On the Closure Problem of Turbulence Model Theory

It is a wrong viewpoint that the turbulence closure problem is due to the non-linearity,of Navier-stokes equation,But this is a wrong viewed for the closure problem of turbulence model theory.In the engineering,the average raged velocity and pressure are not satisfied,on the other hand,even if the N-Sequation were linear,all of the physical quantities would be found.In this paper,were analysed the closure problem and concluded that the closure problem is induced by lack of statistical distribution function.The limit of turbulence model theory and non-possiblity of direct numerical method to solve the turbulence problem had been paiated out.