不同突扩比下空间淹没水跃的水力计算

突扩能够使局部范围内水流紊动剧烈,可以作为水利工程中消能工的一种重要方式．为了探讨突扩比对下游流体水力特性的影响规律,基于RNG k-ε紊流模型和PISO压力-速度耦合算法,采用非均匀结构网格技术,建立了三维紊流数学模型,对突扩比分别为1000,0833,0.667,0500,0333等5种空间水跃进行了多工况数值模拟,结合试验数据,计算结果量纲一化,讨论了不同突扩比大小对下游水力性能的影响,并分析了下游流速、紊动能及消能率等随突扩比的变化规律．数值计算结果表明:突扩比对下游流速、紊动能及消能率影响显著,突扩比越小,下游流速变化越显著,主流在空间内扩散愈迅速,流态转变越明显;随着突扩比的减小,紊动应力愈小,紊动能量愈小,而消能率越大;突扩水跃较典型水跃消能效果明显增强,当突扩比小于0500时,消能率增大不再显著．

Computation of spatial submerged hydraulic jump with different abrupt expansion ratios

 Since the abrupt expansion can enlarge turbulence intensity level in a local range of water flow, it can be utilized as kind of important energy dissipaters. In order to study effects of abrupt expansion ratio on hydraulic characteristics of down stream flow, spatial submerged hydraulic jumps with the abrupt expansion ratios of 1.000, 0.833, 0.667, 0.500, 0.333 are simulated numerically based on a non uniform structured mesh, the RNG k-ε  turbulence model and the pressure and velocity coupling algorithm PISO. It was found that the change of abrupt expansion ratio has obvious influence on down stream velocity, turbulence kinetic energy and energy dissipation rate. The smaller the ratio, the more obvious the change in velocity, the faster the primary flow diffuses, and the more clearly the flow pattern transition develops. With decreasing expansion ratio, the smaller the turbulent stresses, the larger the energy dissipation rate. Compared with a typical hydraulic jump, the spatial submerged hydraulic jump possesses greatly improved energy dissipation rate. However, once the ratio is less than 0.5, the dissipation rate on longer is improved obviously yet.