Modeling the unsteady flow in an intermediate turbine duct in an aero-engine is highly challenging partly owing to the complex physics subjected to unsteady vortical flow upstream. In this paper, the high-fidelity detached eddy simulations of an aggressive intermediate turbine duct are performed and validated against published data. The dominating coherent flow motions are then captured with sparsity-promoting dynamics mode decomposition under different tip gap sizes and rotating speeds of the rotor blade. Furthermore, a novel low-order spectrum reconstruction method based on selected flow modes and Gaussian fitting is proposed for fast prediction of the instantaneous flowfield in the intermediate turbine duct. The sources of error are discussed and a potential approach to improve the prediction accuracy is proposed. It reveals that the proposed method achieves accurate and generalized performance in reconstructing and predicting flow fields with periodic features for a small cost of calculation time. The maximum root mean squared error in the scenario of tip gap size and rotating speed variation is below 5.96 and 8.41, respectively. The error analysis shows that the variation of flow modes under different inflow conditions and nonlinearity of interacting flow structure accounts for the major part of prediction error. By applying a Proper orthogonal decomposition (POD) interpolation on the flow modes, the maximum root mean squared error in the scenario of tip gap size and rotating speed variation can drop to 4.76 and 2.69 without breaking the physical meaning of the representative modes. The novelty of the present work lies at the proposed prediction method combining DMDSP and POD-interpolation, of which the majority of the physical information are maintained and the prediction accuracy is improved. It may provide a promising approach for turbomachinery design, flow prediction, and investigating underlying mechanisms with low data requirements.

对航空发动机中间涡轮管道中的非定常流动进行建模非常具有挑战性，部分原因是上游受到非定常涡流影响的复杂物理场。在本文中，对侵蚀性中间涡轮管道进行了高保真分离涡模拟，并根据已发布的数据进行了验证。然后，在转子叶片的不同尖端间隙尺寸和转速下，通过稀疏性促进动力学模式分解捕获主要的相干流动运动。此外，提出了一种基于选定流动模式和高斯拟合的新型低阶谱重建方法，用于快速预测中间涡轮管道中的瞬时流场。讨论了误差来源，并提出了提高预测精度的潜在方法。它揭示了所提出的方法在重建和预测具有周期性特征的流场方面实现了准确和通用的性能，而计算时间成本很小。尖端间隙尺寸和转速变化情况下的最大均方根误差分别低于5.96和8.41。误差分析表明，不同入流条件下流动模式的变化和相互作用流动结构的非线性是预测误差的主要部分。通过对流动模式应用本征正交分解 (POD) 插值，在不破坏代表性模式的物理意义的情况下，尖端间隙尺寸和转速变化情况下的最大均方根误差可降至 4.76 和 2.69。本工作的新颖之处在于提出了结合 DMDSP 和 POD 插值的预测方法，其中大部分物理信息得以保留并提高了预测精度。它可能为涡轮机械设计、流量预测和研究低数据要求的底层机制提供一种有前途的方法。