scholarly journals EFFECTIVE FLOW CONTROL AROUND A CIRCULAR CYLINDER BY USING BOTH A SPLITTER PLATE AND PLASMA ACTUATORS AS PASSIVE AND ACTIVE CONTROL METHODS

2021 ◽  
pp. 133-140
Author(s):  
Hürrem AKBIYIKL ◽  
Yahya AKANSU
Keyword(s):  
Circular Cylinder ◽  
Flow Control ◽  
Active Control ◽  
Splitter Plate ◽  
Plasma Actuators ◽  
Control Methods

Organization of Cylinder Wake Using a Splitter-Plate Active Flow Control

2010 ◽  
Author(s):  
Chris Weiland ◽  
Pavlos Vlachos
Keyword(s):  
Circular Cylinder ◽  
Flow Control ◽  
Strouhal Number ◽  
Active Flow Control ◽  
Leading Edge ◽  
Splitter Plate ◽  
Cylinder Wake ◽  
Time Resolved ◽  
Image Velocimetry ◽  
Active Flow

Time Resolved Digital Particle Image Velocimetry (TRDPIV) was used in conjunction with spectral analysis to study the effects of Leading Edge Blowing (LEB) flow control on the near-wake of a circular cylinder. The airfoil was placed 1.9 circular cylinder diameters downstream, effectively acting as a splitter plate. Spectral measurements of the TRDPIV results indicated that the presence of the airfoil decreased the Strouhal number from 0.19 to 0.12 as anticipated. When activated the LEB jet organized the circular cylinder wake, effectively neutralizing the effect of the splitter plate and modifying the wake so as to return the Strouhal number to 0.19. Thus the circular cylinder wake returned to its normal shedding frequency, even in the presence of the airfoil. Evidence presented in this study supports the notion that the LEB jet directly excites the circular cylinder shear layers causing instability, roll up, and subsequent vortex shedding.

Active Control Methods for Drag Reduction in Flow Over Bluff Bodies (Keynote)

2002 ◽  
Author(s):  
Haecheon Choi
Keyword(s):  
Circular Cylinder ◽  
Drag Reduction ◽  
Active Control ◽  
High Frequency ◽  
Free Stream ◽  
Free Stream Velocity ◽  
Stream Velocity ◽  
Control Methods ◽  
Periodic Forcing ◽  
Time Periodic

In this paper, we present two successful results from active controls of flows over a circular cylinder and a sphere for drag reduction. The Reynolds number range considered for the flow over a circular cylinder is 40∼3900 based on the free-stream velocity and cylinder diameter, whereas for the flow over a sphere it is 105 based on the free-stream velocity and sphere diameter. The successful active control methods are a distributed (spatially periodic) forcing and a high-frequency (time periodic) forcing. With these control methods, the mean drag and lift fluctuations decrease and vortical structures are significantly modified. For example, the time-periodic forcing with a high frequency (larger than 20 times the vortex shedding frequency) produces 50% drag reduction for the flow over a sphere at Re = 105. The distributed forcing applied to the flow over a circular cylinder results in a significant drag reduction at all the Reynolds numbers investigated.

Numerical investigation of hypersonic flow with repetitive-pulsed plasma actuators

2017 ◽  
Vol 232 (9) ◽  
pp. 1715-1724
Author(s):  
Chin-Cheng Wang ◽  
Li-Chung Hsu
Keyword(s):  
Circular Cylinder ◽  
Flow Control ◽  
Hypersonic Flow ◽  
High Speed ◽  
Numerical Study ◽  
Pressure Ratio ◽  
Plasma Actuators ◽  
Circular Cylinders ◽  
Pulsed Plasma ◽  
Pulsed Discharges

Repetitive-pulsed plasma actuators have become the key enabler for flights in the hypersonic flow control. A numerical study focuses on the effect of the repetitive-pulsed plasma actuators at Mach 6. The geometric effects of circular, square, and triangular cylinders as well as a sphere on the aerodynamic performance are considered in the present study. For flow over the circular cylinder and sphere, shock control by repetitive-pulsed discharges is investigated, respectively. The baseline results are successfully validated with the theoretical and published numerical values for flow past a circular cylinder at Mach 6. Without flow control, results show that the shapes of the triangular cylinder and sphere have much smaller high-pressure regions compared to that of the square and circular cylinders. With repetitive-pulsed plasma, the time-average drag reduction has been reduced by a maximum of 0.8% and the stagnation pressure ratio is reduced by 2.1% for Mach 6 flow over a circular cylinder. Thus, this research shows a great benefit of repetitive-pulsed discharges to the state-of-the-art in high-speed flight design.

Active Control of an Incompressible Axisymmetric Jet

2008 ◽  
Author(s):  
D. Greenblatt ◽  
Y. Singh ◽  
C. N. Nayeri ◽  
C. O. Paschereit ◽  
N. K. Depuru Mohan
Keyword(s):  
Experimental Investigation ◽  
Flow Control ◽  
Active Control ◽  
Jet Noise ◽  
Control Methods ◽  
Streamwise Vortices ◽  
Streamwise Vorticity ◽  
Propulsion Efficiency ◽  
Axisymmetric Jet ◽  
Active Generation

An experimental investigation was conducted to compare the active generation and management of streamwise vortices in an incompressible jet flow using different flow control methods. The lip of the jet was equipped with a small flap deflected away from the stream at an angle of 30°, that incorporated a flow control slot through which steady suction, oscillatory suction and zero mass-flux perturbations were introduced. Data acquired were compared on the basis of momentum addition to the jet, the generation of streamwise vorticity and the generation of turbulent stresses. All active control methods produced an increase in jet momentum, stronger streamwise vortices and higher turbulence levels than those produced by a simple tab. The increase in jet momentum, combined with the generation of strong streamwise vortices and elevated turbulence levels, indicates potential for improvements in propulsion efficiency, mixing and possibly jet noise reduction.

scholarly journals A Critical Review of Supersonic Flow Control for High-Speed Applications

2021 ◽  
Vol 11 (15) ◽  
pp. 6899
Author(s):  
Abdul Aabid ◽  
Sher Afghan Khan ◽  
Muneer Baig
Keyword(s):  
Supersonic Flow ◽  
Flow Control ◽  
Active Control ◽  
Critical Review ◽  
High Speed ◽  
Passive Control ◽  
Control Method ◽  
Sudden Expansion ◽  
Control Approach ◽  
Cost Efficient

In high-speed fluid dynamics, base pressure controls find many engineering applications, such as in the automobile and defense industries. Several studies have been reported on flow control with sudden expansion duct. Passive control was found to be more beneficial in the last four decades and is used in devices such as cavities, ribs, aerospikes, etc., but these need additional control mechanics and objects to control the flow. Therefore, in the last two decades, the active control method has been used via a microjet controller at the base region of the suddenly expanded duct of the convergent–divergent (CD) nozzle to control the flow, which was found to be a cost-efficient and energy-saving method. Hence, in this paper, a systemic literature review is conducted to investigate the research gap by reviewing the exhaustive work on the active control of high-speed aerodynamic flows from the nozzle as the major focus. Additionally, a basic idea about the nozzle and its configuration is discussed, and the passive control method for the control of flow, jet and noise are represented in order to investigate the existing contributions in supersonic speed applications. A critical review of the last two decades considering the challenges and limitations in this field is expressed. As a contribution, some major and minor gaps are introduced, and we plot the research trends in this field. As a result, this review can serve as guidance and an opportunity for scholars who want to use an active control approach via microjets for supersonic flow problems.

scholarly journals Drag Reduction of a Circular Cylinder. 1st Report, Flow Control Using a Small Rod.

1994 ◽  
Vol 60 (573) ◽  
pp. 1554-1560 ◽  
Author(s):  
Tamotsu Igarashi ◽  
Takayuki Tsutsui ◽  
Hirochika Kanbe
Keyword(s):  
Circular Cylinder ◽  
Drag Reduction ◽  
Flow Control
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