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Experimental and numerical investigation on opposing plasma synthetic jet for drag reduction

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Chinese Journal of Aeronautics 2022年第8期35卷 75-91页

作者： Wei XIE Zhenbing LUO Yan ZHOU Wenqiang PENG Qiang LIU Dengpan WANG College of Aerospace engineering National University of Defense TechnologyChangsha 410073China Beijing Special Engineering Design and Research Institute Beijing 100000China

Experimental and numerical studies are carried out to validate the potential of opposing Plasma Synthetic Jet(PSJ)for drag reduction for a hemisphere.Firstly,flow field changes of opposing PSJ are analyzed by comparing the experimental schlieren images and simulation results in a supersonic free stream of Mach number 3.As PSJ is a kind of unsteady pulsed jet,the shock standoff distance increases initially and then decreases under the control of PSJ,which corresponds to the change of the strength of PSJ.Accordingly,the amount of drag reduction of the hemisphere increases initially and then decreases.It is found that there is a short period of“drag rise”during the formation of PSJ before the drag reduction,which is induced by the generation of normal shock waves and the area difference of the cavity wall of PSJ Actuator(PSJA).Secondly,the effects of five parameters,including exit diameter,discharge energy of PSJA,Mach number,static pressure of incoming flow and angle of attack,on drag reduction of opposing PSJ were studied in detail by using numerical method.It is found that the Maximum Pressure Ratio(MPR)has a significant impact on the average drag reduction for a configuration-determined PSJA.For the configuration selected in this study,the flow field of opposing PSJ shows typical Short Penetration Mode(SPM)in a control cycle of PSJ when the MPR is less than 0.89.However,the flow field shows typical Long Penetration Mode(LPM)at some time when the MPR is bigger than 0.89.Relatively better drag reduction is achieved in this case.

关键词： Drag reduction Opposing jet Parameter study Plasma synthetic jet(PSJ) Supersonic flow

Membrane flux dynamics in the submerged ultrafiltration hybrid treatment process during particle and natural organic matter removal

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Journal of Environmental Sciences 2011年第12期23卷 1970-1976页

作者： Wei Zhang Xiaojian Zhang Yonghong Li Jun Wang Chao Chen Department of Environmental Science and engineering Tsinghua University Beijing 100084 China Beijing Special Engineering Design and Research Institute Beijing 100028 China

Particles and natural organic matter （NOM） are two major concerns in surface water, which greatly influence the membrane filtration process. The objective of this article is to investigate the efiect of particles, NOM and their interaction on the submerged ultrafiltration （UF） membrane flux under conditions of solo UF and coagulation and PAC adsorption as the pretreatment of UF. Particles, NOM and their mixture were spiked in tap water to simulate raw water. Exponential relationship, （JP/JP0 = a×exp{-k[t-（n-1）T]}）, was developed to quantify the normalized membrane flux dynamics during the filtration period and fitted the results well. In this equation, coefficient a was determined by the value of JP/JP0 at the beginning of a filtration cycle, refiecting the flux recovery after backwashing, that is, the irreversible fouling. The coefficient k refiected the trend of flux dynamics. Integrated total permeability （ΣJP） in one filtration period could be used as a quantified indicator for comparison of different hybrid membrane processes or under different scenarios. According to the results, there was an additive effect on membrane flux by NOM and particles during solo UF process. This additive fouling could be alleviated by coagulation pretreatment since particles helped the formation of flocs with coagulant, which further delayed the decrease of membrane flux and benefited flux recovery by backwashing. The addition of PAC also increased membrane flux by adsorbing NOM and improved flux recovery through backwashing.

关键词： ultrafiltration membrane flux particles natural organic matter hybrid process backwashing

Underwater Directional Acoustic Source Based on Pentamode Material

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Acta Mechanica Solida Sinica 2024年第1期37卷 1-9页

作者： Binghao Zhao Peng Wang Dongwei Wang Gengkai Hu School of Aerospace engineering Beijing Institute of TechnologyBeijing 100081China Wuhan Second Ship design and research institute Wuhan 430205China

An underwater directional acoustic emitter is conceived with a highly anisotropic lattice material,whose acoustic characteristics manifest strong dependence on the orientation of the lattice material’s principal axis.Exploiting these features,a cylindrical structure made of such anisotropic lattice material is engineered to possess distinct impedance values in different directions,thereby facilitating wave emission along the principal axis while inducing reflection in other directions.Notably,through numerical simulations,it is demonstrated that the emission direction can be effectively manipulated by adjusting the principal axis orientation,concurrently enhancing the emitted power.In contrast to previous directional acoustic structures,the compact emitter presented in this study can get rid of the size-wavelength constraint,enabling effective control of low-frequency waves.

关键词： Underwater Directional emission Pentamode material Broadband frequency

Effect of silicon on ductility of T91 steel in liquid lead-bismuth eutectic environment

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Journal of Iron and Steel research(International) 2023年第2期30卷 363-374页

作者： Ji Li Xi-kou He Gang Yang Bin Xu Zheng-xin Tang research institute of special Steel Central Iron and Steel Research Institute Co.Ltd.Beijing100081China design institute Nuclear Power Institute of ChinaChengdu610014SichuanChina

The tensile tests of T91 and T91Si steels at 200-450℃in air and at 350℃in oxygen-depleted liquid lead-bismuth eutectic(LBE)environment with strain rate of 1×10^(-5)-5×10^(-3)were performed.Results show that the activation energy of T91 steel is 103.45-246.76 kJ/mol and that of T91Si steel is 146.98-172.11 kJ/mol when Portevin-Le Chatelie(PLC)phenomenon occurs.The elongation reduction of T91 steel at 350℃is not specific to LBE environment,whereas the presence of LBE promotes crack initiation and propagation and affects the elongation of the material in the necking stage.With Si addition,the elongation,especially the uniform elongation at 350℃in LBE environment,improves,and the tendency toward crack propagation in T91 steel after slow tensile necking is reduced.The PLC phenomenon can be seen in both T91 and T91Si steels at high temperatures owing to the dynamic strain aging(DSA).The temperature ranges are different when DSA occurs,with 300-350℃and 250-350℃for T91 and T91Si steels,respectively.

关键词： Dynamic strain aging Liquid lead-bismuth eutectic Silicon content T91 steel Portevin-Le Chatelie

Investigation on the dynamic behavior of cloud cavitation around a flexible hydrofoil

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Journal of Hydrodynamics 2023年第4期35卷 712-723页

作者： Yun-qing Liu Wei Zhao Zhi Pan Zhi-pu Guo Rui Yuan Qin Wu School of Mechanical engineering Beijing Institute of TechnologyBeijing100081China Wuhan Second Ship design and research institute Wuhan430205China

The objective of this paper is to investigate the dynamic behavior of cloud cavitating flow around a flexible hydrofoil with experimental and numerical methods.The tightly coupled fluid-structure interaction(FSI)modeling is applied and validated with the experimental data.The Q-criterion andω-criterion are applied to illustrate the interaction between the vortex structures and cavities.The flexibility is seen to result in nose-up twist deformation,causing a reduction of the shedding frequency from an increase in the attached cavity length.Due to the flexibility,the fluctuation of load coefficients of the flexible hydrofoil is larger than that of the rigid hydrofoil.Moreover,the re-entrant jet propagation speed of the flexible hydrofoil is greater than that of the rigid hydrofoil.The shed cloud cavity is observed to be uniform along the flexible hydrofoil span under the combined influence of the strong vibration and the gap flow.

关键词： Cloud cavitation fluid-structure interaction(FSI) vortex structures flexible hydrofoil

Mission Reliability Modeling and Prediction of an Automatic Sprinkler System

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Mission Reliability Modeling and Prediction of an Automatic ...

A Planning Method for Operational Test of UAV Swarm Based on Mission Reliability

作者： Xiao YU Jian-Jun QI Li-Qin WANG Dong-Feng WANG Beijing Special Engineering Design and Research Institute

If the sprinkler system cannot be started at the time of need,it may cause huge economic losses.The system needs to have high reliability.Therefore,in the design stage of sprinkler system,it is necessary to carry out reliability modeling and prediction to ensure that the system reliability can meet the requirements.In this paper,the design scheme of a building sprinkler system is analyzed in depth,and then a task reliability model considering maintenance strategy,stand-by period failure and task period failure is established,and the reliability is predicted to evaluate whether the design scheme of the system can meet the design needs.

关键词： Sprinkler System Mission reliability Reliability modeling Maintenance strategy

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Computer Modeling in engineering & Sciences 2024年第8期140卷 1889-1918页

作者： Jingyu Wang Ping Jiang Jianjun Qi College of Systems engineering National University of Defense TechnologyChangsha410073China beijing special engineering design Institution Beijing100028China

The unmanned aerial vehicle(UAV)swarm plays an increasingly important role in the modern battlefield,and the UAV swarm operational test is a vital means to validate the combat effectiveness of the UAV swarm.Due to the high cost and long duration of operational tests,it is essential to plan the test in advance.To solve the problem of planning UAV swarm operational test,this study considers the multi-stage feature of a UAV swarm mission,composed of launch,flight and combat stages,and proposes a method to find test plans that can maximize mission reliability.Therefore,a multi-stage mission reliability model for a UAV swarm is proposed to ensure successful implementation of the mission.A multi-objective integer optimization method that considers both mission reliability and cost is then formulated to obtain the optimal test plans.This study first constructs a mission reliability model for the UAV swarm in the combat stage.Then,the launch stage and flight stage are integrated to develop a complete PMS(Phased Mission Systems)reliability model.Finally,the Binary Decision Diagrams(BDD)and Multi Objective Quantum Particle Swarm Optimization(MOQPSO)methods are proposed to solve the model.The optimal plans considering both reliability and cost are obtained.The proposed model supports the planning of UAV swarm operational tests and represents a meaningful exploration of UAV swarm test planning.

关键词： UAV swarm PMS MOQPSO BDD mission reliability operational test planning

Influence of desulfurization slag containing oxides of vanadium and titanium on semi-steel pre-desulfurization

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Journal of Iron and Steel research(International) 2022年第6期29卷 939-950页

作者： Bi-wen Yang Yi-hang Hu San-ping Liu Xue-dong Zhang Chao-zhen Zheng Hai-bei Wang research and design institute of Metallurgical BGRIMM Technology GroupBeijing 100160China College of engineering Peking UniversityBeijing 100871China

The desulfurization and resulfurization of slag containing oxides of vanadium and titanium(CaO–SiO_(2)–MgO–Al_(2)O_(3)–V_(2)O_(3)–TiO_(2)–FeO)in the pretreatment of semi-steel desulfurization at 1623 K were investigated.Based on the ionic structure theory of slag,it could be concluded that V_(2)O_(3) and TiO_(2) combined with(O_(2)–)to form complex anions including VO_(3)^(3–),TiO_(4)^(4–),etc.,which reduced the activity of(O_(2)–)and decreased the sulfur partition ratio(LS).And FeO enhanced the activity of[O]at the slag–metal interface,which decreased the desulfurization capacity of the slag.Compared to the binary basicity,the presented basicity expression containing V_(2)O_(3) and TiO_(2) described the relationship between LS and basicity more accurately.Considering the problems of dilute slag,a large amount of residual slag and much resulfurization in the slagging-off process after pretreatment,the effect of CaO+C-based slag modifier on the resulfurization,melting point and viscosity of the desulfurization slag was investigated.It was proposed that adding 5%–10%of the slag modifier to the desulfurization slag after desulfurization decreased the resulfurization effectively.And the added modifier adjusted the slag viscosity well,which helped to reduce iron loss and residual slag.

关键词： Semi-steel Desulfurization Resulfurization Vanadium oxide Titanium oxide Slag modifier

Numerical optimization of transonic natural laminar flow nacelles

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Chinese Journal of Aeronautics 2023年第6期36卷 35-51页

作者： Chongyang YAN Yufei ZHANG Meihong ZHANG School of Aerospace engineering Tsinghua UniversityBeijing 100084China Shanghai Aircraft design and research institute Shanghai 201210China

Natural laminar flow nacelle is a promising technology for drag reduction.In this paper,an optimization platform is established for the design of transonic axisymmetric and threedimensional natural laminar flow nacelles for large civil aircraft.The platform adopts the class/shape transformation method for geometric parameterization,a four-equation transition model for transition prediction,and the differential evolution algorithm combined with the radial basis function surrogate model as the optimization algorithm.The optimized axisymmetric nacelle demonstrates approximately 31%chord length of laminar flow,with the drag reduction of 13.3%.The influence of the Reynolds number and inlet mass flow rate on the optimization result is also investigated.The axis-symmetric nacelle optimization method is further used for the section profile design of a non-axisymmetric nacelle.An equivalent method is used to simulate the different local flow angles at different sections in the circumferential direction of the non-axisymmetric nacelle by using different inlet mass flow rates of the axisymmetric nacelle.The optimized natural laminar flow nacelle maintains over 30%chord length of laminar flow with robustness to the change of the freestream angle of attack.The total drag of the non-axisymmetric nacelle is reduced by 5.4%under cruise conditions.

关键词： Aerodynamic design Nacelle Natural laminar flow Optimization Transonic