Fundamentals and applications of multiscale generated vortical structures

拟议的研究计划旨在解决工业需求，以减少运输部门（航空和公路）内的噪音，阻力和燃料燃烧（因此CO2排放），以及提高涡轮机发电机（风力和水力）的性能，通过从根本上了解这些问题的来源，并开发创新的方法，通过这些方法可以减轻。在由这些工业应用产生的流场的各种流体动力学方面中，旋涡结构被认为起主导作用。它们的能量、尺寸和相干性决定了海崖体的声学特征、钝体的阻力和它们产生的尾流中的速度差。然而，我们缺乏从初始条件充分确定它们的行为的能力，这对于上面列出的各种工业应用来说是最重要的。拟议的研究计划专门旨在通过研究旋涡结构的生命周期来解决这个问题。 为了获得更深入的了解，我们建议使用多尺度几何系统地改变条件下产生的旋涡结构。将研究两种典型的旋涡流，涡对和涡环。涡环通常存在于喷气式飞机（例如喷气发动机）以及三维海崖物体（例如运输卡车）中，不仅会产生噪音，还会产生阻力。它们将在水箱中通过实验产生，从产生到最终衰变和撞击（固体表面）的寿命将通过粒子图像测速仪进行研究。为了进一步了解这些结构，这些涡环的产生方式将通过使用多尺度几何形状来产生它们。由申请人进行的关于平板的先前研究已经表明，这种几何形状能够降低大尺度相干结构的强度，以及改变它们的衰减速率。 涡对，这是在飞机机翼的尖端产生的涡流的代表，也将进行调查，并在一个类似的方式涡环的研究，建议使用多尺度几何形状来修改这些结构的条件下产生的。如果可以证明这些结构的强度在与墙壁撞击时可以显著减轻，则这将不仅对飞机制造商和航空公司通过增加的燃料节省具有实质性的益处，而且对机场也具有实质性的益处。缩短飞机之间的间隔距离将增加机场的容量，因为更多的飞机将能够在给定的时间内降落和起飞。或者，相同数量的飞机可以在较短的时间内降落，这将减少机场内和周围的人口所经历的飞机噪音。

The proposed research program aims at addressing the industrial need to reduce noise, drag and fuel burn (hence CO2 emissions) within the transportation sector (air and road), as well as increase performance of turbine generators (wind and water), by fundamentally understanding the sources of these issues and developing innovative means by which they can be mitigated. Of the various fluid dynamic aspects of the flow field generated by these industrial applications, vortical structures are believed to play a dominant role. Their energy, size and coherence determine the acoustic signature from bluff bodies, the drag force of the body and the velocity deficit in wakes generated by them. Yet our ability to adequately determine their behaviour from initial conditions is lacking, something which would be of upmost importance for the various industrial applications listed above. The proposed research program specifically aims at addressing this by studying the life-cycle of vortical structures. In order to gain a deeper insight, we propose the use of multiscale geometries to systematically change the conditions under which the vortical structures are generated. Two canonical vortical flows will be studied, vortex pairs and vortex rings. Vortex rings are commonly found in jets (for example from jet engines) as well as three-dimensional bluff bodies (for example haulage trucks) and contribute not only to the noise levels but also the drag force. They will be experimentally generated in a water tank and their life-span, from creation to final decay and impact (with a solid surface), will be investigated via particle image velocimetry. To further our understanding of these structures, the manner in which these vortex rings are generated will be modified by using multiscale geometries to generate them. Previous research on flat plates, conducted by the applicant, has suggested that such geometries are able to decrease the intensity of large-scale coherent structures, as well as alter their decay rate. Vortex pairs, which are representative of the vortices created at the tip of aircraft wings, will also be investigated and in a similar fashion to the vortex rings study, it is proposed that multiscale geometries are used to modify the conditions under which these structures are generated. If it can be shown that the strength of these structures can be significantly mitigated upon impact with a wall, this would have substantial benefits not only to the aircraft manufacturer and airline company through added fuel savings, but to the airports as well. Having a shorter separation distance between aircraft would increase the capacity of the airport as more aircraft would be able to land and take-off within a given time period. Alternatively, the same number of aircraft may be able to land within a shorter time period that would reduce aircraft noise experienced by the population in and around the airport.