Prediction of the unsteady turbulent flow in an axial compressor stage. Part 1: Comparison of unsteady RANS and LES with experiments

•Unsteady flow simulation in an axial compressor stage at Reynolds 700,000.•The influence of turbulence and transition modelling is checked on the URANS results.•The influence of grid refinement is estimated on the LES predictions.•Both URANS and LES correctly predict the flow at mid-span.•LES performs better than RANS in the tip flow region.

A better understanding of turbulent unsteady flows is a necessary step towards a breakthrough in the design of modern gas turbine components. With the increase in computing power, LES emerges as a promising method to improve both knowledge of complex physics and reliability of flow solver predictions. However, there is still a lack of evidences in the literature that LES is applicable for turbomachinery at conditions relevant to industrial applications. In that context, the objective of the present work is to investigate the capability of LES to predict the turbulent flow in a stage of an axial compressor and compare the results with unsteady RANS data and experiments. The compressor operates at industrial relevant conditions, with Mach and Reynolds numbers equal to M=0.5M=0.5 and Re=7×105Re=7×105, respectively. This paper presents the numerical method and a comparison of URANS and LES results to experimental data. A particular care is brought to estimate the results sensitivity to grid refinement (LES) and to turbulence and transition modelling (URANS). The comparison to experiments shows that LES better predicts time-dependent quantities than URANS, especially close to the casing. However, both URANS and LES fail to accurately estimate the compressor performance (efficiency and pressure ratio).