Spatial-scaling method and modified large eddy simulation to examine rough-wall turbulence

Abstract

Direct numerical simulations of turbulent boundary layers with roughness elements on a wall were performed to investigate the spatial characteristics of rough-wall turbulence and establish a corresponding prediction method. When the roughness height was larger than the buffer layer, the rough-wall turbulence exhibited different spatial characteristics of the turbulence structures from those pertaining to a smooth wall. A novel spatial scaling method was established to examine the universal spatial characteristics of turbulence structures in the presence and absence of wall roughness. Specifically, the viscous length was determined by modifying the definition of the friction velocity in the region in which the roughness influenced the flow. The rough-wall turbulence could be accurately predicted by performing large eddy simulations using the subgrid scale model with the filter width, which was modified using the proposed spatial scaling method. The proposed model can be used to design more efficient fluid machinery in engineering applications.

Keywords:

• Rough-wall turbulence
• spatial scaling
• turbulence structure
• direct numerical simulation
• large eddy simulation

Acknowledgments

This work was supported by a Kakenhi Grant-in-Aid for Scientific Research (17K06149) from the Japan Society for the Promotion of Science. The research was performed using the supercomputer of the Academic Centre for Computing and Media Studies, Kyoto University. The use of the supercomputer was funded by the Centre for Information Initiative, University of Fukui.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by a Kakenhi Grant-in-Aid for Scientific Research (17K06149) from theJapan Society for the Promotion of Science. The use of the supercomputer was funded by the Centre for Information Initiative, University of Fukui.