The two-dimensional, compressible, mass-averaged Navier-Stokes equations are used to investigate hows about a typical circulation control airfoil. The governing equations are solved using the implicit approximate-fact...The two-dimensional, compressible, mass-averaged Navier-Stokes equations are used to investigate hows about a typical circulation control airfoil. The governing equations are solved using the implicit approximate-factorization algorithm of Beam-Warming with a modified algebraic eddy viscosity model. Results are compared with experimental data, and excellent agreement is obtained. The effects of different jet momentum coefficients and angles of attack on the how are studied. The mechanism of genenating large lift by circulation control is discussed.展开更多
A flow control technique by local vibration is proposed to improve the aerodynamic performance of a typical airfoil NACA 0012. Both wind-tunnel experiments and a large eddy simulation(LES) are carried out to study the...A flow control technique by local vibration is proposed to improve the aerodynamic performance of a typical airfoil NACA 0012. Both wind-tunnel experiments and a large eddy simulation(LES) are carried out to study the effects of local vibration on drag reduction over a wide range of angles of attack. The application parameters of local vibration on the upper surface of the airfoil are first evaluated by numerical simulations.The mounted position is chosen at 0.065–0.09 of chord length from the leading edge.The influence of oscillation frequency is investigated both by numerical simulations and experiments. The optimal frequencies are near the dominant frequencies of shear layer vortices and wake vortices. The patterns of shear vortices caused by local vibration are also studied to determine the drag reduction mechanism of this flow control method. The results indicate that local vibration can improve the aerodynamic performance of the airfoil. In particular, it can reduce the drag by changing the vortex generation patterns.展开更多
The effects of leading-edge blowing-suction on the vortex how past an airfoil at high incidence are investigated numerically by solving the Navier-Stokes equations. The results indicate that the frequency of the flowf...The effects of leading-edge blowing-suction on the vortex how past an airfoil at high incidence are investigated numerically by solving the Navier-Stokes equations. The results indicate that the frequency of the flowfield excited by the periodic blowing-suction locks into the forcing frequency, which is half of the dominant frequency for the flow past a fixed airfoil without injection. In that case, a well-developed primary leading-edge vortex occupies the upper surface of the airfoil and the largest lift augmentation is obtained.展开更多
The unsteady flow around a circulation control (CC) airfoil was investigated with Navier-Stokes method,which includes the flow around CC airfoil with pulsating jet,the flow around oscillating CC airfoil,and the flow a...The unsteady flow around a circulation control (CC) airfoil was investigated with Navier-Stokes method,which includes the flow around CC airfoil with pulsating jet,the flow around oscillating CC airfoil,and the flow around oscillating CC airfoil with pulsating jet.Dynamic properties of the flow and the aerodynamic forces were rewaled.展开更多
In the present study, a numerical investigation is carried out on the aerodynamic performance of a supercritical airfoil RAE 2822. Transonic flow fields are considered where self-excited shock wave oscillation prevail...In the present study, a numerical investigation is carried out on the aerodynamic performance of a supercritical airfoil RAE 2822. Transonic flow fields are considered where self-excited shock wave oscillation prevails. To control the shock oscillation, a passive technique in the form of an open rectangular cavity is introduced on the upper surface of the airfoil where the shock wave oscillates. Reynolds Averaged Navier-Stokes (RANS) equations have been used to predict the aerodynamic behavior of the baseline airfoil and airfoil with cavity at Mach number of 0.729 and at angle of attack of 5°. The aerodynamic characteristics of the baseline airfoil are well validated with the available experimental data. It is observed that the introduction of a cavity around the airfoil upper surface can completely stop the self-excited shock wave oscillation and successively improve the aerodynamic characteristics.展开更多
Flow separation is typically an undesirable phenomenon, and boundary layer control is an important technique for the separation problems on airfoils. The synthetic jet actuator is considered as a promising candidate f...Flow separation is typically an undesirable phenomenon, and boundary layer control is an important technique for the separation problems on airfoils. The synthetic jet actuator is considered as a promising candidate for flow control applications because of its compact nature and ability to generate momentum without the need for fluidic plumbing. In the present study, an active separation control system using synthetic jets is proposed and practically applied to the stall control of the NACA0012 airfoil in a wind tunnel test. In our proposed system, the flow conditions (stalled or unstalled) can be judged by calculating from two static pressure holes on the airfoil upper surface alone. The experimental results indicate that the maximum lift coefficient increases by 11% and the stall angle rises by 4°in contrast to the case under no control. It is confirmed that our proposed system can suppress the stall on the NACA0012 airfoil and that the aerodynamic performance of the airfoil can be enhanced. The proposed system can also be operated prior to the onset of stall. Therefore, separation control is always attained with no stall for all flow fields produced by changing the angle of attack that were examined.展开更多
文摘The two-dimensional, compressible, mass-averaged Navier-Stokes equations are used to investigate hows about a typical circulation control airfoil. The governing equations are solved using the implicit approximate-factorization algorithm of Beam-Warming with a modified algebraic eddy viscosity model. Results are compared with experimental data, and excellent agreement is obtained. The effects of different jet momentum coefficients and angles of attack on the how are studied. The mechanism of genenating large lift by circulation control is discussed.
基金Project supported by the National Natural Science Foundation of China(No.11532011)the Fundamental Research Funds for the Central Universities(No.2017FZA4031)
文摘A flow control technique by local vibration is proposed to improve the aerodynamic performance of a typical airfoil NACA 0012. Both wind-tunnel experiments and a large eddy simulation(LES) are carried out to study the effects of local vibration on drag reduction over a wide range of angles of attack. The application parameters of local vibration on the upper surface of the airfoil are first evaluated by numerical simulations.The mounted position is chosen at 0.065–0.09 of chord length from the leading edge.The influence of oscillation frequency is investigated both by numerical simulations and experiments. The optimal frequencies are near the dominant frequencies of shear layer vortices and wake vortices. The patterns of shear vortices caused by local vibration are also studied to determine the drag reduction mechanism of this flow control method. The results indicate that local vibration can improve the aerodynamic performance of the airfoil. In particular, it can reduce the drag by changing the vortex generation patterns.
基金The project supported by the National Defence Research Fund of China
文摘The effects of leading-edge blowing-suction on the vortex how past an airfoil at high incidence are investigated numerically by solving the Navier-Stokes equations. The results indicate that the frequency of the flowfield excited by the periodic blowing-suction locks into the forcing frequency, which is half of the dominant frequency for the flow past a fixed airfoil without injection. In that case, a well-developed primary leading-edge vortex occupies the upper surface of the airfoil and the largest lift augmentation is obtained.
基金Present address: Institute of Engineering Thermophysics, Chinese Academy of Sciences, Beijing 100080, China.
文摘The unsteady flow around a circulation control (CC) airfoil was investigated with Navier-Stokes method,which includes the flow around CC airfoil with pulsating jet,the flow around oscillating CC airfoil,and the flow around oscillating CC airfoil with pulsating jet.Dynamic properties of the flow and the aerodynamic forces were rewaled.
文摘In the present study, a numerical investigation is carried out on the aerodynamic performance of a supercritical airfoil RAE 2822. Transonic flow fields are considered where self-excited shock wave oscillation prevails. To control the shock oscillation, a passive technique in the form of an open rectangular cavity is introduced on the upper surface of the airfoil where the shock wave oscillates. Reynolds Averaged Navier-Stokes (RANS) equations have been used to predict the aerodynamic behavior of the baseline airfoil and airfoil with cavity at Mach number of 0.729 and at angle of attack of 5°. The aerodynamic characteristics of the baseline airfoil are well validated with the available experimental data. It is observed that the introduction of a cavity around the airfoil upper surface can completely stop the self-excited shock wave oscillation and successively improve the aerodynamic characteristics.
文摘Flow separation is typically an undesirable phenomenon, and boundary layer control is an important technique for the separation problems on airfoils. The synthetic jet actuator is considered as a promising candidate for flow control applications because of its compact nature and ability to generate momentum without the need for fluidic plumbing. In the present study, an active separation control system using synthetic jets is proposed and practically applied to the stall control of the NACA0012 airfoil in a wind tunnel test. In our proposed system, the flow conditions (stalled or unstalled) can be judged by calculating from two static pressure holes on the airfoil upper surface alone. The experimental results indicate that the maximum lift coefficient increases by 11% and the stall angle rises by 4°in contrast to the case under no control. It is confirmed that our proposed system can suppress the stall on the NACA0012 airfoil and that the aerodynamic performance of the airfoil can be enhanced. The proposed system can also be operated prior to the onset of stall. Therefore, separation control is always attained with no stall for all flow fields produced by changing the angle of attack that were examined.
