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201.
C.Z. Wang 《Ocean Engineering》2010,37(4):400-417
Fully nonlinear interactions between water waves and vertical cylinder arrays in a numerical tank are studied based on a finite element method (FEM). The three-dimensional (3D) mesh is constructed through an extension of a 2D Delaunay surface grid along the vertical line. The velocity potential is obtained by solving a linear matrix system of FEM, and a difference scheme is then used to calculate the velocity on the free surface to track its movement. Waves and hydrodynamic forces are obtained for both bottom mounted and truncated cylinders. The simulations have provided many results to show the nature of mutual interference between cylinders in arrays and its effects on waves and forces at the nearly trapped mode frequency. The effect of the tank wall on waves and forces has been investigated, and the nonlinear features of waves and forces have also been discussed. 相似文献
202.
The flow mechanism of contractive and dilative motion was numerically investigated to obtain a propulsive force in a highly viscous fluid. The computing program for the analysis of complicated motions was numerically developed with a cell-centered, unstructured grid scheme. The developed program was validated by the well-known equation of an oscillating plane below viscous fluid for an unsteady problem, which is known as Stokes’ second problem. Validation has continued through comparison with the experimental results.In this case, sinusoidal motion was applied to the validation, instead of trochoidal motion, because it was very difficult to actually simulate trochoidal motion in this experiment. Finally, the validation and comparison with the nodal-point scheme was accomplished by Stokes’ problem, which is the famous problem at a low Reynolds number. The validated code was applied to contractive and dilative motion in a narrow tube, whose motion was embodied by trochoidal movement. In a highly viscous fluid, such as a very sticky honey or a swamp, the computed results show that a viscous force can be used for propulsion instead of a dynamic force.From the present results, it was found that a propulsive force can be obtained by contractive and dilative motion at a low Reynolds number, which can be applied to the propulsion of micro-robots in a highly viscous fluid such as a blood vessel or a swamp. This research could also be considered fundamental research for the propulsion of micro-hydro robots, which are expected to be actively studied in the future in accord with further development of nanotechnology. 相似文献
203.
真实感虚拟人脸合成技术一直是计算机图形学一个重要而富有挑战性的课题。其中,人脸建模是第一步,也是至关重要的一步,而人脸模型特定化技术是其中的关键技术。在研究和实验的基础上,提出了一种基于改进散乱数据插值算法的人脸模型特定化技术。实践证明,该技术可取得较好的效果。 相似文献
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206.
高强度聚乙烯菱形网目经编网片的力学性能初步研究 总被引:7,自引:0,他引:7
给网箱设计与渔用材料的合理选配提供参考,初步研究了渔用高强度聚乙烯菱形网目经编网片(简称HSPE经编网片)的力学性能。研究结果表明,(1)在同等条件下,36股HSPE经编网片网目强力、网片纵向断裂强力分别比36股普通聚乙烯菱形网目经编网片(简称PE经编网片)增加了48.9%,11.6%,而前者的网片纵向断裂伸长率比后者减少了29.4%;(2)在相同网目长度条件下,36股HSPE经编网片网目强力、网片纵向断裂强力分别比42股锦纶菱形网目经编网片(简称PA经编网片)增加了27.2%,37.9%,而前者的网片纵向断裂伸长率比后者减少了33.6%;(3)36股HSPE经编网片较36股PE经编网片和42股PA经编网片具有性能价格比优势;HSPE经编网片在网箱养殖等渔业生产中推广应用上具有可行性。 相似文献
207.
208.
自适应网格与均匀网格在数值模拟中的对比研究 总被引:1,自引:0,他引:1
采用自适应网格和均匀网格两种模式,对1996年8月3—4日发生在山西、河北、河南三省交界地区的暴雨个例进行模拟和对比研究。结果表明,自适应网格模式对所关心的天气系统及其降水的模拟精度高于均匀网格,特别是对降水、风场、急流、涡度场的模拟精度改善显著。这说明自适应网格模拟的中尺度系统特征更清晰。 相似文献
209.
Gervásio Annes Degrazia Umberto Rizza Franciano Scremin Puhales Antônio Gledson Goulart Jonas Carvalho Guilherme Sausen Welter Edson Pereira Marques Filho 《Boundary-Layer Meteorology》2009,131(2):277-292
A variable vertical mesh spacing for large-eddy simulation (LES) models in a convective boundary layer (CBL) is proposed.
The argument is based on the fact that in the vertical direction the turbulence near the surface in a CBL is inhomogeneous
and therefore the subfilter-scale effects depend on the relative location between the spectral peak of the vertical velocity
and the filter cut-off wavelength. From the physical point of view, this lack of homogeneity makes the vertical mesh spacing
the principal length scale and, as a consequence, the LES filter cut-off wavenumber is expressed in terms of this characteristic
length scale. Assuming that the inertial subrange initial frequency is equal to the LES filter cut-off frequency and employing
fitting expressions that describe the observed convective turbulent energy one-dimensional spectra, it is feasible to derive
a relation to calculate the variable vertical mesh spacing. The incorporation of this variable vertical grid within a LES
model shows that both the mean quantities (and their gradients) and the turbulent statistics quantities are well described
near to the ground level, where the LES predictions are known to be a challenging task. 相似文献
210.
潜孔锤钻头冲击钻进的过程是一个高度非线性、大变形、破坏的过程。对这一复杂过程的研究,目前主要是利用实验方法。应用非线性显式三维有限元求解程序LS—DYNA3D,采用与岩石性质较接近的混凝土模型,对潜孔锤钻头硬质合金球齿冲击混凝土板的过程进行了仿真计算,讨论了不同网格尺寸对冲击力、冲击速度及破碎坑深度的影响等。 相似文献