Experimental and numerical study on the growth and collapse of a bubble in a narrow tube

The growth, expansion and collapse of a bubble in a narrow tube are studied using both experiments and numerical simulations. In experiment, the bubble is generated by an electric spark in a water tank and recorded by a highspeed camera system. In numerical simulation, the evolution of the bubble is solved by adopting axisymmetric boundary integral equation, considering the surface tension effect. The results of experiments and numerical simulations are compared and good agreements are achieved. Both of them show that a counter-jet forms and penetrates the bubble at the end of the collapse stage, before a ring type bubble forms. Under the attraction of the tube wall due to Bjerknes force, a ring jet is generated, pointing towards the tube. On the basis of this, some physical quantities like the pressure on the tube wall and kinetic energy are calculated in a case study. The effects of tube diameters and tube lengths on the bubble＇s behaviors are also investigated.

Experimental Study on Hydrodynamic Load Characteristics for A Typical Cross-Section of A Submerged Floating Tunnel

The typical cross-sectional form of a submerged floating tunnel plays a significant role in the dynamic response of the tunnel itself,which directly affects the overall design.In this work,a series of experiments involving wave action on a submerged floating tube cross section is reported to study its hydrodynamic load characteristics.Two typical cross section tube cylinders,circular and rectangular,are chosen.Experiments are carried out in a wave flume with waves of relatively low Keulegan-Carpenter(KC)numbers.Three relative depths of submergence of 0,0.25 and 0.5 are chosen.The measured wave forces in regular waves are used to analyze the horizontal force,vertical force and torque,and then the drag coefficient(Cd)and inertia coefficient(Cm)are derived.The results show that the drag coefficients at low KC numbers are large and decrease sharply with increasing KC number.The inertial coefficient Cm values in the vertical direction are about 70%larger than those in the horizontal direction.With an increase in aspect ratio(the ratio of the height to width of the structure),the ratio of inertia coefficient in the horizontal direction to that in the vertical direction increases remarkably.The inertia force coefficient is very sensitive to the submerged water depth and aspect ratio.The existing results may overestimate the actual force value.

The application of ultrasonic seismic model experiment in quality test of cement mortar injection of Yongjiang river submarine tun－nel tube foundation

Ultrasonic seismic model experiment plays an important role in engineering multi wave seismic prospecting(EMSP), which has been used to do the complex engineering seismic exploration. It is introduced that the application of the technology in quality test of Yongjiang river submarine tunnel tube foundation in the paper. The material of the model was got from on the spot. The successful test has been made with results of the model experiment.

Experimental study on attenuation of Stoneley wave under different fracture factors

To quantitatively determine the effect of different factors such as fracture width,dip angle,extension and filling material on Stoneley wave amplitude decreasing,the shock tube experiment method was changed from fixing the sample and vertically moving the sensor in the borehole to fixing the sensors along the shock tube wall and vertically moving the sample without drilling the borehole in it.The measurement accuracy and the signal-to-noise ratio of the first Stoneley wave were improved by the time corrections and amplitude corrections of Stoneley wave signals.At the same time,21 sets of core models with different fracture parameters were processed for this measurement method by using full-diameter carbonate core,and relative amplitudes were defined to characterize Stoneley wave amplitude decreasing.The experimental results show that the relative amplitude of Stoneley wave exponentially decreases with increasing fracture width.The relative amplitude of Stoneley wave linearly decreases with increasing fracture dip angle.The relative amplitude of Stoneley wave exponentially decreases with increasing fracture extension.The relative amplitude of Stoneley wave decreases with increasing the permeability of filling material in the fracture.Under the above four conditions,the fracture width has the greatest effect on the decreasing of Stoneley wave amplitude,followed by the fracture extension and the permeability of filling material,and finally the fracture dip angle.

Experimental Study on Phase Characteristics of CO2 Injection in BZ13-2 Strong Volatile Oil Reservoir in Bohai Sea Buried Hills

BZ13-2 oil field is a deep submerged strongly volatile reservoir in Bohai Sea. This oil reservoir has the characteristics of high gas oil ratio and small difference in formation pressure and saturation point pressure. It usually adopts gas injection development to avoid crude oil degassing and fast decreasing production capacity. However, the phase characteristics and miscibility mechanism of this high-temperature and high-pressure fluid after gas injection are not clear. Therefore, it is necessary to study the feasibility of CO2 injection to improve oil recovery in near critical volatile oil reservoirs through CO2 injection experiments. In the early stage of the depletion experiment, the content of heavy components in the remaining oil increased significantly, so the depletion method is not conducive to the development of such reservoirs. With the increase of CO2 injection, the volumetric expansion coefficient of formation crude oil increases significantly, while the saturation pressure and formation crude oil viscosity remain basically unchanged. The minimum miscible pressure experiment shows that CO2 injection under formation pressure conditions can achieve multiphase miscibility. Based on experimental research results, the BZ13-2 oilfield is suitable for early gas injection development and can significantly improve recovery.

Validation of the TASS/SMR-S Code for the Core Heat Transfer Model on the Steady Experimental Conditions

The SMART （System-integrated Modular Advanced ReacTor） which is a 330 MWt advanced integral PWR was developed by the KAERI （Korea Atomic Energy Institute） for electricity generation and seawater desalination. To enhance its safety, the various design concepts were adopted such as the most containing of the RCS （reactor coolant system） components and a PRHRS （passive residual heat removal system）. To ensure the safety and performance of the SMART, a thermal hydraulic evaluation and safety analysis are performed by the TASS/SMR-S code. It uses a one dimensional node/path modeling and point kinetics for the core power simulation. The code also has specific models reflecting the design features of the SMART such as a helical tube and PRHRS heat transfer models. In this study, the validation of the core heat transfer model in the TASS/SMR-S code on the steady conditions was performed with the Bennett＇s heated tube tests and THTF （thermal hydraulic test facility） experiment. From the results of the TASS/SMR-S code calculation, the CHF （critical heat flux） point and the fuel rod surface temperature were predicted conservatively compared to the test results.

内皮细胞特异性骨形态发生蛋白2对血管新生的影响:生物信息学分析和实验验证

背景:血管新生是心血管疾病的主要干预靶点,骨形态发生蛋白2具有调控血管新生作用,但内皮细胞特异性骨形态发生蛋白2对血管新生的调控作用不清楚。目的:探讨内皮细胞特异性骨形态发生蛋白2对血管新生的影响。方法:(1)生物信息学分析:通过Panglao DB公共基因表达数据库单细胞转录组荟萃分析观察骨形态发生蛋白2细胞群表达丰度和定位。血管新生小鼠和内皮(心内膜)过表达骨形态发生蛋白2小鼠转录组测序数据集探索内皮细胞骨形态发生蛋白2对血管新生信号通路的调控作用。(2)体内实验验证:建立小鼠后肢缺血模型,对比模型小鼠患侧与健侧缺血后肢7,14和21 d血流灌注情况,免疫荧光和免疫组织化学染色评估小鼠骨形态发生蛋白2和CD31的表达定位情况。(3)体外实验验证:体外培养人脐静脉内皮细胞,分为对照组、缺氧组和骨形态发生蛋白2抑制剂(Noggin蛋白)干预组,培养24 h,观察各组内皮细胞血管新生情况。结果与结论:(1)内皮细胞是表达骨形态发生蛋白2的重要细胞亚群,在血管新生内皮细胞和骨形态发生蛋白2过表达内皮细胞转录组再分析均发现骨形态发生蛋白2表达明显升高,血管新生通路明显激活。(2)缺血7 d小鼠新生血管周围骨形态发生蛋白2阳性血管明显增加(P<0.05),缺血2周骨形态发生蛋白2阳性血管明显减少(P<0.001)。(3)体外培养人脐静脉内皮细胞,缺氧干预后,内皮细胞迁移能力和血管出芽明显增加,血管新生因子血管内皮生长因子和血小板衍生生长因子的表达明显升高,Noggin明显减少了缺氧诱导的内皮细胞血管新生(P<0.001),并下调血管内皮生长因子和血小板衍生生长因子的表达(P<0.01)。(4)结果证实,内皮细胞特异性骨形态发生蛋白2具有调控血管新生作用,靶向性内皮细胞骨形态发生蛋白2可望改善血管新生。

Axial Compression Behavior and Analytical Method of L-Shaped Column Composed of Concrete-Filled Square Steel Tubes

Based on the characteristics of an L-shaped column composed of concrete-filled square steel tubes, the axial compression experiment and nonlinear finite element analysis were carried out to study the mechanical property of the L-shaped column. The load-displacement curve for the L-shaped column, the deflection and load-strain curves for the mono columns were obtained by the axial compression experiment. The results show that the L-shaped column exhibits a flexural-torsional buckling failure mode. The numerical simulation by the finite element analysis shows that the bearing capacity and failure mode are in accordance with those of the axial compression experiment and the feasi- bility of the finite element analysis is proved. For the calculation of the bearing capacity of the L-shaped column com- posed of concrete-filled square steel tubes, an analytical method is proposed based on the theory of the elastic stability and spatial truss model. The results of the analytical method are in good agreement with those of the axial compression experiment and the finite element analysis.

Heat transfer and friction factor of Therminol liquid phase heat transfer fluid in a ribbed tube

Experiments and simulations on flow and heat transfer behavior of Therminol-55 liquid phase heat transfer fluid have been conducted in a ribbed tube with the outer diameter and inner diameter 25.0 and 20.0 mm,pitch and rib height of 4.5 and 1.0 mm.respectively.Experimental results show that the heat transfer and thermal performance of Therminol-55 liquid phase heat transfer fluid in the ribbed tube are considerably improved compared to those of the smooth tube.The Nusselt number increase with the increase of Reynolds number.The increase in heat transfer rate of the ribbed tube has a mean value of 2.24 times.Also,the pressure drop results reveal that the average friction factor of the ribbed tube is in a range of 2.4 and 2.8 times over the smooth tube.Numerical simulations of three-dimensional flow behavior of Therminol-55 liquid phase heat transfer fluid are carried out using three different turbulence models in the ribbed tube.The numerical results show that the heat transfer of ribbed tube is improved because vortices are generated behind ribs,which produce some disruptions to fluid flow and enhance heat transfer compared with smooth tube.The numerical results prove that the ribbed tube can improve heat transfer and fluid flow performances of Therminol liquid phase heat transfer fluid.

高档次不锈钢(焊)管的制造与订购——美国Plymouth Tube公司的经验和对美国标准的系统解读

介绍了美国Plymouth Tube公司的生产经验,并分析讨论了所涉美国不锈钢焊接钢管标准的系统特征。分析认为:美国ASTM/ASME不锈钢钢管(材)标准由产品标准和通用材质标准组成;ASTM技术标准(正文部分)实际上只规定了不锈钢钢管的最低设计和检验要求,仅按照该标准未必能订购到质量有保证的优质钢管;ASTM/ASME不锈钢钢管(材)标准不仅在不断补充新品种和新内容,也经常在纠正各种错误或修正认识;全面系统地解读美国标准,对我国不锈钢(焊)管的生产、销售和订购十分有益。

最优尺寸参数对涡流管能量分离效应影响的研究

为确定出涡流管各因素的主次顺序,找出最优的参数组合,提出正交试验设计和极差分析法,找到涡流管能量分离效应的最优化尺寸参数。实验设定涡流管进气温度为26℃,环境温度为27.1℃,结果表明,4个尺寸参数对涡流管能量分离影响排序为:长径比>喷嘴数目>冷端直径>进气压力,每个参数的最优值各为长径比为25.0、喷嘴个数为6、冷端直径为5 mm、进气压力为0.8 MPa,并通过对试验结果的验证,发现涡流管的冷热端出口温差为95.2℃。根据正交试验设计方案找出了涡流管各部件的最优尺寸参数。

测压管长度对单测点信号的影响及修正效果验证

测压试验中,测压管的存在会导致风压信号产生畸变,影响后续数据分析的精度。通过实际测定测压管路频响函数,获得测压管对信号的影响规律,并揭示了“B-T理论”的不足。在实际紊流作用下研究测压管长度对单测点压力数据和模型整体力的影响,并验证“B-T理论”的修正效果。结果表明:对于单测点压力数据,测压管将不会影响数据均值和变异系数,标准差随管长增加先增后减,信号时域随管长增加而整体向均值靠近,相位则不断滞后,信号频域值随管长和频率的增加逐渐偏离真实值;对于整体力,整体阻力、各力的相关性、相干性均可认为不受测压管影响,力谱的变化规律与单测点频域值相同;“B-T理论”在信号时域上修正效果较差,在频域修正方面表现良好。

锥形阶梯流管无阀压电泵仿真及实验

针对锥形流管无阀压电泵输出流量小、回流流量多等问题,结合锥形流管和溢流坝阶梯式结构的阻流作用,研制了一种锥形阶梯流管无阀压电泵。对锥形阶梯流管的流阻特性进行了理论分析,利用有限元软件对锥形阶梯流管无阀压电泵和锥形无阶梯无阀压电泵进行了流场仿真对比,制作了锥形阶梯流管无阀压电泵实验样机,测量不同频率和驱动电压下两种泵的流量。实验结果表明:当驱动电压峰峰值为180 V、驱动频率为18 Hz时,锥形无阶梯流管无阀压电泵流量最大为6.20 ml/min,锥形阶梯流管无阀压电泵输出流量最大为8.04 ml/min,与锥形无阶梯流管无阀压电泵相比泵最大输出流量提升了29%,验证了锥形阶梯流管无阀压电泵能有效抑制锥形流管中的回流现象,且相比于无阶梯流管无阀压电泵具有更好的输出流量。

PBL抗剪传力钢筋连接接头受拉力学性能试验

装配式混凝土构件间钢筋的连接是其适用性和经济性的关键环节,针对国内工程常用的灌浆套筒和约束浆锚钢筋连接技术存在施工难度大、效率低、质量不易检验等问题,本文提出了PBL-穿孔钢筋连接接头、PBL-穿孔钢管连接接头和PBL-U形钢筋连接接头3种钢筋连接接头,实现预制混凝土单元间钢筋应力的传递,具有施工简便、质量易保证、成本低等优势。对这3种钢筋接头进行了6组参数共18个钢筋接头试件的拉伸性能试验,研究了新型接头试件的破坏模式、承载力和变形能力等,得到各参数对新型接头拉伸强度的影响规律,并对不同接头的受拉力学性能进行对比分析。研究结果表明:3种钢筋连接接头能够实现钢筋应力的有效传递,验证了新型钢筋连接接头的可行性。

压力振荡管内波系运动行为的可视化实验研究

气波制冷机具有制冷效率高、可带液工作等优点。为深入研究气波制冷机核心部件压力振荡管内部波系运动,设计了一套双开口压力振荡管可视化流场测量平台,利用视场拼接和纹影技术获得压力振荡管内密度梯度场的定量表达,并将实验结果与二维欧拉方程理论计算结果进行了交叉对比验证,误差为3.2%,证明基于纹影技术追踪管内复杂波系运动的方法不仅直观可视且准确可靠。基于上述方法,对不同压比和转速下的压力振荡管内波系开展了实验研究。实验结果表明,增大压比或转速均会提升激波马赫数。压比由1.5增大至3.0时,激波强度和膨胀波强度均显著增大,强化了对近管口区间气体的膨胀作用。转速由800 r/min提高至2400 r/min时,膨胀波波系运动路径逐渐向管口方向弯曲,降低了膨胀波在管口运动的速度,增加了膨胀波对近管口区间气体的作用时间。

真性球麻痹吞咽障碍患者间歇经口至食管管饲体验

目的了解真性球麻痹吞咽障碍患者间歇经口至食管管饲(intermittent oral-esophageal tube feeding,IOE)的真实体验,为IOE在真性球麻痹吞咽障碍患者中的优化应用提供参考。方法以目的性抽样法选取2022年3月至2023年3月在长治市某三级甲等医院康复医学科住院的真性球麻痹吞咽障碍患者16名为研究对象,对其进行半结构化访谈,采用Colaizzi现象学资料分析法并在Nvivo 11.0软件的辅助下整理分析资料。结果共凝练3个主题,即心理应激反应、感知益处、管饲照护需求。结论医护人员应重视真性球麻痹吞咽障碍患者的应激反应,强化益处体验,提供多元化支持,优化IOE应用策略。

泡沫铝复合结构隔声性能的仿真和实验研究

泡沫铝材料在交通运输、航天和建筑隔声等方面具有广阔的应用前景,然而单层泡沫铝其内部孔径和孔隙率不同严重影响了材料的隔声效果。构造两种复合结构,分别采用COMSOL软件仿真和实验室阻抗管测试两种手段对隔声性能进行了研究,结果表明:泡沫铝-玻璃纤维吸音棉复合结构在低频和中高频的隔声性能有一定的改进,而对于泡沫铝-三聚氰胺海绵复合结构,其隔声性能在各个频段均得到了极大提升,平均隔声量提升了将近6.8dB。

Dynamic Experimental Study of a Multi-bypass PulseTube Refrigerator with Two-bypass Tubes

A dynamic experimental apparatus to measure the instantaneous velocity and pressure in the multi-bypass pulse tube refrigerator (MPTR) was designed and constructed. Some theortant experimental results of the instantaneous measurements of the velocity and the pressure in the MPTR with two-bypass tubes during actual operation are presented. The effects of the middle-bypass version on the dynamic pressure and mass flow rate at the cold end of the pulse tube are evaluated from experimental measurements.DC-flow phenomena are observed in this MPTR. The reasons of the multi-bypass version improved the performance of pulse tube refrigerator are given.

Experimental study on the mechanical behavior and deformation characteristics of gravel cushion in an immersed tube tunnel

The immersed tube tunnel section of the Shenzhen-Zhongshan Link exhibits complex geological conditions and high back sludge strength. The tunnel cushion adopts the gravel and flaky stone combined cushion. The major influencing factors of the mechanical deformation characteristics of the gravel and flaky stone composite cushion are studied through a physical model experiment. The following results are reported.(1) The load–settlement curves of the flaky stone cushion become more compact with a dense increment under the design load. These curves can be regarded as nonlinear mechanical characteristics. The load–settlement curves of the gravel cushion and the gravel and flaky stone composite cushion exhibit the characteristics of a two-stage linear change.(2) The flatness of the top of flaky stone cushion considerably affects settlement and secant modulus. The flatness of the top of flaky stone should be ensured during construction.(3) Gradation and thickness exert no evident effect on the compressibility of a cushion. The preloading pressure caused by the construction height difference of the cushion materials plays an important role in improving the initial stiffness of a cushion and reducing initial settlement and overall settlement.(4) This study investigates the preloading under 30 kPa of the 0.7-m flaky stone and 1.0-m gravel combination cushion. It recommends the following secant modulus values: 48.89 MPa for the section of 0–30 kPa and 10.47 MPa for the section of 30–110 kPa.

Experimental study of an ellipsoidal particle in tube Poiseuille flow

Behaviors of a prolate ellipsoid inside circular tube Poiseuille flow are studied experimentally. In the study, Reynolds number Re ∈ (100,700) and the confinement ratio D/A ∈ (1.2,2.8) are considered, where D is the diameter of the tube and A is the length of the major axis of the ellipsoid. Two typical stable motion modes are identified, namely, the horizontal, and inclined modes. Then another inclined mode (inclined mode II) is found at high Reynolds number (Re ∈ (1000,3200)) and small D/A, and the inclined angle of ellipsoid increases with the increase of Re. The possible mechanism is explained. Our experiment shows that the lagging velocity U increases as Re increases. Further numerical analysis using FLUENT shows that due to the increase of U, the moment acting on the particle would make the inclined angle of the particle increase.