Grid‐independent depth‐averaged simulations with a collocated unstructured finite volume scheme

In this article, the depth‐averaged transport equations are written in a new way so that it is possible to solve the transport equations for very small water depths. Variables are interpolated into the cell face with two different schemes and, the schemes are compared in terms of computational cost and accuracy. The bed source terms are computed using two different assumptions. The effect of these assumptions on numerical simulations is then investigated. Solutions of transport equations on different types of unstructured triangular grids are compared and, an appropriate choice of grid is suggested. Copyright © 2011 John Wiley & Sons, Ltd.     

4D variational data assimilation for locally nested models: Complementary theoretical aspects and application to a 2D shallow water model

We consider the application of a four‐dimensional variational data assimilation method to a numerical model, which employs local mesh refinement to improve its solution. We focus on structured meshes where a high‐resolution grid is embedded in a coarser resolution one, which covers the entire domain. The formulation of the nested variational data assimilation algorithm was derived in a preliminary work (Int. J. Numer. Meth. Fluids 2008; under review). We are interested here in complementary theoretical aspects. We present first a model for the multi‐grid background error covariance matrix. Then, we propose a variant of our algorithms based on the addition of control variables in the inter‐grid transfers in order to allow for a reduction of the errors linked to the interactions between the grids. These formulations are illustrated and discussed in the test case experiment of a 2D shallow water model. Copyright © 2010 John Wiley & Sons, Ltd.     

Development of a multi‐scale ocean model by using particle Laplacian method for anisotropic mass transfer

The direct injection of CO₂ into the deep ocean is one of the feasible ways for the mitigation of the global warming, although there is a concern about its environmental impact near the injection point. To minimize its biological impact, it is necessary to make CO₂ disperse as quickly as possible, and it is said that injection with a pipe towed by a moving ship is effective for this purpose. Because the injection ship moves over a spatial scale of O(10²km), a mesoscale model is necessary to analyse the dispersion of CO₂. At the same time, since it is important to investigate high CO₂ concentration near the injection point, a small‐scale model is also required. Therefore, in this study, a numerical model was developed to analyse CO₂ dispersion in the deep ocean by using a fixed mesoscale and a moving small‐scale grid systems, the latter of which is nested and moves in the former along the trajectory of the moving ship. To overcome the artificial diffusion of mass concentration at the interface of the two different grid systems and to keep its spatial accuracy almost the same as that in the small‐scale, a particle Laplacian method was adopted and newly modified for anisotropic diffusion in the ocean. Copyright © 2010 John Wiley & Sons, Ltd.     

Numerical simulation of 2D lid‐driven cavity flow with CLEARER algorithm on extremely highly skewed grids at high Reynolds numbers

It is crucial to deal with the grid non‐orthogonality effectively in solving the flow in complex geometries, especially at high Reynolds numbers. In this study, the newly proposed Coupled and Linked Equations Algorithm Revised‐ER (CLEARER) algorithm is adopted to solve this problem successfully. In CLEARER algorithm the second relaxation factor is introduced in constructing the contravariant interface velocities, by setting it to a low value. CLEARER algorithm can overcome the severe grid non‐orthogonality and non‐linearity of equations effectively. After the numerical results with CLEARER are validated with the benchmark solutions, this algorithm is used to solve the lid‐driven flow in inclined cavity with inclination angles varying from 10 to 170^°, and Reynolds numbers varying from 5000 to 15 000. The streamlines and the centerline velocity distributions are provided in detail for all cases, which may offer some guidance for the study in this area. Copyright © 2010 John Wiley & Sons, Ltd.     

Modified form of binary and ternary 3-point subdivision schemes

Binary 3-point scheme, developed by Hormann and Sabin [Hormann, K. and Sabin, Malcolm A., 2008, A family of subdivision schemes with cubic precision, Computer Aided Geometric Design, 25, 41-52], has been modified by introducing a tension parameter which generates a family of C¹ limiting curves for certain range of tension parameter. Ternary 3-point scheme, introduced by Siddiqi and Rehan [Siddiqi, Shahid S. and Rehan, K., 2009, A ternary three point scheme for curve designing, International Journal of Computer Mathematics, In Press, DOI: 10.1080/00207160802428220], has also been modified by introducing a tension parameter which generates family of C¹ and C² limiting curves for certain range of tension parameter. Laurent polynomial method is used to investigate the continuity of the subdivision schemes. The performance of modified schemes has been demonstrated by considering different examples along with its comparison with the established subdivision schemes.     

Novel procedure for complete in-plane composite characterization using a single T-shaped specimen

This paper deals with the direct identification of the in-plane elastic properties of orthotropic composite plates from heterogeneous strain fields. The shape of the tested specimen is that of a T subjected to a complex stress state. As a result, the entire set of unknown parameters is directly involved in the strain and displacement responses of the sample. No exact analytical solution is available for such a geometry, and a specific strategy is used to identify the different stiffness components from the whole-field displacements measured over the tested specimen with a suitable optical method. The paper focuses mainly on the experimental aspects of the procedure, and an example of mechanical characterization of a fabric-reinforced composite plate is given.     

土地资源多级网格平台高效处理机制研究

为实现海量土地资源数据多级网格管理和高效处理,设计了基于网格服务架构的土地资源多级网格化管理平台LR-MGSP（Land Resource Multi-Grid Service Platform）,从网格任务分解、空间信息服务缓存和增量统计等方面探讨了提高平台处理性能的策略和方法.原型平台与非网格化的土地资源管理系统的性能对比测试结果表明,LR-MGSP达到了预期的目标,能够满足海量土地资源数据高效管理和处理的需求,也为其他行业开展跨机构协同处理海量空间数据工作提供了借鉴.     

DPW系列会议述评与思考

验证与确认一直是困扰计算流体力学(computational fluid dynamics, CFD)发展的关键问题.由AIAA组织的阻力预测会议(Drag Prediction Workshop, DPW)是CFD验证与确认方面的一项重要学术活动, 其宗旨是提供一个开放、公正的平台, 考核CFD方法、程序和模型的效能, 评价CFD作为应用空气动力学工具的现状.本文综述了4次DPW系列会议, 对会议的结果和结论进行了详细述评, 对其反映的一些问题进行了深入探讨. 最后根据多年对DPW的关注和研究, 提出了一些由DPW引发的思考.      

Implementation of a novel two-attractor grid multi-scroll chaotic system

This paper proposed a method of generating two attractors in a novel grid multi-scroll chaotic system.Based on a newly generated three-dimensional system,a two-attractor grid multi-scroll attractor system can be generated by adding two triangular waves and a sign function.Some basic dynamical properties,such as equilibrium points,bifurcations,and phase diagrams,were studied.Furthermore,the system was experimentally confirmed by an electronic circuit.The circuit simulation results and numerical simulation results verified the feasibility of this method.