共查询到20条相似文献，搜索用时 265 毫秒
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针对长江中游洞庭湖防洪系统规模庞大、水流复杂、资料短缺和预报时限紧迫的实际条件,提出了具有层次和模块结构特点、一维与二维水流模拟、水力学与水文学方法、理论模型与补充信息相结合的建模途径.所建模型的湖泊部分采用无结构网格二维非恒定流高性能有限体积格式,以适应湖区复杂的边界形状和保持水量平衡;河网部分采用一维非恒定流守恒型显格式,避免隐格式矩阵算法的复杂性,同时有利于与二维模型的耦合及与各种复杂连通关系的显式连接.这种一、二维混合非恒定流模型可用于长江干流、洞庭湖河网及湖泊、堤垸区的洪水演进和防洪调度的水流仿真. 相似文献
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计算明渠非恒定流的一个Lattice BGK模型 总被引：4，自引：1，他引：3
分析了Lattice Boltzmann(LB)方法的建模原理,通过比较LB的多尺度方程和明渠St.Venant方程,建立了计算一维明渠非恒定流的一个Lattice BGK模型。对几个典型应用实例进行了模拟分析,与Preissmann隐格式及特征线法作了比较,证明将该方法引入实际明渠非恒定流计算是可行的。 相似文献
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以长江中下游(宜昌-大通)防洪系统为对象,在水文、河道及湖盆地形现状条件下,建立了一个能适应各种复杂条件的一二维非恒定流模型,来进行长江干流、河网、湖泊、分蓄洪区垸及水库的洪水演进和调度仿真.所建模型的洞庭湖部分采用无结构网格二维非恒定有限体积格式,以适应湖区复杂的边界形状和保持水量平衡.河网区部分采用一维非恒定流显隐结合的分块三级算法,以准确实现河网汊点流量的自动分配和往复流动.为了提高模拟精度和扩展模拟功能,在水流数值模拟的范围内侧重讨论了内外动边界处理、分蓄洪运用及阻力项计算等环节,提出了合理可行的数值处理方法.采用20世纪80年代至90年代共6年汛期洪水资料对所建模型进行了严格的率定和检验,高精度的模拟结果证实了模型的合理性和有效性. 相似文献
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用变化的特征差分格式进行水位推流 总被引：2，自引：0，他引：2
笔者就高洪期由水位直接推算流量问题,提出了变化的特征差分格式,并证明了在理想条件下格式的稳定性。最后将电算成果与明渠非恒定流理论解及实测资料进行了比较.结果表明,该格式在稳定性、收敛性及精度方面,均具有较大优越性。 相似文献
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以圣维南方程组、对流扩散方程以及未确知信息理论为基础,建立了环状河网一维水动力与未确知水质数学模型。采用Preissman四点隐格式法对圣维南方程组进行离散和采用显式差分对对流扩散方程进行离散,对河网水动力与水质分别进行了合理的编码,并考虑了泵闸等控制工程、降雨径流的影响,采用河网的三级解法编制河网非恒定流的计算程序求解各断面的水位Z和流量Q,实现了水动力和水质两模块之间的数据连接,且对微分形式的水质模型运用未确知数学理论进行了含有两个未确知参数的水质计算,从而不仅能获得污染物浓度区间值,还能得到相应的可信度。实例研究表明,建立的河网水动力模型和未确知信息的水质模型是可靠的,可以用于河网水质治理工程的数值模拟研究和水环境评估。 相似文献
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现行水库洪水优化调度数学模型存在泄流闸门开度不断调整及时段间流量突变的问题。针对这些问题,将水库防洪优化调度数学模型分为时段内出库流量线性变化的瞬时出流模型和时段内出流不变的恒定出流模型。对于1个水库和1个防洪控制点所组成的基本防洪系统,应用矩形入流条件的河道洪水演进方法,以时段内恒定的出库流量为决策变量,构建水库防洪优化补偿调度数学模型。实例计算结果表明:恒定出流模型比瞬时出流模型占用的防洪库容减小0.05%~0.18%、最大下泄流量有增有减,即恒定出流模型既不劣于瞬时出流模型,也能很好地解决瞬时出流模型存在的问题。同时,实例揭示的水库二次补偿调节比等蓄量调度方式减小防洪库容10.6%,为确定水库的防洪库容提供了新的方法。 相似文献
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明渠非恒定流流速分布及非恒定流作用下推移质运动分别是水力学和泥沙运动力学研究中的重要问题之一。近几十年来,国内外许多学者在这些领域做过很多探索,取得了一定进展,也存在较多问题。在总结相关研究成果的基础上,简述了明渠非恒定流试验方法、流速分布、床面切应力、非恒定流输沙与水流运动不同步现象、产生原因、以及非恒定流推移质输沙公式等方面的成果,指出了现有研究中存在的不足,提出了需要进一步研究的关键问题:应用先进的量测仪器,研究非恒定流作用下非均匀沙运动输移规律。 相似文献
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冰湖溃决洪水的二维水动力学数值模拟 总被引：1，自引：0，他引：1
为分析冰湖溃决洪水过程,建立了一个二维非恒定流数值模型,可以定量的开展冰湖溃决洪水预测.数值模型的基本控制方程采用二维浅水水流方程,数值方法采用可以捕捉激波的WAF TVD二阶精度格式,并用非界面追踪的方法处理干湿边界.通过理想情况下一维解析解的验证和二维复杂地形情况的数值试验,证明数值模型具有较好的精度和可靠性,并且可以适应复杂地形.将数值模型应用于一个典型的冰湖溃决事件,定量地预估了该冰湖溃决洪水过程,结果表明:水流流速很高,床面剪切应力很大,可能诱发活跃的泥沙运动,形成泥石流灾害. 相似文献
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根据雅砻江下游梯级水库水电站的布置和河道生态环境要求,分别设置了两个流量控制断面:锦屏二级电站引水闸址下减水河段、二滩电站坝址下游河段.针对这两个控制断面河道流量的要求,提出了25组生态流量控泄方案,建立了以梯级水电站群发电量最大为目标的长期优化调度模型,并采用动态规划法进行求解,获得各个方案下梯级水电站群多年平均发电量及水库调度出流过程.比较分析了减水河段生态流量及二滩水库泄流控制方案对发电量的影响,定义并计算了生态需水电能损失指标.对梯级水库调度出流过程进行了初步评价.结果表明:二滩水库出流维持天然径流模式,将限制水库调节能力和减少梯级电站发电效益. 相似文献
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基于非线性规划的有限元塑性极限分析下限法研究 总被引：1，自引：0，他引：1
在分析Sloan建立的有限元塑性极限分析线性规划数学模型存在的局限性基础上,提出了基于非线性规划的有限元塑性极限分析下限法数学模型。采用非线性屈服条件构建了下限法静力容许应力场,建立了求解超载系数、强度储备系数的下限法数学模型,并提出了针对塑性极限分析非线性规划数学模型的求解策略;最后对一个经典算例进行了深入分析,验证了方法的正确性。 相似文献
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下限分析有限单元法将下限定理这一数学变分问题转化为一个数学规划问题,克服了人为构造可静应力场的困难,在实际工程中具有广阔的应用前景。通过有限元离散得到的非线性下限规划模型中包含大量的优化变量与约束条件,常规优化算法难以求解。为此,在分析非线性下限规划模型自身特点的基础上,引入可行弧技术和Wolfe非精确搜索技术改进其优化求解效率。算例分析表明,基于可行弧技术和Wolfe非精确搜索技术,下限分析有限单元法优化求解程序的收敛速度和步长搜索效率得到明显的提升,并且其数值稳定性良好、计算精度较高,可以较好地适应实际工程问题的计算。 相似文献
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Through the rapid development of the watersheds in Turkey with projects developed by incorporated companies, a problem has arisen of how to operate a cascade reservoir system composed of state- and private sector-owned reservoirs in terms of the volume and timing of water releases to meet downstream water demands. This study presents a catchment-based optimization model based on inflow forecast with frequent updating for the integrated operation of hydropower plants under various sales methods. The model is formulated in terms of nonlinear programming (NLP) on a monthly basis for a 1-year period to assess the production strategies of the system reservoirs for that year. This model provides the basic constraints on the reservoir volume for daily and hourly optimization procedures. Forecasted flows are generated using seasonal autoregressive integrated moving average (ARIMA) models based on historical flow values. The proposed model is tested on the Garzan Hydropower System using historical, mean, and forecasted flow values. The results show that the integrated operation plan and improvement in the accuracy of inflow forecasts yield economic benefits as a consequence of optimal reservoir operation. 相似文献
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在实际隧道施工过程中,隧道开挖引起地下岩体应力重分布使得围岩的微裂纹扩展损伤,并伴随有塑性流动变形。在地下水环境中对于孔隙和微裂隙围岩介质受到应力作用时,在内部将产生高孔隙水压力影响岩石的力学性质,也改变了围岩的破坏模式。为了研究损伤引起的刚度退化和塑性导致的流动两种破坏机制的耦合作用,从弹塑性力学和损伤理论的角度出发,同时引入修正有效应力原理来考虑孔隙水压力的作用,建立基于Drucker-Prager屈服准则的弹塑性损伤本构模型;针对该本构模型推导了孔隙水压力作用下弹塑性损伤本构模型的数值积分算法-隐式返回映射算法,分别对预测应力返回到屈服面的光滑圆锥面或尖点奇异处两种可能的情况给出了详细的描述,隐式返回映射算法具有稳定性和准确性的特点;大多数弹塑性损伤模型中涉及参数多且不易确定的问题,采用反分析方法获得损伤参数,解决了损伤参数不易确定的难题;采用面向对象的编程方法,使用C++语言编制了弹塑性损伤本构求解程序,并对所建立的弹塑性损伤模型和所编程序进行了试验和数值两个方面的验证;最后将其在吉林抚松隧道工程中进行应用,模拟了塑性区和损伤区的发展变化。研究结果表明：所建立的弹塑性损伤本构模型能够较好地描述岩石的力学性能、塑性和损伤变化趋势,所编程序能够进行实际工程问题的模拟,对现场施工给予一定的指导。 相似文献
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感潮河网水流不仅受径流、潮汐动力的双重影响,还常受水闸调度等人类活动的影响,水动力条件极为复杂。针对水闸调度影响下感潮河网复杂水动力及其伴随物质输移扩散模拟,提出了考虑水闸调度并集成输运对流项的水流-输运通量耦合求解器,建立了基于非结构网格Godunov格式的二维水流-输运耦合数学模型。采用具有时空二阶精度的MUSCL-Hancock预测-校正格式,结合变量重构限制器技术,在保证计算精度的同时避免了数值振荡。运用斜底三角单元网格表达水闸线状地形,并通过地形调整模拟了水闸启闭过程。算例研究表明,该模型计算精度高,可有效模拟水闸调度影响下感潮河网水流运动及污染物输运过程,具有较好的推广应用价值。 相似文献
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Comparison of surrogate models with different methods in groundwater remediation process 总被引：3，自引：0，他引：3
Surrogate modelling is an effective tool for reducing computational burden of simulation optimization. In this article, polynomial regression (PR), radial basis function artificial neural network (RBFANN), and kriging methods were compared for building surrogate models of a multiphase flow simulation model in a simplified nitrobenzene contaminated aquifer remediation problem. In the model accuracy analysis process, a 10-fold cross validation method was adopted to evaluate the approximation accuracy of the three surrogate models. The results demonstrated that: RBFANN surrogate model and kriging surrogate model had acceptable approximation accuracy, and further that kriging model’s approximation accuracy was slightly higher than RBFANN model. However, the PR model demonstrated unacceptably poor approximation accuracy. Therefore, the RBFANN and kriging surrogates were selected and used in the optimization process to identify the most cost-effective remediation strategy at a nitrobenzene-contaminated site. The optimal remediation costs obtained with the two surrogate-based optimization models were similar, and had similar computational burden. These two surrogate-based optimization models are efficient tools for optimal groundwater remediation strategy identification. 相似文献
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Venkatesh Uddameri E. Annette Hernandez Felipe Estrada 《Environmental Earth Sciences》2014,71(6):2559-2572
As groundwater is a slowly replenishing resource that can be depleted relatively easily, there is a growing interest in actively managing aquifer resources. Participatory, multi-stakeholder driven approaches are increasingly being adopted to plan groundwater use such that the resource is available for present as well as future needs. The state of Texas requires neighboring GCDs (local regulatory bodies) within a groundwater management area (GMA) to engage in joint planning activities and define desired future conditions (DFCs) for the aquifers they regulate. The DFCs are then used to estimate modeled available groundwater which defines how much water is available within an aquifer in a given region. The groundwater joint planning process was modeled using a combined simulation–optimization modeling scheme in this study. The response surface methodology was used to establish regional-scale aquifer stress-response relationships. In addition to average county-wide drawdown, other aquifer responses including stream-aquifer exchanges, coastal-aquifer exchanges and GMA-wide drawdown were considered to define the DFCs. A constrained linear regression was used in conjunction with a regional groundwater flow model to obtain the necessary response functions which formed the basis for a crisp optimization model whose objective was maximizing groundwater production while ensuring that the prescribed DFCs are not violated (constraints). This model was transformed into a fuzzy linear programming model to account for the fact that groundwater planners find it difficult to specify DFCs with a high degree of precision. Using linear membership functions, the decision makers’ preferences were captured using two values––a minimum preferred cut-off and the maximum allowable value for the metric. For estimating groundwater availability, the fuzzy optimization model reconciles production and maximizes the goal and the constraints representing the DFCs. The developed framework was illustrated by applying it to joint planning in Groundwater Management Area 15 in South Texas. The optimization models were highly sensitive to acceptable average drawdowns, while the coastal-aquifer interactions had secondary impacts. The fuzzy optimization model yielded lower estimates of groundwater availability in comparison to the crisp optimization scheme. The fuzzy optimization model is therefore consistent with the precautionary principle and recommended for use in the early stages of groundwater planning where incomplete understanding of the aquifer dynamics precludes specification of precise limits for the DFCs. 相似文献
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Pre-processing data using wavelet transform and PCA based on support vector regression and gene expression programming for river flow simulation 总被引：1，自引：0，他引：1
Abazar Solgi Amir Pourhaghi Ramin Bahmani Heidar Zarei 《Journal of Earth System Science》2017,126(5):65
An accurate estimation of flow using different models is an issue for water resource researchers. In this study, support vector regression (SVR) and gene expression programming (GEP) models in daily and monthly scale were used in order to simulate Gamasiyab River flow in Nahavand, Iran. The results showed that although the performance of models in daily scale was acceptable and the result of SVR model was a little better, their performance in the daily scale was really better than the monthly scale. Therefore, wavelet transform was used and the main signal of every input was decomposed. Then, by using principal component analysis method, important sub-signals were recognized and used as inputs for the SVR and GEP models to produce wavelet-support vector regression (WSVR) and wavelet-gene expression programming. The results showed that the performance of WSVR was better than the SVR in such a way that the combination of SVR with wavelet could improve the determination coefficient of the model up to 3% and 18% for daily and monthly scales, respectively. Totally, it can be said that the combination of wavelet with SVR is a suitable tool for the prediction of Gamasiyab River flow in both daily and monthly scales. 相似文献