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81.
ABSTRACT: A simple simulator was constructed, calibrated, programmed and used in management studies of a hydraulic system containing two pumping stations in series, connected by canals and reservoirs. The features of the model, its calibration and use are described, and comparisons between measured and computed hydraulic behavior are presented. 相似文献
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Jeffrey R. Brook Leiming Zhang Yifan Li David Johnson 《Atmospheric environment (Oxford, England : 1994)》1999,33(30):804
Numerical sensitivity tests and four months of complete model runs have been conducted for the Routine Deposition Model (RDM). The influence of individual model inputs on dry deposition velocity as a function of land-use category (LUC) and pollutant (SO2, O3, SO2−4 and HNO3) were examined over a realistic range of values for solar radiation, stability and wind speed. Spatial and temporal variations in RDM deposition velocity (Vd) during June – September 1996 time period generated using meteorological input from a mesoscale model run at 35 km resolution over north-eastern North America were also examined. Comparison of RDM Vd values to a variety of measurements of dry deposition velocities of SO2, O3, SO2−4 and NHO3 that have been reported in the literature demonstrated that RDM produces realistic results. Over northeastern NA RDM monthly averaged dry deposition velocities for SO2 vary from 0.2 to 3.0 cm s−1 with the highest deposition velocities over water surfaces. For O3, the monthly averaged dry deposition velocities are from 0.05 to 1.0 cm s−1 with the lowest values over water surfaces and the highest over forested areas. For HNO3, the monthly averaged dry deposition velocities have the range of 0.5 to 6 cm s−1, with the highest values for forested areas. For SO2−4, they range from 0.05–1.5 cm s−1, with the lowest values over water and the highest over forest. The monthly averaged dry deposition velocities for SO2 and O3 are higher in the growing season compared to the fall, but this behaviour is not apparent for HNO3 and sulphate. In the daytime, the hourly averaged dry deposition velocities for SO2, O3, SO2−4 and HNO3 are higher than that in the nighttime over most of the vegetated area. The diurnal variation is most evident for surfaces with large values for leaf area index (LAI), such as forests. Based on the results presented in this paper, it is concluded that RDM Vd values can be combined with measured air concentrations over hourly, daily or weekly periods to determine dry deposition amounts and with wet deposition measurements to provide seasonal estimates of total deposition and estimates of the relative importance of dry deposition. 相似文献
84.
采用高速摄影技术,考察了液化四氟乙烷发生小孔泄漏时,其水平泄漏和垂直泄漏的初始云团演化行为、泄漏的质量流率、喷射速度和喷射角,并与理论计算公式进行了对比。结果表明:水平喷射两相云团尾部出现涡流,涡流大幅加快了云团向空气中扩散的速率;垂直喷射的两相云团在地面形成液池,液池大幅增加了液化气体向空气中蒸发的速率。水平泄漏试验的喷射角与容器内超压变化规律相似,泄放初期喷射角逐渐增大,经历一段平坦期,到泄放末期喷射角减小。水平泄漏和垂直泄漏的初始喷射速度分别为25 m/s和20 m/s,与理论值26.6 m/s基本吻合。水平泄漏的质量流率的试验值和理论值分别为0.0598 kg/s和0.0684 kg/s,垂直泄漏的分别为0.0472 kg/s和0.059 6 kg/s,结果对比基本吻合,推荐的泄漏质量流率和小孔喷射速度公式可以用于液化四氟乙烷小孔泄漏。 相似文献
85.
The evaluation of vulnerability of process equipment to explosion is a central issue in the analysis of industrial risks. In this work, we have developed a simplified model, however based on fundamental equations, which includes structural and fluid–dynamic parameters for the target (the industrial equipment) and for the impacting pressure wave (shock waves) or object (fragment, debris) produced by different type of chemical explosions.The validity of methodology has been assessed by case histories. Several insights on the dynamic of structural interaction of the explosion with the target have been obtained, with specific reference to escalation effects.The model derives from the well-known Johnson's number, often adopted in impact engineering. 相似文献
86.
Ozone concentrations, flux and potential effect on yield during wheat growth in the Northwest-Shandong Plain of China 总被引:1,自引:0,他引:1
Ozone (O3) concentration and flux (Fo) were measured using the eddy covariance technique over a wheat field in the Northwest-Shandong Plain of China. The O3-induced wheat yield loss was estimated by utilizing O3 exposure-response models. The results showed that: (1) During the growing season (7 March to 7 June, 2012), the minimum (16.1 ppbV) and maximum (53.3 ppbV) mean O3 concentrations occurred at approximately 6:30 and 16:00, respectively. The mean and maximum of all measured O3 concentrations were 31.3 and 128.4 ppbV, respectively. The variation of O3 concentration was mainly affected by solar radiation and temperature. (2) The mean diurnal variation of deposition velocity (Vd) can be divided into four phases, and the maximum occurred at noon (12:00). Averaged Vd during daytime (6:00–18:00) and nighttime (18:00–6:00) were 0.42 and 0.14 cm/sec, respectively. The maximum of measured Vd was about 1.5 cm/sec. The magnitude of Vd was influenced by the wheat growing stage, and its variation was significantly correlated with both global radiation and friction velocity. (3) The maximum mean Fo appeared at 14:00, and the maximum measured Fo was − 33.5 nmol/(m2·sec). Averaged Fo during daytime and nighttime were − 6.9 and − 1.5 nmol/(m2·sec), respectively. (4) Using O3 exposure-response functions obtained from the USA, Europe, and China, the O3-induced wheat yield reduction in the district was estimated as 12.9% on average (5.5%–23.3%). Large uncertainties were related to the statistical methods and environmental conditions involved in deriving the exposure-response functions. 相似文献
87.
The coupled fluid-structure-rupture model was developed to study the propagation and intensity of blast wave from hydrogen pipe rupture due to internal detonation. The dynamic rupture of pipe and propagation of blast wave were well coupled together in every timestep during the simulation. The numerical model was validated with experiments in terms of both typical rupture profiles and blast overpressures. Results reveal that crack branching of pipe can dramatically increase the rupture opening rate which controls the intensity and shape of the resultant blast wave. Due to the process of crack initiation and extension, the blast wave out of the pipe first forms and then is strengthened by the subsequent compression waves. This makes the maximum peak overpressure appears at a certain standoff distance above the rupture. Despite consuming some percentages of energy, the dynamic rupture of pipe generally presents positive effects (up to 2–3 times) on the blast wave intensity along the jetting direction due to the convergence effect of rupture opening on the release of internal high-pressure gas. Finally, through defining normalized overpressure and impulse based on the same hydrogen detonation in open spaces, the quantitative influences of pipe rupture on the blast wave intensity in cases of different detonation pressures and standoff distances are clarified. 相似文献
88.
89.
90.
为了研究废砂浆中碳化硅粉和硅粉的分离情况,选用混合模型对柱型水力旋流器多相流流场进行数值模拟。模拟结果表明:柱型水力旋流器的分离效率与入口速度、进口浓度等因素有关,并分析出一定条件下当主、次相的入口速度均为1.1m/s时颗粒分离效果较好,分离效率较高,实验检测分离性能较好,为进一步实验研究提供一定的指导。 相似文献