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英文论文代写 Thermal Counterflow Past A Cylinder

英文论文代写 Thermal Counterflow Past A Cylinder

注入流体,固体颗粒可以通过使用它,用了几年的标准方法的PIV技术跟踪。在一个正常的流体中的固体颗粒有望跟随流动但最近实验的氦II采用PIV技术已显示出一些意想不到的结果。实验结果表明,令人惊讶的是之前提到的存在显然平稳正常的流体涡旋热逆流过去一缸。

为了解释这些观察两个问题可以得到解决。首先,在流体中的粒子究竟是什么痕迹?一个可能的答案是,粒子跟踪正常的流体,因为在实验中的小颗粒的斯托克斯阻力是远远大于正常流体所施加的其他力。但从另一方面固体颗粒与量子化涡旋可以重新连接到粒子表面,导致外观的附加力作用在粒子相互作用的超流。

另一个问题是,如果颗粒运动地图正常漩涡或结果从正常流体和量子化涡旋的超流成分复杂的相互作用的循环细胞。一个建议是,由于涡缠结是相对较稀的,预期的粒子运动映射的正常流动。另一个建议是,所观察到的大涡结构的原因是由两个流体组分之间的复杂的相互作用。

在目前的工作中认为大尺度涡结构的存在是由量子化涡旋与正常流体可充分利用经典流体动力学没有呼吁正常和超流体旋涡之间的相互作用来解释之间的相互摩擦引起的。

这个项目的目标首先是指那些固定配置的涡的存在反涡旋对,后面和前面的磁盘。另一个目标是表明,位于足够接近的相应的固定点的旋涡将保持接近他们的初始位置,以及多久,他们仍然接近他们。最后,探讨正常流体涡旋的形成与涡流纠结在氦的超流成分的极化之间的可能联系

Introduction

Solid particles that are injected into fluids can be tracked by using the PIV technique which is the standard method that used for several years. In a normal fluid the solid particles are expected to follow the fluid flow but a recently experiment for helium II by using the PIV technique has shown some unexpected results. That surprising experimental results have shown as it mention before the existence of apparently stationary normal fluid eddies in the thermal counterflow past a cylinder.

In order to interpret these observations two questions could be addressed. First, what do the particles in the fluid actually trace? One possible answer is that the particle traces the normal fluid because the Stokes drag of small particles in the experiment is much larger than the other forces exerted by the normal fluid. But from the other hand the solid particles interact with the quantized vortices which may reconnect to the particle surface and lead to the appearance of the additional force exerted on particles by the superfluid.

The other question is if the circulation cells of the particulate motion map the normal eddies or result from complex interactions of both normal fluid and quantized vortices of the superfluid component. One suggestion was that since the vortex tangle was relatively dilute was expected that the particle motion maps the normal flow. Another suggestion was that the observed large vortex structures were cause by the complex interaction between the two fluid components of He II.

In the present work it is believed that the existence of large – scale vortex structures is caused by the mutual friction between quantized vortices and the normal fluid and can be explained fully by using classical fluid dynamics without appeal to an interaction between the normal and the superfluid vortices.

The objectives of this project are first of all to show the existence of those stationary configurations of the vortex – antivortex pairs, both behind and in front of the disk. Another objective is to show that the vortices located sufficiently close to the corresponding stationary points will remain close to their initial locations and how long do they remain close to them. Finally, is to discuss a possible connection between the emergences of normal fluid eddies and the polarization of the vortex tangle in the superfluid component of helium II.

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