A Mesh Adaptation Strategy to Predict Pressure Losses in LES of Swirled Flows

Abstract

Large-Eddy Simulation (LES) has become a potent tool to investigate instabilities in swirl flows even for complex, industrial geometries. However, the accurate prediction of pressure losses on these complex flows remains difficult. The paper identifies localised near-wall resolution issues as an important factor to improve accuracy and proposes a solution with an adaptive mesh h-refinement strategy relying on the tetrahedral fully automatic MMG3D library of Dapogny et al. (J. Comput. Phys. 262, 358-378, 2014) using a novel sensor based on the dissipation of kinetic energy. Using a joint experimental and numerical LES study, the methodology is first validated on a simple diaphragm flow before to be applied on a swirler with two counter-rotating passages. The results demonstrate that the new sensor and adaptation approach can effectively produce the desired local mesh refinement to match the target losses, measured experimentally. Results shows that the accuracy of pressure losses prediction is mainly controlled by the mesh quality and density in the swirler passages. The refinement also improves the computed velocity and turbulence profiles at the swirler outlet, compared to PIV results. The significant improvement of results confirms that the sensor is able to identify the relevant physics of turbulent flows that is essential for the overall accuracy of LES. Finally, in the appendix, an additional comparison of the sensor fields on tetrahedral and hexahedral meshes demonstrates that the methodology is broadly applicable to all mesh types.

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“…The coldflow LES strategy is validated for Conf. A against the experimental results by both Daviller et al [15] and Kaiser et al [16].…”

“…A. An iterative mesh h-refinement strategy is applied, which is based on the work of Daviller et al [15] (see zones of localized high refinement in Fig. 4).…”

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“…For meshing, the mesh adaptation strategy proposed by Daviller et al [54] is employed, resulting in three meshes M1, M2, M3 presented in Table 1 , where h is the characteristic cell size in a particular mesh area.…”

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“…Fire safety researchers have been interested in a number of techniques, which involve the use of numerical methods and experimental studies on different scales. G. Daviller et al [2] demonstrated a new sensor and approach to effectively produce the desired local mesh refinement to match the target losses, which are measured experimentally. Utyuzhnikov et al [3] numerically simulated the combustion of fuel droplet vapor releases in the atmosphere and there are a number of studies that have been performed, especially on the use of LES methodology [4][5][6].…”