Large eddy simulation of turbomachinery flows using a high-order implicit residual smoothing scheme

• Published in: Computers & fluids Vol. 198; p. 104395
• Main Authors: Hoarau, J.-Ch, Cinnella, P., Gloerfelt, X.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier Ltd 15.02.2020; Elsevier BV; Elsevier
• Subjects: Computational fluid dynamics; Computer simulation; Computing time; Cost control; Engineering Sciences; Finite element method; Fluids mechanics; Heat transfer coefficients; Implicit residual smoothing; Kinetic energy; Large eddy simulation; LES; Mechanics; Runge-Kutta method; Smoothing; Turbines; Turbomachinery; Vortices; Turbomachinery; Implicit residual smoothing; LES
• ISSN: 0045-7930; 1879-0747
• DOI: 10.1016/j.compfluid.2019.104395

HIGHLIGHTS•A novel 4th-order accurate implicit residual smoothing scheme (IRS4) is investigated.•Global CPU time reduced by a factor 3÷5 compared to an explicit scheme.•Solution accuracy is preserved if the CFL number is less than 10.•IRS4 is applied to the LES of the VKI LS-89 turbine cascade.•IRS4 is a good strategy for relaxing stability constraints in LES of complex flows. A recently developed fourth-order accurate implicit residual smoothing scheme (IRS4) is investigated for the large eddy simulation of turbomachinery flows, characterized by moderate to high Reynolds numbers and subject to severe constraints on the maximum allowable time step if an explicit scheme is used. For structured multi-block meshes, the proposed approach leads to the inversion of a scalar pentadiagonal system by mesh direction, which can be done very efficiently. On the other hand, applying IRS4 at each stage of an explicit Runge–Kutta time scheme allows to increase the time step by a factor 5 to 10, leading to substantial savings in terms of overall computational time. With respect to standard second-order fully implicit approaches, the IRS4 does not require approximate linearization and factorization procedures nor inner Newton-Raphson subiterations. As a consequence, it represents a better cost-accuracy compromise for the numerical simulations of turbulent flows where the maximum time step is controlled by the lifetime of the smallest resolved turbulent structures. Numerical results for the well-documented high-pressure VKI LS-89 planar turbine cascade illustrate the potential of IRS4 for significantly reducing the overall cost of turbomachinery large eddy simulations, while preserving an accuracy similar to the explicit solver even for sensitive quantities like the heat transfer coefficient and the turbulent kinetic energy field.