knudsen number

简明释义

克努森数

英英释义

例句

1.In microfluidic applications, the flow behavior is often analyzed using the knudsen number (库德森数) to determine whether the continuum assumption is valid.

在微流控应用中，流动行为通常通过分析库德森数 (knudsen number) 来确定连续假设是否有效。

2.A high knudsen number (库德森数) indicates that the mean free path of molecules is larger than the characteristic length of the system.

高库德森数 (knudsen number) 表明分子的平均自由程大于系统的特征长度。

3.When designing vacuum systems, engineers must consider the knudsen number (库德森数) to ensure proper gas flow dynamics.

在设计真空系统时，工程师必须考虑库德森数 (knudsen number) 以确保气体流动动态的正确性。

4.The knudsen number (库德森数) is crucial in predicting the behavior of gases in nanoscale devices.

在预测纳米级设备中气体行为时，库德森数 (knudsen number) 是至关重要的。

5.In rarefied gas dynamics, the knudsen number (库德森数) helps to define the transition between continuum and free molecular flow.

在稀薄气体动力学中，库德森数 (knudsen number) 有助于定义连续流动与自由分子流动之间的过渡。

作文

The concept of the Knudsen number is an essential aspect of fluid dynamics and gas kinetics, particularly when dealing with systems where the mean free path of molecules is comparable to the characteristic dimensions of the system. The Knudsen number, often denoted as Kn, is defined as the ratio of the molecular mean free path to a representative physical length scale, such as the diameter of a pipe or the distance between two surfaces. Understanding this dimensionless number is crucial for engineers and scientists working in fields like microfluidics, aerodynamics, and material science.In essence, the Knudsen number helps categorize the flow regime of gases. When the Knudsen number is much less than one (Kn < 1), the flow can be considered continuum, meaning that the behavior of the gas can be described by classical fluid dynamics equations. In contrast, when the Knudsen number is greater than one (Kn > 1), the gas flow is rarefied, and the behavior of individual molecules becomes significant. This transition from continuum to rarefied flow is critical in various applications, such as the design of micro-electromechanical systems (MEMS) and the study of atmospheric re-entry vehicles.One practical example of the Knudsen number in action can be seen in the field of aerospace engineering. As a spacecraft re-enters the Earth’s atmosphere, it encounters air at high speeds. The conditions during re-entry create a scenario where the Knudsen number is significant, as the density of the atmosphere decreases rapidly with altitude. Engineers must consider the Knudsen number to accurately predict the heating and aerodynamic forces acting on the spacecraft. If they fail to account for the effects of rarefied gas flow, it could lead to catastrophic failures or inefficient designs.Furthermore, the Knudsen number also plays a vital role in the development of nanotechnology. At the nanoscale, the surface area-to-volume ratio increases dramatically, leading to different physical and chemical properties compared to bulk materials. In these scenarios, the Knudsen number can influence how gases interact with surfaces, affecting processes such as adsorption, catalysis, and even the behavior of nanoparticles in various environments. Researchers must carefully measure and model the Knudsen number to optimize reactions and functionalities in nanomaterials.In conclusion, the Knudsen number is more than just a theoretical construct; it is a critical parameter that influences a wide range of scientific and engineering disciplines. By understanding the implications of the Knudsen number, professionals can better design systems that operate under varying flow conditions, ensuring efficiency and safety. Whether in aerospace, microfluidics, or nanotechnology, the Knudsen number provides invaluable insight into the behavior of gases, enabling advancements in technology and our understanding of the physical world.

“Knudsen number”的概念是流体动力学和气体动力学中的一个重要方面，特别是在处理分子平均自由程与系统特征尺寸相当的系统时。Knudsen number通常用Kn表示，定义为分子的平均自由程与代表性物理长度尺度（如管道直径或两个表面之间的距离）的比率。理解这个无量纲数对于在微流体学、空气动力学和材料科学等领域工作的工程师和科学家至关重要。从本质上讲，Knudsen number有助于对气体流动状态进行分类。当Knudsen number远小于1（Kn < 1）时，流动可以被视为连续流动，这意味着气体的行为可以用经典流体动力学方程来描述。相反，当Knudsen number大于1（Kn > 1）时，气体流动是稀薄的，单个分子的行为变得重要。这种从连续流动到稀薄流动的过渡在各种应用中至关重要，例如微电子机械系统（MEMS）的设计和大气再入飞行器的研究。一个实际的例子是航空航天工程领域的Knudsen number的应用。当航天器重新进入地球大气层时，它以高速遇到空气。在再入过程中，条件创造了一个Knudsen number显著的场景，因为大气的密度随着高度迅速下降。工程师必须考虑Knudsen number来准确预测作用于航天器的加热和气动力。 如果他们未能考虑稀薄气体流动的影响，可能会导致灾难性的故障或低效的设计。此外，Knudsen number在纳米技术的发展中也发挥着至关重要的作用。在纳米尺度上，表面积与体积的比率急剧增加，导致与块状材料相比，具有不同的物理和化学性质。在这些情况下，Knudsen number可能会影响气体与表面的相互作用，从而影响吸附、催化甚至纳米颗粒在各种环境中的行为。研究人员必须仔细测量和建模Knudsen number以优化反应和纳米材料的功能。总之，Knudsen number不仅仅是一个理论构造；它是影响广泛科学和工程学科的关键参数。通过理解Knudsen number的含义，专业人士可以更好地设计在不同流动条件下运行的系统，确保效率和安全性。无论是在航空航天、微流体学还是纳米技术中，Knudsen number都为气体行为提供了宝贵的见解，推动了技术进步和我们对物理世界的理解。