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Study on the mechanism of near-field underwater explosion on supported thin plates with prefabricated holes

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Acta Mechanica Sinica 2024年第8期40卷 32-44页

作者： Si Chen Jian Qin Xiangyao Meng Zhichao Lai Yanbo Wen Ruiyuan Huang School of Mechatronical Engineering Beijing Institute of TechnologyBeijing100081China Naval Academy Beijing100161China College of Civil Engineering Fuzhou UniversityFuzhou350116China

In this study,underwater explosion tests with 2.5 g trinitrotoluene explosive under different fixed plates with prefabricated holes were *** experimental results showed that the air inflow from the prefabricated hole caused the bubble to collapse earlier with an increase in the hole *** addition,the deformation mode of the thin plate transitioned from“convex”to“concave”(up to down).Next,the coupled Eulerian-Lagrangian method was used to perform the corresponding numerical *** accuracy of the numerical simulation method was verified through a comparison with the experimental *** addition,a series of numerical simulations were conducted with different prefabricated-hole diameters,blast distances,and prefabricated-hole *** results showed that the bubble-pulsating water jet substantially influenced the deformation of the thin plate when the diameter of the prefabricated hole was within the theoretical maximum bubble *** the blast distance was within the theoretical maximum bubble radius,the thin plate was subjected to only a single bubble pulsation owing to the air inflow from the prefabricated hole.

关键词： Underwater explosion Hole high-speed camera Bubble pulsation Fixed plate

Comparing kernel damage of different threshing components using high-speed cameras

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International Journal of Agricultural and Biological Engineering 2020年第6期13卷 215-219页

作者： Zheng Ma Min Han Yaoming Li Shuncheng Yu Farman Ali Chandio Key Laboratory of Modern Agricultural Equipment and Technology Ministry of EducationHigh-tech Key Laboratory of Agricultural Equipment and Intelligence of Jiangsu ProvinceSchool of Agricultural Equipment and EngineeringJiangsu UniversityZhenjiang 212013JiangsuChina Sindh Agriculture University Faculty of Agricultural EngineeringTandojamSindhPakistan

Grain damage research has been a focus of many experts in the agriculture machinery industry.A threshing test-bed was developed to investigate the movement and influence of different threshing and separating units on maize *** damage to maize grains was analyzed with a high-speed camera to observe the movement and damage received by the maize *** results showed that the threshing and separating effects of the perforated concave plate were obviously lower than that of the round steel concave plate,the threshing effects of the rigid rasp bar and polyurethane rasp bar were similar,and the damage ratio of the polyurethane rasp bar was relatively *** also indicated that moisture content has a significant effect on the damage ratio and damage type of maize *** different threshing component types used in this study had an obvious effect on the degree of damage to high moisture content maize grains and the damage to high-moisture kernels during threshing could be further *** results can provide a reference for the design of threshing and separating devices in the maize combine harvesting machinery.

关键词： maize grain damage threshing process high-speed camera

Development characteristics of cloud-to-ground lightning with multiple grounding points

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Science China Earth Sciences 2018年第8期61卷 1127-1135页

作者： Bin FAN Ping YUAN Xuejuan WANG Yang ZHAO Jianyong CEN Yanling SU Key Laboratory of Atomic and Molecular Physics and Functional Materials of Gansu Province College of Physics and Electronic Engineering Northwest Normal University School of Atmospheric Physics Nanjing University of Information Science and Technology College of Physics and Information Engineering Shanxi Normal University

Using the optical images of a cloud-to-ground lightning flash with multiple grounding points obtained by a highspeed video system in the Qinghai Province of China along with synchronous radiated electric field information, the propagation characteristic and the electric field change features of the leaders and the grounding behavior of discharge channels are *** addition, the two-dimensional velocity of the leader was estimated and its correlation with the time interval of the corresponding subsequent return stroke, and that with the peak current of return stroke are investigated. The results show that the average distance between the three obvious grounded points of the first return stroke channel is about 512.7 m, and the average time interval between the pulses of the corresponding electric field fast changes is 3.8 μs. Further, the average time interval between electric field pulses from the stepped leader is smaller than that of normal single grounding lightning. The observed lightning in our study has two main channels, namely the left and right channels. Based on our observations, it is clear that the dart leader comes close to the ground in case of the left channel after the first return stroke, but it fails to form a return ***, the right channel exhibits a relatively rare phenomenon in that the subsequent return stroke R2 occurred about 2.1 ms after the dart leader arrived at the ground, which was unusually long; this phenomenon might be attributed to the strong discharge of the first return stroke and insufficient charge accumulation near the grounded point in a timely manner. The two-dimensional velocities for the stepped leader of the two main channels are about 1.23×105 and 1.16×105 m s-1, respectively. A sub-branch of stepped leader for the left channel fails to reach the ground and develops into an attempt leader eventually; this might be attributed to the fact that the main branch connects considerably many sub-branches, which lea

关键词： Multiple grounding lightning high-speed camera Electric field changes Leader

Experimental investigation on the plasma morphology of ablative pulsed plasma thruster with tongue-shaped and flared electrodes

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Plasma Science and Technology 2020年第9期22卷 51-58页

作者： Jianjun WU Yu ZHANG Yang OU Hua ZHANG College of Aerospace Science and Engineering National University of Defense TechnologyChangsha 410073People’s Republic of China Jiuquan Satellite Launch Centre Jiuquan 735000People's Republic of China

Ablative pulsed plasma thrusters(APPTs)are considered as an attractive propulsion option for station-keeping and drag makeup purposes for mass-and power-limited *** order to understand the physical mechanism of APPTs,high-speed camera and optical emission spectroscopy are utilized to investigate the plasma characteristics including the spatial distribution and composition between the *** plume images and spectra at different times and positions are experimentally recorded,and the spatial distribution,composition,and trajectory of plasmas can be concluded through analyzing *** the increase of the distance from the ablation surface,two clusters of plasmas near the anode and cathode meet downstream,and the species and density of plasmas tend to be uniform.

关键词： pulsed plasma thruster high-speed camera optical emission spectrum plume distribution

Experimental investigation and numerical analysis of unsteady attached sheetcavitating flows in a centrifugal pump

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Journal of Hydrodynamics 2013年第3期25卷 370-378页

作者：刘厚林刘东喜王勇吴贤芳王健杜辉 Research Center of Fluid Machinery Engineering and Technology Jiangsu University

This paper studies the attached sheet cavitation in centrifugal pumps. A pump casted from Perspex is used as the test subject. The cavitation bubbles were observed in the entrance of the impeller and the drops of the head coefficients were measured under different operating conditions. A Filter-Based Model （FBM）, derived from the RNG k-e model, and a modified Zwart model are adopted in the numerical predictions of the unsteady cavitating flows in the pump. The simulations are carded out and the results are compared with experimental results for 3 different flow coefficients, from 0.077 to 0.114. Under four operating conditions, qualitative comparisons are made between experimental and numerical cavitation patterns, as visualized by a high-speed camera and described as isosurfaces of the vapour volume fraction ctv = 0.1. It is shown that the simulation can truly represent the development of the attached sheet cavitation in the impeller. At the same time, the curves for the drops of the head coefficients obtained from experiments and calculations are also quantitatively compared, which shows that the decline of the head coefficients at every flow coefficient is correctly captured, and the prediction accuracy is high. In addition, the detailed analysis is made on the vapour volume fraction contours on the plane of span is 0.5 and the loading distributions around the blade section at the midspan. It is shown that the FBM model and the modified Zwart model are effective for the numerical simulation of the cavitating flow in centrifugal pumps. The analysis results can also be used as the basis for the further research of the attached sheet cavitation and the improvement of centrifugal pumps.

关键词： centrifugal pump attached sheet cavitation high-speed camera modified Zwart model Filter-Based Mode (FBM)

Flow and penetration behavior of submerged side-blown gas

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International Journal of Minerals,Metallurgy and Materials 2023年第6期30卷 1067-1077页

作者： Shuai Zhu Qiuyue Zhao Xiaolong Li Yan Liu Tianci Li Ting’an Zhang Key Laboratory of Ecological Metallurgy of Multi-metal Intergrown Ores of Ministry of Education Shenyang 110819China School of Metallurgy Northeastern UniversityShenyang 110819China

To assess the widely used submerged side-blowing in pyrometallurgy,a high-speed camera-digital image processing-statistical approach was used to systematically investigate the effects of the gas flow rate,nozzle diameter,and inclination angle on the space-time distribution and penetration behavior of submerged side-blown gas in an air-water *** results show that the gas motion gradually changes from a bubbling regime to a steady jetting regime and the formation of a complete jet structure as the flow rate *** the flow rate is low,a bubble area is formed by large bubbles in the area above the *** the flow rate and the nozzle diameter are significant,a bubble area is formed by tiny bubbles in the area above the *** increased inclination angle requires a more significant flow rate to form a complete jet *** the sampling time,the dimensionless horizontal and vertical penetration depths are Gaussian *** the nozzle diameter and increasing the flow rate or inclination angle will increase the distribution range and *** correlations for a penetration depth with an error of±20%were obtained through dimensional *** dimensionless horizontal penetration depth of an argon-melt system in a 120 t converter calculated by the correlation proposed by the current study is close to the result calculated by a correlation in the literature and a numerical simulation result in the literature.

关键词： submerged side-blowing jet high-speed camera image processing dimensional analysis

Experimental and numerical investigation of unsteady cavitating flows through a 2D hydrofoil

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Science China(Technological Sciences) 2011年第7期54卷 1801-1812页

作者： HUANG Biao WANG GuoYu School of Vehicle and Transportation Engineering Beijing Institute of Technology Beifing 100081 China

In the present study, firstly, the unsteady cavitating flows around a hydrofoil are studied based on the flow visualization and detail velocity measurement, a high-speed video camera is used to visualize the flow structures, and a particle image velocimetry （PIV） technique is applied to the measurement of the time-averaged and instantaneous velocity and vorticity fields. The results show that the unsteadiness of mass transfer process between the vapor and the two-phase regions is substantial, a self-oscillatory behavior of the whole sheet cavitation is obtained, with large length fluctuations and vapor cloud shedding, and also the cavitation structure depends on the interaction of the water-vapor mixture and the periodic vortex shedding. The main purpose of this experimental study is to offer information for validating computational models, and shed light on the unsteady multiphase transport process of cavitating flows. Furthermore, with an emphasis on the dynamics of the attached turbulent cavitating flows, a filter-based model （FBM） is derived from the k-6 two-equation model, a conditional averaging method aimed at improving unsteady simulation is applied to computation. In comparison to the standard k-ε model, overall, the filter-based model is shown to improve the predictive capability considerably.

关键词： unsteady cavitating flows high-speed camera particle image velocimetry mass transfer ~ter-based turbulence models

Experimental study on failure evolution mechanism of clastic rock considering cementation and intermediate principal stress

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Journal of Rock Mechanics and Geotechnical Engineering 2023年第7期15卷 1636-1650页

作者： Feiyan Wang Xia-Ting Feng Yangyi Zhou Xiaojun Yu Key Laboratory of Ministry of Education on Safe Mining of Deep Metal Mines School of Resources and Civil EngineeringNortheastern UniversityShenyang110819China Key Laboratory of Liaoning Province on Deep Engineering and Intelligent Technology Northeastern UniversityShenyang110819China

The study of clastic rock failure evolution under true triaxial stress is an important research topic;however,it is rarely studied systematically due to the limitation of monitoring *** this study,true triaxial compression tests were conducted on clastic rock specimens to investigate the effect of cementation and intermediate principal stress(s2)on the failure *** complete stressestrain curves were obtained,while the acoustic emission(AE)was monitored to indirectly evaluate the evo-lution of tensile and shear cracks,and crack evolution under true triaxial compression was imaged in real time by a high-speed *** results showed that the deformation and failure characteristics of clastic rock were closely related to the cementation type and intermediate principal *** the basis of the distribution characteristics of the ratio of rise time to amplitude(RA)and the average frequency(AF)of AE signals,tensile cracks of the contact cementation specimen propagated ***,the enhancement of specimen cementation promoted the evolution of shear cracks,and the increase inσ_(2)promoted the evolution of tensile ***,the mesoscale cracking mechanism of clastic rock caused by cementation andσ_(2)under true triaxial compression was *** failure patterns of clastic rock under true triaxial compression were divided into three modes:structure-induced,structure-stress-induced and stress-induced *** study confirms the feasibility of high-speed camera technology in true triaxial testing,and has important implications for elucidating the disaster mechanism of deep tunnels in weak rocks.

关键词： True triaxial compression Cementation Failure evolution Acoustic emission(AE) high-speed camera

Experimental investigation on the spray characteristics of agricultural full-cone pressure swirl nozzle

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International Journal of Agricultural and Biological Engineering 2023年第4期16卷 29-40页

作者： Xiuyun Xue Xufeng Xu Shilei Lyu Shuran Song Xin Ai Nengchao Li Zhenyu Yang Zhen Li College of Electronic Engineering(College of Artificial Intelligence) South China Agricultural UniversityGuangzhou 510642China National Citrus Industry Technical System Machinery Research Office Guangzhou 510642China Engineering Research Center for Monitoring Agricultural Information of Guangdong Province Guangzhou 510642China Meizhou SCAU-Zhensheng Research Institute for Modern Agricultural Equipment Meizhou 514781China

The spray characteristics of a full-cone pressure swirl nozzle have been investigated in this *** results were defined by Reynolds number,which focuses on the breakup of liquid film,droplet size,velocity,and liquid volume flux under different Reynolds numbers at the near-field *** spray structure was visualized using a high-speed camera,and the characteristics of droplets were measured using a Phase Doppler Anemometer(PDA)in both the radial and axial *** tests were carried out at varying spray pressures(0.2 to 1.0 MPa),corresponding to different Reynolds numbers(5369 to 12006).It was found that when the Reynolds number rises,the liquid became more unstable after leaving the nozzle,causing the liquid film to break up *** to the measurements of PDA,the coalescence of droplets increased due to the centrifugal ***’s more,the velocity of the droplets fluctuates significantly in the radial direction,and the droplets with a smaller particle size had a higher average *** the perspective of liquid distribution,the increase in Reynolds number caused the spray liquid to move in the radial direction *** contrast,the liquid volume distribution changed in the radial direction more obviously than in the axial direction,growing to the maximum along the radial direction and gradually *** can provide a reference for selecting operating parameters for actual agricultural spray operations and the design of electrostatic nozzles through the research on breakup and droplet characteristics.

关键词： full-cone pressure swirl nozzle droplet size droplet velocity liquid volume flux high-speed camera PDA