冷流吸积被成功引入星系形成的半解析模型模型，很好地揭示了星系、特别是高红移星系的基本观测事实。冷流吸积的数值模拟研究近年来也取得显著进展，但在核心物理过程仍有很多尚未解决的问题。本项目旨在基于星系形成的冷/热双模式吸积模型的基本框架，借助高精度N体-流体动力学数值模拟，细致研究气体在暗物质晕周围的分布以及在暗物质晕中的吸积过程，探讨 (1) 暗物质晕连接的纤维结构中气体的分布，以及热力学和动力学性质；（2）激波加热的热气体泡和冷流的相互作用，以及可能破坏冷流吸积的热传导、湍流和流体不稳定性；(3) 高红移星星系盘大尺度湍流、引力不稳定性以及气体团块的产生和分裂。期待通过该项研究，可以加深对星系形成理论中的双吸积模式，高红移星系盘的恒星形成和动力学演化的认识，同时得到的分析拟合结果可以给星系形成的半解析模型提供基本的物理输入.

Cold stream accretion had been successfully incorporated into the semi-analytical model of galaxy formation, and made excellently explanations of observational evidences of galaxies, especially at high redshifts. The significant progresses have been also made in the numerical simulation of cold flows, but there are still many unsolved problems to be addressed by further analytical, numerical and observational approaches. Using high resolution hybrid N-body/hydrodynamic numerical simulation, this project is aimed to explore many physical aspects of the bimodal gas model. The key problems to be addressed include (1) gas distribution around the filamentary structure linking the dark matter halos, and moreover thermal kinematic and dynamical states;(2) interaction between shock-heated hot bubbles and cold stream, and the possible destructive mechanism for cold streams including thermal conduction, turbulence and various hydrodynamic instabilities. (3) the large scale turbulence stimulated in the early galaxy disks, disk instability, condensation and fragmentation of gas clumps. The numerical approach made in this project will be helpful to advance our understanding of the bimodal accretion model in dark matter halos, star formation in the high-redshift galaxy disks and its dynamical evolution. It is also expected that the analytical fitting results extracted from out simulations will provide basic and valuable physical inputs for the semi-analytical model of galaxy formation.