Assessment of hybrid RANS/LES models for the prediction of the flow and scour around a wall-mounted cylinder

IF 4 2区 环境科学与生态学 Q1 WATER RESOURCES
Alban Gilletta , Cyrille Bonamy , Marie Robert , Julien Chauchat
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引用次数: 0

Abstract

In many environmental flow situations, a solid body emerges from a sediment bed. This may occur in natural systems, for example when a tree-root emerges from the bed, or around a man-made structure such as a bridge pier or a wind turbine foundation. When this situation occurs, various flow-structure interactions such as the horseshoe vortex or vortex shedding lead to the scour process, namely the erosion pattern around the solid obstacle. In this context, accurate numerical prediction of the flow-structure interactions is of primary importance. In this contribution, three-dimensional hydrodynamic simulations are performed using the single-phase incompressible flow solver pimpleFOAM (OpenFOAMv2206plus). Two hybrid RANS-LES turbulence models available in OpenFOAM are tested: the non-zonal kωSST-SAS model and the zonal kωSST-IDDES model. As a first benchmark, a plane channel flow configuration at large bulk Reynolds number (Reb=1.9 × 104) is investigated to evaluate the mesh requirements and to determine a set of acceptable numerical parameters. These simulations show that while the kωSST-IDDES model allows to simulate some features of the fluctuating motions with fewer grid requirements than LES, the kωSST-SAS model behaves as a RANS model. Concerning the wall-mounted cylinder flow at high Reynolds number (Reb=1.8 × 105), the conclusions are quite different, the kωSST-SAS model switches to LES in the region of interest namely the horseshoe-vortex region and the wake thanks to its non-zonal property. The kωSST-SAS model provides better predictions than the kωSST-IDDES model in terms of amplitude of the bimodal oscillation and vortex merging processes in the horseshoe vortex at lower CPU cost than LES. After this benchmarking and assessment of the hybrid RANS-LES model, a new kω2006-SAS turbulence model has been developed for the two-phase flow solver sedFOAM. The model is then applied to a scour configuration around a wall-mounted cylinder and successfully represents the upstream scour depth. The simulations improve the resolution of the complex horseshoe-vortex dynamics which is directly influencing the morphological pattern of the scour process compared with RANS two-phase flow simulations. It also demonstrates interesting mesh convergence properties that RANS does not achieve.
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来源期刊
Advances in Water Resources
Advances in Water Resources 环境科学-水资源
CiteScore
9.40
自引率
6.40%
发文量
171
审稿时长
36 days
期刊介绍: Advances in Water Resources provides a forum for the presentation of fundamental scientific advances in the understanding of water resources systems. The scope of Advances in Water Resources includes any combination of theoretical, computational, and experimental approaches used to advance fundamental understanding of surface or subsurface water resources systems or the interaction of these systems with the atmosphere, geosphere, biosphere, and human societies. Manuscripts involving case studies that do not attempt to reach broader conclusions, research on engineering design, applied hydraulics, or water quality and treatment, as well as applications of existing knowledge that do not advance fundamental understanding of hydrological processes, are not appropriate for Advances in Water Resources. Examples of appropriate topical areas that will be considered include the following: • Surface and subsurface hydrology • Hydrometeorology • Environmental fluid dynamics • Ecohydrology and ecohydrodynamics • Multiphase transport phenomena in porous media • Fluid flow and species transport and reaction processes
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