scholarly journals A New Low Reynolds Number Facility for Active Flow Control Applications

2008 ◽  
Author(s):  
Matthew Munson ◽  
William Dickson ◽  
Tim Colonius ◽  
Morteza Gharib
Keyword(s):  
Reynolds Number ◽  
Flow Control ◽  
Low Reynolds Number ◽  
Active Flow Control ◽  
Control Applications ◽  
Low Reynolds ◽  
Active Flow

Low Reynolds Number Laminar Airfoil with Active Flow Control

2010 ◽  
Author(s):  
Michael Thake ◽  
Nathan Packard ◽  
Carlos Bonilla ◽  
Jeffrey Bons
Keyword(s):  
Reynolds Number ◽  
Flow Control ◽  
Low Reynolds Number ◽  
Active Flow Control ◽  
Low Reynolds ◽  
Active Flow

Design of a Highly Loaded Turbine Exit Case Airfoil With Active Flow Control

2016 ◽  
Author(s):  
Julia Kurz ◽  
Martin Hoeger ◽  
Reinhard Niehuis
Keyword(s):  
Reynolds Number ◽  
Flow Control ◽  
Design Process ◽  
Low Reynolds Number ◽  
Active Flow Control ◽  
Number Range ◽  
German Armed Forces ◽  
Low Reynolds ◽  
Active Flow ◽  
Highly Loaded

In this paper a design process of a highly loaded profile for a turbine exit case (TEC) application is described. The profile has an increased pitch to chord ratio which is approximately 50% higher compared to conventional airfoils. For the design of the airfoil a two-dimensional (2D) computational fluid dynamics (CFD) prediction method was used in addition to in-house design rules and low Reynolds number experience from previous experiments. Furthermore, common knowledge from turbine and compressor design as well as turbine exit guide vane studies was evaluated and taken as basis for the new design. To verify the highly loaded design, the profile was tested over a wide Reynolds number range in the high speed cascade wind tunnel of the Institute of Jet Propulsion (ISA) at the University of the German armed forces in Munich. The experiments showed a very good agreement between the CFD predictions and the measurements for high Reynolds numbers. In the low Reynolds number regime the tendency to massive flow separation was slightly underestimated by the CFD predictions. It is particularly challenging as the CFD predictions still have problems to calculate open separation bubbles. Active flow control (AFC) by fluidic oscillators was also part of the design process and successfully applied on the profile.

Comparative Evaluation of Dielectric Materials for Plasma Actuators Active Flow Control and Heat Transfer Applications

2021 ◽  
Author(s):  
F. F. Rodrigues ◽  
J. Nunes-Pereira ◽  
M. Abdollahzadeh ◽  
J. Pascoa ◽  
S. Lanceros-Mendez
Keyword(s):  
Heat Transfer ◽  
Flow Control ◽  
Dielectric Layer ◽  
Active Flow Control ◽  
Thermal Power ◽  
Dielectric Materials ◽  
Plasma Actuators ◽  
Dbd Plasma ◽  
Control Applications ◽  
Active Flow

Abstract Dielectric Barrier Discharge (DBD) plasma actuators are simple devices with great potential for active flow control applications. Further, it has been recently proven their ability for applications in the area of heat transfer, such as film cooling of turbine blades or ice removal. The dielectric material used in the fabrication of these devices is essential in determining the device performance. However, the variety of dielectric materials studied in the literature is very limited and the majority of the authors only use Kapton, Teflon, Macor ceramic or poly(methyl methacrylate) (PMMA). Furthermore, several authors reported difficulties in the durability of the dielectric layer when the actuators operate at high voltage and frequency. Also, it has been reported that, after long operation time, the dielectric layer suffers degradation due to its exposure to plasma discharge, degradation that may lead to the failure of the device. Considering the need of durable and robust actuators, as well as the need of higher flow control efficiencies, it is highly important to develop new dielectric materials which may be used for plasma actuator fabrication. In this context, the present study reports on the experimental testing of dielectric materials which can be used for DBD plasma actuators fabrication. Plasma actuators fabricated of poly(vinylidene fluoride) (PVDF) and polystyrene (PS) have been fabricated and evaluated. Although these dielectric materials are not commonly used as dielectric layer of plasma actuators, their interesting electrical and dielectric properties and the possibility of being used as sensors, indicate their suitability as potential alternatives to the standard used materials. The plasma actuators produced with these nonstandard dielectric materials were analyzed in terms of electrical characteristics, generated flow velocity and mechanical efficiency, and the obtained results were compared with a standard actuator made of Kapton. An innovative calorimetric method was implemented in order to estimate the thermal power transferred by these devices to an adjacent flow. These results allowed to discuss the ability of these new dielectric materials not only for flow control applications but also for heat transfer applications.

Comparison of Two Active Flow Control Mechanisms of Pure Blowing and Pure Suction on a Pitching NACA0012 Airfoil at Reynolds Number of 1 × 106

2018 ◽  
Author(s):  
Ehsan Asgari ◽  
Mehran Tadjfar
Keyword(s):  
Reynolds Number ◽  
Flow Control ◽  
Active Flow Control ◽  
Hysteresis Loops ◽  
Leading Edge ◽  
Control Mechanisms ◽  
Airfoil Surface ◽  
Naca0012 Airfoil ◽  
Maximum Angle ◽  
Active Flow

In this study, we have applied and compared two active flow control (AFC) mechanisms on a pitching NACA0012 airfoil at Reynolds number of 1 × 106 using 2-D computational fluid dynamics (CFD). These mechanisms are continuous blowing and suction which are applied separately on the airfoil which pitches around its quarter-chord in a sinusoidal motion. The location for suction and blowing was determined in our previous study based on the formation of a counter clock-wise vortex near the leading-edge. In our current study, we have compared the effectiveness of pure blowing and pure suction in suppressing the dynamic stall vortex (DSV) which is the main contributor to the drag increase, particularly near the maximum angle of attack (AOA) and in early downstroke motion. The blowing/suction slot is considered as a dent on the airfoil surface which enables the AFC to perform in a tangential manner. This configuration would allow blowing jet to penetrate further downstream and was shown to be more effective compared to a cross-flow orientation. We have compared the two aforementioned mechanisms in terms of hysteresis loops of lift and drag coefficients and have demonstrated the dynamics of flow in controlled and uncontrolled situations.

Active Flow Control of Dynamic Stall by Means of Continuous Jet Flow at Reynolds Number of 1 × 106

2017 ◽  
Vol 140 (1) ◽  
Author(s):  
Mehran Tadjfar ◽  
Ehsan Asgari
Keyword(s):  
Reynolds Number ◽  
Flow Control ◽  
Pressure Difference ◽  
Active Flow Control ◽  
Velocity Ratio ◽  
Dynamic Stall ◽  
Hysteresis Curve ◽  
Small Range ◽  
Active Flow ◽  
The Impact

We have studied the influence of a tangential blowing jet in dynamic stall of a NACA0012 airfoil at Reynolds number of 1 × 106, for active flow control (AFC) purposes. The airfoil was oscillating between angles of attack (AOA) of 5 and 25 deg about its quarter-chord with a sinusoidal motion. We have utilized computational fluid dynamics to investigate the impact of jet location and jet velocity ratio on the aerodynamic coefficients. We have placed the jet location upstream of the counter-clockwise (CCW) vortex which was formed during the upstroke motion near the leading-edge; we have also considered several other locations nearby to perform sensitivity analysis. Our results showed that placing the jet slot within a very small range upstream of the CCW vortex had tremendous effects on both lift and drag, such that maximum drag was reduced by 80%. There was another unique observation: placing the jet at separation point led to an inverse behavior of drag hysteresis curve in upstroke and downstroke motions. Drag in downstroke motion was significantly lower than upstroke motion, whereas in uncontrolled case the converse was true. Lift was significantly enhanced during both upstroke and downstroke motions. By investigating the pressure coefficients, it was found that flow control had altered the distribution of pressure over the airfoil upper surface. It caused a reduction in pressure difference between upper and lower surfaces in the rear part, while substantially increased pressure difference in the front part of the airfoil.

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