wake and delays three-dimensional breakdown of the vortices.

scholarly journals The drag-adjoint field of a circular cylinder wake at Reynolds numbers 20, 100 and 500

2013 ◽  
Vol 730 ◽  
pp. 145-161 ◽  
Author(s):  
Qiqi Wang ◽  
Jun-Hui Gao
Keyword(s):  
Circular Cylinder ◽  
Flow Field ◽  
Unsteady Flow ◽  
Numerical Solutions ◽  
Reynolds Numbers ◽  
Adjoint Equations ◽  
Cylinder Wake ◽  
Near Wake ◽  
Navier Stokes Equation ◽  
D 20

AbstractThis paper analyses the adjoint solution of the Navier–Stokes equation. We focus on flow across a circular cylinder at three Reynolds numbers, ${\mathit{Re}}_{D} = 20, 100$ and $500$. The quantity of interest in the adjoint formulation is the drag on the cylinder. We use classical fluid mechanics approaches to analyse the adjoint solution, which is a vector field similar to a flow field. Production and dissipation of kinetic energy of the adjoint field is discussed. We also derive the evolution of circulation of the adjoint field along a closed material contour. These analytical results are used to explain three numerical solutions of the adjoint equations presented in this paper. The adjoint solution at ${\mathit{Re}}_{D} = 20$, a viscous steady state flow, exhibits a downstream suction and an upstream jet, the opposite of the expected behaviour of a flow field. The adjoint solution at ${\mathit{Re}}_{D} = 100$, a periodic two-dimensional unsteady flow, exhibits periodic, bean-shaped circulation in the near-wake region. The adjoint solution at ${\mathit{Re}}_{D} = 500$, a turbulent three-dimensional unsteady flow, has complex dynamics created by the shear layer in the near wake. The magnitude of the adjoint solution increases exponentially at the rate of the first Lyapunov exponent. These numerical results correlate well with the theoretical analysis presented in this paper.

Laminar Near Wake of a Circular Cylinder at Hypersonic Speeds

AIAA Journal ◽  
2010 ◽  
Vol 48 (1) ◽  
pp. 236-248 ◽  
Author(s):  
Gisu Park ◽  
Sudhir L. Gai ◽  
Andrew J. Neely
Keyword(s):  
Circular Cylinder ◽  
Near Wake ◽  
Hypersonic Speeds
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