超快激光加热薄膜的格子玻尔兹曼模拟

Using the Lattice Boltzmann method to simulate the heat conduction in a thin film induced by ultra-fast laser

超快激光加热技术已广泛用于微/纳米器件中,传统的傅立叶导热定律不能有效地描述超快速和超小尺寸的传热问题,因此研究超快激光加热纳米尺度薄膜的传热过程,对微/纳米器件中散热器制造具有重要的理论意义。文章采用格子玻尔兹曼方法(LBM)数值模拟激光加热薄膜的热传导过程,并与傅立叶定律获得的结果进行比较分析。结果表明:在系统特征尺度和分子平均自由程相当的过渡区,LBM结果中当薄膜受到激光扰动后其内部的热量传递会出现波状行为,但傅立叶定律的结果却无法展示这一现象;利用LBM数值模拟激光加热硅薄膜的一维导热问题,发现克努森数对薄膜内无量纲能量密度的分布具有重要的影响;当利用超快激光对加热硅薄膜的2个表面同时加热时,会产生2组沿相反方向传播的热波,当其交汇时,彼此的碰撞会引发能量的显著提升。

Ultra-fast laser heating technology has been widely used in the micro-/nano-devices.The classical Fourier law cannot simulate the ultrafast and ultra-small size heat transfer problems.Therefore it is of great importance to investigate the heat transfer induced by ultra-fast laser heating of nano-devices.The Lattice Boltzmann method(LBM)is employed to simulate the heat conductions of laser heating appeared in a thin film,and compared the results obtained by the Fourier law and LBM withthe results obtained by the LBM.The results show that a wavelike behavior is appeared in the film when it is heated by a laser,but this behavior cannot be found in Fourier prediction.The temperatures within the film may be seriously underestimate by Fourier law when the system characteristic scale is the same with the molecular mean free path.Moreover,simultaneously heating both surfaces of a thin silicon film by ultra-fast lasers can induce two thermal waves traveling in the opposite directions,and when they meet together,the energy will enhance significantly.