Experimental Investigation of Flow Separation Control Using an Array of Synthetic Jets

AIAA Journal ◽  
2010 ◽  
Vol 48 (3) ◽  
pp. 611-623 ◽  
Author(s):  
Shanying Zhang ◽  
Shan Zhong
Keyword(s):  
Experimental Investigation ◽  
Flow Separation ◽  
Synthetic Jets ◽  
Separation Control ◽  
Flow Separation Control

scholarly journals Fluidic-Oscillator-Based Pulsed Jet Actuators for Flow Separation Control

Fluids ◽  
2021 ◽  
Vol 6 (4) ◽  
pp. 166
Author(s):  
Stephan Löffler ◽  
Carola Ebert ◽  
Julien Weiss
Keyword(s):  
Flow Separation ◽  
Oscillation Frequency ◽  
Current Knowledge ◽  
Industrial Applications ◽  
Synthetic Jets ◽  
Separation Control ◽  
Test Surface ◽  
Flow Separation Control ◽  
Pulsed Jet ◽  
Jet Actuators

The control of flow separation on aerodynamic surfaces remains a fundamental goal for future air transportation. On airplane wings and control surfaces, the effects of flow separation include decreased lift, increased drag, and enhanced flow unsteadiness and noise, all of which are detrimental to flight performance, fuel consumption, and environmental emissions. Many types of actuators have been designed in the past to counter the negative effects of flow separation, from passive vortex generators to active methods like synthetic jets, plasma actuators, or sweeping jets. At the Chair of Aerodynamics at TU Berlin, significant success has been achieved through the use of pulsed jet actuators (PJA) which operate by ejecting a given amount of fluid at a specified frequency through a slit-shape slot on the test surface, thereby increasing entrainment and momentum in a separating boundary layer and thus delaying flow separation. Earlier PJAs were implemented using fast-switching solenoid valves to regulate the jet amplitude and frequency. In recent years, the mechanical valves have been replaced by fluidic oscillators (FO) in an attempt to generate the desired control authority without any moving parts, thus paving the way for future industrial applications. In the present article, we present in-depth flow and design analysis which affect the operation of such FO-based PJAs. We start by reviewing current knowledge on the mechanism of flow separation control with PJAs before embarking on a detailed analysis of single-stage FO-based PJAs. In particular, we show that there is a fundamental regime where the oscillation frequency is mainly driven by the feedback loop length. Additionally, there are higher-order regimes where the oscillation frequency is significantly increased. The parameters that influence the oscillation in the different regimes are discussed and a strategy to incorporate this new knowledge into the design of future actuators is proposed.

Flow separation control on a highly loaded compressor cascade using endwall synthetic jets

2017 ◽  
Vol 232 (11) ◽  
pp. 2059-2075 ◽  
Author(s):  
Yong Qin ◽  
Yanping Song ◽  
Ruoyu Wang ◽  
Huaping Liu ◽  
Fu Chen
Keyword(s):  
Boundary Layer ◽  
Flow Separation ◽  
Pressure Rise ◽  
Synthetic Jets ◽  
Separation Control ◽  
Compressor Cascade ◽  
Flow Separation Control ◽  
Maximum Loss ◽  
Wall Flows ◽  
Highly Loaded

This paper presents flow separation control conducted on a highly loaded compressor stator cascade using endwall synthetic jets. Numerical methods are employed and mechanisms of endwall synthetic jets in improving the cascade performance are discussed in detail. The influence of several actuation parameters is also investigated. Results show that endwall synthetic jets are able to improve the flows in the blade passage significantly, a maximum loss reduction of 21.63% and a pressure rise increment of 5.60% are obtained at design condition. Apart from energizing the low momentum fluid inside endwall boundary layer by streamwise momentum addition, endwall synthetic jets could induce a streamwise jet vortex and impede the transverse movement of endwall boundary layer through upwash and downwash. Hence, at the expense of slightly degraded near-wall flows, the formation and further evolution of passage vortex would be delayed and flows in the midspan region would be improved notably. The effectiveness of endwall synthetic jets relies on the proper selection of actuation position and jet angle. Flow control turns out to be the most efficient when the actuator is positioned at just upstream of corner separation region with a relatively small jet angle, and a large enough injected momentum is also necessary. Additionally, the adaptability of the actuation at off-design conditions is validated in the present study.

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