Fast advancing layer method for viscous mesh generation

An efficient Advancing Layer Method(ALM)is presented to create semi-structured prisms on viscous walls,in which a procedure that checks possible front intersections is essential to its efficiency.This paper develops various novel schemes to improve the algorithm’s efficiency precisely while not sacrificing its robustness and the resulting mesh quality.First,it employs a set of new techniques,and data structures are developed to improve the efficiency of the frontcheck procedure.Then,within each octant,a new filter is developed to reduce the intersection computations in the searching process.In addition,data structures are well designed to store the contiguously accessed data in each computing-intensive loop in a contiguous space for a potentially better cache hit ratio.We built a geometry model library formed by examples of industrial complexity to demonstrate the practicability of the algorithm.All the efforts mentioned above enable us to reduce the percentage of computing time taken by intersection check to an acceptable level(approximately 26%),which make it no longer be the most time-consuming part.

Hybrid grid generation for viscous flow simulations in complex geometries

In this paper,we present a hybrid grid generation approach for viscous flow simulations by marching a surface triangulation on viscous walls along certain directions.Focuses are on the computing strategies used to determine the marching directions and distances since these strategies determine the quality of the resulting elements and the reliability of the meshing procedure to a large extent.With respect to marching directions,three strategies featured with different levels of efficiencies and robustness performance are combined to compute the initial normals at front nodes to balance the trade-off between efficiency and robustness.A novel weighted strategy is used in the normal smoothing scheme,which evidently reduces the possibility of early stop of front generation at complex corners.With respect to marching distances,the distance settings at concave and/or convex corners are locally adjusted to smooth the front shape at first;a further adjustment is then conducted for front nodes in the neighbourhood of gaps between opposite viscous boundaries.These efforts,plus other special treatments such as multi-normal generation and fast detection of local/global intersection,as a whole enable the setup of a hybrid mesher that could generate qualitied viscous grids for geometries with industry-level complexities.

A new multi-level algorithm for balanced partition problem on large scale directed graphs

Graph partition is a classical combinatorial optimization and graph theory problem,and it has a lot of applications,such as scientific computing,VLSI design and clustering etc.In this paper,we study the partition problem on large scale directed graphs under a new objective function,a new instance of graph partition problem.We firstly propose the modeling of this problem,then design an algorithm based on multi-level strategy and recursive partition method,and finally do a lot of simulation experiments.The experimental results verify the stability of our algorithm and show that our algorithm has the same good performance as METIS.In addition,our algorithm is better than METIS on unbalanced ratio.