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81.
Comparing analytical and numerical solution of nonlinear two and three‐dimensional hydrostatic flows
New test cases for frictionless, three‐dimensional hydrostatic flows have been derived from some known analytical solutions of the two‐dimensional shallow water equations. The flow domain is a paraboloid of revolution and the flow is determined by the initial conditions, the nonlinear advective terms, the Coriolis acceleration and by the hydrostatic pressure. Wetting and drying is also included. Some specific properties of the exact solutions are discussed under different hypothesis and relative importance of the forcing terms. These solutions are proposed for testing the stability, the accuracy and the efficiency of numerical models to be used for simulating environmental hydrostatic flows. The computed solutions obtained with a semi‐implicit finite difference—finite volume algorithm on unstructured grid are compared with the corresponding analytical solutions in both two and three space dimension. Excellent agreement are obtained for the velocity and for the resulting water surface elevation. Comparison of the computed inundation area also shows a good agreement with the analytical solution with degrading accuracy observed when the inundation area becomes relatively large and for long simulation time. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
82.
A numerical technique is presented for the approximation of vertical gradient of the non‐hydrostatic pressure arising in the Reynolds‐averaged Navier–Stokes equations for simulating non‐hydrostatic free‐surface flows. It is based on the Keller‐box method that take into account the effect of non‐hydrostatic pressure with a very small number of vertical grid points. As a result, the proposed technique is capable of simulating relatively short wave propagation, where both frequency dispersion and non‐linear effects play an important role, in an accurate and efficient manner. Numerical examples are provided to illustrate this; accurate wave characteristics are already achieved with only two layers. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
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塑性成型弹塑性有限元模拟的静水压力间接计算法 总被引:1,自引:0,他引:1
在单元内偏应力导数精度分析的基础上,了偏应力导数佳点逐层积分建立了修正的静水压力间接算法,将该方法应用于金属成型过程的弹塑性有限元模拟中,较好了解决了大步长时应力计算精度低的问题,提高了计算效率,算例表明,在变形总量和应变步长都较大的情况下。用庐方法计算得到的应力和变形载荷仍具有较好的精度。 相似文献
85.
The shape and gravitational field of ellipsoidal satellites are studied by using the tidal theory. For ellipsoidal satellites, the following conclusions were obtained: Firstly, in the early stage of the satellite formation, strong tidal friction allowed the satellites move in a synchronous orbit and evolve into a triaxial ellipsoidal shape. Because the tidal potential from the associated primary and the centrifugal potential from the satellite spin are nearly fixed at the surface, the early satellites are the viscoelastic celestial body, and their surfaces are nearly in the hydrostatic equilibrium state. The deformation is fixed in the surface of the satellite. By using the related parameters of primary and satellite, the tidal height and the theoretical lengths of three primary radii of the ellipsoidal satellite are calculated. Secondly, the current ellipsoidal satellites nearly maintain their ellipsoidal shape from solidification, which happened a few billion years ago. According to the satellite shape, we estimated the orbital period and spinning angular velocity, and then determined the evolution of the orbit. Lastly, assuming an ellipsoidal satellite originated in the hydrostatic equilibrium state, the surface shape could be determined by tidal, rotation, and additional potentials. However, the shape of the satellite’s geoid differs from its surface shape. The relationship between these shapes is discussed and a formula for the gravitational harmonic coefficients is presented. 相似文献
86.
Electromechanical-induced antiferroelectricben ferroelectric phase transition in PbLa(Zr,Sn,Ti)O3 ceramic 下载免费PDF全文
Antiferroelectric—ferroelectric (AFE—FE) phase transition in ceramic Pb0.97La0.02(Zr0.75Sn0.136Ti0.114)O3 (PLZST) was studied by dielectric spectroscopy as functions of frequency (102—105 Hz) and pressure (0—500 MPa) under a DC electric field. The hydrostatic pressure-dependent remnant polarization and dielectric constant were measured. The results show that remnant polarization of the metastable rhombohedral ferroelectric PLZST poled ceramic decreases sharply and depoles completely at phase transition under hydrostatic pressure. The dielectric constant undergoes an abrupt jump twice during a load and unload cycle under an electric field. The two abrupt jumps correspond to two phase transitions, FE—AFE and AFE—FE. 相似文献
87.
Xingke Duan Yu Zhu Congying Shu Jihui Gao Fengxia Liu Siyi Pan 《Molecules (Basel, Switzerland)》2022,27(12)
Satsuma mandarin peel pectin was extracted by high hydrostatic pressure-assisted citric acid (HHPCP) or hydrochloric acid (HHPHP), and the physiochemical, structural, rheological and emulsifying characteristics were compared to those from conventional citric acid (CCP) and hydrochloric acid (CHP). Results showed that HHP and citric acid could both increase the pectin yield, and HHPCP had the highest yield (18.99%). Structural characterization, including NMR and FTIR, demonstrated that HHPHP showed higher Mw than the other pectins. The viscosity of the pectin treated with HHP was higher than that obtained with the conventional method, with HHPHP exhibiting significantly higher viscosity. Interestingly, all the pectin emulsions showed small particle mean diameters (D4,3 being 0.2–1.3 μm) and extremely good emulsifying stability with centrifugation and 30-day storage assays, all being 100%. Satsuma mandarin peel could become a highly promising pectin source with good emulsifying properties, and HHP-assisted acid could be a more efficient method for pectin extraction. 相似文献
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本文提供了提高现有活塞圆筒式高压装置流体静压强的一种实验方法。成功地制作了锰铜丝压力计,并利用铋丝相变准确地做了压力校正。各箍的应力检测分析和相对位移测量都表明:无论压腔空载或充液时,在0.000 1~3.08 GPa均不显示出同步箍紧作用;上下缸的压强差偏大带来高压暴露的危险。为把流体静压强提高到3.08 GPa以上,建议改进设计;(1)内箍中箍合二为一,外箍分为上下二层,将增加箍力;(2)调整各箍之间接触圆锥面的面积,将有助于同步箍紧;(3)增大密封套圈的无支承面,将减少上下缸压差,有利于安全运行。 相似文献
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