Constrained large-eddy simulation of turbulent flow over inhomogeneous rough surfaces. Issue 1 (January 2021)

• Record Type: Journal Article
• Authors: Zhang, Wen; Wan, Minping; Xia, Zhenhua; Wang, Jianchun; Lu, Xiyun; Chen, Shiyi
• Is Part Of: Theoretical & applied mechanics letters. Volume 11:Issue 1(2021)
• Publication Date: 2021-01
• Subjects: Wall turbulence -- Large-eddy simulation -- Roughness -- Inhomogeneity; Mechanics, Applied -- Periodicals; Mechanics, Analytic -- Periodicals; Mechanics, Analytic; Mechanics, Applied; Periodicals; 620.1
• DOI: 10.1016/j.taml.2021.100229
• Languages: English
• ISSNs: 2095-0349

Abstract

Highlights: The constrained large-eddy simulation (CLES) method is modified to simulate the turbulent flow over inhomogeneous rough walls. Theformulation of the subgrid-scale stress of CLES is interpreted as the additional stress induced by surface roughness. The new CLES model is used to simulate the turbulent flow over the inhomogeneous rough walls, and the secondary vortices are found to be induced by the roughness inhomogeneity. The CLES model is also used to investigate the response of wall turbulence to the sudden change of the surface roughness, and it is found that the secondary flow induced by the roughness inhomogeneity has little impact on the growth of the internal boundary layer. Abstract: In this work we extend the method of the constrained large-eddy simulation (CLES) to simulate the turbulent flow over inhomogeneous rough walls. In the original concept of CLES, the subgrid-scale (SGS) stress is constrained so that the mean part and the fluctuation part of the SGS stress can be modelled separately to improve the accuracy of the simulation result. Here in the simulation of the rough-wall flows, we propose to interpret the extra stress terms in the CLES formulation as the roughness-induced stress so that the roughness inhomogeneity can be incorporated by modifying the formulation of the constrained SGS stress. This is examined with the simulations of the channel flow with the spanwise alternating high/low roughness strips. Then the CLES method is employed to investigate the temporal response of the turbulence to the change of the wall condition from rough to smooth. We demonstrate that the temporal development of the internal boundary layer is just similar to that in a spatial rough-to-smooth transition process, and the spanwise roughness inhomogeneity has little impact on the transition process.