Novel yaw effector of a flying wing aircraft based on reverse dual synthetic jets

For achieving the nice stealth performance and aerodynamic maneuverability of a Flying Wing Aircraft(FWA),a novel yaw effector based on Reverse Dual Synthetic Jets(RDSJ)was proposed without the movement of rudders.Effects on aerodynamic characteristics of a small-sweep FWA and control mechanism were investigated by numerical simulations.Finally,reverse dual synthetic jet actuators were integrated into a real FWA and flight tests were firstly carried out.Numerical results show that RDSJ could make drag coefficient increase and weaken lift coefficient,which generate a yawing moment and a rolling moment in the same direction,realizing control of heading attitudes,but strong coupling with the pitching moment occurs at large angles of attack.For control mechanism,RDSJ could produce two reverse synthetic jets out of phases,improve the reverse pressure gradient and hence form alternate recirculation zones or even early large-area separation,which cause the rise of pressures before exits and the dip of pressures behind exits,achieving improvement of drag and the yawing moment.The results of flight tests support that RDSJ could realize control of heading attitudes without deflections of rudders during the cruise stage and achieve the maximal yaw angular velocity of 10.12(°)/s,verifying the feasibility of this novel yaw effector.

Novel roll effector based on zero-mass-flux dual synthetic jets and its flight test

The autonomous and controllable Dual Synthetic Jet Actuator(DSJA)is firstly integrated into the Unmanned Aerial Vehicle(UAV),and flight tests without the deflection of rudders are carried out to verify the viability of DSJA to control the attitudes of UAV during cruising.DSJA is improved into an actuator with two diaphragms and three cavities,which has higher energy levels.Actuators,differentially distributed on both sides of the wings,are installed on the trailing edge close to the wing tips.Flight tests,containing Differential Circulation Control(DCC)using double-side actuators,Positive Circulation Control(PCC)using left-side actuators and Negative Circulation Control(NCC)using right-side actuators,are implemented at cruising speed of 25 m/s.Results show that roll attitude control without rudders could be realized by DSJAs.DCC and NCC can generate the rightward roll and yaw angular velocity,prompting UAV to turn right.The stronger controlling ability can be achieved by DCC,with the maximum roll angular velocity of 15.62(°)/s.PCC can generate a rightward roll moment,but a leftward yaw moment will be produced at the same time.Leftward yaw induces the leftward rolling moment,which weakens the roll control effect,making UAV keep to yaw to the left with a small slope.

Vortical structures and density fluctuations analysis of supersonic forward-facing step controlled by self-sustaining dual synthetic jets

Shock wave/boundary layer interaction(SWBLI)is still one of the unresolved bottlenecks that restrict the development of more advanced flight vehicles.Supersonic forward-facing step(FFS),an extreme case of compression ramp,often occurs severe SWBLIs with a large separation bubble.In this paper,experimental investigations on vortical structures and density fluctuations characteristics of supersonic FFS controlled by self-sustaining dual synthetic jets(SDSJ)are carried out in a Mach number 2.95 wind tunnel.High spatial–temporal resolution flowfield images of FFS without/with active flow control are captured by adopting nano-particle-based planar laser scattering technique.The control effects of the distance between the actuator and the step are mainly compared.The paper finds that the SDSJ can effectively change the feature of flowfield,eliminate the separation shock and the reattachment shock,compel the original shock induced by the step leading edge to distort and reduce its intensity finally.Density fluctuations analysis demonstrates that the whole flows seem to move upstream with the increase of distance(dS-J).Discrete Fourier transformation spectrums results reveal that the fluctuations are mainly located in the low-frequency region at first.High-frequency components and frequency bandwidth increase slightly after the SDSJ are applied.

Experimental investigations for parametric effects of dual synthetic jets on delaying stall of a thick airfoil

A promising strategy of synthetic jet arrays （SJA） control for NACA0021 airfoil in preventing flow separation and delaying stall is investigated. Through aerodynamic forces, flowfield and velocity profiles measurements, it indicates that the synthetic jet （S J） could enlarge the mixing of the shear layer and then enhance the stability of boundary layer, resulting in scope reduction of the flow separation zone. Furthermore, the control effects of dual jet arrays positioned at 15%c （Actuator 1） and 40%c （Actuator 2） respectively are systematically investigated with different jet parameters, such as two typical relative phase angles and various incline angles of the jet. The jet closer to the leading edge of airfoil is more advantageous in delaying the stall of airfoil, and overall, the flow control performances of jet arrays are better than those of single actuator. At the angle of attack （AoA） just approaching and larger than the stall AoA, jet array with 180° phase difference could increase the lift coefficient more significantly and prevent flow separation. When momentum coefficient of the jet arrays is small, a larger jet angle of Actuator 2 is more effective in improving the maximum lift coefficient of airfoil. With a larger momentum coefficient of jet array, a smaller jet angle of Actuator 2 is more effective.

Theoretical modeling of vectoring dual synthetic jet based on regression analysis

The excellent vectoring characteristic of Dual Synthetic Jet(DSJ)provides a new control strategy for the active flow control,such as thrust vectoring control,large area cooling,separated flow control and so on.For incompressible flow,the influence relation of source variables,such as structure parameters of actuators,driving parameters and material attributes of piezoelectric vibrating diaphragm,on the vectoring DSJ and a theoretical model are established based on theoretical and regression analysis,which are all verified by numerical simulations.The two synthetic jets can be deemed as a main flow with a higher jet velocity and a disturbing flow with a lower jet velocity.The results indicate that the influence factors contain the low-pressure area formed at the exit of the disturbing flow,which could promote the vectoring deflection,and the impact effect of the disturbing flow and the suppressive effect of the main flow with the effect of restraining the vectoring deflection.The vectoring angle is a complex parameter coupled by all source variables.The detailed theoretical model,whose error is controlled within 3.6 degrees,can be used to quantitatively assess the vectoring feature of DSJ and thus to provide a guidance for designing the control law applied in the active flow control.

Lift enhancement based on virtual aerodynamic shape using a dual synthetic jet actuator

The Dual Synthetic Jet Actuator(DSJA) is used to develop a new type of lift enhancement device based on circulation control, and to control the flow over the two-dimensional(2D)NACA0015 airfoil. The lift enhancement device is composed of a DSJA and a rounded trailing edge(Coanda surface). The two outlets of the DSJA eject two jets(Jet 1 and Jet 2). Jet 1 ejects from the upper trailing edge, which increases the circulation of airfoil with the help of the Coanda surface. Jet2 ejects from the lower trailing edge, which acts as a virtual flap. The Reynolds number based on the airfoil chord length and free flow velocity is 250000. The results indicate that the circulation control method based on Dual Synthetic Jet(DSJ) has good performance in lift enhancement, whose control effect is closely related to momentum coefficient and reduced frequency. With the increase of the reduced frequency, the control effect of the lift enhancement is slightly reduced. As the momentum coefficient increases, the control effect becomes better. When the angle of attack is greater than 4°, the increments of lift coefficients under the control of DSJ are larger than those under the control of the steady blowing at a same momentum coefficient. The maximum lift augmentation efficiency can reach 47 when the momentum coefficient is 0.02, which is higher than the value in the case with steady blowing jet circulation control.