Prof. Le Fang   

Ecole Centrale Pekin, Beihang University, China

Speech Title: Hexagonal periodic condition in the simulation of two-dimensional flows 

Abstract

In order to simulate numerically the isotropic turbulence, traditional methods are to use periodic boundary conditions. However, using periodic conditions will involve problems of background anisotropy at large scales, which prevents to generate the truly isotropic turbulence. According to qualitative calculations, we show that this background anisotropy is principally related to the shape of the energy spectrum. In two-dimensional cases, we designed a fast Fourier transfer (FFT) algorithm for hexagonal periodic conditions, which can be used in pseudo-spectral methods. Using this algorithm, the hexagonal periodic conditions are involved to reduce the large-scale background anisotropy.  

Biography

Le Fang is presently professor of Ecole Centrale Pekin, Beihang University, Beijing, China. He is also the director of Sino-french research & teaching center, Research Institute of Aero-Engine, Beihang University, Beijing, China. Aiming at recognizing the non-equilibrium turbulence, he builds a bridge between fundamental research and practical engineering. New mechanism on the generation of non-equilibrium turbulence was proposed by assuming perturbations on transfer. Multiscale definitions were proposed to provide theoretical supports for non-equilibrium turbulence. New rational subgrid-scale models were proposed. It was illustrated that non-equilibrium turbulence is important in aero-engines. New turbulence models considering non-equilibrium properties were proposed to improve the simulation of corner separation. He published more than 50 SCI-indexed papers. Contributions were collected by the NASA turbulence model database, and employed by Whittle laboratory. The new model has been applied in improving the accuracy of flow flux of high-speed fan at least 15% in practical engineering.