Study on Flow Separation Control by Vortex Generator Jets with Different Parameters

2012 ◽  
Vol 588-589 ◽  
pp. 1786-1789
Author(s):  
Yong Hui Xie ◽  
Zhong Yang Shen ◽  
Tao Fan
Keyword(s):  
Flow Control ◽  
Flow Separation ◽  
Vortex Generator ◽  
Separation Control ◽  
Flow Separation Control ◽  
Profound Influence ◽  
Orthogonal Analysis ◽  
Conical Diffuser ◽  
Flow Charts ◽  
Vortex Generator Jets

In order to investigate the mechanism of flow separation control in conical diffuser by vortex generator jets (VGJs) method, numerical simulations were conducted to discuss the effect of VGJs with different parameters on flow control. The aerodynamic performance in conical diffuser with angle of 14° was tested and analyzed based on Shear-Stress-Transport (SST) simulation. The flow charts at several sections were analyzed, illuminating the formation of complex vortices. Moreover, the effects of 5 VGJs parameters on the diffuser were analyzed by orthogonal analysis. It was shown that the number of jets and the pitch angle of jet showed more profound influence on the flow control by VGJs.

Vortex generator jets - Means for flow separation control

AIAA Journal ◽  
1990 ◽  
Vol 28 (6) ◽  
pp. 989-994 ◽  
Author(s):  
James P. Johnston ◽  
Michihiro Nishi
Keyword(s):  
Flow Separation ◽  
Vortex Generator ◽  
Separation Control ◽  
Flow Separation Control ◽  
Vortex Generator Jets

Numerical Investigations of Flow Separation Control for a Low Pressure Turbine Blade Using Steady and Pulsed Vortex Generator Jets

2010 ◽  
Author(s):  
Xiaomin Liu ◽  
Haiyang Zhou
Keyword(s):  
Turbine Blade ◽  
Flow Separation ◽  
Vortex Generator ◽  
Suction Side ◽  
Low Pressure ◽  
Pulse Frequency ◽  
Separation Control ◽  
Flow Separation Control ◽  
Low Pressure Turbine ◽  
Vortex Generator Jets

This paper investigated numerically the application of Vortex Generator Jets (VGJs) to control flow separation on the suction side of a low pressure turbine blade. Firstly, numerical simulations of flow separation for a LPT blade, which based on Menter’s SST k-ω turbulence model coupled with Langtry-Menter transition model, were performed for different Reynolds numbers Re∼100,000, 75,000, 50,000 and 25,000, for three freestream turbulence intensity (FSTI) of 0.08%, 2.35% and 6.0%. The pressure distributions around the turbine blade and streamline plots showing the flow separation were presented in this paper. Good agreement of the numerical and experimental results also showed the validity of the numerical scheme for simulating the flow separation occurring on a low pressure turbine blade. And then, steady Vortex Generator Jets (steady VGJs) having pitch angle of 30°, skew angle of 90°, blowing ratio of 2.0 were used to control the flow separation in the suction side of the low pressure turbine blade. Although steady VGJs have been illustrated to be extremely robust at suppressing low Reynolds number separation, the practical application of VGJs in the low pressure turbine engine is in the pulsed mode. The injection mass flow requirements of pulsed Vortex Generator Jets (pulsed VGJs) can be reduced drastically when similar flow control effect is obtained using steady VGJs. For pulsed VGJs, the pulse frequency has been found to be an important control parameter for the flow separation control. In this paper, cases with the duty cycle of 0.5 were studied for the pulse frequency ranging from 2.5Hz to 10Hz at Re = 25,000 and freestream turbulence level of 0.08%. The numerical results showed that pulsed VGJs can effectively reduce and even eliminate the flow separation on the blade suction surface while there is an optimal pulse frequency. The flow control mechanism of VGJs on LPT blade was also revealed.

Flow Structure Formed by a Sweeping Jet Ejected Into a Main Flow

2018 ◽  
Author(s):  
Masaki Fuchiwaki ◽  
Surya Raghu
Keyword(s):  
Flow Control ◽  
Electric Power ◽  
Flow Structure ◽  
Flow Separation ◽  
High Velocity ◽  
Main Flow ◽  
Separation Control ◽  
Flow Separation Control ◽  
Fluidic Oscillator ◽  
Piv Measurement

Various methods of controlling flow separation have been proposed and many studies have been performed on active separation control in correspondence with the flow state. However, their efficiency has been hampered by the requirement of electric power for the added stream. Recently, an active flow separation control device based on a fluidic oscillator that does not require electric power has been reported. This device is able to generate a sweeping jet over a wide spatial range as well as fluid oscillations, and its internal structure eliminates the need for a drive unit. The studies of the flow separation control techniques using the fluidic oscillator have been reported. However, most of these results are mainly contribution of the dynamic forces from the viewpoint of the flow control and the study on the flow mechanism for the separation flow control using the fluidic oscillator have not been understood. Especially, it is not known the interaction between the sweeping jet from the fluidic oscillator and the main flow and the flow structure due to the interaction. In order to make a flow separation control devise with high efficiency using the fluidic oscillator, it is require to be understood the complex flow structure by the interaction between the sweeping jet from the fluidic oscillator and the main flow. The purpose of the present study is to investigate the flow structure by the interaction between the sweeping jet from the fluidic oscillator and the main flow quantitatively by the stereo PIV measurement. The sweeping jet ejected from a fluidic oscillator evidently disrupts the main flow at high velocity ratios, leading to a significant change in flow structure. A high-speed jet appears at the center part of the structure, accompanied by low-speed flow at the outside, producing a 3D distribution. The sweeping jet ejected from the fluidic oscillator maintains the spreading angleas a result of the interaction between the two flows at high velocity ratios.

Flow separation control of NACA-2412 airfoil with bio-inspired nose

2019 ◽  
Vol 91 (7) ◽  
pp. 1058-1066 ◽  
Author(s):  
Mohamed Arif Raj Mohamed ◽  
Ugur Guven ◽  
Rajesh Yadav
Keyword(s):  
Flow Control ◽  
Flow Separation ◽  
Control Method ◽  
Angle Of Attack ◽  
Leading Edge ◽  
Separation Control ◽  
Cetacean Species ◽  
Aerodynamic Efficiency ◽  
Content Type ◽  
Flow Separation Control

Purpose The purpose of this paper is to achieve an optimum flow separation control over the airfoil using passive flow control method by introducing bio-inspired nose near the leading edge of the NACA 2412 airfoil. Design/methodology/approach Two distinguished methods have been implemented on the leading edge of the airfoil: forward facing step, which induces multiple accelerations at low angle of attack, and cavity/backward facing step, which creates recirculating region (axial vortices) at high angle of attack. Findings The porpoise airfoil (optimum bio-inspired nose airfoil) delays the flow separation and improves the aerodynamic efficiency by increasing the lift and decreasing the parasitic drag. The maximum increase in aerodynamic efficiency is 22.4 per cent, with an average increase of 8.6 per cent at all angles of attack. Research limitations/implications The computational analysis has been done for NACA 2412 airfoil at low subsonic speed. Practical implications This design improves the aerodynamic performance and increases structural strength of the aircraft wing compared to other conventional high-lift devices and flow-control devices. Originality/value Different bio-inspired nose designs which are inspired by the cetacean species have been analysed for NACA 2412 airfoil, and optimum nose design (porpoise airfoil) has been found.

Flow separation control using a bio-inspired nose for NACA 4 and 6 series airfoils

2021 ◽  
Vol 93 (2) ◽  
pp. 251-266
Author(s):  
Mohamed Arif Raj Mohamed ◽  
Rajesh Yadav ◽  
Ugur Guven
Keyword(s):  
Flow Control ◽  
Flow Separation ◽  
Control Method ◽  
Leading Edge ◽  
Aircraft Design ◽  
Separation Control ◽  
Cetacean Species ◽  
Aerodynamic Efficiency ◽  
Content Type ◽  
Flow Separation Control

Purpose This paper aims to achieve an optimum flow separation control over the airfoil using a passive flow control method by introducing a bio-inspired nose near the leading edge of the National Advisory Committee for Aeronautics (NACA) 4 and 6 series airfoil. In addition, to find the optimised leading edge nose design for NACA 4 and 6 series airfoils for flow separation control. Design/methodology/approach Different bio-inspired noses that are inspired by the cetacean species have been analysed for different NACA 4 and 6 series airfoils. Bio-inspired nose with different nose length, nose depth and nose circle diameter have been analysed on airfoils with different thicknesses, camber and camber locations to understand the aerodynamic flow properties such as vortex formation, flow separation, aerodynamic efficiency and moment. Findings The porpoise nose design that has a leading edge with depth = 2.25% of chord, length = 0.75% of chord and nose diameter = 2% of chord, delays the flow separation and improves the aerodynamic efficiency. Average increments of 5.5% to 6° in the lift values and decrements in parasitic drag (without affecting the pitching moment) for all the NACA 4 and 6 series airfoils were observed irrespective of airfoil geometry such as different thicknesses, camber and camber location. Research limitations/implications The two-dimensional computational analysis is done for different NACA 4 and 6 series airfoils at low subsonic speed. Practical implications This design improves aerodynamic performance and increases the structural strength of the aircraft wing compared to other conventional high lift devices and flow control devices. This universal leading edge flow control device can be adapted to aircraft wings incorporated with any NACA 4 and 6 series airfoil. Social implications The results would be of significant interest in the fields of aircraft design and wind turbine design, lowering the cost of energy and air travel for social benefits. Originality/value Different bio-inspired nose designs that are inspired by the cetacean species have been analysed for NACA 4 and 6 series airfoils and universal optimum nose design (porpoise airfoil) is found for NACA 4 and 6 series airfoils.

Active Flow Separation Control Using Endwall Vortex Generator Jets in Highly Loaded Compressor Cascades

2015 ◽  
Author(s):  
Yanyan Feng ◽  
Yanping Song ◽  
Fu Chen ◽  
Huaping Liu
Keyword(s):  
Flow Separation ◽  
Active Flow Control ◽  
Vortex Generator ◽  
Control Technique ◽  
Flow Separation Control ◽  
Positive Effects ◽  
Loss Coefficients ◽  
Vortex Generator Jets ◽  
Active Flow ◽  
Highly Loaded

An active flow control technique of endwall vortex generator jets (VGJs) was used in two kinds of highly loaded compressor cascades. Numerical investigations were carried out on a NACA 65 profile with a large camber angle at low subsonic and high subsonic speeds, and a CDA profile at high subsonic speed respectively. The results indicate that the endwall VGJs can restrain flow separation effectively by reenergizing the boundary layer fluid and resisting the transverse movement of endwall secondary flow. At Mach number 0.23, the results of the jet blowing ratio study illustrate that the increasing jet velocity shows noteworthy potential to improve the cascade aerodynamic performance. The double jets structures were investigated yet gains weaker beneficial effects than single jet. It is probably attributed to the complex flow structure, leading to strong disturbance and large-scale mixing loss. Under −5°, 0° and +5° angles of attack, the loss coefficients are maximally reduced by 4.1%, 9.5% and 17.3% respectively. Under high subsonic conditions, the endwall VGJs still has significantly positive effects on NACA 65 profile. Considering the small separation region of CDA, the loss coefficients increase slightly although the flow separation is weakened further by VGJ.

Sign in / Sign up

Export Citation Format

Share Document