基于异构GPU集群的并行分布式编程解决方案

由于超强的计算能力、高速访存带宽、支持大规模数据级并行程序设计等特点,GPU已经成为超级计算机和高性能计算(HPC)集群的主流加速器。随着处理单元的发展和集群节点的拓展,GPU集群不仅在节点层面呈现异构化,节点内也趋于异构化,大大提高了在GPU集群中编程的复杂度。主流GPU异构集群系统大多采用针对GPU的异构计算编程模型与面向分布式内存的消息传递模型的简单结合方式,这种方式使得GPU集群程序设计缺乏确定的准则,往往是低效而且易错的。为了提高在GPU集群中编程的效率,降低编程复杂度,以及实现平台无关性,提出一套异构GPU集群的并行分布式编程的解决方案。该方案通过采用扩展语言方法提出了编程框架DISPAR,并实现了预处理器系统StreamCC。实验证明了其可行性。     

Numerical study on laminar burning velocity and NO formation of premixed methane–hydrogen–air flames

Numerical study on laminar burning velocity and NO formation of the premixed methane–hydrogen–air flames was conducted at room temperature and atmospheric pressure. The unstretched laminar burning velocity, adiabatic flame temperature, and radical mole fractions of H, OH and NO are obtained at various equivalence ratios and hydrogen fractions. The results show that the unstretched laminar burning velocity is increased with the increase of hydrogen fraction. Methane-dominated combustion is presented when hydrogen fraction is less than 40%, where laminar burning velocity is slightly increased with the increase of hydrogen addition. When hydrogen fraction is larger than 40%, laminar burning velocity is exponentially increased with the increase of hydrogen fraction. A strong correlation exists between burning velocity and maximum radical concentration of H + OH radicals in the reaction zone of premixed flames. High burning velocity corresponds to high radical concentration in the reaction zone. With the increase of hydrogen fraction, the overall activation energy of methane–hydrogen mixture is decreased, and the inner layer temperature and Zeldovich number are also decreased. All these factors contribute to the enhancement of combustion as hydrogen is added. The curve of NO versus equivalence ratio shows two peaks, where they occur at the stoichiometric mixture due to Zeldovich thermal-NO mechanism and at the rich mixture with equivalence ratio of 1.3 due to the Fenimore prompt-NO mechanism. In the stoichiometric flames, hydrogen addition has little influence on NO formation, while in rich flames, NO concentration is significantly decreased. Different NO formation responses to stretched and unstretched flames by hydrogen addition are discussed.