The core of smoothed particle hydrodynamics （SPH） is the nearest neighbor search subroutine. In this paper, a nearest neighbor search algorithm which is based on multiple background grids and support variable smooth...The core of smoothed particle hydrodynamics （SPH） is the nearest neighbor search subroutine. In this paper, a nearest neighbor search algorithm which is based on multiple background grids and support variable smooth length is introduced. Through tested on lid driven cavity flow, it is clear that this method can provide high accuracy. Analysis and experiments have been made on its parallelism, and the results show that this method has better parallelism and with adding processors its accuracy become higher, thus it achieves that efficiency grows in pace with accuracy.展开更多
This paper presents an automatic mesh generation procedure on a 2D domain based on a regular background grid. The idea is to devise a robust mesh generation scheme with equal emphasis on quality and efficiency. Instea...This paper presents an automatic mesh generation procedure on a 2D domain based on a regular background grid. The idea is to devise a robust mesh generation scheme with equal emphasis on quality and efficiency. Instead of using a traditional regular rectangular grid, a mesh of equilateral triangles is employed to ensure triangular element of the best quality will be preserved in the interior of the domain. As for the boundary, it is to be generated by a node/segment insertion process. Nodes are inserted into the background mesh one by one following the sequence of the domain boundary. The local structure of the mesh is modified based on the Delaunay criterion with the introduction of each node. Those boundary segments, which are not produced in the phase of node insertion, will be recovered through a systematic element swap process. Two theorems will be presented and proved to set up the theoretical basic of the boundary recovery part. Examples will be presented to demonstrate the robustness and the quality of the mesh generated by the proposed technique.展开更多
以并网点电压谐波为反馈量的有源阻尼控制(voltage-harmonic-based active damping,VHBAD)可提高变流器对弱电网的适应能力,但会削弱系统对背景谐波电压扰动的抑制能力,影响并网电流质量。首先,建立了弱电网下并网变流器的数学模型,分...以并网点电压谐波为反馈量的有源阻尼控制(voltage-harmonic-based active damping,VHBAD)可提高变流器对弱电网的适应能力,但会削弱系统对背景谐波电压扰动的抑制能力,影响并网电流质量。首先,建立了弱电网下并网变流器的数学模型,分析了电网等值电感对系统稳定性的影响;进而提出一种基于并网电流谐波反馈的有源阻尼策略(current-harmonic-based active damping,CHBAD),该策略将有源阻尼支路的作用点由参考信号移至调节器输出端,可在提高变流器弱电网适应能力的同时兼顾到并网电流质量。最后,通过Plecs仿真软件搭建仿真模型,时域仿真结果与理论分析一致,验证了该策略的有效性。展开更多
基金Project supported by the National Natural Science Foundation of China(Grant No.11002086)the Shanghai Leading Academic Discipline Project(Grant No.J50103)
文摘The core of smoothed particle hydrodynamics （SPH） is the nearest neighbor search subroutine. In this paper, a nearest neighbor search algorithm which is based on multiple background grids and support variable smooth length is introduced. Through tested on lid driven cavity flow, it is clear that this method can provide high accuracy. Analysis and experiments have been made on its parallelism, and the results show that this method has better parallelism and with adding processors its accuracy become higher, thus it achieves that efficiency grows in pace with accuracy.
文摘This paper presents an automatic mesh generation procedure on a 2D domain based on a regular background grid. The idea is to devise a robust mesh generation scheme with equal emphasis on quality and efficiency. Instead of using a traditional regular rectangular grid, a mesh of equilateral triangles is employed to ensure triangular element of the best quality will be preserved in the interior of the domain. As for the boundary, it is to be generated by a node/segment insertion process. Nodes are inserted into the background mesh one by one following the sequence of the domain boundary. The local structure of the mesh is modified based on the Delaunay criterion with the introduction of each node. Those boundary segments, which are not produced in the phase of node insertion, will be recovered through a systematic element swap process. Two theorems will be presented and proved to set up the theoretical basic of the boundary recovery part. Examples will be presented to demonstrate the robustness and the quality of the mesh generated by the proposed technique.
文摘为了提高复杂组合曲面四边形网格生成的鲁棒性和边界单元质量,提出一种边界优先的Delaunay-层推进网格生成方法.首先在剖分域内粗的约束Delaunay背景网格的辅助下,以物理域的位置偏差为引导,在参数域中迭代计算边界点的法矢量;然后结合层推进策略,在几何特征附近生成各向异性或各向同性正交网格;最后使用Coring技术加速内部网格的生成并进行单元合并,得到四边形为主的网格.若干复杂平面区域和组合曲面模型的剖分结果表明,所提方法可生成等角扭曲度和纵横比优于主流商业软件的网格;在12个线程的PC平台上,使用OpenMP并行剖分包含21772张曲面的引擎模型只用了38.68 s.
文摘以并网点电压谐波为反馈量的有源阻尼控制(voltage-harmonic-based active damping,VHBAD)可提高变流器对弱电网的适应能力,但会削弱系统对背景谐波电压扰动的抑制能力,影响并网电流质量。首先,建立了弱电网下并网变流器的数学模型,分析了电网等值电感对系统稳定性的影响;进而提出一种基于并网电流谐波反馈的有源阻尼策略(current-harmonic-based active damping,CHBAD),该策略将有源阻尼支路的作用点由参考信号移至调节器输出端,可在提高变流器弱电网适应能力的同时兼顾到并网电流质量。最后,通过Plecs仿真软件搭建仿真模型,时域仿真结果与理论分析一致,验证了该策略的有效性。
