Fundamentals and applications of multiscale generated vortical structures

拟议的研究计划旨在通过从根本上了解这些问题的根源并开发可以缓解这些问题的创新方法，来满足工业需求，以减少运输部门(空中和道路)内的噪音、阻力和燃料消耗(因此二氧化碳排放)，并提高涡轮机的性能(风力和水)。在这些工业应用所产生的流场的各种流体动力学方面，涡旋结构被认为是起主导作用的。它们的能量、大小和相干性决定了钝体的声学特征、物体的阻力和由它们产生的尾迹的速度差。然而，我们缺乏从初始条件充分确定它们行为的能力，这对于上面列出的各种工业应用将是最重要的。拟议的研究方案专门旨在通过研究涡旋结构的生命周期来解决这一问题。 为了获得更深入的认识，我们提出使用多尺度几何来系统地改变涡旋结构产生的条件。文中将研究两种正则涡流：涡对和涡环。涡环通常存在于喷气式飞机(例如喷气发动机)和三维钝体(例如牵引车)中，不仅对噪声水平有影响，而且对拖拉力也有影响。它们将在水箱中以实验方式产生，并将通过粒子图像测速仪研究它们的寿命，从创建到最终衰变和撞击(具有固体表面)。为了加深我们对这些结构的理解，这些涡环的生成方式将通过使用多尺度几何来生成它们来修改。申请人之前对平板进行的研究表明，这种几何形状能够降低大规模相干结构的强度，并改变它们的衰减率。 还将研究代表飞机机翼尖端产生的涡对的涡对，并以类似于涡环研究的方式，建议使用多尺度几何来修改产生这些结构的条件。如果能够证明，这些结构的强度可以在与墙相撞时显著降低，这不仅对飞机制造商和航空公司有实质性的好处，因为它增加了燃料节省，而且对机场也是如此。缩短飞机之间的间隔距离将增加机场的容量，因为在给定的时间段内将有更多的飞机能够降落和起飞。或者，同样数量的飞机可以在较短的时间内降落，这将减少机场内和机场周围居民感受到的飞机噪音。

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.