运用分子动力学模拟方法,对水蒸汽均匀核化凝结过程进行了研究.采用分形理论分维数统计中的小盒计数法,对二维条件下凝结核的分维数的变化规律进行了统计计算.模拟结果表明,水蒸汽均匀核化过程中所形成的凝结核表面的分维数并非一过程量,凝结核表面分维数并不随凝结核的长大而变化,当凝结核长大到一定程度后,其表面分维数将达到一恒定值.本文对初始温度为500 ℃,密度分别为100和200 kg/m^3的过热水蒸气冷却到20 ℃的过程进行了模拟,水蒸汽在二维均匀核化过程中所形成的凝结核表面分维数为1.79.
The homogenous nucleation of water vapor molecules in the process of condensation is studied by molecular dynamic simulation. The characteristic of fractional dimension number of condensation nucleus under the condition of two dimensions is analyzed theoretically based on the fractal theory. It is shown that fractional dimension number of condensation nucleus is not process parameter and will not change always with increase of nucleus growth. The fractional dimension number of condensation nucleus will develop to a constant when condensation nucleus grows to certain degree. The fractional dimension number of condensation nucleus is 1.79 when the superheated vapor of 500 ℃, 100 kg/m^3 and 200 kg/m^3 separately is cooled to 20 ℃.