Discrete Vortex Simulation of Pulsating Flow Behind a Normal Plate

1994 ◽  
Vol 116 (4) ◽  
pp. 862-869 ◽  
Author(s):  
Hyung Jin Sung ◽  
Young Nam Kim ◽  
Jae Min Hyun
Keyword(s):  
Numerical Study ◽  
Flow Characteristics ◽  
Separated Flow ◽  
Vortex Method ◽  
Threshold Value ◽  
Numerical Results ◽  
Pulsation Frequency ◽  
Discrete Vortex ◽  
Freestream Velocity ◽  
Variable Position

A numerical study is made of the separated flow behind a flat plate. The plate is placed normal to the direction of the approach flow. The oncoming freestream velocity contains a pulsating part, U∞ = U0(1 + A0cosfpt). The temporal behavior of vortex shedding patterns is scrutinized over broad ranges of the two externally specified parameters, i.e., the pulsation amplitude (A0≤ 0.6), and the dimensionless pulsation frequency, (fp≤0.32). A version of the discrete vortex method is utilized. The variable-position nascent vortex technique is applied, and it proves to be adequate for pulsating approach flows. The numerical results clearly capture the existence of lock-on when fp exceeds a threshold value. The modulation of vorticity shedding is also detected when fp is reasonably low. The influence of A0 on the flow characteristics is examined in detail. As A0 increases to a moderate value (e.g., A0≤0.6), an appreciable broadening is seen of the range of fp for which lock-on occurs. Based on the numerical results, three characteristic flow modes in the wakes are identified. These findings are qualitatively consistent with the existing flow-visualization studies for a cylinder.

A Correction Formula for Wall Effects on Unsteady Forces of Two-Dimensional Bluff Bodies

1994 ◽  
Vol 116 (3) ◽  
pp. 414-418 ◽  
Author(s):  
Terukazu Ota ◽  
Yasunori Okamoto ◽  
Hiroyuki Yoshikawa
Keyword(s):  
Flow Characteristics ◽  
Separated Flow ◽  
Elliptic Cylinder ◽  
Vortex Method ◽  
Bluff Bodies ◽  
Two Dimensional ◽  
Wall Effects ◽  
Discrete Vortex ◽  
Correction Formula ◽  
Wide Range

In wind tunnel studies on the flow around bluff bodies accompanying a large separated wake, the walls of the test section severely effect the flow characteristics around them. Proposed in this paper is a correction formula for the wall effects upon two-dimensional (2-D) unsteady separated flow of incompressible fluid around bluff bodies. The proposed formula is derived from numerical results with the discrete vortex method on 2-D separated flows around an inclined flat plate, a square cylinder, and also an elliptic cylinder located between two parallel walls. It is found that the present correction formula estimates reasonably well the wall effects upon the mean and fluctuating force coefficients over a wide range of blockage ratio and angle of attack through comparing the present calculated results with numerous experimental ones by several authors.

scholarly journals A numerical study of flow around an impulsively started circular cylinder by a deterministic vortex method

1991 ◽  
Vol 233 ◽  
pp. 243-263 ◽  
Author(s):  
Chien-Cheng Chang ◽  
Ruey-Ling Chern
Keyword(s):  
Finite Difference ◽  
Circular Cylinder ◽  
Numerical Study ◽  
Vortex Method ◽  
Reynolds Numbers ◽  
Numerical Results ◽  
High Reynolds Numbers ◽  
Small Times ◽  
Axis Of Symmetry ◽  
High Reynolds

Impulsively started flow around a circular cylinder at various Reynolds numbers is studied by a deterministic hybrid vortex method. The key feature of the method consists in solving the viscous vorticity equation by interlacing a finite-difference method for diffusion and a vortex-in-cell method for convection. The vorticity is updated along the surface of the cylinder to satisfy the no-slip condition. The present method is basically different from previous applications of vortex methods, which are primarily in the context of random vortex algorithms. The Reynolds numbers of the flows under investigation range from 300 to 106. Numerical results are compared with analytical solutions at small times, and compared with finite-difference solutions and flow visualization results at relatively long times. Satisfactory agreement is found in the evolutions of the separation angles, wake lengths, surface pressure and drag coefficients, streamline patterns, and some velocities on the axis of symmetry behind the circular cylinder. The present hybrid vortex method is highly stable and suffers from little numerical diffusivity, yielding convincing numerical results for unsteady vortical flows at moderately high Reynolds numbers.

scholarly journals Effect of structural interaction on the aerodynamic properties

2020 ◽  
Vol 17 (3) ◽  
pp. 79-86
Author(s):  
R. N. Guzeev ◽  
◽  
E. S. Goloviznina ◽  
Keyword(s):  
Cross Sections ◽  
Mutual Influence ◽  
Numerical Study ◽  
Vortex Method ◽  
Discrete Vortex ◽  
Discrete Vortex Method ◽  
Structural Interaction ◽  
Cable Stayed Bridge ◽  
Aspect Ratios ◽  
Aerodynamic Properties

Effect of structural interaction on drag coefficient is considered. Numerical study is performed using discrete vortex method. There have been obtained dependences of the mutual influence of rectangular cross sections with different aspect ratios depending on the reduced distance between the cross sections, on their aerodynamics. The effect of structural interaction of cable-stayed bridge pylon legs is investigated on the examples of Golden Bridge and Russian Bridge in Vladivostok.

Numerical study of two-airfoil arrangements by a discrete vortex method

2020 ◽  
Vol 34 (1-2) ◽  
pp. 79-103 ◽  
Author(s):  
Thierry M. Faure ◽  
Laurent Dumas ◽  
Olivier Montagnier
Keyword(s):  
Numerical Study ◽  
Vortex Method ◽  
Discrete Vortex ◽  
Discrete Vortex Method
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