Lagrangian随机轨道方法在三维非光滑贴体网格内的应用

Application of Largrangian Stochastic Trajectory Mathod in 3-D Non-Smooth Body-Fitted Meshes

采用Lagrangian随机轨道方法,基于流场计算中曲线贴体网格计算四角切圆炉内颗粒运动,提出了三维贴体网格中追踪颗粒轨迹的新方法,包括:判断颗粒与任意形状六面体单元相对位置关系,选择最优的颗粒飞出单元体时的积分步长,以及校验并确保粒子进入新单元的处理方法等。解决了局部非光滑六面体网格中,因离散的面元向量交线不连续而对判断粒子相对位置造成的困难,同时可高效地处理复杂的内外边界条件。应用本方法计算670t/h冷态模化炉膛,并将20μm玻璃珠在燃烧器区和炉膛出口区的速度分布与3D-PDA实验测量结果相对比,两者较好吻合。说明本方法可高效可靠地应用于采用贴体网格的大型复杂工程问题计算。

Particle dispersion in tangentially-fired boiler is simulated with Lagrangian stochastic trajectory approach, based on the Eulerian body-fitted meshes of gas field calculation. A particle tracking method for 3-D non-smooth curvilinear grid is developed. The method consists of following steps as: to locate a particle relative to an arbitrary hexahedral control volume; to optimize the integral step after which particle leaves the current cell; and to checkout and guarantee that the particle enters into the next cell. It is found that minute aperture exists between adjacent discretized cell surfaces, especially for the highly non-smooth and skew 3-D meshes. Special treatment is empolyed to cope with the difficuly in locating the particle trapped into such aperture. The method is also advantageous in that complex inner and outer boundary conditions can be treated conveniently. The comparison is made between the computational and experimental results for a 670t/h boiler furnace. The general good agreement approves that the methodology is valuable for numerical study of gas-soild character in complex engineering problem involving the body-fitted meshes. Figs 7 and refs 6.