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Dynamic stall control over an airfoil by NS-DBD actuation

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Chinese Physics B 2020年第10期29卷 370-379页

作者： He-Sen Yang Guang-Yin Zhao Hua Liang Biao Wei Science and Technology on Plasma Dynamics Laboratory Air Force Engineering UniversityXi'an 710038China State Key Laboratory of Aerodynamics China Aerodynamics Research and Development CenterMianyang 621000China

The wind tunnel test was conducted with an NACA 0012 airfoil to explore the flow control effects on airfoil dynamic stall by NS-DBD plasma actuation. Firstly, light and deep dynamic stall states were set, based on the static stall characteristics of airfoil at a Reynolds number of 5.8 × 105. Then, the flow control effect of NS-DBD on dynamic stall was studied and the influence law of three typical reduced frequencies (k = 0.05, k = 0.05, and k = 0.15) was examined at various dimensionless actuation frequencies (F+ = 1, F+ = 2, and F+ = 3). For both light and deep dynamic stall states, NS-DBD had almost no effect on upstroke. However, the lift coefficients on downstroke were increased significantly and the flow control effect at F+ = 1 is the best. The flow control effect of the light stall state is more obvious than that of deep stall state under the same actuation conditions. For the same stall state, with the reduced frequency increasing, the control effect became worse. Based on the in being principles of flow separation control by NS-DBD, the mechanism of dynamic stall control was discussed and the influence of reduced frequency on the dynamic flow control was analyzed. Different from the static airfoil flow separation control, the separated angle of leading-edge shear layer for the airfoil in dynamic stall state is larger and flow control with dynamic oscillation is more difficult. The separated angle is closely related to the effective angle of attack, so the effect of dynamic stall control is greatly dependent on the history of angles of attack.

关键词： flow control dynamic stall dielectric barrier discharge(DBD) nanosecond pulse reduced frequency

Abnormal changes of dynamic derivatives at low reduced frequencies

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Chinese Journal of Aeronautics 2018年第7期31卷 1428-1436页

作者： Weiwei ZHANG Yiming GONG Yilang LIU School of Aeronautics Northwestern Polytechnical University

A number of studies have found that abnormal changes of dynamic derivatives occurred at very low reduced frequencies, but its inducement mechanism is not very clear. This paper has researched the abnormal changes and analyzed the influence on some parameters by solving the unsteady flow around forced oscillation airfoils based on Navier-Stokes equations. Results indicate that when the reduced frequency approaches to zero, the dynamic derivatives obtained by the numerical method will diverge. We have also proven it in theory that this phenomenon is not physical but completely caused by numerical singularity. Furthermore, the abnormal phenomenon can be effectively mitigated by using the time spectral method to solve the aerodynamic forces and the integral method to obtain the dynamic derivatives. When the reduced frequency is in the range of 0.001–0.01, the dynamic derivative maintains nearly unchanged for the whole speed region. This study can provide a reference for the reasonable choice of the reduced frequency in calculations and experiments of dynamic derivatives.

关键词： Dynamic derivatives Numerical diverge reduced frequency Time spectral method Unsteady flow

折合频率对三维跨声速压气机颤振稳定性的影响

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风机技术 2022年第3期64卷 1-9页

作者： Ruichao Shi Yufang Li Dingxi Wang Wuhan Second Ship Design and Research Institute Wuhan430205China School of Power and Energy Northwestern Polytechnical UniversityXi'an710129China AVIC Xi'an Aircraft Industry Group Company Lud. Xi'an710089China

It is well known that fan/compressor blade flutter stability increases with the increase of reduced *** well-known is that the least stable inter blade phase angle(IBPA)increases with the drop of reduced ***,it is quite striking that little can be found in the open literature about the mechanism to the *** this paper,a numerical investigation is carried out to uncover the mechanism of the effect of reduced frequency on flutter stability and the least stable *** NASA rotor 67 has been used as the test vehicle with its first bending and torsion modes being *** time domain harmonic balance method together with the influence coefficient method is used to obtain the worksum-IBPA curves for all *** is found that:1)the deterioration of flutter stability with the decrease of reduced frequency is dictated by the dominant decrease of aerodamping due to a blade own vibration;2)the increase of the least stable IBPA with the decrease of reduced frequency arises largely from the increase of the least stable IBPA of the aerodamping from the nearest blade on a blade pressure side.

关键词： Compressor Blade Flutter reduced frequency Inter Blade Phase Angle

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Numerical Simulation of Uniform Flow past an In-Line Oscillating Circular Cylinder

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Tsinghua Science and Technology 2002年第5期7卷 475-480页

作者：刘松符松 Department of Engineering Mechanics Tsinghua University Beijing 100084 China

The time-dependent viscous incompressible flow around an in-line oscillating circular cylinder at Reynolds numbers of 200 and 855 was analyzed using a finite volume method. The Navier-Stokes equations were solved on a moving grid system using a time-dependent coordinate transformation. Several numerical schemes were tested to investigate the vortex-shedding characteristics and the effects of Reynolds number and other dimensionless parameters such as the reduced amplitude and the reduced frequency. The numerical results indicate that several types of vortex shedding modes depend on the reduced frequency and the reduced amplitude due to synchronization or lock-on.

关键词： circular cylinder in-line oscillating vortex shedding reduced frequency