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.

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.

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.

New Fluidic-Oscillator Concept for Flow-Separation Control

AIAA Journal ◽  
2013 ◽  
Vol 51 (2) ◽  
pp. 397-405 ◽  
Author(s):  
V. Tesař ◽  
S. Zhong ◽  
F. Rasheed
Keyword(s):  
Flow Separation ◽  
Separation Control ◽  
Flow Separation Control ◽  
Fluidic Oscillator

Numerical Investigation of Three-dimensional Separation Control on a High-speed Compressor Stator Vane with Tailored Synthetic Jet

2020 ◽  
Vol 37 (4) ◽  
pp. 383-397 ◽  
Author(s):  
Yong Qin ◽  
Yanping Song ◽  
Ruoyu Wang ◽  
Huaping Liu
Keyword(s):  
Flow Control ◽  
Flow Separation ◽  
High Speed ◽  
Numerical Study ◽  
Three Dimensional ◽  
Synthetic Jet ◽  
Separation Control ◽  
Flow Separation Control ◽  
Control Efficiency ◽  
Stator Vane

AbstractA numerical study on the performance of synthetic jet for flow separation control on a high-speed compressor stator vane is performed. Four control schemes including full-span and part-span configurations are investigated at both design and off-design conditions. Results indicate that both full-span and part-span schemes could effectively delay flow separation and reduce total pressure loss for the compressor stator vane, the adaptability of the flow control under off-design conditions is also validated. Within the investigated incidence range, the full-span configuration is able to gain the most significant performance improvement, by which a maximum loss reduction of 23.8 % is obtained at i=2 deg. The part-span configuration could reorganize the vortex structures more efficiently and cut off the interaction between the ring-like vortex and the passage vortex, thus improving its performance in the corner region. In terms of flow control efficiency, the part-span configurations turn out to be more superior, where the highest control efficiency of 614.0 % is achieved at i=0 deg with the total height of the actuator being 40 %H. The flow control efficiency for all the schemes is higher than 100 % within the whole operating range, demonstrating a promising prospect for the application of synthetic jet in axial compressors.

scholarly journals Flow Separation Control of Nacelle in Crosswind by Microsecond Pulsed Surface Dielectric Barrier Discharge Plasma Actuator

2021 ◽  
Author(s):  
Yuhao Jia ◽  
Hua Liang ◽  
Qikun He ◽  
Zhi Su ◽  
Guoxing Song
Keyword(s):  
Flow Control ◽  
Flow Separation ◽  
Barrier Discharge ◽  
Pulse Frequency ◽  
Plasma Actuator ◽  
Separation Control ◽  
Control Effect ◽  
Dielectric Barrier ◽  
Flow Separation Control ◽  
Surface Dielectric Barrier Discharge

Abstract Flow separation under crosswind conditions seriously jeopardizes the quality of the nacelle’s flow field. In this paper, microsecond pulsed surface dielectric barrier discharge (µSDBD) is used to suppress the flow separation and reduce the crosswind distortion of the nacelle. The flow structure induced by the µSDBD is first explored by a high-speed schlieren system. The pressure waves composed of a cylindrical wave surrounding the electrodes and a flat wave at the top of the cylindrical one can be perceived, which indicates the fast gas heating produced by the µSDBD. A set of wind tunnel tests are then conducted to verify the ability of µSDBD to suppress the nacelle flow separation and study the influence laws of pulse frequency, coverage area, and the actuator layout on the flow control effects. Results show that plasma actuation can not only improve the total pressure at the exit of the nacelle but also suppress the flow distortion caused by the crosswind. The best flow control effect can be achieved at the pulse frequency of 500Hz, with the value of sectional distortion coefficient reduced by 57.76% compared with the baseline condition. The flow control effect with the plasma actuator covering 120° of the nacelle perimeter is better than that of 60° and 180° coverage, showing the highest flow control efficiency in the 120° condition. The µSDBD can improve mixing between the boundary layer and the main flow, enhancing the ability of the boundary layer to resist the adverse pressure gradient, which is beneficial to flow separation control.

scholarly journals Active flow separation control at the outer wing

2019 ◽  
Vol 11 (4) ◽  
pp. 823-836 ◽  
Author(s):  
J. P. Rosenblum ◽  
P. Vrchota ◽  
A. Prachar ◽  
S. H. Peng ◽  
S. Wallin ◽  
...  
Keyword(s):  
Flow Separation ◽  
Separation Control ◽  
Flow Separation Control ◽  
Active Flow
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