Accurate and Efficient Models for Microscopic Transport Processes in Gases

气体微观输运过程的准确高效模型

• 批准号: RGPIN-2016-03679
• 负责人: Struchtrup, Henning
• 金额: $ 2.11万
• 依托单位: University of Victoria
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2020
• 资助国家: 加拿大
• 起止时间: 2020-01-01 至 2021-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=708082
• 关键词: Accurate; Efficient; Models; Microscopic; Transport

Advanced microfabrication techniques now allow to design and build devices on the micro- and nano-meter 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 the reduction of (costly!) prototyping, moreover they give detailed insight into the processes in the device, which are not accessible to measurements. The proposed research centers on the further development and application of effective transport models for gas flows in, and around, microdevices, which allow for fast and accurate numerical solutions of gas microflows. The same models can be used for simulation of low pressure gas flows, e.g., for applications in the vacuum industry. In solids, heat transfer is affected by the phonon gas (quantized lattice vibrations, similar to photons), which can be described very similar to classical gases, with relevant applications in micro- and nano-devices. Processes in gases are governed by the mean free path, which is the mean distance a gas particle travels between collisions with other particles or obstacles. If the mean free path is comparable to the size of the device, the usual and well established laws of fluid dynamics and heat transfer cease to be valid. Therefore, alternative models must be used for the simulation of gas flows in microdevices. The microscopic descriptionthe gas as an ensemble of atoms or particlesis well established, but very costly due to extremely long simulation times. In the past decade, we had outstanding success in developing and applying methods to derive advanced flow models from the microscopic description which refine the equations of fluid dynamics, and extend the validity towards microflows. Using pencil and paper, as well as appropriate computer models for the numerical solutions, we have shown that the refined equations are excellent approximations of the microscopic models, and describe all of the the interesting transport regimes in rarefied gases. The planned research builds up on the methods and models established by the applicant with students and co-workers in the recent past, by considering more detailed, and thus more realistic, microscopic descriptions of rarefied polyatomic gases, gas mixtures, and advanced phonon models for micro heat transfer. Special consideration will be given to the interaction of gases and phonons with boundaries, with and without condensation or adsorption processes. While calculations and simulations give deep insight into the world of rarefied flows, full experimental verification is difficult. As part of the research we plan to identify new experiments which are markedly influenced by rarefied flows, so that these can be visualized.

先进的微制造技术现在允许在微米和纳米尺度上设计和构建器件，例如，微传感器和其他微机电系统（MEMS）。微器件工艺过程的计算机模拟对于器件行为的预测和设计性能的优化是非常有用的。事实上，良好的模拟模型可以减少（昂贵的！）此外，它们还提供了对设备中的过程的详细了解，这些过程是测量无法访问的。 拟议的研究集中在进一步开发和应用有效的传输模型的气体流动中，周围，微器件，这使得快速和准确的数值解的气体微流。相同的模型可用于模拟低压气流，例如，用于真空行业。 在固体中，热传递受声子气体（量子化晶格振动，类似于光子）的影响，声子气体可以被描述为非常类似于经典气体，在微型和纳米器件中具有相关应用。 气体中的过程由平均自由程控制，平均自由程是气体粒子与其他粒子或障碍物碰撞之间的平均距离。如果平均自由程与设备的尺寸相当，则通常和公认的流体动力学和传热定律不再有效。因此，必须使用替代模型来模拟微器件中的气体流动。将气体作为原子或粒子系综的微观模拟已经很好地建立起来，但是由于非常长的模拟时间，成本非常高。 在过去的十年中，我们在开发和应用方法方面取得了突出的成功，这些方法从微观描述中推导出先进的流动模型，这些模型完善了流体动力学方程，并将有效性扩展到微流。使用铅笔和纸，以及适当的计算机模型的数值解，我们已经表明，精细方程是很好的近似的微观模型，并描述了所有有趣的传输制度在稀薄气体。 计划中的研究建立在申请人与学生和同事在最近的过去建立的方法和模型的基础上，通过考虑更详细，因此更现实的微观描述稀薄多原子气体，气体混合物和先进的声子模型用于微观传热。将特别考虑气体和声子与边界的相互作用，有和没有冷凝或吸附过程。 虽然计算和模拟可以深入了解稀薄流的世界，但很难进行全面的实验验证。作为研究的一部分，我们计划确定新的实验，显着影响稀薄流，使这些可以可视化。