共查询到20条相似文献,搜索用时 125 毫秒
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考虑入流过程洪水预报误差的随机性,基于Nash汇流理论建立了河道洪水演算的随机模型,在预报误差近似独立且服从正态分布时,推导了出流过程的计算公式和方差函数,定义了洪水预报误差随机性的传递函数,分析了洪水预报误差的随机性在河道洪水演算过程中的传递特征。实例应用结果表明,上游入流的洪水预报误差经过河槽调蓄或经由Nash汇流模型演算后,其不确定性会大为降低。同时,根据建立的河道洪水演算随机模型,还可以确定出流过程的置信区间,从而为估计河道防洪控制断面可能出现的风险提供理论依据。 相似文献
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漳河水库入库洪水预报方案研究 总被引:1,自引:0,他引:1
在分析漳河水库入库洪水误差特点的基础上.建立了入库洪水产汇流预报方案。并进一步采用自适应实时校正技术,使本次制作的漳河水库洪水预报方案平均确定性系数达到91.09%,洪峰合格率为100%,峰现时间合格率为90.91%。 相似文献
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北京市山丘地区洪水具有汇流快、历时短、破坏强的特点,多发于夏秋季汛期,损失惨重。为此需建立水文预报系统,采用分布式水文模型(EasyDHM)和马斯京根汇流模型演算方法分别进行产、汇流计算,模拟再现漫水河站近几十年内发生的洪水事件。结果发现,率定期参数敏感性分析和优化之后的模型模拟精度有明显提高;验证期模拟洪水发生年份距离模型率定年份越近模拟效果越好,且模拟洪水的洪量模拟效果优于洪峰模拟。 相似文献
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流域分散入流非线性汇流模型及其应用 总被引:9,自引:2,他引:9
考虑到流域降雨的时空变化和流域地形、河道特征对流域汇流的非线性影响,建立了以并联水库模式为基础的流域分散入流非线性汇流模型。将模型应用于洋河水库洪水预报,取得较为满意的效果。 相似文献
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何长春 《电网与水力发电进展》1990,(2)
模型包括由已降雨量和预报雨量进行入库洪水预报两个部分.第一部分重点阐述水库形成后水力条件及水文特性改变对洪水的影响问题,并提出与之汇流特性相适应的计算方法.第二部分着重对降雨发展过程中未来短时段降雨量估报的可能性及其计算途径进行研究,以增长入库洪水预报的预见期. 相似文献
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基于数字高程模型,并结合国外在河网水系提取的研究成果,归纳出提取河网水系的方法,并将其应用于实际的水系提取.建立了流域尺度的概念型分布式新安江模型,该模型在栅格单元中采用新安江模型作产流计算,根据单元的不同属性 (坡地、河道)及所推求的汇流时间场建立汇流模型.将此模型应用于淮河黄泥庄以上集水区域,对黄泥庄站的洪水过程进行了模拟研究,模拟结果符合洪水预报的规范要求. 相似文献
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A lattice Boltzmann model for the liquid–vapor phase change heat transfer is proposed in this paper. Two particle distribution functions, namely the density distribution function and the temperature distribution function, are used in this model. A new form of the source term in the energy equation is derived and the modified pseudo-potential model is used in the proposed model to improve its numerical stability. The commonly used Peng–Robinson equation of state is incorporated into the proposed model. The problem of bubble growth and departure from a horizontal surface is solved numerically based on the proposed model. 相似文献
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The zone model has been widely applied in control analysis of heating, ventilation and air conditioning (HVAC) systems to achieve a high building efficiency. This paper proposed a modified zone model which is much simpler in the HVAC system simulation and has the similar accuracy to the complicated simulation model. The proposed model took into consideration the effect of envelop heat reservoir on the room indoor temperature by introducing the thermal admittance of the inner surfaces of the building enclosure. The thermal admittance for the building enclosure was developed based on the building thermal network analytical theory and transfer function method. The efficacy of the proposed model was demonstrated by comparing it with the complicated model — heat balance method (HTB2 program). The predicted results from the proposed model well agreed with those from the complicated simulation. The proposed model can then make the HVAC system dynamic simulation much faster and more acceptable for control design due to its simplicity and efficiency. 相似文献
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针对现场实际负荷成分的时变性、随机性、复杂性、多样性和非线性的特点,在考虑实际负荷暂态特性的基础上,提出一种基于神经网络的配电网受控电流源负荷模型的方法。该方法根据负荷群在稳态运行条件下的电压和电流暂态特性,通过神经网络学习负荷群的电压电流特性,用受控电流源代替实际的负荷群,受控电流源的电流大小受神经网络控制,并利用Matlab/Simlink对所提出的负荷模型建立方法进行仿真验证。仿真结果表明所建立的负荷模型在单相短路、两相短路和三相短路条件下均具有良好的稳定性和准确性。 相似文献
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《International Journal of Thermal Sciences》2007,46(5):426-433
In this paper, a fractal model for the high heat flux nucleate boiling region and for the critical heat flux (CHF) is proposed. The expression for the critical heat flux (CHF) is derived based on the fractal distribution of nucleation sites on boiling surfaces. The proposed fractal model for CHF is found to be a function of wall superheat, the contact angle and physical properties of fluid. The relation between CHF and the number of active nucleation sites is obtained from the fractal distribution of active nucleation sites on boiling surfaces. The contact angle and the physical properties of fluid have the important effects on CHF. The predicted CHF from a boiling surface based on the proposed fractal model is compared with the existing experimental data. An excellent agreement between the proposed model predictions and experimental data is found. 相似文献
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Swanand M. Bhagwat 《传热工程》2013,34(18):1485-1494
The specific objective of this work is to develop an empirical model to predict the existence of stratified flow in horizontal and downward inclined gas-liquid two-phase flow. The proposed model is in nondimensional form and attempts to emulate the qualitative trend of the Taitel and Dukler mechanistic model. The key advantage of the proposed method is that it is explicit in nature and, unlike Taitel and Dukler, it does not require use of a graphical or iterative solution. The empirical parameters used in the proposed model account for the effect of pipe diameter, pipe orientation, and the liquid density on the transition line between stratified and nonstratified flow. The accuracy of the proposed model is verified against the flow visualization data collected from more than 16 data sources consisting of 8 fluid combinations, pipe diameter in a range of 8.9 to 300 mm, liquid density in a range of 780 to 1420 kg/m3, and all downward pipe inclinations including horizontal. 相似文献