颗粒相双尺度湍流模型及其在提升管稠密两相流中的应用

Particle Two-scale Turbulence Model and Its Application to Dense Two-phase Flow in a Riser

稠密两相流动是当前国际上的研究热点,大多数湍流模型都基于单个时间尺度及长度尺度,然而实际的湍流脉动包含了很宽的涡旋尺度范围及时间尺度范围。为了较合理地模拟湍流脉动及其所造成的各向异性,基于多尺度概念,该文建立了颗粒相的双尺度湍流模型,包括颗粒相大尺度脉动湍动能方程,小尺度脉动湍动能方程,大尺度脉动能量传递率方程,小尺度脉动耗散率方程等。利用该模型对循环流化床提升管内的稠密气固两相流动进行了数值模拟,所得颗粒浓度及速度分布和实验数据吻合较好,该模型的结果较kf-εf-kp-εp-θ两相湍流模型的结果有所改进。

The dense two-phase flow attracts more and more attention in recent years. Most turbulence models are based on a single time and size scale concept, actually, there are different scales of turbulent eddies. To reasonably simulate the anisotropic turbulent two-phase flow, based on the multiple-scale concept, a particle two-scale turbulence model is proposed. The particle kinetic energy equation for two-scale fluctuation, particle energy transfer rate equation for large-scale fluctuation, particle turbulent kinetic energy dissipation rate equation for small-scale fluctuation are derived and closed. This model is used to simulate dense gas-particle flows in a riser of circulating fluidized beds. The predicted results are in reasonable agreement with the experimental results. It is found that the two-scale model is somewhat better than five-equation turbulence model which combines single-scale k-epsilon model for two-phase turbulence with the particle kinetic theory for the inter-particle collision.