Drag reduction of a circular cylinder at high Reynolds numbers

1997 ◽  
Author(s):  
A. Krothapalli ◽  
C. Shih ◽  
L. Lourenco ◽  
S. Walker ◽  
P. Moriarty ◽  
...  
Keyword(s):  
Circular Cylinder ◽  
Drag Reduction ◽  
Reynolds Numbers ◽  
High Reynolds Numbers ◽  
High Reynolds

TRANSONIC CROSS FLOW (M∞ = 0.8) OVER A CIRCULAR CYLINDER AT HIGH REYNOLDS NUMBERS

2012 ◽  
Vol 43 (5) ◽  
pp. 589-613
Author(s):  
Vyacheslav Antonovich Bashkin ◽  
Ivan Vladimirovich Egorov ◽  
Ivan Valeryevich Ezhov ◽  
Sergey Vladimirovich Utyuzhnikov
Keyword(s):  
Circular Cylinder ◽  
Cross Flow ◽  
Reynolds Numbers ◽  
High Reynolds Numbers ◽  
High Reynolds

Flow Control Over a Circular Cylinder Using Pulsed DBD Actuators

2012 ◽  
Author(s):  
William C. Schneck ◽  
Walter F. O’Brien
Keyword(s):  
Circular Cylinder ◽  
Flow Control ◽  
Gas Turbine ◽  
Electric Fields ◽  
Active Flow Control ◽  
Reynolds Numbers ◽  
Pressure Gradients ◽  
High Reynolds Numbers ◽  
Pulsed Dc ◽  
High Reynolds

Immersed bodies such as struts, vanes, and instrumentation probes in gas turbine flow systems will, except at the lowest of flow velocities, shed separated wakes. These wakes can have both upstream and downstream effects on the surrounding flow. In most applications, surrounding components are designed to be in the presence of a quasi-steady or at least non-variant flow field. The presence of unsteady wakes has both aerodynamic and structural consequences. Active flow control of wake generation can therefore be very valuable. One means to implement active flow control is by the use of plasma actuation. Plasma actuation is the use of strong electric fields to generate ionized gas that can be actuated and controlled using the electric fields. The controlling device can be based on AC, DC, or pulsed-DC actuation. The present research was conducted using pulsed-DC from a capacitive discharge power supply. The study demonstrates the applicability of, specifically, pulsed-DC plasma flow control of the flow on a circular cylinder at high Reynolds numbers. The circular cylinder was selected because its flow characteristics are related to gas turbine flowpath phenomena, and are well characterized. Further, the associated pressure gradients are some of the most severe encountered in fluid applications. The development of effective plasma actuators at high Reynolds numbers under the influence of severe pressure gradients is a necessary step toward developing useful actuators for gas turbine applications beyond laboratory use. The reported experiments were run at Reynolds numbers varying from 50,000 to 97,000, and utilizing various pulse frequencies. Further, the observed performance differences with varying electric field strengths are discussed for these Reynolds numbers. The results show that flow behaviors at high Reynolds numbers can be influenced by these types of actuators. The actuators were able to demonstrate a reduction in both wake width and momentum deficit.

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.

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