英文论文代写 Thermal Counterflow Past A Cylinder
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.