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The Numerical Simulation of collapse pressure and Boundary of the Cavity Cloud in Venturi

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Chinese Journal of Chemical Engineering 2009年第6期17卷 896-903页

作者：张晓冬付勇李志义赵宗昌 R&D Institute of Fluid and Powder Engineering College of Chemical Engineering Dalian University of Technology Dalian 116012 China

The idea that the collapse proceeds from the outer boundary of the cavity cloud towards its center for the ultrasonic cavitation proposed by Hasson and Morch in 1980s is further developed for calculating the collapse pressure and boundaries of cavity cloud at the collapse stage of bubbles for hydraulic cavitation flow in Venturi in present research. The numerical simulation is carried out based on Gilmore＇s eouations of bubble dynamics, which take account of the compressibility of fluid besides the viscosity and interfacial tension. The collapse of the cavity cloud is considered to proceed layer by layer from the outer cloud towards its inner part. The simulation results indicate that thepredicted boundaries of the cavity cloudat the collapse stage *** with the exPerimental *** is also found that the maximum collapse pressure of the cavity cloud is several times as high as the collapse pressure of outside boundary, and it is located at a point in the axis, where the cavity cloud disappears completely. This means that a cavity cloud has higher collapse pressure or strength than that of a single bubble due to the interactions of the bubbles. The effects of operation and structural parameters on the collapse pressure are also analyzed in detail.

关键词： cavity cloud collapsing layer by layer laydrodynamic cavitation collapse pressure bubble dynamics

Experimental study on the cavity evolution and liquid spurt of hydrodynamic ram

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Defence Technology（防务技术） 2022年第11期18卷 2008-2022页

作者： Anran Chen Xiangdong Li Lanwei Zhou Yangziyi Ji School of Mechanical Engineering Nanjing University of Science and TechnologyNanjing210094China

In research of the characteristics of the cavity evolution, the pressure, and the liquid spurt in hydrodynamic ram, the experiment of the high-velocity fragment impacting the water-filled container had been conducted. The relationships between the above three characteristics have been researched. The evolution of the cavity can be divided into three processes according to its shape characteristics. The first liquid spurt occurred in Process Ⅱ and the rest of it occurred in Process Ⅲ. The duration of the second liquid spurt is longer than the first liquid spurt. When the impact velocity of the fragment is less than996 m/s, the velocity of the second liquid spurt is the highest. When the velocity of the fragment is greater than 996 m/s, the velocity of the first liquid spurt is the highest. The maximum velocities of the first and second liquid spurt are 111 m/s and 94 m/s respectively. The pressure fluctuated sharply in Processes Ⅰ and Ⅲ. The maximum peak pressures in the shock and the cavity oscillation phases are15.51 MPa and 7.96 MPa respectively. The time interval of the two adjacent pressure pulses increases with the increase of the fragment velocity.

关键词： Hydrodynamic ram Cavity oscillation collapse pressure Liquid spurt

Energy analysis of face stability of deep rock tunnels using nonlinear Hoek-Brown failure criterion

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Journal of Central South University 2015年第8期22卷 3079-3086页

作者：张佳华李永鑫许敬叔 School of Civil Engineering Central South University

The nonlinear Hoek-Brown failure criterion was introduced to limit analysis by applying the tangent method. Based on the failure mechanism of double-logarithmic spiral curves on the face of deep rock tunnels, the analytical solutions of collapse pressure were derived through utilizing the virtual power principle in the case of pore water, and the optimal solutions of collapse pressure were obtained by using the optimization programs of mathematical model with regard of a maximum problem. In comparison with existing research with the same parameters, the consistency of change rule shows the validity of the proposed method. Moreover, parametric study indicates that nonlinear Hoek-Brown failure criterion and pore water pressure have great influence on collapse pressure and failure shape of tunnel faces in deep rock masses, particularly when the surrounding rock is too weak or under the condition of great disturbance and abundant ground water, and in this case, supporting measures should be intensified so as to prevent the occurrence of collapse.

关键词： tunnel face limit analysis failure criterion pore water pressure collapse pressure

Wellbore stability analysis of layered shale based on the modified Mogi-Coulomb criterion

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Petroleum 2020年第3期6卷 246-252页

作者： Xu Yang Xiangchao Shi Yingfeng Meng Xiaoyong Xie State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation Southwest Petroleum UniversityChengdu610500China Key Laboratory Deep Underground Science and Engineering (Sichuan University)Ministry of EducationChengdu610065China Yibin University Yibin644000China

Borehole instability was frequently encountered during shale gas *** conventional models are not applicable to layered formation's wellbore stability analysis on account of anisotropic strength *** this study,an empirical equation for predicting anisotropic strength was implemented in the Mogi–Coulomb criterion to describe variations of cohesive strength and friction angle of shale formations.A collapse pressure model and its appropriate solution method for layered shale formations were *** impact of different strength criteria and rock anisotropy type on rock strength and collapse pressure was *** analysis indicated that the predicted strength of our modified criterion was usually higher than the weak plane failure *** collapse pressure calculated by the modified Mogi–Coulomb criterion was lower than the weakplane failure ***,it was more consistent with real mud ***,the anisotropy type of rock notably influences wellbore *** significant anisotropy coefficients correspond to higher strengths,which results in smaller collapse pressure *** anisotropy coefficients can over-or underpredict the collapse *** estimates of collapse pressure of anisotropic rocks can be made through the modified Mogi–Coulomb criterion using limited experimental data and the anisotropy rock type.

关键词： Shale Wellbore stability collapse pressure Anisotropy

Nonlinear Contact Between Inner Walls of Deep Sea Pipelines in Buckling Process

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Journal of Ocean University of China 2015年第1期14卷 75-83页

作者： MA Weilin YU Jianxing ZHOU Qingji XIE Bin CAO Jing LI Zhibo State Key Laboratory of Hydraulic Engineering Simulation and Safety Tianjin University CNOOC Research Institute

In order to study buckling propagation mechanism in deep sea pipelines, the contact between pipeline's inner walls in buckling process was studied. A two-dimensional ring model was used to represent the pipeline and a nonlinear spring model was adopted to simulate the contact between inner walls. Based on the elastoplastic constitutive relationship and the principle of virtual work theory, the coupling effect of pipeline's nonlinear large deformation and wall contact was included in the theoretical analysis with the aid of MATLAB, and the application scope of the theoretical model was also discussed. The calculated results show that during the loading process, the change in external pressure is closely related to the distribution of section stress, and once the walls are contacting each other, the external pressure increases and then remains stable after it reaches a specific value. Without fracture, the pipeline section will stop showing deformation. The results of theoretical calculations agree well with those of numerical simulations. Finally, in order to ensure reliability and accuracy of the theoretical results, the collapse pressure and propagation pressure were both verified by numerical simulations and experiments. Therefore, the theoretical model can be used to analyze pipeline's buckling deformation and contact between pipeline's inner walls, which forms the basis for further research on three-dimensional buckling propagation.

关键词： deep sea pipeline buckling propagation nonlinear contact collapse pressure propagation pressure

The collapse Intensity of Cavities and the Concentration of Free Hydroxyl Radical Released in Cavitation Flow

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Chinese Journal of Chemical Engineering 2008年第4期16卷 547-551页

作者：张晓冬付勇李志义赵宗昌 R＆D Institute of Fluid and Powder Engineering Dalian University of Technology Dalian 116012 China

Enhancing the chemical reaction processes by means of the energy released in the collapse of micro bubbles or cavities in the cavitation flow is a new research area. In the previous work, a new approach of measuring concentration of free hydroxyl radicals induced in cavitation flow by using methylene blue as the indicator was developed and used to study concentration of free radical induced in Venturi cavitation flow under various experimental conditions. In the present research, the radial evolution of a cavity bubble and the corresponding collapse pressure in sonic cavitation field are obtained by solving three different bubble dynamics equations： Rayleigh equation, Rayleigh-Plesset equation and Gilmore equation. By comparing with the experimental data on the radial evolution of a cavity bubble in the literature, it is found that the predicted results by the Gilmore equation, which takes account of the compressibility of fluid in addition to the viscosity and interfacial tension, agree with the experimental ones better than those by other two equations. Moreover, the theoretically predicted collapse pressures are consistent with the concentration of the free hydroxyl radical induced in the experimental venture. Thus, the concentration of the liberated free hydroxyl radical not only influences the reaction rate but also is used as an available parameter for measuring collapse intensity of cavities.

关键词： hydrodynamic cavitation collapse pressure numerical simulation free hydroxyl radical

Ultimate Strength Assessment of Steel-Welded Hemispheres under External Hydrostatic pressure

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Journal of Marine Science and Application 2020年第4期19卷 615-633页

作者： Sang-Rai Cho Teguh Muttaqie Seung Hyun Lee Jaewoo Paek Jung Min Sohn Ulsan Lab Inc.UlsanSouth Korea School of Naval Architecture and Ocean Engineering University of UlsanUlsanSouth Korea Department of Naval Architecture and Marine Systems Engineering Pukyong National UniversityBusanSouth Korea Agency for the Assessment and Application of Technology Center of Technology for Defense and Security Industries-BPPTJakartaIndonesia Hyundai Mipo Dockyard UlsanSouth Korea Hyundai Heavy Industries UlsanSouth Korea Interdisciplinary Program of Marine Convergence Design Pukyong National UniversityBusanSouth Korea

This paper focusses on steel-welded hemispherical shells subjected to external hydrostatic *** experimental and numerical investigations were performed to study their failure *** model was fabricated from mild steel and made through press forming and *** therefore considered the effect of initial shape imperfection,variation of thickness and residual stress obtained from the actual *** hemisphere models designed with R/t from 50 to 130 were tested until *** to the test,the actual geometric imperfection and shell thickness were carefully *** comparisons of available design codes(PD 5500,ABS,DNV-GL)in calculating the collapse pressure were also highlighted against the available published test data on steel-welded ***,the nonlinear FE simulations were also conducted to substantiate the ultimate load capacity and plastic deformation of the models that were *** dependence of the level of sphericity,varying thickness and residual welding stresses were also numerically considered in the benchmark *** structure behaviour from the experiments was used to verify the numerical *** this work,both collapse pressure and failure mode in the numerical model were consistent with the experimental model.

关键词： Steel-welded hemisphere collapse pressure Experiment Nonlinear FEA Ultimate strength formulation

THEORETICAL AND EXPEREIMENTAL RESEARCH OF THE SPHERICAL pressure HULL

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THEORETICAL AND EXPEREIMENTAL RESEARCH OF THE SPHERICAL PRES...