用于预测轴流压气机内角区分离的RANS和SBES方法评估

Assessment of RANS and SBES Methods for Prediction of Corner Separation in Axial Flow Compressors

关键词:  压气机  角区分离  雷诺平均  湍流  剪应力输运模型  非平衡  各向异性  应力融合涡模拟

Key words:  Compressor  Corner separation  RANS  Turbulence  SST model  Non-equilibrium  Anisotropy  Stress-blended eddy simulation

摘要:

为了提高压气机内角区分离的RANS建模精度，基于剪应力输运模型（SST模型），本文评估了湍流非平衡和各向异性修正对压气机角区分离预测的影响。结果表明，角区分离区上游端壁二次流以及角区分离流均呈现出很强的湍流非平衡和各向异性行为，结合非平衡和各向异性修正而提出的NSST-Helicity-QCR模型能够在各类工况下给出最为准确的角区分离预测结果。为了进一步验证提出的NSST-Helicity-QCR模型能够合理捕捉压气机端区流动物理，基于一种新型混合RANS-LES方法——应力融合涡模拟（SBES）构建的高保真时间精确湍流数据库，本文对NSST-Helicity-QCR模型进行评估反馈。结果表明，NSST-Helicity-QCR模型合理捕捉了端壁二次流以及角区分离流的湍流非平衡行为，但仍低估了角区分离区内的湍流各向异性行为。

Abstract:

To improve the RANS modelling accuracy of corner separation in compressors， based on the Shear Stress Transport model （SST model）， the impact of the non-equilibrium and anisotropic modifications on the compressor corner separation prediction is evaluated. The results show that both the endwall secondary flow upstream of the corner separation region and the corner separation flow exhibit strong turbulence non-equilibrium and anisotropic behaviors. The NSST-Helicity-QCR model， which combines the turbulence non-equilibrium and anisotropic modifications， gives the most accurate corner separation prediction results under various operating conditions. To demonstrate that the proposed NSST-Helicity-QCR model reasonably captures the compressor endwall flow physics， based on a high fidelity time-accurate turbulence database constructed by a newly developed hybrid RANS-LES method， Stress-Blended Eddy Simulation （SBES）， the NSST-Helicity-QCR model is evaluated. The results show that NSST-Helicity-QCR model reasonably captures the turbulence non-equilibrium in the endwall secondary flow and corner separation flow， but still underestimates the strength of turbulence anisotropy within the corner separation region.