Accurate and efficient models for microscopic transport processes in gases

先进的微加工技术可以设计和制造微米和纳米级的器件，例如微型传感器和其他微电子机械系统(MEMS)。微器件中工艺的计算机模拟对于预测器件行为和优化设计性能非常有用。事实上，好的模拟模型可以减少(昂贵的！)此外，它们还提供了对测量无法访问的设备中的过程的详细了解。 这项研究计划的目标是开发和应用微设备内和周围气体流动的有效传输模型，从而快速准确地解决气体微流动问题。同样的模型将用于低压气体流动的模拟，例如真空工业中的应用。 气体中的过程受平均自由程的控制，即气体粒子在与其他粒子碰撞之间的平均距离。如果平均自由程与装置的大小相当，那么公认的流体动力学定律就不再有效。因此，必须使用替代模型来模拟微器件中的气体流动。微观上的描述--气体是粒子的集合--已经得到了很好的证实，但由于模拟时间长，成本非常高。 将采取以下步骤：(1)先进的流动模型是从微观描述，该模型完善了流体动力学方程，并适用于微观流动。(2)针对导出方程的数值解设计了合适的计算机模型。(3)通过基准实验和精确的微观模拟对所建立的流动模型进行了验证。(4)在微器件流动和真空流动中的应用。 该研究项目广泛建立在申请者在过去几年与学生和同事建立的模型基础上。目前的模型将扩展到包括更详细的气体物理，并适用于复杂的几何形状。

Advanced microfabrication techniques allow to design and build devices on the micro and nanometer scale, e.g., micro sensors and other micro-electro-mechanical systems (MEMS). Computer simulations of the processes in microdevices are extremely useful for the prediction of device behavior, and for optimization of design performance. Indeed, good simulation models allow to reduce the amount of (costly!) prototyping, moreover they give detailed insight into the processes in the device, which are not accessible to measurements. The goal of this research program is the development and application of effective transport models for gas flows in, and around, microdevices, which allow for fast and accurate solutions of gas microflows. The same models will be used for simulation of low pressure gas flows, e.g., for applications in the vacuum industry. Processes in gases are governed by the mean free path, i.e., the mean distance a gas particle travels between collisions with other particles. If the mean free path is comparable to the size of the device, the well established laws of fluid dynamics cease to be valid. Therefore, alternative models must be used for the simulation of gas flows in microdevices. The microscopic description--the gas as an ensemble of particles--is well established, but very costly due to huge simulation times. The following steps will be taken: (1) Advanced flow models are derived from the microscopic description; the models refine the equations of fluid dynamics, and are valid for microflows. (2) Appropriate computer models are designed for the numerical solutions of the derived equations. (3) The derived flow models are tested and validated against benchmark experiments and accurate microscopic simulations. (4) Applications to flows in microdevices and vacuum flows. The research program builds extensively on a model established by the applicant, with students and co-workers, in the last few years. The present model will be extended to include more detailed physics of the gas, and for the implementation to complex geometries.