scholarly journals An Inviscid Model of Discrete-Vortex Shedding for Two-Dimensional Oscillating Flow around a Flat Plate

1979 ◽  
Vol 1979 (145) ◽  
pp. 54-62
Author(s):  
Kimiaki Kudo
Keyword(s):  
Flat Plate ◽  
Vortex Shedding ◽  
Oscillating Flow ◽  
Two Dimensional ◽  
Discrete Vortex

A Numerical Solution for Potential Flows Including the Effects of Vortex Shedding

1993 ◽  
Vol 115 (2) ◽  
pp. 111-115
Author(s):  
L. H. Wong ◽  
S. M. Calisal
Keyword(s):  
Flat Plate ◽  
Boundary Element ◽  
Vortex Shedding ◽  
Potential Flow ◽  
Vortex Method ◽  
Vortex Sheet ◽  
Oscillating Flow ◽  
Discrete Vortex ◽  
Discrete Vortex Method ◽  
Inner Region

This paper reports on an attempt to include vortex shedding effects into potential flow calculations using the boundary element method. Significant computational advantages result because of the relatively simple approach to handling separation at the sharp edges while working only with the boundary values. A discrete vortex method was incorporated into a time domain boundary element algorithm for the numerical simulation of oscillating flow past a normal flat plate. Separation from a sharp edge results in the formation of a vortex sheet issuing from the edge. This vortex sheet is modeled by a series of discrete vortices introduced one at a time into the flow field at regular intervals. The motion of each vortex is traced over time using its convection velocity. As long as the Keulegan-Carpenter number is small enough, vortex shedding takes place close to the edge. The discrete vortex method can, in such cases, be looked upon as the inner region solution to the problem of normal oscillating flow past the flat plate. This inner region solution has to be matched with the outer potential flow solution. The combination of boundary element and discrete vortex methods provides this matching and at the same time does not require calculations inside the domain.

A contribution to an inviscid vortex-shedding model for an inclined flat plate in uniform flow

1977 ◽  
Vol 82 (2) ◽  
pp. 223-240 ◽  
Author(s):  
Masaru Kiya ◽  
Mikio Arie
Keyword(s):  
Flat Plate ◽  
Vortex Shedding ◽  
Separated Flow ◽  
Flow Patterns ◽  
Shear Layers ◽  
Visualization Technique ◽  
Time Intervals ◽  
Discrete Vortex ◽  
Kutta Condition ◽  
Vorticity Transport

Unsteady separated flow behind an inclined flat plate is numerically studied through the use of the discrete-vortex approximation, in which the shear layers emanating from the edges of the plate are represented by an array of discrete vortices introduced into the flow field at appropriate time intervals at some fixed points near the edges of the plate. The strengths of the nascent vortices are chosen so as to satisfy the Kutta condition at the edges of the plate. Numerical calculations are performed for a plate at 60° incidence impulsively started from rest in an otherwise stationary incompressible fluid, by systematically changing the distance between the location of the nascent vortices and the edges of the plate. The temporal changes in the drag force, the rate of vorticity transport at both edges of the plate and the velocity of the separated shear layers are given together with the flow patterns behind the plate on the basis of this model. The results of the computation show that the vortex street behind the plate inclines as a whole towards the direction of the time-averaged lift force exerted on the plate. It is also predicted from the calculations that the vortex shedding at one edge of the plate will not occur at the mid-interval of the successive vortex shedding at the other edge. The predicted flow patterns are not inconsistent with a few experimental observations based on the flow-visualization technique.

An inviscid numerical simulation of vortex shedding from an inclined flat plate in shear flow

1977 ◽  
Vol 82 (2) ◽  
pp. 241-253 ◽  
Author(s):  
Masaru Kiya ◽  
Mikio Arie
Keyword(s):  
Shear Flow ◽  
Flat Plate ◽  
Strouhal Number ◽  
Vortex Shedding ◽  
Initial Conditions ◽  
Shear Layers ◽  
Discrete Vortex ◽  
Uniform Shear ◽  
Uniform Shear Flow ◽  
Shear Parameter

Two-dimensional vortex shedding behind an inclined flat plate in uniform shear flow is numerically investigated by means of an inviscid discrete-vortex approximation. The points of appearance of the vortices are fixed in the plane of the plate at a short distance downstream of the edges of the plate. The strengths of the vortices are determined from the Kutta condition. On the assumption that the steadily periodic flow patterns are independent of initial conditions, the numerical calculations are performed for an inclined flat plate immersed in an incompressible fluid which is set in motion impulsively from rest with the velocity profile of uniform shear flow. The results of analysis show that the Strouhal number of vortex shedding and the time-averaged values of other hydrodynamic characteristics of the flow such as the outer-edge velocity of the separated shear layers, the convective velocity of the shear layers and the drag force exerted on the plate vary closely linearly with the shear parameter of the approaching shear flow. A linear relation between the Strouhal number and the shear parameter is confirmed by an air-tunnel experiment. The effects of the shear parameter on the calculated vortex patterns in the wake are also presented.

Fluid-Dynamic Force Characteristics of an Auto Rotating Flat Plate

2007 ◽  
Author(s):  
Takahiro Yasuda
Keyword(s):  
Flat Plate ◽  
Vortex Shedding ◽  
Fluid Dynamic ◽  
Vortex Method ◽  
Dynamic Force ◽  
Discrete Vortex ◽  
Dynamic Forces ◽  
Plate Rotation ◽  
Unsteady Fluid ◽  
Force Characteristics

When a thin flat pate is released in still air, the plate automatically sets into a rotational motion. This phenomenon is called autorotation. The autorotating flat plate is loaded by unsteady fluid-dynamic forces. It is guessed that the forces are contributed by one due to vortex shedding from the edges of the plate and one due to the plate rotation, but the detail force characteristics have not been clear yet. In this study, we calculated the two types of flow by the discrete vortex method, one is flow around a rotating flat plate hinged about its center at constant rotating frequency in the uniform flow and the other is flow around a freely falling flat plate. The computed result in both types of flow agree well with the experiment. In the case of freely falling plate, autorotation phenomena could be predicted. By computed fluid dynamic forces, the contributions of vortex shedding from the plate to fluid dynamic forces and feedback effect of the fluid dynamic forces were found.

Aerodynamics of a two-dimensional bluff body with the cross-section of a train

2020 ◽  
Vol 23 (12) ◽  
pp. 2679-2693 ◽  
Author(s):  
Huan Li ◽  
Xuhui He ◽  
Hanfeng Wang ◽  
Si Peng ◽  
Shuwei Zhou ◽  
...  
Keyword(s):  
Reynolds Number ◽  
Vortex Shedding ◽  
Large Amplitude ◽  
High Speed ◽  
Bluff Body ◽  
Mean Amplitude ◽  
Two Dimensional ◽  
Aerodynamic Forces ◽  
Moderate Reynolds Number ◽  
Amplitude Mode

Experiments on the aerodynamics of a two-dimensional bluff body simplified from a China high-speed train in crosswinds were carried out in a wind tunnel. Effects of wind angle of attack α varying in [−20°, 20°] were investigated at a moderate Reynolds number Re = 9.35 × 104 (based on the height of the model). Four typical behaviors of aerodynamics were identified. These behaviors are attributed to the flow structure around the upper and lower halves of the model changing from full to intermittent reattachment, and to full separation with a variation in α. An alternate transition phenomenon, characterized by an alteration between large- and small-amplitude aerodynamic fluctuations, was detected. The frequency of this alteration is about 1/10 of the predominant vortex shedding. In the intervals of the large-amplitude behavior, aerodynamic forces fluctuate periodically with a strong span-wise coherence, which are caused by the anti-symmetric vortex shedding along the stream-wise direction. On the contrary, the aerodynamic forces fluctuating at small amplitudes correspond to a weak span-wise coherence, which are ascribed to the symmetric vortex shedding from the upper and lower halves of the model. Generally, the mean amplitude of the large-amplitude mode is 3 times larger than that of the small one. Finally, the effects of Reynolds number were examined within Re = [9.35 × 104, 2.49 × 105]. Strong Reynolds number dependence was observed on the model with two rounded upper corners.

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