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181.
土工织物防护工程反滤准则试验研究 总被引:1,自引:0,他引:1
土工合成材料的出现,为岩土工程施工技术带来了重要的影响。但将土工合成材料应用在堤岸防护工程中所出现的一些问题还有进行深入科学研究的必要。尤其是保土性准则一直是研究的热点问题。本文结合较大孔径织造布在堤岸防护工程中多年应用实践,通过室内反滤试验,野外淘刷试验及工程应用实例分析研究,提出了O90≤(210)d90防护工程中织造布保土性设计新准则,突破了目前普遍采用的O90≤(12)d90设计指标。 相似文献
182.
183.
C. Miqueu J. Satherley B. Mendiboure J. Lachaise A. Graciaa 《Fluid Phase Equilibria》2001,180(1-2):327-344
This study has investigated the influence of varying the ratio of paraffin, naphthene and aromatic (P/N/A) components in narrow, wide and real petroleum fractions on the parachors of the fractions. Surface tension and density measurements have been made on synthetic hydrocarbon mixtures simulating real SC8, SC10, SC13 groups, their mixtures and a kerosene sample covering the range SC4–SC14 in order to determine their experimental parachors. Two methods to compute the parachors of fractions are proposed based on the equation of Broseta, the correlations of Riazi and Al-Sahhaf and the pseudocompound approach of Daubert. The first, denoted method I, is given byand the second, denoted method II, bywhere Pa is the parachor of the cut, ω the acentric factor, P, N and A the P/N/A components, zP/N/A the mole fractions of the P/N/A components and the other terms have their usual meaning. Both of these methods were found to compute the parachors of mixtures representing the SC8, SC10 and SC13 groups, mixtures of these groups and the kerosene sample with an absolute deviation of 2%. Comparison of the experimental parachors with calculated ones show that the parachor of a petroleum fraction depends not only on its molecular weight but also on the ratio of the P/N/A components. It was also found that the parachor of each of the families of P, N and A components could be expressed as a linear function of molecular weight leading to the following expression for a mixture containing P, N and A componentswhere the A and B terms were those found in the linear regression fit for each family. The approach proposed gives quantitatively better results than methods such as that of Fawcett, where the P/N/A distribution is not taken into account in the computation of petroleum fraction parachors. 相似文献
Pa(cut)=zPPa(P)+zAPa(A)+zNPa(N)
Pa(cut)=(zPAP+zNAN+zAAA)MW+(zPBP+zNBN+zABA)
184.
Flow pattern and flow characteristics for counter-current two-phase flow in a vertical round tube with wire-coil inserts 总被引:1,自引:0,他引:1
Flow pattern, void fraction and slug rise velocity on counter-current two-phase flow in a vertical round tube with wire-coil inserts are experimentally studied. Flow pattern and slug rise velocity are measured visually with a video camera. The void fraction is measured by the quick-closing valve method. Four kinds of coils with different coil pitches and coil diameters are used as inserts. The presence of wire-coil inserts induces disturbance into gas and liquid flows so that the shape and motion of gas slug or bubbles in a wire-coil inserted tube are quite different from those observed in a smooth tube without insert. The bubbly flow occurs in the low gas superficial velocity region in the wire-coil inserted tube, while the slug or churn/annular flow only appears in the smooth tube without insert over the all test range. The measured slug rise velocity in the wire-coil inserted tube is higher than that in the smooth tube. With modified mean flow velocity calculated with core area, the slug rise velocity in wire-coil tube inserted is in good agreement with Nicklin's correlation. The void fraction in a wire-coil inserted tube is lower than that in a smooth tube in the range of high gas superficial velocities. By introducing a simple assumption on considering the effective flowing area, the measured void fractions in a wire-coil inserted tube are in relatively good agreement with the predicted result based on the drift flux model proposed by others with the correlation for slug rise velocity given by others when the coil pitch is dense. 相似文献
185.
本简要介绍了传感器、微机的作用,以及将其引入到物理实验教学中的重要性,进而说明了将传感器与微机相结合改革物理实验已是大势所趋。 相似文献
186.
187.
Since Newton first considered the motion of a spherical pendulum over 200 years ago, many researchers have studied its dynamic
response under a variety of conditions. The characteristic of the problem that has invited so much investigation was that
a spherical pendulum paradigms much more complex phenomena. Understanding the response of a paradigm gives an almost multiplicative
effect in the understanding of other phenomena that can be modeled as a variant of the paradigm. The spherical pendulum has
been used to damp irregular motion in helicopters and on space stations as well as for many other applications. In this study
an inverted impacting spherical pendulum with large deflection was investigated. The model was designed to approximate an
ideal pendulum, with the pendulum bob contributing the vast majority of the mass moment of inertia of the system. Two types
of bearing mechanisms and tracking devices were designed for the system, one of which had low damping coefficient and the
other with a relatively high damping coefficient. An experimental investigation was performed to determine the dynamics of
an inverted, impacting spherical pendulum with large deflection and vertical parametric forcing. The pendulum system was studied
with nine different bobs and two different base configurations. During the experiments, the frequency of the excitation remained
between 24.6 and 24.9 Hz. It was found that sustained conical motions did not naturally occur. The spherical pendulum system
was analyzed to determine under what conditions the onset of Type I response (a repetitive motion in which the pendulum bob
does not traverse through the apex. The bob strikes the same general area of the restraint without striking the opposite side
of the restraint.), sustainable Type II response (this is the repetitive motion in which the pendulum bob traverses through
the apex. The bob strikes opposite sides of the restraint.), and mixed mode response (motion in which the pendulum bob randomly
strikes either the same area of the restrain or the opposite side of the restraint) occurred. 相似文献
188.
应用ANSYS 软件对低活化马氏体/铁素体钢(RAFMs)中厚板多道焊接过程进行三维有限元模拟,将得到的温度场和应力场分别与实验对比,对焊缝区和热影响区宽度进行预测,并通过焊接实验进行验证,同时对焊后的试件进行了金相分析和硬度测试。结果表明:温度场和应力场模拟结果和实测结果基本一致,焊缝区以及热影响区宽度的模拟结果和实测结果基本吻合;采用316L 焊丝填充的焊缝,焊缝与母材熔合较好,焊缝没有明显缺陷;硬度检测呈现:焊缝的硬度大大高于热影响区和母材。 相似文献
189.
190.
《Particuology》2023
The internal erosion of pipelines in oil and gas storage and transportation engineering is highly risky. High gas velocity of annular flow entrained sand will cause damage to the pipelines, and may further result in thinning of the wall. If this damage lasts for a long time, it may cause pipeline leakage and cause huge economic losses and environmental problems. In this research, an experimental device for studying multiphase flow erosion is designed, including an erosion loop and an experimental elbow that can test the erosion rate. The annular flow state and pipe wall erosion morphology can also be tested by the device. The computational fluid dynamics (CFD) method is combined with the experiment to further study the annular flow erosion mechanism in the pipeline. The relationship between gas-liquid-solid distribution and erosion profile was studied. The results show that the most eroded region occurs between 22.5° and 45° in the axial angle direction and between 90° and 135° in the circumferential angle direction of the elbow. The pits and deep scratches form on the surface of the sample after the sand collision. 相似文献