Large Eddy Simulation Of Turbulent Channel Flow

Most practical computation of turbulent flows relies on turbulence modeling. However, there is no universally valid model for turbulence, while direct numerical simulation needs vast resources of computer which makes it unpractical. Thus, we need a method which needs only a reasonable computer resources and is sufficiently universal. Large eddy simulation is just such a method, which was first proposed by meteorologist Smagorinsky in 1963. Its basic idea is that the instantaneous turbulent quantities, including pulsating quantities, can be decomposed into two parts, namely, large scale motion and small scale motion, by some kind of filtering method. The large scale motion should be computed directly, while the small scale motion should be modeled. In this thesis, by means of LES, turbulent channel flow were computed for several different Reynolds numbers. The wall law has been examined by analyzing the dependence of and on Reynolds numbers. The Reynolds stress distribution for different Reynolds number were analyzed, and we found that the position of the peak of the Reynolds stress was closer to the wall when the Reynolds number increased, when measured by channel width. On the other hand, the position of the peak of Reynolds stress moves away from the wall when measured by wall units. The rms of fluctuating velocity, as well as the mean velocity profiles, for different Reynolds number has also been studied.Our LES computation used relatively few grid points while the results were reasonably good, which is important for the practical of LES computation for engineering purposes.