n.稀薄；稀薄化
Simulation results show that rarefaction effect plays an important role in gas damping, which decreases as Kn Number increases. 数值模拟结果表明，稀薄效应对气体阻尼的影响较大，随着克努森数的不断增大，气体阻尼逐渐减小。
Several applications require consideration of rarefaction, which motivates the present thesis to focus on simulation of driven cavity flows in this region. 因此本文的动机是模拟空穴流场在稀薄区域上的应用。
