排序方式： 共有43条查询结果，搜索用时 218 毫秒
21.
运用一种移动粒子半隐式法建立无网格水流数值模型,探讨该模型在结构物水动力特性研究中的可能性。在无网格条件下,粒子间的相互作用通过核子函数来表示,并通过建立物理量光滑模型、梯度模型和二阶导数模型来离散控制方程。流体的不可压缩性是通过引入粒子数密度概念实现的。该方法不受流体变形程度和固边界形状的限制,因而具有特定的适应性。运用该模型模拟了水柱倒塌后有无透空块体两种情况下右端直墙上的压力过程。计算结果表明透空块体可使直墙压力减小42%。 相似文献
22.
A primitive equation spectral model has been successfully integrated for five days starting with the initial data of 26 February
1982. The geopotential heights and wind strengths are well predicted up to day 3. The 24-hour accumulated precipitation of
the model reasonably agrees only up to two days, with the observed rainfall under the influence of western disturbance that
prevailed over Afghanistan, Pakistan and north India till 3 March 1982. For one day global integration of the model, the CPU
time requirement in Cyber 170/730 is about one hour. 相似文献
23.
A semi-implicit semi-Lagrangian global nonhydrostatic model and the polar discretization scheme 总被引：2，自引：0，他引：2
YANG XueSheng CHEN JiaBin HU JiangLin CHEN DeHui SHEN XueShun ZHANG HongLiang State Key Laboratory of Severe Weather Chinese Academy of Meteorological Sciences Beijing China State Key Laboratory of Numerical Modeling for Atmospheric Sciences Geophysical Fluid Dynamics Institute of Atmospheric Physics Beijing China 《中国科学D辑(英文版)》2007,50(12):1885-1891
The Global/Regional Assimilation and PrEdiction System(GRAPES) is a newly developed global non-hydrostatic numerical prediction model,which will become the next generation medium-range opera-tional model at China Meteorological Administration(CMA).The dynamic framework of GRAPES is featuring with fully compressible equations,nonhydrostatic or hydrostatic optionally,two-level time semi-Lagrangian and semi-implicit time integration,Charney-Phillips vertical staggering,and complex three-dimensional pre-conditioned Helmholtz solver,etc.Concerning the singularity of horizontal momentum equations at the poles,the polar discretization schemes are described,which include adoption of Arakawa C horizontal grid with ν at poles,incorporation of polar filtering to maintain the computational stability,the correction to Helmholtz equation near the poles,as well as the treatment of semi-Lagrangian interpolation to improve the departure point accuracy,etc.The balanced flow tests validate the rationality of the treatment of semi-Lagrangian departure point calculation and the polar discretization during long time integration.Held and Suarez tests show that the conservation proper-ties of GRAPES model are quite good. 相似文献
24.
将两时间层稳定外插方案(Stable Extrapolation Two-Time-Level Scheme,SETTLS)引入GRAPES区域模式,并将其用于上游点和非线性项的时间外插计算。对线性项采用二阶精度的非中央权重时间平均,并取等温参考大气的温度大于实际大气平均温度,以保证半隐式积分方案的稳定性。原GRAPES时间积分方案对线性项做一阶非中央权重时间平均,对参考大气的选择并无限制,而为保证稳定性,须取较大的非中央权重系数,但非中央权重系数会对低波数波动产生较强的衰减作用。理想试验结果表明,相比原GRAPES半隐式半拉格朗日(SISL)时间积分方案,新SISL时间积分方案计算稳定且对波动的衰减作用较弱。 相似文献
25.
Semi-implicit algorithms are popularly used to deal with the gravitational
term in numerical models. In this paper, we adopt the method of
characteristics to compute the solutions for gravity waves on a sphere
directly using a semi-Lagrangian advection scheme instead of the
semi-implicit method in a shallow water model, to avoid expensive matrix
inversions. Adoption of the semi-Lagrangian scheme renders the numerical
model always stable for any Courant number, and which saves CPU time. To
illustrate the efficiency of the characteristic constrained interpolation
profile (CIP) method, some numerical results are shown for idealized test
cases on a sphere in the Yin-Yang grid system. 相似文献
26.
XUE Jishan 《大气科学进展》2004,21(3):467-474
The recent progresses in the research and development of (NWP) in China are reviewed in this paper. The most impressive achievements are the development of direct assimilation of satellite irradiances with a 3DVAR (three-dimentional variational) data assimilation system and a non-hydrostatic model with a semi-Lagrangian semi-implicit scheme. Progresses have also been made in model physics and model application to precipitation and environmental forecasts. Some scientific issues of great importance for further development are discussed. 相似文献
27.
A flux-form semi-Lagrangian transport scheme(FFSL) was implemented in a spectral atmospheric GCM developed and used at IAP/LASG.Idealized numerical experiments show that the scheme is good at shape preserving with less dissipation and dispersion,in comparison with other conventional schemes.Importantly,FFSL can automatically maintain the positive definition of the transported tracers,which was an underlying problem in the previous spectral composite method(SCM).To comprehensively investigate the impact of FFSL on GCM results,we conducted sensitive experiments.Three main improvements resulted:first,rainfall simulation in both distribution and intensity was notably improved,which led to an improvement in precipitation frequency.Second,the dry bias in the lower troposphere was significantly reduced compared with SCM simulations.Third,according to the Taylor diagram,the FFSL scheme yields simulations that are superior to those using the SCM:a higher correlation between model output and observation data was achieved with the FFSL scheme,especially for humidity in lower troposphere.However,the moist bias in the middle and upper troposphere was more pronounced with the FFSL scheme.This bias led to an over-simulation of precipitable water in comparison with reanalysis data.Possible explanations,as well as solutions,are discussed herein. 相似文献
28.
In the present study,a semi-implicit finite difference model for non-bydrostatic,free-surface flows is analyzed and discussed.The governing equations are the three-dimensional free-surface Reynolds-averaged Navier-Stokes equations defined on a general,irregular domain of arbitrary scale.At outflow,a combination of a sponge layer technique and a radiation boundary condition is applied to minimize wave reflection.The equations are solved with the fractional step method where the hydrostatic pressure component is determined first,while the non-hydrostatic component of the pressure is computed from the pressure Poisson equation in which the coefficient matrix is positive definite and symmetric.The advectiou and horizontal viscosity terms are discretized by use of a semi-Lagrangian approach.The resulting model is computationally efficient and unrestricted to the CFL condition.The developed model is verified against analytical solutions and experimental data,with excellent agreement. 相似文献
29.
完全非内插半拉格朗日格式在一维
Burgers方程及二维浅水波方程上的应用 总被引：3，自引：2，他引：1
在作者过去提出的完全非内插半拉格朗日格式的基础上,针对半拉格朗日格式由于内插带来预报场人为的光滑性问题,进一步发展了这种计算格式,证明了此格式的计算稳定性。为检验这种新的计算格式的性能,在一维和二维问题上进行了应用。在一维问题中采用了一维无粘Burgers方程（方程中有突变点）;二维问题采用了浅水波方程,同时将这些计算结果与Ritchie方案及欧拉方案或一般半拉格朗日内插方案的计算结果进行了比较,发现新格式消除了内插和预报场的人为光滑,并且计算精度有一定程度的提高,这为以后将此格式推广到全球谱模式打下了基础。 相似文献
30.
中国数值天气预报的自主创新发展 总被引：1，自引：0，他引：1
数值天气预报是天气预报业务和防灾、减灾的核心科技。中国数值天气预报研究和业务应用一直受到高度重视,在理论、方法和数值模式研究方面取得了有广泛国际影响的研究成果。在回顾新中国数值天气预报自主创新研究成果的基础上,重点对GRAPES（Global Regional Assimilation and PrEdiction System）半隐式半拉格朗日格点模式与物理过程的研发和业务应用的状况以及所取得的重要科学进展进行了综述。近年来,通过自主研发建立了中国数值天气预报业务体系—GRAPES体系。首次以自主技术实现了从区域3—10 km到全球25—50 km分辨率的确定性预报和集合预报系统,并在模式动力框架、四维变分同化和卫星资料同化技术等方面有所突破,建立了大气化学数值天气预报、台风数值预报和海浪预报等系统。自主研发的数值天气预报体系的建立是长期坚持既定科学技术方向以及研究和业务紧密结合、经验不断积累的结果,是中国自主发展数值天气预报技术的重要起点。 相似文献