基于模态分解的轴向通流共转腔流场特性分析

Analysis of flow characteristics in rotating cavity with axial throughflow based on modal decomposition

为了深入理解高压压气机旋转盘腔内的流场特性,基于雷诺平均N-S方程对轴向通流共转盘腔进行非定常数值模拟。采用本征正交分解方法识别了流场的相干结构,并对比分析了不同浮升力参数、罗斯比数以及盘轴旋转比下模态空间结构和平均流场的变化规律。结果表明,盘腔高半径处观察到一对非定常大尺度气旋/反转环流,借助本征正交分解方法能够有效提取其运动状态。低阶的旋进驱动模态主要反映了大尺度流动结构的旋进状态,对应盘腔内流场在整个径向范围的主频成分;高阶的谐振诱导模态则主要反映了腔内相干结构诱导的复杂涡系,对应主频的高阶倍频成分。气旋/反转环流结构的相干性随浮升力参数增加而增强(旋进驱动模态能量占比提高23.2%),随罗斯比数增加而减弱(相应能量占比降低12.3%)。盘轴反转会削弱低半径区域的环形涡,而对高半径区域流场影响较小。

To gain insight into the flow characteristics in the rotating cavity of a high-pressure compressor,unsteady numerical simulations were conducted in a rotating cavity with axial throughflow based on the Reynolds averaged N-S equation.The proper orthogonal decomposition method was used to identify the coherent structure of the flow field.Spatial distribution of modes and mean flow field were analyzed under different buoyancy parameters,Rossby numbers,and rotation ratios.The motion state of a pair of unsteady large-scale cyclonic/anticyclonic circulations at the high radius of the cavity can be effectively extracted using the proper orthogonal decomposition method.The low-order Precession-Driven modes mainly reflect the precession state of large-scale flow structures,corresponding to the dominant frequency component of the flow in the entire radial range within the cavity.The higher-order Resonance-Induced modes mainly reflect induced complex vortex system between coherent structures within the cavity,corresponding to the higher-order harmonic of the dominant frequency.The coherence of cyclonic/anticyclonic circulations increases with the increase of buoyancy parameter(The modal energy proportion of the Precession-Driven increased by 23.2%),and decreases with the increase of Rossby number(decreased by 12.3%).The reverse rotation of the disc and shaft weakens the toroidal vortex in the low-radius region,while the impact on the flow field in the high-radius region is relatively small.