Multispecies Coevolution Particle Swarm Optimization Based on Previous Search History

A hybrid coevolution particle swarm optimization algorithm with dynamic multispecies strategy based on K-means clustering and nonrevisit strategy based on Binary Space Partitioning fitness tree (called MCPSO-PSH) is proposed. Previous search history memorized into the Binary Space Partitioning fitness tree can effectively restrain the individuals’ revisit phenomenon. The whole population is partitioned into several subspecies and cooperative coevolution is realized by an information communication mechanism between subspecies, which can enhance the global search ability of particles and avoid premature convergence to local optimum. To demonstrate the power of the method, comparisons between the proposed algorithm and state-of-the-art algorithms are grouped into two categories: 10 basic benchmark functions (10-dimensional and 30-dimensional), 10 CEC2005 benchmark functions (30-dimensional), and a real-world problem (multilevel image segmentation problems). Experimental results show that MCPSO-PSH displays a competitive performance compared to the other swarm-based or evolutionary algorithms in terms of solution accuracy and statistical tests

Parallel adaptive mesh refinement within the PUMAA3D Project

To enable the solution of large-scale applications on distributed memory architectures, we are designing and implementing parallel algorithms for the fundamental tasks of unstructured mesh computation. In this paper, we discuss efficient algorithms developed for two of these tasks: parallel adaptive mesh refinement and mesh partitioning. The algorithms are discussed in the context of two-dimensional finite element solution on triangular meshes, but are suitable for use with a variety of element types and with h- or p-refinement. Results demonstrating the scalability and efficiency of the refinement algorithm and the quality of the mesh partitioning are presented for several test problems on the Intel DELTA

DYNAMIC MESHING AROUND FLUID-FLUID INTERFACES WITH APPLICATIONS TO DROPLET TRACKING IN CONTRACTION GEOMETRIES

The dynamic meshing procedure in an open source three-dimensional solver for calculating immiscible two-phase flow is modified to allow for simulations in two-dimensional planar and axisymmetric geometries. Specifically, the dynamic mesh refinement procedure, which functions only for the partitioning of three-dimensional hexahedral cells, is modified for the partitioning of cells in two-dimensional planar and axisymmetric flow simulations. Moreover, the procedure is modified to allow for computing the deformation and breakup of drops or bubbles that are very small relative to the mesh of the flow domain. This is necessary to avoid mass loss when tracking small drops or bubbles through flow fields. Three test cases are used to validate the modifications: the deformation and breakup of a two-dimensional drop in a linear shear field; the formation and detachment of drops in a two-dimensional micro T-junction channel; and an axisymmetric bubble rising from a pore into a static liquid. The tests show that the modified code performs very well, giving accurate results for much less computational time when compared to corresponding simulations without dynamic meshing. The modified code is then applied to study drop breakup conditions inside a spray nozzle when an emulsion is sprayed to produce a powder. This is done by tracking droplets of various sizes through the flow field within the nozzle and determining conditions under which they break up. The particular interest is in determining the largest drop sizes for which breakup does not occur. The effects of viscosity ratio, capillary number, shear rate, and fluid rheology on the critical drop sizes are determined. Although the code modifications performed for this research were implemented for dynamic mesh refinement of cells close to fluid-fluid interfaces, they may be adapted to other regions in the domain and for other types of flow problems