Detached Eddy Simulations of a Synthetic Jet for a High-angle-of-attack Airfoil -Influence of the Jet Angle-

2014 ◽  
Author(s):  
Yuichi Ishibashi ◽  
Koji Miyaji
Keyword(s):  
Angle Of Attack ◽  
Synthetic Jet ◽  
High Angle ◽  
High Angle Of Attack

Active flow control of bi-stable asymmetric vortices on a slender body by alternating synthetic jets

2017 ◽  
Vol 232 (13) ◽  
pp. 2477-2488
Author(s):  
Qite Wang ◽  
Keming Cheng ◽  
Yunsong Gu ◽  
Wei Zuo
Keyword(s):  
Angle Of Attack ◽  
Stable State ◽  
Synthetic Jet ◽  
Synthetic Jets ◽  
Slender Body ◽  
Symmetric Distribution ◽  
High Angle ◽  
Symmetric State ◽  
High Angle Of Attack ◽  
Control Frequency

A synthetic jet actuator with double nozzles is developed to control the leeward vortices behind the slender body at a high angle of attack. Periodic alternating disturbance at the nose tip of the slender body is continuously provided by the alternating synthetic jets. A series of experiments is conducted in a low speed and low turbulence wind tunnel. The results show that the alternating synthetic jets at the nose tip can achieve a suitable control effect in which the lateral force is eliminated. For a very high angle of attack, the leeward vortices behind the slender body are in the inherently bi-stable state; in this state, the symmetric distribution formation by the leeward vortices is nearly impossible. However, the alternating disturbance of the nose tip can break the bi-stable state and transform it into other two states, which are the unsteady switched state of the leeward vortices and the quasi-steady symmetric state. Varying the control frequency significantly affects the state of the leeward vortex. In the range of the lower control frequency, the leeward vortices switch back and forth and follow the cycle of the alternating disturbance at the nose tip. In the range of the higher control frequency, the leeward vortices are in a stable symmetric distribution state. As the alternating disturbance frequency increases from lower to higher, the switched amplitude of the leeward vortices decreases and the unsteady switched state of the leeward vortices gradually changes to the quasi-steady symmetric state. This amplitude reduction occurs because the position of the leeward vortices is very sensitive to the alternating disturbance of the nose tip and is related to the inertia effect of the fluid.

scholarly journals Roll Control of Morphing Aircraft with Synthetic Jet Actuators at a High Angle of Attack

2021 ◽  
Vol 11 (2) ◽  
pp. 505
Author(s):  
Wencheng Li ◽  
Wenyun Wang ◽  
Xiaomao Huang ◽  
Shun Zhang ◽  
Chenyang Li
Keyword(s):  
Input Saturation ◽  
Angle Of Attack ◽  
Synthetic Jet ◽  
Control Surface ◽  
Roll Motion ◽  
High Angle ◽  
High Angle Of Attack ◽  
Morphing Aircraft ◽  
Roll Control ◽  
Saturation Constraint

Flow separation and dynamic stall occurring at a high angle of attack will lead to difficulty in control and maneuverability for morphing aircraft. This study proposes a novel active flow control technology using a synthetic jet actuator for the roll motion of morphing aircraft. With the help of the computational fluid dynamics method and vortex lattice method, the roll control model of morphing aircraft undergoing large shape change at a high angle of attack is established. In this model, both the array of the actuator with an optimized cavity shape and morphing span, which are subject to the input saturation constraint, are used to mimic the conventional control surface. Integrated flight control based on the sliding mode control method is designed to ensure the desired closed-loop asymptotic stability, wherein the radial basis function neural network is employed to provide the compensation induced by the input saturation constraint. To demonstrate the effectiveness of the control scheme, various control strategies for different combinations of input are proposed to maintain the roll motion. The numerical results show that the designed control law could track the target signal well, which suggests that the virtual control surface is an effective tool for maintaining the high flight performance of morphing aircraft.

Numerical Investigation on the Coanda Effect Over the S809 Airfoil With Synthetic Jet Actuator at High Angle of Attack

2014 ◽  
Author(s):  
Mohammad Moshfeghi ◽  
Nahmkeon Hur
Keyword(s):  
Angle Of Attack ◽  
Synthetic Jet ◽  
Coanda Effect ◽  
Detached Eddy Simulation ◽  
High Angle ◽  
High Angle Of Attack ◽  
Injection Angle ◽  
Eddy Simulation ◽  
Momentum Coefficient ◽  
Coandǎ Effect

Synthetic jet actuators (SJA) have shown their efficiency in manipulating the aerodynamic forces on airfoils and blades. Generally, the injection angle is assumed to be an important factor for the injection-based flow control techniques, especially in moderate separation. However, it is important to know the level of effectiveness and the aerodynamic mechanism through which a SJA may affect an airfoil at a high angle of attack. The present research studies the effects of angle between the injected flow and the surface’s tangent line (Coanda effect) over the S809 airfoil equipped with a SJA, using detached eddy simulation (DES). The airfoil is assumed to be at an angle of attack of 25°. Three different cases with jet flow angles of 5°, 15° and 25° are simulated at a constant momentum coefficient of 4.5×10−3. The SJA frequency is 125 Hz for all cases and the simulations are conducted at the Reynolds number of one million. The effects of the jet angle on the streamline, pressure distribution and lifts and drag values are investigated.

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