Characterization of the transonic flow in a diffusive passage
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In this work, a transonic diffuser is investigated, representative of future advanced high work low pressure turbines and diffusive high pressure turbines suitable for rotating detonation engines. We perform Large Eddy Simulations (LES) to reproduce the flow observed in a wind tunnel experiment. The numerical results are first validated against pressure measurements obtained on the bottom wall of the test section, which features a hump-like geometry. The flow dynamics are then characterized using Proper Orthogonal Decomposition (POD) applied to the CFD solution. Two inlet Mach numbers, 0.31 and 0.40, are investigated, corresponding to Reynolds numbers of 2.67 × 10^5 and 3.60 × 10^5, respectively, based on the hump height. The computational domain consists of a spanwise extrusion of the midplane geometry, assuming an approximately two-dimensional flow. A structured mesh is employed, with average dimensionless spacings of y+ ≈ 2, x+ ≈ 90, and z+ ≈ 50. The simulations are carried out using SOD2D, a high-order, low-dissipation spectral element method solver. This study represents a first step toward high-fidelity simulations of transonic diffusers. To the authors’ knowledge, previous numerical studies of this configuration usually employ second-order URANS solvers.
