表面等离激元、光学热与力等多物理场的快速仿真算法

The proposal is the combination of traditional computational electromagnetics and the newly emerged discipline PLASMONICS. The light energy absorbed by the metallic nano particle can be transformed to heat, which alters the temperature distribution of the nano particle and its surrounding solution. In turn, nano-bubbles may arise under some conditions. The bubbles would changes its shapes and motions due to the fluid convection resulted from the heating as well as that from the exerted optical force. That newly discovered phenomenon attracts interest of many researchers from different disciplines and engineering areas because it is promising in medical treatment, energy transfer, imaging, chemical process, nano fluid control, etc. However, the bubble phenomenon is a typical complex multi-physical coupling involving electromagnetic wave, heat, convection and force. Only a few preliminary simulation works have been reported but left many vital issues open. This proposal would establish the suitable mathematical model from the theoretical respect and proposed a well-performed approach to linearize the possible non-linear coupling. In algorithm’s regard, we would choose the suitable existing methods or conduct the necessary improvement on them according to the requirement of the accurate and efficient computation. In addition, the proposal would work on the fast parameter-sweeping algorithm to accelerate the simulation or optimization.

项目是传统的计算电磁学与新兴学科等离激元学的交叉。等离激元气泡现象指：光能量被金属纳米粒子吸收后转换成热，造成纳米粒子温度升高，并在纳米粒子周围产生气泡的现象。气泡在流体对流的作用下运动，而光学压力也会影响纳米粒子和气泡的运动，并改变气泡的形状。在医疗、能量输送、成像、化学反应、微流控制等诸多方面有着潜在的巨大应用价值，等离激元气泡是当前研究的热点。它涉及电磁场、光学热、光学压力、流体对流等多物理场的耦合，是典型的多物理场问题，其仿真非常复杂，数学模型和算法设计目前均不完善。项目从理论上为等离激元气泡建立数学建模，提出并实现非线性耦合的线性化方法，保证仿真的稳定性。算法上，根据多物理场间的耦合需求，研究单个物理场求解算法的优化选择和改造，保证仿真精度和效率。应用上，研究参数选取和抽样规则，提出参数扫描的快速算法，减少仿真过程中重复求解各单个物理场的次数，实现大规模纳米阵列气泡现象的仿真。

项目是传统的计算电磁学与新兴学科等离激元学的交叉。等离激元气泡现象指：光能量被金属纳米粒子吸收后转换成热，造成纳米粒子温度升高，并在纳米粒子周围产生气泡的现象。气泡在流体对流的作用下运动，而光学压力也会影响纳米粒子和气泡的运动，并改变气泡的形状。课题研究涉及电磁场、光学热、光学压力、流体对流等多物理场的耦合，是典型的多物理场问题，其仿真非常复杂，数学模型和算法设计目前均不完善。项目从理论上为等离激元气泡建立数学建模，通过研究电磁场、温度场和应力场的时间尺度，发现在课题涉及多物理场耦合过程中，电磁场的变化尺度远大于温度的变化尺度，因此可以首先开展稳态情况下的先线性建模。据此，课题以Gummel算法为基础，提出并实现了非线性耦合的线性化方法，保证仿真的稳定性。算法上，根据多物理场间的耦合需求，研究单个物理场求解算法的优化选择和改造，保证仿真精度和效率。为了更好地获取纳米粒子内部的场强，课题基于电磁体积分方程计算纳米粒子内部电磁场，并结合骨元技术和多极子技术加速求解过程。应用上，研究参数选取和抽样规则，提出了基于骨元技术的参数扫描的快速算法，减少仿真过程中重复求解各单个物理场的次数，实现大规模纳米阵列气泡现象的仿真。为了进一步拓展算法的计算能力，课题还开发了基于骨元的参数扫描算法的MPI并行版本，并且研究了该MPI并行算法与物理场求解算法的MPI版本的集成。