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991.
微重条件下非稳态燃烧过程的数值模拟   总被引:2,自引:0,他引:2  
在建立气固相界面耦合燃烧理论模型的基础上,对微重条件下火焰在固相材料表面的蔓延进行了三维非稳态数值模拟,模型中考虑了气相燃烧过程、固相的热解和传热过程,给出了相界面的处理方法。不同算例的计算研究了环境氧浓度、环境压力对微重火蔓延的影响,并与正常重力条件下的计算结果进行了分析对比.结果基本合理。  相似文献   
992.
火灾现象的数值模拟及其应用   总被引:1,自引:0,他引:1  
本文讨论了模拟火灾现象的数值方法及其应用。着重研究了火焰发热、空气流动和烟尘传播的数学模型,讨论了紊流模型中浮力项的处理和边界条件的简化,并介绍了这一课题的研究现状和发展方向。  相似文献   
993.
用于风险评估的二维爆炸场的数值模拟   总被引:3,自引:0,他引:3  
采用多流体Uuler型方法,对爆轰产物采用可变指数的多方气体状态方程,给出了对二维爆炸场进行模拟的方法,该法可为用压力一冲量准则对可能发生的爆炸事故进行风险评估提供基础。数值计算结果表明,该法适合于各种不同的几何外型,与现有实验结果符合较好。  相似文献   
994.
本文提出了防灾工程中计算机仿真的作用、思路及主要技术关键,并通过若干例子,包括混凝土构件破坏,岩石块体崩塌,地震作用下房屋碎片分布,房屋在爆炸作用下倒塌等说明仿真技术的应用。  相似文献   
995.
ABSTRACT: We assessed the potential effects of increased temperature and changes in amount and seasonal timing of precipitation on the hydrology and vegetation of a semi-permanent prairie wetland in North Dakota using a spatially-defined, rule-based simulation model. Simulations were run with increased temperatures of 2°C combined with a 10 percent increase or decrease in total growing season precipitation. Changes in precipitation were applied either evenly across all months or to individual seasons (spring, summer, or fall). The response of semi-permanent wetland P1 was relatively similar under most of the seasonal scenarios. A 10 percent increase in total growing season precipitation applied to summer months only, to fall months only, and over all months produced lower water levels compared to those resulting from the current climate due to increased evapotranspiration. Wetland hydrology was most affected by changes in spring precipitation and runoff. Vegetation response was relatively consistent across scenarios. Seven of the eight seasonal scenarios produced drier conditions with no open water and greater vegetation cover compared to those resulting from the current climate. Only when spring precipitation increased did the wetland maintain an extensive open water area (49 percent). Potential changes in climate that affect spring runoff, such as changes to spring precipitation and snow melt, may have the greatest impact on prairie wetland hydrology and vegetation. In addition, relatively small changes in water level during dry years may affect the period of time the wetland contains open water. Emergent vegetation, once it is established, can survive under drier conditions due to its ability to persist in shallow water with fluctuating levels. The model's sensitivity to changes in temperature and seasonal precipitation patterns accentuates the need for accurate regional climate change projections from general circulation models.  相似文献   
996.
ABSTRACT: This paper presents the development of a mathematical model to compute the advance of water flowing over flat soil surfaces. The solution is of interest to the design and management of irrigation systems, and the model can also be applied to overland flow problems. The hydraulics of water flow during the advance phase is simulated by the Lewis-Milne integral equation. The general solution to this equation is obtained by using the Laplace transform theory. A particular solution was developed, based on series expansions, that uses the modified Kostiakov equation to predict infiltration. The solution is given by a double infinite series that has terms of alternate sign. Results from this model show satisfactory agreement when compared with field data collected by the author.  相似文献   
997.
ABSTRACT: The application of a low-flow assessment model is illustrated for the Monogahela River Basin. The model simulates the impact of reservoir operating rules and consumptive use limitation policies on low-flow frequency at downstream locations in the basin. Policies are evaluated using an observed flow sequence and synthetic flow inputs. The paper reviews the historical development of flow management on the Monogahela to provide background for the current study.  相似文献   
998.
Remotely sensed variables such as land cover type and snow-cover extent can currently be used directly and effectively in a few specific hydrologic models. Regression models can also be developed using physiographic and snow-cover data to permit estimation of discharge characteristics over extended periods such as a season or year. Most models, however, are not of an appropriate design to readily accept as input the various types of remote sensing parameters that can be obtained now or in the future. Because this new technology has the potential for producing hydrologic data that has significant information content on an areal basis, both inexpensively and repetitively, effort should be devoted now to either modifying existing models or developing new models that can use these data. Minor modifications would at least allow the remote sensing data to be used in an ancillary way to update the model state variables, whereas major structural modifications or new models would permit direct input of the data through remote sensing compatible algorithms. Although current remote sensing inputs to hydrologic models employ only visible and near infrared data, model modification or development should accommodate microwave and thermal infrared data that will be more widely available in the future.  相似文献   
999.
ABSTRACT: A soil erosion simulation model that considered the physical conditions of agricultural watersheds and that interfaced with the modified USDAHL-74 watershed hydrology model was developed. The erosion model simulates the detachment and transport of soil particles caused by raindrop impact and overland flow from rill and interrill areas. The model considers temporal and spatial variation of plant residue, crop canopy cover, snow cover, and the moisture content of surface soil as modifying factors of the erosive forces of raindrop impact and overland flow. The hydrology model simulates overland flow and some of the physical parameters that are used in the erosion model. The simulation is executed in the time interval determined by the rainfall rate or snowmelt rate. The erosion model compares the transport capacity of the overland flow and the sediment loaded in the overland flow to determine the fate account for the free soil particles that have already been detached and are readily available to be transported by the overland flow. The model was tested with data from two small agricultural watersheds in the Palouse region of the Pacific Northwest dryland. The model was calibrated by trial-and-error to determine the coefficients of the model.  相似文献   
1000.
ABSTRACT; This paper presents a numerical model for the prediction of optimal ground water withdrawal from a two-aquifer system by observing a set of constraints determined by the ecological conditions of the ground water basin. The aquifer system consists of an upper unconfined and a lower confined aquifer with a leaky stratum between them. It is assumed that water is withdrawn from the confined aquifer only, but the unconfined aquifer will also be affected due to the leakiness of the layer separating the upper and lower aquifers. Simulation and linear programming are employed for developing a computer model for the optimal management of such systems, with the objectives of determining withdrawal rates for predetermined ground water levels.  相似文献   
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