基于RANS/LES混合方法的三维L型弯管流场特性数值模拟

Numerical Simulation on the Flow Characteristics of a Three-Dimensional L-Bend Pipe Based on Hybrid RANS/LES Methods

L型弯管是船用典型部件,可实现流体质量输运和热量交换等功能。由于弯曲段曲率的影响,其内部流动十分复杂。传统的雷诺平均方法(RANS)无法模拟弯曲段的复杂流动,而大涡模拟方法(LES)则计算量太大。为此,采用RANS/LES混合方法对经典L型弯管进行数值模拟研究,该方法在近壁面区域采用RANS方法,在湍流核心区采用LES方法,不仅可保持模拟精度,而且网格需求量较低更适用于工程应用。针对商软中的2类RANS/LES方法——脱体涡方法(IDDES)及应力混合涡模拟(SBES)方法,比较分析其在L型弯管内部流场仿真方面的优劣,并同时考虑流向曲率修正的影响。结果表明:SBES方法对弯管内二次流(迪恩涡)的预测能力优于IDDES方法,且曲率修正模型可进一步改善SBES方法的仿真结果。

L-bend pipe is a typical shipboard component,which can realize the functions of fluid mass transport and heat exchange.Due to the influence of geometric curvature,the flow in the L-bend pipe is extremely complicated.The traditional reynolds averaged method(RANS)is unable to simulate the complex three-dimensional flow in the pipe while the large eddy simulation method(LES)bears large computational cost.Therefore,the hybrid RANS/LES method is adopted to conduct a numerical research on the flow characteristics in the classic L-bend pipe.this method adopts RANS method in the near-wall region and LES method in the turbulent core region,which can not only maintain the simulation accuracy but also be suitable for engineering applications with low grid demand.Two types of RANS/LES methods in commercial software,i.e.improved delayed detached-eddy simulation method(IDDES)and stress blended eddy simulation method(SBES),are compared and analyzed for the simulation of the flow characteristics.Moreover,the influence of the curvature correction model is also considered.The results show that the SBES method possesses a better ability of simulation on the secondary flow(Dean Vortex)in the bend pipe compared with the IDDES method.Besides,the curvature correction model could further improve the ability of SBES.