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→一般形式
===一般形式===
===一般形式===
The general equation can then be written as
The general equation can then be written as玻尔兹曼方程的一般形式可以写作：
<math>
<math>
</math>
</math>
其中“force”一词指外界对粒子施加的力（而不是粒子间的作用），“diff”表示粒子扩散，“coll”表示粒子碰撞，指碰撞中粒子间相互的作用力。上述三项的具体形式将会在下文给出。注意，一些作者会使用 '''v''' 表示粒子的速度，而不是动量 '''p。'''这两个物理量可以通过动量的定义'''p''' = m'''v'''联系起来。
where the "force" term corresponds to the forces exerted on the particles by an external influence (not by the particles themselves), the "diff" term represents the diffusion of particles, and "coll" is the collision term – accounting for the forces acting between particles in collisions. Expressions for each term on the right side are provided below. The assumption in the BGK approximation is that the effect of molecular collisions is to force a non-equilibrium distribution function at a point in physical space back to a Maxwellian equilibrium distribution function and that the rate at which this occurs is proportional to the molecular collision frequency. The Boltzmann equation is therefore modified to the BGK form:
where the "force" term corresponds to the forces exerted on the particles by an external influence (not by the particles themselves), the "diff" term represents the diffusion of particles, and "coll" is the collision term – accounting for the forces acting between particles in collisions. Expressions for each term on the right side are provided below. The assumption in the BGK approximation is that the effect of molecular collisions is to force a non-equilibrium distribution function at a point in physical space back to a Maxwellian equilibrium distribution function and that the rate at which this occurs is proportional to the molecular collision frequency. The Boltzmann equation is therefore modified to the BGK form: