两种湍流参数化方案针对水体温度演变过程的模拟与比较     

马洪余  乔方利  郭景松 《海洋学报》2012,34(4):35-40

依据山东跋山水库的观测数据,采用MY2.5参数化方案和κ-ε参数化方案在不同的表面边界条件下模拟观测的温度剖面演化过程。模拟结果显示,在风应力强迫的表面边界条件下,采用这两种参数化方案的模拟结果差别不大;当考虑Mellor和Blumberg的波浪破碎表面边界条件时,采用MY2.5参数化方案的模拟结果没有明显的改善,但采用κ-ε参数化方案的模拟结果有明显的改善,得到与观测相符的模拟结果。  相似文献   

频率域波动方程正演基于多重网格预条件的迭代算法研究          下载免费PDF全文

曹健  陈景波  曹书红 《地球物理学报》2015,58(3):1002-1012

频率域全波形反演是重要的地震成像方法,而频率域波动方程数值模拟是频率域全波形反演的基础.对于大规模的问题,由于受存储和计算量的限制,基于LU分解的直接方法一般不再适用,而是采用迭代方法.基于多重网格预条件的双共轭梯度稳定化方法是一种重要的迭代方法.本文重点讨论了多重网格预条件求解过程中的松弛因子选择方法,研究结果表明,(1)对于一般选取的松弛因子,随模型复杂性的增加,所能计算的重数逐渐下降,方法的实用性也随之下降;(2)对于复杂模型,采用局部模式分析方法选取松弛因子,提高了所能计算的重数,保证了多重网格方法的收敛性和实用性.这些研究成果对基于多重网格预条件的迭代算法的实际应用具有重要意义.  相似文献   

Development of a grid‐based version of the SWAT landscape model          下载免费PDF全文

H. Rathjens  N. Oppelt  D. D. Bosch  J. G. Arnold  M. Volk 《水文研究》2015,29(6):900-914

Integrated river basin models should provide a spatially distributed representation of basin hydrology and transport processes to allow for spatially implementing specific management and conservation measures. To accomplish this, the Soil and Water Assessment Tool (SWAT) was modified by integrating a landscape routing model to simulate water flow across discretized routing units. This paper presents a grid‐based version of the SWAT landscape model that has been developed to enhance the spatial representation of hydrology and transport processes. The modified model uses a new flow separation index that considers topographic features and soil properties to capture channel and landscape flow processes related to specific landscape positions. The resulting model is spatially fully distributed and includes surface, lateral and groundwater fluxes in each grid cell of the watershed. Furthermore, it more closely represents the spatially heterogeneous distributed flow and transport processes in a watershed. The model was calibrated and validated for the Little River Watershed (LRW) near Tifton, Georgia (USA). Water balance simulations as well as the spatial distribution of surface runoff, subsurface flow and evapotranspiration are examined. Model results indicate that groundwater flow is the dominant landscape process in the LRW. Results are promising, and satisfactory output was obtained with the presented grid‐based SWAT landscape model. Nash–Sutcliffe model efficiencies for daily stream flow were 0.59 and 0.63 for calibration and validation periods, and the model reasonably simulates the impact of the landscape position on surface runoff, subsurface flow and evapotranspiration. Additional revision of the model will likely be necessary to adequately represent temporal variations of transport and flow processes in a watershed. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

适于声波方程数值模拟的时间-空间域有限差分算子改进线性算法          下载免费PDF全文

梁文全  赖永明  姜琳  吴超凡 《地震工程学报》2016,38(5):815-821

有限差分法广泛应用于地震波场的数值延拓,确定合适的有限差分算子以减小数值频散是有限差分法的一个重要研究内容。近年来为了进一步抑制数值频散和增加时间步长,新的有限差分模板得到了应用,对于此,前人使用泰勒展开方法和最小二乘方法确定有限差分算子系数。本文在以前工作的基础上,使用改进的线性方法确定新模板的有限差分系数,并与传统模板线性方法进行对比;通过频散分析和正演模拟验证出新模板线性方法能够更好地保持频散关系,在相同的精度下效率提高了一倍,从而说明了改进的线性方法的有效性。  相似文献   

YSU边界层参数化方案中不同地形订正方法对地面风速及温度模拟的影响   总被引：3，自引：3，他引：0       下载免费PDF全文

郑亦佳  刘树华  缪育聪  王姝 《地球物理学报》2016,59(3):803-815

为了修正中尺度气象模式WRF(Weather Research and Forecasting model)对低层风速模拟的系统性误差,有学者在新版本WRF模式的YSU(Yonsei University)边界层参数化方案中加入了两个地形订正方法:Jiménez方法和UW(University of Washington method)方法.本文利用这两个地形订正方法,选取了两个时间段,对北京地区的地面气象要素以及气象要素垂直廓线进行了个例模拟研究,模拟结果和观测数据的比对表明在北京地区:是否采用地形订正,对地面温度的模拟几乎没有影响;采用地形订正后,模式对地面风速的模拟有明显的改进,两种方法对风速模拟的差别主要体现在山/丘陵地区;Jiménez方法在山/丘陵地区的模拟风速明显偏大,而采用UW方法进行订正后,模拟的风速减小,更接近观测值;两种方法在山谷地区对风速均有一定的过度订正.通过分析气象要素的垂直廓线发现,不同地形订正方法主要影响的是2000m以下的低层风速.总体而言,UW地形订正方法在北京地区更为适用,采用UW方法后,模拟得到的地面气象要素的各项统计参数基本达到了统计基准值.  相似文献   

Gender and power contestations over water use in irrigation schemes: Lessons from the lake Chilwa basin     

《Physics and Chemistry of the Earth》2016

Over the past two decades, Malawi has been adversely hit by climatic variability and changes, and irrigation schemes which rely mostly on water from rivers have been negatively affected. In the face of dwindling quantities of water, distribution and sharing of water for irrigation has been a source of contestations and conflicts. Women who constitute a significant section of irrigation farmers in schemes have been major culprits. The study seeks to analyze gender contestations and conflicts over the use of water in the schemes developed in the Lake Chilwa basin, in southern Malawi. Using oral and written sources as well as drawing evidence from participatory and field observations conducted at Likangala and Domasi irrigation schemes, the largest schemes in the basin, the study observes that women are not passive victims of male domination over the use of dwindling waters for irrigation farming. They have often used existing political and traditional structures developed in the management of water in the schemes to competitively gain monopoly over water. They have sometimes expressed their agency by engaging in irrigation activities that fall beyond the control of formal rules and regulations of irrigation agriculture. Other than being losers, women are winning the battle for water and land resources in the basin.  相似文献   

三维过渡等参单元在岩土工程有限元分析中的应用     

董威信  王翔南  王远  于玉贞 《岩土力学》2015,36(5):1455-1462

土石坝等复杂土工结构物有限元三维建模中多采用精度较高的六面体单元辅以部分过渡用的退化单元,而退化单元由于形态不好,会导致有限元计算精度较差。解决该问题的途径之一是采用过渡性的等参元。总结了几种常遇到的过渡等参单元（楔形体、四面体、金字塔）的插值函数和高斯积分局部坐标和权重,并编入了有限元程序。通过比较六面体单元和金字塔单元剖分理想土石坝的有限元计算结果,说明所引入的金字塔单元是满足精度要求的。将各种过渡单元应用于实际土石坝工程的有限元计算,结果表明,使用过渡等参单元是可以在一定程度上提高计算精度的。最后讨论了二次单元在弹塑性有限元动力计算中的应用。二次单元的使用,可以改善动力计算中的超静孔压分布,提高计算精度。  相似文献   

求解二阶线性常微分方程的一个显式差分格式     

杨韧  周钰谦 《成都信息工程学院学报》2010,(6):328-332

在求解常微分方程的方法中,有限差分法是使用最广泛的方法之一。考虑一个二阶线性常微分方程的边值问题,利用有限差分法,建立了一个具有二阶精度的显式差分格式。首先,通过讨论该显式差分格式的系数矩阵,证明了该显式差分格式解的存在性。然后,通过定义的3种不同范数之间的关系,证明了显式差分格式解的收敛性和稳定性。最后,通过计算机编程对实例的计算,验证了该显式差分格式的数值结果具有二阶精度,并且该显式格式数值结果绘制的图形稳定、光滑,与解析结果吻合较好。  相似文献   

A Hybrid Finite-Volume and Finite Difference Scheme for Depth-Integrated Non-Hydrostatic Model     

YIN Jing  SUN Jia-wen  WANG Xing-gang  YU Yong-hai  SUN Zhao-chen 《海洋工程》2017,31(3):261-271

A depth-integrated, non-hydrostatic model with hybrid finite difference and finite volume numerical algorithm is proposed in this paper. By utilizing a fraction step method, the governing equations are decomposed into hydrostatic and non-hydrostatic parts. The first part is solved by using the finite volume conservative discretization method, whilst the latter is considered by solving discretized Poisson-type equations with the finite difference method. The second-order accuracy, both in time and space, of the finite volume scheme is achieved by using an explicit predictor-correction step and linear construction of variable state in cells. The fluxes across the cell faces are computed in a Godunov-based manner by using MUSTA scheme. Slope and flux limiting technique is used to equip the algorithm with total variation dimensioning property for shock capturing purpose. Wave breaking is treated as a shock by switching off the non-hydrostatic pressure in the steep wave front locally. The model deals with moving wet/dry front in a simple way. Numerical experiments are conducted to verify the proposed model.  相似文献   

基于二维浅水方程的滑坡体兴波数值模型          下载免费PDF全文

房克照  尹晶  孙家文  焦子峰 《水科学进展》2017,28(1):96-105

基于有限体积方法和结构化网格,建立了海底滑坡引起的波浪传播数值模型。模型控制方程为考虑了海床随时间变化的二维浅水方程。采用中心迎风格式计算控制体界面数值通量,采用线性重构技术、局部海床高程处理技术和全隐式离散底摩阻项,保证了格式的和谐性、守恒性和水深非负性,有效处理了海岸动边界问题。时间积分采用具有强稳定性质的二阶龙格-库塔方法（ssp RK）。针对滑坡体兴波经典算例开展数值模拟,将计算结果与解析解、实验结果及其他模型计算结果进行比较和分析。结果表明,对于所考虑的计算工况,模型能较合理地模拟滑坡兴波的产生、传播和爬高过程。  相似文献