当前位置: X-MOL 学术Aerosp. Sci. Technol. › 论文详情
Our official English website, www.x-mol.net, welcomes your feedback! (Note: you will need to create a separate account there.)
Flow mechanism of bimodal phenomenon in intermittent corner separation in a linear compressor cascade using a hybrid RANS/LES method
Aerospace Science and Technology ( IF 5.0 ) Pub Date : 2021-07-19 , DOI: 10.1016/j.ast.2021.106949
Bingxiao Lu 1 , Mingmin Zhu 1 , Jinfang Teng 1 , Xiaoqing Qiang 1 , Wei Ma 1
Affiliation  

To gain a better knowledge of the bimodal phenomenon in intermittent corner separation, a hybrid RANS/LES turbulence model is applied to simulate the unsteady flow in a linear cascade. After the validation of the Stress Blended Eddy Simulation (SBES) model with the detailed experimental data, the flow mechanisms of intermittent coherent vortical structures and bimodal phenomenon are clarified according to unsteady numerical results. An indicator is proposed to evaluate the degree of the bimodal phenomenon. Firstly, the intermittency in corner separation is found, which arises from the formation of coherent vortical structures. The collision of the boundary layer and backflow near the trailing edge gives rise to large-scale coherent vortices around the separation surface. Then, according to the histogram of velocity probability density functions (PDF), the bimodal phenomenon found near the separation surface indicates that there are two non-periodic switching flow modes. Combination of vortical structures and velocity distributions manifests that the intermittency of coherent vortical structure is responsible for the switching flow modes around the separation surface. Thirdly, three characteristic parameters are defined to describe the features of two flow modes, corresponding to two Gaussian distributions that PDF decomposed into. The indicator Ra, which measures the difference between two flow modes, is used to evaluate the degree of the bimodal phenomenon. A larger Ra represents the higher probability of bimodal phenomenon occurring in flow fields, which can be used to quantitatively determine the position and fluctuation of the corner separation surface.



中文翻译:

基于混合RANS/LES方法的线性压气机叶栅间歇角分离双峰现象的流动机制

为了更好地了解间歇角分离中的双峰现象,应用混合 RANS/LES 湍流模型来模拟线性级联中的不稳定流动。在用详细的实验数据验证应力混合涡流模拟 (SBES) 模型后,根据非定常数值结果阐明了间歇相干涡流结构和双峰现象的流动机制。提出了一个指标来评估双峰现象的程度。首先,发现角分离的间歇性,这是由相干涡旋结构的形成引起的。边界层的碰撞和后缘附近的回流会在分离表面周围产生大规模的相干涡流。然后,根据速度概率密度函数(PDF)直方图,分离面附近发现的双峰现象表明存在两种非周期性切换流动模式。涡结构和速度分布的组合表明,相干涡结构的间歇性是导致分离表面周围流动模式切换的原因。第三,定义了三个特征参数来描述两种流动模式的特征,对应于PDF分解成的两个高斯分布。指标 涡结构和速度分布的组合表明,相干涡结构的间歇性是导致分离表面周围流动模式切换的原因。第三,定义了三个特征参数来描述两种流动模式的特征,对应于PDF分解成的两个高斯分布。指标 涡结构和速度分布的组合表明,相干涡结构的间歇性是导致分离表面周围流动模式切换的原因。第三,定义了三个特征参数来描述两种流动模式的特征,对应于PDF分解成的两个高斯分布。指标Ra测量两种流动模式之间的差异,用于评估双峰现象的程度。较大的Ra代表流场中出现双峰现象的概率较高,可用于定量确定角分离面的位置和波动。

更新日期:2021-07-30
down
wechat
bug