ON SUB-GRID SCALE TURBULENCE CHARACTERISTICS

A backward-facing step turbulent flow is numerically studied by means of large eddy simulation(LES).The flow Reynolds number was 18,400 based on step height and mean inlet velocity.The flow field structure and spatial distribution of SGS turbulent kinetic energy and SGS dissipation are given and their characteristics are discussed.SGS turbulent viscosity predicted by LES is compared with the equivalent turbulent viscosity calculated by turbulent model.SGS turbulent kinetic energy and SGS turbulent dissipation decrease with the flow developing spatially and both are weaker in the recirculation region than in other flow regions.The flow has maximum SGS turbulent kinetic energy and SGS turbulent dissipation at the profile of y/H=1.SGS turbulent kinetic energy is lower than fluctuation kinetic energy.SGS turbulent viscosity is lower than equivalent viscosity.