Numerical Study of Three Dimensional Wake Structure Behind a Yawed Circular Cylinder

1993 ◽  
pp. 175-178 ◽  
Author(s):  
Tetuya Kawamura ◽  
Tsutomu Hayashi
Keyword(s):  
Circular Cylinder ◽  
Numerical Study ◽  
Three Dimensional ◽  
Wake Structure

Wake Structure Behind Circular Cylinder by Plasma Actuators

2011 ◽  
Author(s):  
Shunsuke Yamada ◽  
Koui Shibata ◽  
Hikaru Yanagihara ◽  
Takahiro Doi ◽  
Hitoshi Ishikawa ◽  
...  
Keyword(s):  
Circular Cylinder ◽  
Bluff Body ◽  
Three Dimensional ◽  
Plasma Actuators ◽  
Dimensional Structure ◽  
Separation Flow ◽  
Driving Frequency ◽  
Dbd Plasma ◽  
Wake Structure ◽  
Body Boundary

The separation flow causes the decrease of the driving efficiency of the fluid machines. It is important to control the separation on the bluff body, boundary layer and so on. The purpose of the present study is to control the separation on a circular cylinder and investigate the wake structure using the induced by dielectric barrier discharge (DBD) plasma. The electrode of the DBD plasma was mounted. In previous study, it is reported that the three dimensional wake structures are effective for the drag reduction. We investigate the three dimensional structure of the wake due to three dimensional jets of plasma actuators. The plasma actuators have pulse driving frequency of 0, 0.22, 1.0 and 2.0. A voltage of 4 kVpp and a frequency of 10 kHz are applied to the electrode. The velocity profiles behind the circular cylinder were measured by X type hot-wire anemometer at a Reynolds number of 1.0 × 103. The wake structure changes because the roll up of vortex is suppressed using pulse driving of the plasma actuators. The effect of plasma actuators is evaluated based on the half width and Reynolds stress in the wake.

Numerical Study of Vortex Shedding From a Circular Cylinder in Linear Shear Flow

1999 ◽  
Vol 121 (2) ◽  
pp. 460-468 ◽  
Author(s):  
A. Mukhopadhyay ◽  
P. Venugopal ◽  
S. P. Vanka
Keyword(s):  
Circular Cylinder ◽  
Stokes Equations ◽  
Numerical Study ◽  
Experimental Studies ◽  
Three Dimensional ◽  
Slip Condition ◽  
Navier Stokes ◽  
Finite Volume Scheme ◽  
Constant Frequency ◽  
Wall Boundary Conditions

A three-dimensional numerical simulation of linearly sheared flow past a circular cylinder has been performed for a shear parameter β of 0.02 and a mean Reynolds number of 131.5. A cylinder of 24 diameters span is considered. A second-order accurate finite volume scheme is used to integrate the unsteady Navier-Stokes equations. Present computations confirm both qualitatively and quantitatively, the aspects of cellular shedding as reported by several investigators through experimental studies. Up to five constant frequency cells of obliquely shedding vortices are observed. The nondimensional frequencies of these cells are observed to be lower than those given by parallel shedding correlations at the equivalent Reynolds numbers. It is also observed that the cell boundaries continuously move in time. Detailed distributions of vorticity and velocity components are presented to describe the flow. The influence of end-wall boundary conditions is studied by computing two cases, one with free-slip condition, and the other with no-slip condition on disks of radius of five cylinder diameters.

Uniform Flow Past a Rotary Oscillating Circular Cylinder

2011 ◽  
Author(s):  
Lue Derek Du ◽  
Charles Dalton
Keyword(s):  
Circular Cylinder ◽  
Vortex Shedding ◽  
Stokes Equations ◽  
Three Dimensional ◽  
Uniform Flow ◽  
Resonance Phenomenon ◽  
Curvilinear Coordinates ◽  
Wake Structure ◽  
Flow Past ◽  
Wide Range

In this paper, we study uniform flow past a rotary oscillating circular cylinder computationally. The objective is to determine the effect the oscillating rotation has on the lift and drag forces acting on the cylinder, on the wake structure, and on vortex shedding. A combination of finite-difference and spectral methods is used to calculate the three-dimensional incompressible unsteady Navier-Stokes equations in primitive variable form in nonorthogonal curvilinear coordinates. Wake turbulence is modeled by an LES technique. The Reynolds number considered is Re = 1.5×104, which is the same as that in the experimental study of Tokumaru & Dimotakis (1991), who suggested this technique as a means of reducing drag. We fix the forcing amplitude at the moderate value of Ω = 2 and vary the forcing frequency in a wide range to study its effect on the flow. The resonance phenomenon and drag reduction effect are carefully examined. The wake structure and vortex shedding process is visualized by means of computational streaklines. These results have a practical application in offshore engineering.

A Numerical Study of Oblique Water Entry Problems

2020 ◽  
Author(s):  
Yanni Chang ◽  
Albert Y. Tong
Keyword(s):  
Circular Cylinder ◽  
Transient Flow ◽  
Numerical Study ◽  
Piecewise Linear ◽  
Three Dimensional ◽  
Water Entry ◽  
Air Entrapment ◽  
Pressure Distributions ◽  
Parametric Studies ◽  
Inclined Angle

Abstract A series of numerical experiments have been carried out on the water entry problem of three-dimensional multi-degree-freedom cylinders. The circular cylinder was released above the water with a specified inclined angle and velocity at entry. The hydrodynamics of the water entry problem have been investigated numerically. The Piecewise Linear Interface Calculation (PLIC) schemes have been applied in conjunction with the Volume of Fluid (VOF) method to capture the interface. Overset meshes have been adopted to handle the moving object. The numerical model is built on the framework of OpenFOAM which is an open-source C++ toolbox. Numerical results have been obtained. Transient flow and pressure distributions have been generated. The presence of air entrapment which has been reported experimentally has also been confirmed in the numerical solution. The fluid physics of the oblique water entry problem such as the formation and development of the air entrapment has been explored. The transient positions and inclined angles of the moving circular cylinder have been found to be in good agreement with the experimental results. Parametric studies have been performed with major findings reported.

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