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为保证计算格式的和谐性,通过特殊的底坡源项处理技术,在三角形网格上建立了求解二维浅水流动方程的具有空间二阶精度的Godunov格式。应用准确Riemann解求解法向数值通量,用改正的干底Riemann解处理动边界问题。经典型算例和钱塘江河口涌潮计算验证,表明模型健全,分辨率高,具有较大的推广应用价值。 相似文献
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建立了一种在非规则结构化网格上求解平面二维浅水流动的有限体积方法。通过采用地形在离散网格内双线性变化及离散网格界面间地形连续的地形逼近方法和应用可以有效处理间断问题的Roe格式来离散浅水方程中的对流项,并通过VanLeer提出的状态插值法提高格式精度。在计算原始变量在网格内的插值梯度时,采用最小二乘方法求变量的最优梯度代替差分计算梯度,从而可采用任意形状的不规则四边形网格离散计算域。计算实例表明,该方法能够计算间断问题并能够处理各种复杂流态的过渡,具有较好适应性和计算精度,能够满足不同实际问题的计算要求。 相似文献
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针对当前复杂环境水流模拟的需求,建立了新型的基于特征型高分辨率数值算法的三维非结构网格浅水动力模型。模型采用有限体积法离散sigma坐标下的三维浅水方程,运用Roe黎曼近似解评估水平界面通量。模型网格拟合边界能力强,可根据需要局部加密;格式数值性能优良,具有守恒性、单调迎风性、高数值分辨率等特性。同时,应用干湿判别法处理动边界,以适应浅滩地形漫/露过程模拟的需要。封闭水池内部风生环流、干河床上溃坝过程和长江口实际潮流场的模拟从不同侧面展示了模型的特点,结果表明它能够准确地预测水流的三维流动结构,而且计算简单高效,具有良好的数值稳定性。 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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Preissmann窄缝法模拟明满流过渡过程方法简单,但存在明显的非物理振荡,抑制非物理振荡是该方法应用的关键。基于Godunov格式和精确Riemann求解器对明满流过渡过程进行模拟,针对Riemann问题代数恒等式在明满流交界处不光滑问题,提出了三阶收敛方法与二分法结合的迭代求解方法,保证迭代收敛至真实解;针对由于变量空间重构方法不能准确表达变量在空间中真实物理状态而导致的非物理振荡,提出了基于精确Riemann解的变量空间重构方法,准确表达激波间断在单元内的空间分布状态,从机理上抑制了非物理振荡。实例研究表明,数值计算结果与解析解或实测值吻合良好,研究成果为明满流过渡过程的高精度数值模拟提供了新的方法。 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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RegCM3模式在西北地区的应用研究Ⅱ:区域选择及参数化方案的敏感性 总被引:15,自引:3,他引:12
通过数值模拟方法,研究了降水对区域尺度、积云对流参数化等的敏感性.结果表明:由于较小区域尺度的模式内部场和大尺度分析场激发的外强迫之间有更强的束缚,这种束缚使得内外强迫更容易达到一致.小区域尺度模拟的降水型比大的区域尺度的模拟更好,但同时,大的区域尺度消弱了由于模式侧边界效应产生的虚假动力效应,模拟的降水在量值上更加接近于观测值.因此,进行区域气候模拟时,须根据需要对模式区域进行仔细的选择.结果同时表明,由于Grell方案倾向于模拟更多的对流降水,因此Kuo-Anthes方案对西北地区降水型和量值的模拟比Grell方案更接近于实际.由于地形对于降水的重要意义,在复杂地形下进行区域气候模拟时有必要在模式中仔细描述地形. 相似文献
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利用浅水流动的可压缩流比拟来认识浅水方程组的特性及其有关物理现象,过去的讨论多限于矩形断面棱柱形明渠的最简单情况。本文首先将该模拟推广到任意断面非棱柱形明渠的一般情况,给出了等价绝热指数公式γ=H/h.(H为水力水深,hc为形心水深),并指出γ=2为矩形断面的特例.然后着重阐明这一数学模拟对计算水力学具有普遍实用价值,并将计算气体动力学中的两种通量向量分裂(FVS)算法通过比拟应用于浅水流动计算。最后,本文讨论了浅水流动可压缩流模拟与一般完全气体可压缩流物理特性的异同点,据此提出正确应用这一模拟所应遵循的原则。 相似文献
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A numerical program developed for field application is presented in this paper. We use the generalized Julien and Lan [8] rheological model to simulate debris flows. Due to the derivative discontinuous nature of the constitutive law, flow is
separated into plug region and bottom region (with stress greater than yield stress). The program solves the plug flow layer
solution first, and then corrects the solution with the bottom layer approximation. Numerical scheme with upwind method and
central difference in space and Adam–Bashforth third-order scheme in time is used for both layers. The scheme is tested against
analytical solutions and laboratory experiments with very good results. Application to a field case with more complicated
geometry also achieves good agreement, with error less than 5% compared to field measurements. The final example demonstrates
how this numerical program is used in a preliminary design. 相似文献
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为精细化模拟明渠中水电站瞬变过程引发的涌浪,克服以往低维模型无法细致刻画涌浪的横向和垂向运动、以及高维模型计算效率偏低等问题,基于水位预测矫正法,提出了一维-三维耦合的明渠瞬变流模拟方法。通过潮汐波浪运动、局部溃坝波和顺直明渠瞬变流算例验证了方法的有效性和准确性,模拟结果与渐进理论解、商用软件模拟结果等吻合较好。将该方法应用在实际工程中,计算了葛洲坝水利枢纽瞬变过程中库区的涌浪过程,分析了瞬变过程的最大、最小涌浪波高和涌浪的衰减规律,结果与频谱分析结果吻合较好,说明了本方法能准确模拟实际的明渠瞬变流过程。 相似文献
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Sedimentology of the debris-flow-dominated Warm Spring Canyon alluvial fan, Death Valley, California 总被引:4,自引:0,他引:4
Terence C. Blair 《Sedimentology》1999,46(5):941-965
Facies analysis of widely distributed exposures of the 32·6 km2 and 8·1-km-long Warm Spring Canyon fan, central Death Valley, shows that it has been built principally by debris-flow deposits. These deposits were derived from a mature Panamint Range catchment mostly underlain by Precambrian mudrock, quartzite and dolomite. Stacked, clast-rich and matrix-supported debris-flow lobes of slightly bouldery, muddy, pebble–cobble gravel in beds 20–150 cm thick dominate the fan from apex to toe, accounting for 75–98% of most exposures. Interstratified with the debris flows are less abundant (2–25% of cuts), thinner (5–30 cm) and more discontinuous beds of clast-supported and imbricated, pebble–cobble gravel deposited by overland flows and gully flows. This facies formed by the surficial fine-fraction water winnowing of the debris flows primarily during recessional flood stage of the debris-flow events. Two other facies associations make up a small part of the fan. The incised-channel tract consists of a 250-m-wide clast-supported ribbon of irregularly to thickly bedded, boulder, pebble, cobble gravel nested within debris-flow deposits. This channel fill is oriented generally perpendicular to the Panamint range front. It formed by extensive erosion and winnowing of debris flows deposited within the incised channel, into which all water discharge from the catchment is funnelled. The limited presence of this facies only straddling the present incised channel indicates that this channel overall has maintained a consistent position on the fan except for slight lateral shifts, some caused by strike-slip offset. Fault offset temporarily closed the upper incised channel, causing recessional debris-flow mud to be ponded behind the dam. The other local facies assemblage consists of subrounded to rounded, moderately sorted pebble gravel in low-angle cross-beds that slope both basinwards and fanwards. This gravel was deposited in beachface, backshore and shoreface barrier-spit environments that developed where Lake Manly impinged on the Warm Spring fan during late Pleistocene time. These deposits straddle headcuts into, and were derived from, erosion of the debris-flow deposits. Wave energy sorted finer sediment from the shore zone, concentrated coarser sediment and rounded the coarse to very coarse pebble fraction by selective reworking. 相似文献
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R. Bruce Rains John Shaw Darren B. Sjogren Mandy J. Munro-Stasiuk K. Robert Skoye Robert R. Young Robin T. Thompson 《Quaternary International》2002,90(1)
At some time close to the Last Glacial Maximum (LGM) high-energy, subglacial, Laurentide, meltwater flows eroded a series of discontinuous tunnel channels into the northeastern flanks of the Porcupine Hills and adjacent parts of the high plains near Nanton, Stavely and Claresholm. Discrete channel segments, kilometers long, up to about 1 km wide, and 100 m deep, were carved into Paleocene sandstone and shale of the Porcupine Hills Formation. Floors of Pine, Boneyard, and Crocodile channels all occur at elevations between 1050 and 1175 m a.s.l., and share the characteristic of strongly convex-up long profiles. Intrachannel drainage divides on each channel floor are tens of meters above the water entry and exit points. Formative flows, therefore, must have been pressurized in the subglacial Nye-channels. Prominent scour-holes at some major bends in the channels now host ephemeral ponds or lakes. During the channel erosion, the overlying Laurentide ice surface was probably close to its local LGM maximum elevation of ca. 1400–1500 m a.s.l. Misfit modern streams now drain in opposite directions within the tunnel channels, and there are only minor, local, distal accumulations of sediment derived from the tunnel channel erosion. 相似文献