关于湍流理论中的不封闭性的讨论

On the Closure Problem of Turbulence Model Theory

有一种观点认为湍流的不封闭性是由于Ｎ－Ｓ方程的非线性，这是一似是而非的错误说法。因为工程上要求的量并不仅仅限于湍流的平均速度和平均压力，即使方程式是线性的，也无法把工程上要求的这些量逐个求出来。本文论证了湍流的不封闭性来源于目前的湍流理论中缺少了一个与实际情况符合的有关分布函数，并且进一步说明了湍流模式理论的局限性和用Ｎ－Ｓ方程直接计算机模拟亦是相当困难的原因。

It is pointed out that the closure problem of turbulence model theory be due to the non-Iinearity 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-S equation were linear. all of the physical quantities would be found. In this paper, we re-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 pointed out.