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| 1 | Review of zero-net-mass-flux jet and its application in separation flow control显示文摘Since the zero-net-mass-flux (ZNMF) jet was first used as a laboratory flow control method in 1990's, it has attracted much attention. The ZNMF jet has unique features such as compact actuator, no requirement for external air supply, complex piping, etc., and becomes a hot topic research subject in fluid mechanics. This review introduces the state of the art in the development of ZNMF jet in the quiescent fluid, the interaction of the ZNMF jet with the cross flow and its application in the separation flow control. The evolution of the vortex ring/pair and the spacial flow structure of the ZNMF in quicent fluid or cross flow are presented, as well as the key parameter effects. At last, the applications of ZNMF jet in the wake control of the circular cylinder, the separation control on the airfoil and the aerodynamic force or moment control on MAV/UAV are presented. | ZHANG PanFeng WANG JinJun FENG LiHao | 2008 | Science China(Technological Sciences)2008，51，9： | 30 |
| 2 | Experimental investigation on control of vortex shedding mode of a circular cylinder using synthetic jets placed at stagnation points显示文摘Control of flow around a circular cylinder by synthetic jets has been experimentally investigated in a water tunnel with particle image velocimetry(PIV) technique.The synthetic jets are positioned at both the front and rear stagnation points.With power spectrum analysis,proper orthogonal decomposition(POD) method and other techniques for data processing,particular attention is paid to the control of vortical structures around the circular cylinder,in which the excitation frequency f e is one to three times of the natural frequency f0 and the cylinder Reynolds number and the excitation amplitude are fixed.The influenced-scope of the synthetic jet enlarges as the excitation frequency increases,and thus the synthetic jet dominates the global flow field gradually.For the natural case and the control case at fe/f0=1,the distributions of the first two POD modes and the power spectra for their POD coefficients all exhibit the characteristics of the natural shedding with antisymmetric mode.For fe/f0=2 and fe/f0=3,the variations in the third and fourth POD modes and the corresponding power spectra indicate that the wake vortex shedding mode changes and the dominant frequency becomes the excitation frequency.For fe/f0=2,the wake vortex sheds downstream with either the antisymmetric or the symmetric mode;for fe/f0=3,the synthetic jet vortex pair interacts with the near wake shear layers from both sides to induce a pair of the symmetric wake vortices,which is gradually converted into an antisymmetric mode when shedding downstream. | MA LiQun FENG LiHao | 2013 | Science China(Technological Sciences)2013，56，1： | 11 |
| 3 | Experimental investigations on separation control and flow structure around a circular cylinder with synthetic jet显示文摘Circular cylinder separation control and flow structure influenced by the synthetic jet have been experimentally investigated in a water channel. The synthetic jet is- sues from a slot and ejects toward upstream from the front stagnation point of the cylinder. It has been found that, similar to the traditional synthetic jet which is po- sitioned near the separation point or inside the separation region, the present synthetic jet arrangement constitutes an efficient way to control flow separation of the circular cylinder, but with a different control mechanism. The present synthetic jet leads to an upstream displacement of the front stagnation point and the forma- tion of a vortex pair near both sides of the exit orifice. When ReU based on the synthetic jet average exit orifice velocity is about lower than 43, a closed envelope forms in front of the windward side of the cylinder during the blowing cycle of syn- thetic jet, which acts as an apparent modification for the cylinder configuration. When ReU is high enough, an open envelope forms upstream of the cylinder, and the flow around the cylinder becomes much energetic. Thus, regardless of ReU, the present synthetic jet can improve separation for flow around a circular cylinder. With regard to the leeward side, as ReU increases, the flow separation region be- hind the cylinder gradually disappears. The flow over cylinder may be fully attached when the open envelope forms upstream of the cylinder and ReU is greater than 344. Then, the flow past the cylinder will converge near the back stagnation point of the cylinder, where a new vortex pair shedding periodically is generated due to the high shear layer. | WANG JinJun FENG LiHao XU ChaoJun | 2007 | Science China(Technological Sciences)2007，50，5： | 9 |
| 4 | Fourier mode decomposition of PIV data.显示文摘The modal decomposition technique is one of the most effective methods for studying the flow dynamics in a complex flow. By rejuvenating the discrete Fourier transform(DFT), this paper proposes a Fourier mode decomposition(FMD) method for the time series of particle image velocimetry(PIV) data from the fluid field. An experimental case concerning the control of the flow around a circular cylinder by a synthetic jet positioned at the rear stagnation point is used to demonstrate the use of the FMD method. In the three different regimes where the natural shedding frequency and actuation frequency dominate respectively or simultaneously, it is found that the FMD method is capable of extracting the dynamic mode along with its amplitude and phase according to the selected characteristic frequency based on the global power spectrum. For the quasiperiodic flow phenomena presented in this particular case, the FMD method can reconstruct the original flow field using the zero-th mode and the selected mode corresponding to the characteristic frequency. Similarities and differences between the FMD method and the dynamical mode decomposition(DMD) and proper orthogonal decomposition(POD) methods are also discussed. | MA LiQun FENG LiHao PAN Chong GAO Qi WANG JinJun | 2015 | Science China(Technological Sciences)2015，58，11： | 6 |
| 5 | Influence of orifice-to-wall distance on synthetic jet vortex ring simpinging on a fixed wall显示文摘Two-dimensional particle image velocimetry (PIV) is used to investigate the influence of the orifice-to-wall distance on synthetic jet vortex rings impinging on a fixed wall. Both evolutions of vortical structures and statistical characteristics of flow fields at different orifice-to-wall distances are presented. It is found that different orifice-to-wall distances have different effects in terms of the vortex strength and impinging speed when the vortex rings are approaching the wall. The secondary vortex ring can be observed within the shear layer only when the dimensionless orifice-to-wall distance is close to or less than the dimensionless stroke length. Consequently, an appropriate orifice-to-wall distance plays a vital role in the sense of impingement effect. The statistical analysis of the flow field indicates that a wall jet forms after impingement, while both the decay rate of the maximum radial velocity and the spreading rate of the half-width decrease with the increasing orifice-to-wall distance. The non-dimensional wall jet velocity profiles at different orifice-to-wall distances all exhibit self-similar behaviors, which is consistent with the theoretical solution of the laminar wall jet. | XU Yang FENG LiHao | 2013 | Science China(Technological Sciences)2013，56，7： | 3 |
| 6 | The prior rules of designing Ti_(3)C_(2)T_(x) MXene-based gas sensors显示文摘Working temperature,sensitivity,and selectivity are some of the characteristics of the applied gas sensors.How to design and fabricate an ideal gas sensor working at room temperature is still challenging and attracting lots of interest.Two-dimensional(2D)materials with ultra-thin structure have been demonstrated as a family of ideal candidates to achieve this goal.Among them,Ti_(3)C_(2)T_(x) MXene,a kind of layered sheet synthesized by selectively etching MAX phases materials,shows remarkable potential to be the sensitive materials solely or in a composite.However,their designing rules are still lacking critical thinking from the viewpoint of the intrinsic property of Ti_(3)C_(2)T_(x) MXene based materials.In this article,two critical features,i.e.,the thickness of the sensitive materials,and the scope of the analytes,are elaborated towards Ti_(3)C_(2)T_(x) MXene based gas sensors after characterizing the performance of sensing reducing gases(NH3 and CO)and oxidizing gas(NO2).First,the thinner the Ti_(3)C_(2)T_(x) MXene sensitive layer,the better the sensitivity.Second,the Ti_(3)C_(2)T_(x) MXene based gas sensor is not suitable for strong and moderate oxidation gas due to its ease of oxidation.These two rules are demonstrated,and could be considered with priority both in the future researches and practical applications. | Yingying Jian Danyao Qu Lihao Guo Yujin Zhu Chen Su Huanran Feng Guangjian Zhang Jia Zhang Weiwei Wu Ming-Shui Yao | 2021 | Frontiers of Chemical Science and Engineering2021，15，3： | 3 |
| 7 | Experimental and numerical investigation of threedimensional vortex structures of a pitching airfoil at a transitional Reynolds number显示文摘This research examines the vortex behaviors and aerodynamic forces in dynamic stall phenomena at a transitional Reynolds number(Re=90000)using experimental and numerical approaches.Periodic sinusoidal pitching motion at two different reduced frequencies is used to achieve the dynamic stall of a NACA 0012 airfoil.Several leading edge vortices form and detach in the dynamic stall stage.The flow then quickly transitions to a full separation zone in the stall stage when the angle of attack starts to decrease.There is discrepancy between the phaseaveraged and instantaneous flow field in that the small flow structures increased with angle of attack,which is a characteristic of the flow field at the transitional Reynolds number.The interaction between the streamwise vortices in the three-dimensional numerical results and the leading edge vortex are the main contribution to the turbulent flow.In addition,the leading edge vortex that supplies vortex lift is more stable at higher reduced frequency,which decreases the lift fluctuation in the dynamic stall stage.The leading edge vortex at higher reduced frequency is strong enough to stabilize the flow,even when the airfoil is in the down-stroke phase. | Zhenyao LI Lihao FENG Hamid Reza KARBASIAN Jinjun WANG Kyung Chun KIM | 2019 | Chinese Journal of Aeronautics2019，32，10： | 2 |
| 8 | Individual influence of pitching and plunging motions on flow structures over an airfoil during dynamic stall显示文摘The individual influence of pitching and plunging motions on flow structures is studied experimentally by changing the phase lag between the geometrical angle of attack and the plunging angle of attack.Five phase lags are chosen as the experimental parameters,while the Strouhal number,the reduced frequency and the Reynolds number are fixed.During the motion of the airfoil,the leading edge vortex,the reattached vortex and the secondary vortex are observed in the flow field.The leading edge vortex is found to be the main flow structure through the proper orthogonal decomposition.The increase of phase lag results in the increase of the leading edge velocity,which strongly influences the leading edge shear layer and the leading edge vortex.The plunging motion contributes to the development of the leading edge shear layer,while the pitching motion is the key reason for instability of the leading edge shear layer.It is also found that a certain increase of phase lag,around 34.15°in this research,can increase the airfoil lift. | Zhenyao LI Lihao FENG Jinjun WANG | 2020 | Chinese Journal of Aeronautics2020，33，3： | 1 |
| 9 | Recent developments in DBD plasma flow control显示文摘 | WANG Jinjun Choi K S FENG Lihao | 2013 | Progress in Aerospace Sciences2013，62，4： | 1 |
| 10 | Multimodal critical-scenarios search method for test of autonomous vehicles显示文摘Purpose–The purpose of this paper is to search for the critical-scenarios of autonomous vehicles(AVs)quickly and comprehensively,which is essential for verification and validation(V&V).Design/methodology/approach–The author adopted the index F1 to quantitative critical-scenarios’coverage of the search space and proposed the improved particle swarm optimization(IPSO)to enhance exploration ability for higher coverage.Compared with the particle swarm optimization(PSO),there were three improvements.In the initial phase,the Latin hypercube sampling method was introduced for a uniform distribution of particles.In the iteration phase,the neighborhood operator was adapted to explore more modals with the particles divided into groups.In the convergence phase,the convergence judgment and restart strategy were used to explore the search space by avoiding local convergence.Compared with the Monte Carlo method(MC)and PSO,experiments on the artificial function and critical-scenarios search were carried out to verify the efficiency and the application effect of the method.Findings–Results show that IPSO can search for multimodal critical-scenarios comprehensively,with a stricter threshold and fewer samples in the experiment on critical-scenario search,the coverage of IPSO is 14%higher than PSO and 40%higher than MC.Originality/value–The critical-scenarios’coverage of the search space is firstly quantified by the index F1,and the proposed method has higher search efficiency and coverage for the critical-scenarios search of AVs,which shows application potential for V&V. | Tianyue Feng Lihao Liu Xingyu Xing Junyi Chen | 2022 | Journal of Intelligent and Connected Vehicles2022，5，3： | 0 |
| 11 | Pepper variome reveals the history and key loci associated with fruit domestication and diversification显示文摘Pepper(Capsicum spp.)is an important vegetable crop that provides a unique pungent sensation when eaten.Through construction of a pepper variome map,we examined the main groups that emerged during domestication and breeding of C.annuum,their relationships and temporal succession,and the molecular events underlying the main transitions.The results showed that the initial differentiation in fruit shape and pungency,increase in fruit weight,and transition from erect to pendent fruits,as well as the recent appearance of large,blocky,sweet fruits(bell peppers),were accompanied by strong selection/fixation of key alleles and introgressions in two large genomic regions.Furthermore,we identified Up,which encodes a BIG GRAIN protein involved in auxin transport,as a key domestication gene that controls erect vs pendent fruit orientation.The up mutation gained increased expression especially in the fruit pedicel through a 579-bp sequence deletion in its 5′upstream region,resulting in the phenotype of pendent fruit.The function of Up was confirmed by virus-induced gene silencing.Taken together,these findings constitute a cornerstone for understanding the domestication and differentiation of a key horticultural crop. | Yacong Cao Kang Zhang Hailong Yu Shumin Chen Donghui Xu Hong Zhao Zhenghai Zhang Yinqing Yang Xiaozhen Gu Xinyan Liu Haiping Wang Yaxin Jing Yajie Mei Xiang Wang Véronique Lefebvre Weili Zhang Yuan Jin Dongliang An Risheng Wang Paul Bosland Xixiang Li IIan Paran Baoxi Zhang Giovanni Giuliano Lihao Wang Feng Cheng | 2022 | Molecular Plant2022，15，11： | 0 |
| 12 | Exploring ternary organic photovoltaics for the reduced nonradiative recombination and improved efficiency over 17.23%with a simple large-bandgap small molecular third component显示文摘Ternary strategy is one of the most effective methods to further boost the power conversion efficiency(PCE)of organic photovoltaic cells(OPVs).In terms of high-efficiency PM6:Y6 binary systems,there is still room to further reduce energy_(loss)(E_(loss))through regulating molecular packing and aggregation by introducing a third component in the construction of ternary OPVs.Here we introduce a simple molecule BR1 based on an acceptor-donor-acceptor(A-D-A)structure with a wide bandgap and high crystallinity into PM6:Y6-based OPVs.It is proved that BR1 can be selectively dispersed into the donor phase in the PM6:Y6 and reduce disorder in the ternary blends,thus resulting in lower E_(loss,non-rad)and E_(loss).Furthermore,the mechanism study reveals well-develop phase separation morphology and complemented absorption spectra in the ternary blends,leading to higher charge mobility,suppressed recombination,which concurrently contributes to the significantly improved PCE of 17.23%for the ternary system compared with the binary ones(16.21%).This work provides an effective approach to improve the performance of the PM6:Y6-based OPVs by adopting a ternary strategy with a simple molecule as the third component. | Huanran Feng Yvjie Dai Lihao Guo Di Wang Hao Dong Zhihui Liu Lu Zhang Yvjin Zhu Chen Su Yongsheng Chen Weiwei Wu | 2022 | Nano Research2022，15，4： | 0 |
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