颗粒的湍流扩散

PARTICLE DIFFUSION IN TURBULENCE

1引言 在淤浆输送、流态化、分离、搅拌等化工过程中,经常涉及颗粒在湍流中的扩散,对这类问题,一般先确定颗粒的湍流扩散系数,然后用类似Fi。k定律的梯度扩散定律处理。因此,如何确定颗粒的湍流扩散系数是解决问题的关键。目前有关颗粒湍流扩散系数的计算公式主要适用于小颗粒。

A new equation of particle diffusion coefficient in turbulence was presented. It was compared with numerical simulation of particle diffusion in turbulence and the results calculated with Hinze- Tchen equation and Govan equation The equation agreed with the numerical simulation very well on the conditions that the relaxation time of particle is greater then the turbulent characteristic time scale and the settling velocity of particle is less than the fluctuating velocity of turbulence. The Hinze- Tchen equation was applicable only when the relaxation time of particle was less than the turbulent characteristic time scale, and the Govan equation was useful only when the settling velocity of particle was much greater than the fluctuating velocity of turbulence.