Utilising a Naturally Occurring Drag Reduction Method

现在很明显，全球气候正在发生变化。2018年10月，联合国洲际气候变化专门委员会发布了一份关于全球变暖影响的特别报告。报告指出，为了在2050年前实现二氧化碳排放“净零”，将需要“迅速而深远的”变化。目前，二氧化碳排放的最大来源之一直接源于为运输目的燃烧化石燃料。仅海运每年就排放约9.4亿吨二氧化碳，约占全球温室气体排放总量的2.5%。众所周知，全球燃料消耗(以及温室气体排放)的一个主要贡献因素是皮肤摩擦阻力。此力与所有物体在流体中移动时所经历的阻力有关。无论流体是空气、水还是其他流体，都将始终存在表面摩擦阻力，并且需要能量来克服其影响。这包括人类在竞技游泳和自行车比赛中的能量投入。考虑到全球变暖带来的切实有害影响和相关的社会后果，近几十年来，减少汽车、飞机和轮船表面摩擦阻力的技术研究得到了加强。这些减阻技术的灵感来源之一是对飞行员和游泳者的研究。为了生存，鸟类和鱼类已经适应了几千年。科学家们最感兴趣的就是这些适应。更具体地说，研究界一直专注于这样一个观点，即进化确保了这些物种通过以流体为中心的栖息地高效地转移不可思议的东西。一个相对较新的例子引起了流体机械学家的极大关注，特别是通过引入鲨鱼皮般的粗糙表面来减少表面摩擦阻力，特别是当附着在柔性膜上时。边界层流动是在边界表面上方或下方的薄层流体的流动。这些类型的流动是无处不在的，可以直接受到壁面摩擦阻力的影响。这个项目将从理论上研究通过在自然界中观察到的生物启发的减阻技术来主动控制边界层流动的想法。调查的目标将是开发可用于对这种流动的控制进行建模的数学技术，并特别侧重于推迟湍流转变开始的能力。湍流在降低燃油效率方面发挥着重要作用，就化石燃料发动机而言，还会对增加有害的二氧化碳排放产生相关影响。关于道路上电动汽车数量的增加以及相关的英国政府推动停止柴油和汽油汽车的生产，改进的减阻技术将产生更好的里程性能，这是目前公众认为不愿采用该技术的一个原因。这项研究的结果将为主动流量控制方法提供新的见解，然后可以利用这些方法来减少阻力的影响，并改善全球燃料消耗，从而产生经济效益。

It is now evident that the global climate is changing. In October of 2018, the United Nations (UN) Intercontinental Panel on Climate Change issued a special report on the impacts of global warming. The report notes that "rapid and far-reaching" changes will be required in order to achieve "net-zero" CO2 emissions by 2050. At present, one of the largest sources of CO2 emissions stems directly from the burning of fossil fuels for transportation purposes. Maritime transport alone emits around 940 million tonnes of CO2 annually and is responsible for around 2.5% of the total global greenhouse gas emissions. It is well understood that a major contributing factor to this worldwide fuel consumption (and, by proxy, greenhouse gas emissions) is skin-friction drag. This force is associated with the drag that all bodies experience as they move through a fluid. Whether that fluid be air, water or otherwise, skin-friction drag will always be present and energy is required to overcome its effect. This includes human energy input in competitive swimming and cycling.Given the tangible detrimental effects and related societal consequences of global warming, research into techniques that act to reduce skin-friction drag in cars, aeroplanes, ships has intensified in recent decades. One source of inspiration for these drag reduction techniques has come from the study of fliers and swimmers. For the purposes of survival, birds and fish have been adapting for many millennia. It is these adaptations that have most interested scientists. More specifically, the research community has focused on the idea that evolution has ensured that these species move incredibility efficiently through their fluid-centred habitats. A relatively recent example that has garnered a great deal of attention from fluid mechanists is the reduction of skin-friction drag via the introduction of shark-skin-like rough surfaces when attached to flexible membranes, in particular. A boundary-layer flow is the flow of a thin layer of fluid above or below a bounding surface. These types of flow are pervasive and can be directly affected by skin-friction drag. This project will investigate, theoretically, the idea that boundary-layer flows can be actively controlled via biologically-inspired drag reduction techniques observed operating in the natural world. The goal of the investigation will be to develop mathematical techniques that can be used to model the control of such flows with a specific focus on the ability to delay the onset of turbulent transition. Turbulent flows play a significant role in reducing fuel efficiency and, in the case of fossil-fuel burning engines, have an associated impact in increasing harmful CO2 emissions. In relation to the increasing number of electrical vehicles the road and the associated UK Government's advancement of the cessation of diesel and petrol vehicle production, improved drag reduction techniques would produce improved range performance, that at present to the public is a perceived reason for not readily adopting the technology. The results that stem from this study will provide new insights into active flow control methods which can then be utilised to reduce the effects of drag and improve global fuel consumption with resultant economic benefits.