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The effect of gravity on self-similarity of Worthington jet after water entry of a two-dimensional wedge

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Theoretical & Applied Mechanics Letters 2023年第5期13卷 382-386页

作者： Yan Du Jingzhu wang Zhiying wang yiwei wang Key Laboratory for Mechanics in Fluid Solid Coupling Systems Institute of MechanicsChinese Academy of SciencesBeijing 100190China School of Engineering Science University of Chinese Academy of SciencesBeijing 100049China Guangdong Aerospace Research Academy Guangzhou 511458China School of Future Technology University of Chinese Academy of SciencesBeijing 100049China

The effect of gravity on the self-similarity of jet shape at late stage of Worthington jet development is investigated by experiment in the *** addition,the particle image velocimetry(PIV)method is introduced to analyze the development of flow *** is a linear scaling regarding the axial velocity of the jet and the scaling coefficient increases with the Froude number.

关键词： Wortington jet Self-similarity Jet shape PIV

Multi-scale physics-informed neural networks for solving high Reynolds number boundary layer flows based on matched asymptotic expansions

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Theoretical & Applied Mechanics Letters 2024年第2期14卷 76-81页

作者： Jianlin Huang Rundi Qiu Jingzhu wang yiwei wang Key Laboratory for Mechanics in Fluid Solid Coupling Systems Institute of MechanicsChinese Academy of SciencesBeijing 100190China School of Future Technology University of Chinese Academy of SciencesBeijing 100049China School of Engineering Science University of Chinese Academy of SciencesBeijing 100049China Guangdong Aerospace Research Academy Guangzhou 511458China

Multi-scale system remains a classical scientific problem in fluid dynamics,biology,*** the present study,a scheme of multi-scale Physics-informed neural networks is proposed to solve the boundary layer flow at high Reynolds numbers without any *** flow is divided into several regions with different scales based on Prandtl's boundary *** regions are solved with governing equations in different *** method of matched asymptotic expansions is used to make the flow field continuously.A flow on a semi infinite flat plate at a high Reynolds number is considered a multi-scale problem because the boundary layer scale is much smaller than the outer flow *** results are compared with the reference numerical solutions,which show that the msPINNs can solve the multi-scale problem of the boundary layer in high Reynolds number *** scheme can be developed for more multi-scale problems in the future.

关键词： Physics-informed neural networks(PINNs) Multi-scale Fluid dynamics Boundary layer

Development of EPDM composites reinforced by CNTs@SiO_(2)for thermal protection systems of aerospace propulsion:Significant improvement in oxidation and ablation resistance properties

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Chinese Journal of Aeronautics 2024年第2期37卷 471-481页

作者： Li wang Jiang LI Kang LI yiwei wang Chenyang MA Science and Technology on Combustion Internal Flow and Thermal-Structure LaboratoryNorthwestern Polytechnical UniversityXi’an 710072China

Carbon Nanotubes(CNTs)reinforced Polymer-Matrix Composites(PMCs)is widely used as insulation materials in thermal protection system of aerospace ***,CNTs are prone to oxidation and have high thermal conductivities,which makes it difficult to improve the ablation resistance of insulation materials that contain ***_(2)was encapsulated onto the surface of CNTs(CNTs@SiO_(2)),which were then added to Ethylene Propylene Diene Monomer(EPDM)rubber to prepare the insulation *** analysis and ablation test were used to evaluate the resistance of the insulation materials to thermal oxidation and ***,scanning electron microscopy was performed to analyze their *** revealed that the addition of CNTs@SiO_(2)could visibly reduce the effects of hot corrosion and ablation on insulation *** C-CNTs@SiO_(2)-1 formulation had the best ablative ***,compared with the unencapsulated formulation(C-CNTs-10),the C-CNTs@SiO_(2)-1 formulation reduced the line ablation rate by 51%to 0.0130 mm/s after oxygen-acetylene ***,the ablation mechanism was investigated based on the effects of the CNTs@SiO_(2)additive on their ***,the improvement in ablation performance may be attributed to CNTs@SiO_(2)-induced decreases in thermal conductivity,improvement in the hot corrosion resistance in the char layer,and changes in the microstructure.

关键词： Polymer-Matrix Composites(PMCs) Carbon Nanotubes(CNTs) Thermal properties Ablation Oxidation

Influence of tunnel length on the pressure wave generated by high-speed trains passing each other

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Science China(Technological Sciences) 2012年第1期55卷 255-263页

作者： wang yiwei YANG GuoWei HUANG ChengGuang wang Wei Key Laboratory for Hydrodynamics and Ocean Engineering Institute of Mechanics Chinese Academy of Sciences Beijing 100190 China Key Laboratory of High Temperature Gas Dynamics Institute of Mechanics Chinese Academy of Sciences Beijing 100190 China Institute of Mechanics Chinese Academy of Sciences Beijing 100190 China

The prediction of the pressure wave amplitude produced when two trains pass each other in the tunnel is important to the train design for airtightness and tunnel conditions in *** this paper,the key factors of this problem were firstly stud-ied based on theoretical *** equation of the worst tunnel length for the global maximum and minimum pressure values was ***,the influence of tunnel length on global minimum pressure and the critical region in which the global minimum pressure varies rapidly were ***,a numerical method based on two-dimensional Na-vier-Stokes equations was *** conditions of two trains passing-by in tunnels of different lengths were *** theoretical and computational results agree with each other closely.

关键词： passing in tunnel air pressure wave tunnel length numerical simulation

Deformation behavior of non-rigid airships in wind tunnel tests

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Chinese Journal of Aeronautics 2019年第3期32卷 611-618页

作者： Lingling LU Hongwei SONG yiwei wang Chenguang HUANG Key Laboratory for Mechanics in Fluid Solid Coupling Systems Institute of Mechanics Chinese Academy of Sciences School of Engineering Science University of Chinese Academy of Sciences

Deformation behavior of non-rigid airships in wind tunnel tests is studied by considering three factors, including internal pressure, flow velocity and angle of attack. Fiber Bragg grating strain sensors are used to measure the deformation of non-rigid airships. Wind tunnel tests in the case of different flow velocities and angles of attack are conducted. The measurement results reveal that the airship deformation is in proportion to internal pressure. For the tensile region,the airship deformation is in proportion to flow velocity. Effects of angle of attack on structural deformation are more complicated and there is no clear relationship existing between airship deformation and angle of attack.

关键词： Angle of attack Fiber Bragg grating sensor Flow velocity Internal pressure Non-rigid airship Wind tunnel test

Necessary Condition for the Success of Synchronous GNSS Spoofing

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Chinese Journal of Electronics 2023年第3期32卷 438-452页

作者： wang yiwei KOU Yanhong HUANG Zhigang School of Electronics and Information Engineering Beihang University

A synchronous GNSS generator spoofer aims at directly taking over the tracking loops of the receiver with the lowest possible spoofing to signal ratio(SSR) without forcing it to lose lock. This paper investigates the factors that affect spoofing success and their relationships. The necessary conditions for successful spoofing are obtained by deriving the code tracking error in the presence of spoofing and analyzing the effects of SSR,spoofing synchronization errors, and receiver settings on the S-curve ambiguity and code tracking trajectory. The minimum SSRs for a successful spoofing calculated from the theoretical formulation agree with Monte Carlo simulations at digital intermediate frequency signal level within 1 dB when the spoofer pulls the code phase in the same direction as the code phase synchronization error, and the required SSRs can be much lower when pulling in the opposite direction. The maximum spoofing code phase error for a successful spoofing is tested by using TEXBAT datasets, which coincides with the theoretical results within 0.1 chip. This study reveals the mechanism of covert spoofing and can play a constructive role in the future development of spoofing and anti-spoofing methods.

关键词： Global navigation satellite system Tracking loops Codes Target tracking Simulation Receivers Trajectory

An Experimental Study on the Performance of a Stainless Steel-Water Loop Heat Pipe under Natural Cooling Condition

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Journal of Thermal Science 2014年第1期23卷 91-95页

作者： wang yiwei CEN Jiwen JIANG Fangming ZHU Xiong Laboratory of Advanced Energy Systems CAS Key Laboratory of Renewable EnergyGuangzhou Institute of Energy ConversionChinese Academy of Sciences (CAS) Qingyuan Resource Development Co.Ltd of China National Electric Power Corporation

Aiming to improve the thermal characteristics of modern electronics, we experimentally study the performance of a stainless steel/water loop heat pipe(LHP) under natural cooling condition. The LHP heat transfer performance, including start-up performance, temperature oscillation and total thermal resistance at different heat loads and with different incline angles have been investigated systematically. Experimental results show that at an optimal heat load(i.e. 60 W) and with the LHP being inclined 60 to the horizontal plane, the total thermal resistance is lowered to be ~0.24 K/W, and the temperature of evaporator could be controlled steadily at around 90 C.

关键词： Loop heat pipe cooling of electronics heat dissipation thermal resistance

Experimental and numerical investigations into flow features in an intake duct for the waterjet propulsion under mooring conditions

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Acta Mechanica Sinica 2021年第5期37卷 826-843,I0003页

作者： Renfang Huang Ruizhi Zhang yiwei wang Xianwu Luo Lei Zhu Key Laboratory for Mechanics in Fluid Solid Coupling Systems Institute of MechanicsChinese Academy of SciencesBeijing 100190China Science and Technology on Water Jet Propulsion Laboratory Shanghai 200011China College of Engineering Science University of Chinese Academy of SciencesBeijing 100049China State Key Laboratory of Hydroscience and Engineering Department of Energy and Power EngineeringTsinghua UniversityBeijing 100084China China Institute of Water Resources and Hydropower Research Beijing 100038China

The waterjet propulsion is widely applied in the marine vessels over 30 knots,and the intake duct is considered as an essential component that strongly relates to the propulsion *** paper sheds light on the flow features inside an intake duct under mooring conditions by using the particle image velocimetry(PIV)technique with three-dimensional(3D)numerical *** hydraulic loss gradually increase as the flow-rate *** to analyses via the Bernoulli equation,the hydraulic loss is composed of the frictional head loss(h_(f)~V^(1.75))and the local head loss(h_(j)~V^(2.0)).A recirculation region is observed near the duct lower wall with a high-velocity flow near the upper wall,and subsequently a shear flow presents in the horizontal straight pipe with an obvious velocity ***-dimensional simulations demonstrate that the vortex pair is very strong in the recirculation region and then it gradually decreases as the fluid flows *** the flow-rate increasing,the non-uniformity at the duct outlet firstly increases to a peak and then slightly decreases,while the perpendicularity at the duct outlet dramatically decreases to a minimum and then *** work not only reveals some physics of the waterjet propulsion under mooring conditions,but also promotes its efficient operation.

关键词： Waterjet propulsion Particle image velocimetry(PIV) Intake duct Waterjet pump Mooring conditions

Constant False Alarm Rate Acquisition Algorithm for Compass B1C Signal

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China Communications 2019年第11期16卷 201-211页

作者： Wengang Li Tianrong Qian yiwei wang Chen Huang State Key Laboratory of Integrated Service Networks Xidian University

In order to improve the sensitivity of the Compass B1C signal acquisition for the receiver,the principle of constant false alarm rate(CFAR)is applied for the B1C pilot channel acquisition to realize the dynamic adjustment of the threshold of acquisition against the carrier to noise *** non-coherent data/pilot combined acquisition algorithm for B1C signal is analyzed to make full use of the power of the B1C signal under the condition of low carrier to noise *** this basis,to improve the acquisition sensitivity of the receiver,the principle of constant false alarm probability is applied for the non-coherent data/pilot combined acquisition *** analysis and simulations show that the non-coherent data/pilot combined acquisition algorithm with CFAR improves the B1C signal acquisition sensitivity of the receiver significantly,and achieves a better Receiver Operating Characteristic compared with the traditional acquisition algorithms.

关键词： B1C signal non-coherent acquisition acquisition threshold constant false alarm rate(CFAR)