方形钝体受限绕流的三维数值模拟

Three dimensional large eddy simulation of the flow field and energy loss characterisation of a ribbed duct trubulent flow

采用一种具有二阶精度的分裂步有限元方法作为大涡模拟的空间离散格式,经过标准算例的验证后,对Re=1.0×104条件下的方形钝体三维受限湍流绕流流场进行了数值模拟。计算中,为消除初始效应,略去初始段的计算结果。数值分析表明在均匀来流条件下,该湍流场沿槽道轴面对称,并呈现出一定的拟周期特性。在流场特性分析的基础上,进行了湍流能耗场的分析,结果表明,方形钝体受限绕流的能耗主要集中在大涡丰富的流动区段内。计算过程反映出,采用该空间离散格式的大涡模拟方法,能够捕捉到非常丰富的涡系及涡动的时变过程,适用于方形钝体受限绕流的数值模拟。

The steady increase in power output and thermal efficiency requirements for turbine engines has called for significant advancement in turbine blade internal duct cooling technology. Numerical simulation of turbulent ribbed duct flow is important for the augmentation of heat transfer. Cooperated with Large-Eddy-Simulation （LES）, a second order fractional step finite element method is used to simulate the turbulent flow over a square blunt body fitted in a square pipe with pitch-to-height ratio equals 2.0. On the basis of precision checking by a three dimensional lid driven cavity flow at Re=100, the method is then applied as the diseretizing scheme for the computation of the turbulent flow around the blunt body at Re=1. 0× 10^4. In order to avoid the influence of the initial conditions on the process of analysing, datas at initial staged are excluded. It is shown by the results, that the field is symetric and quasiperiodic, Based on the flow field analysis, energy loss field is also computed. It can be concluded that energy loss rate is much higher at the scfions with more large eddies. As the results shown, cooperated with the spatial diseretized scheme of appropriate order, LES is good at identifying large eddies and their history correspondingly.