[D*]stratify: harnessing energetics to control thermally stratified fluids

每个人都知道暖空气上升，冷空气下沉。然而，这个看似简单的现象的含义既没有得到广泛的认识，也没有得到正确的理解。这种现象产生了温度的垂直变化，称为热分层，在土木和环境工程中起着深远的作用。热分层决定了需要多少热能和机械能才能在房间的最低部分产生舒适的温度。通过限制气流方向，热分层也决定了空气中病原体的最终命运，因此对影响SARS-CoV-2等病毒在建筑物内的传播至关重要。在油藏管理中，热分层通常在生物学上是不可取的；因此，能量用于混合以使水分层。另一方面，在水箱中，热分层被用作储存太阳热能的有效手段。在所有情况下，评估适当的设计和控制策略需要了解热流体和冷流体如何相互作用以产生或破坏分层，这是当前湍流研究前沿的一个极具挑战性和开放性的问题。该项目将解决由于密闭空间的不均匀加热和冷却而产生的热分层预测的突出问题，并最终采用一种称为[D*]stratify的设计工具，该工具将通过识别和使用有限数量的关键测量来实现分层的预测和控制。我们的方法将超越现有的模型，通过发现和计算湍流羽流和热分层背后的能量，将理论与实时测量相结合。利用现有的基础设施，我们将启动一个独特的工作实验室，用于产生热分层，同时直接数值模拟受限湍流羽流。我们的发现和建模将为研究和操作提供热分层的预测、设计和操作，同时提供有关潜在能量转换的基本信息。

Everyone knows that warm air rises and cold air sinks. Yet the implications of this apparently simple phenomenon are neither widely appreciated nor properly understood. The phenomenon produces vertical variations in temperature, known as thermal stratifications, that play a profound role in civil and environmental engineering. Thermal stratifications determine how much thermal and mechanical energy is needed to produce comfortable temperatures in the lowest parts of a room. By restricting the direction of air flow, thermal stratifications also determine the eventual fate of airborne pathogens and are therefore crucial in influencing the spread of viruses such as SARS-CoV-2 inside buildings. In reservoir management, thermal stratification is often biologically undesirable; hence energy is used for mixing to destratify the water. In water tanks, on the other hand, thermal stratifications are used as an effective means of storing solar-thermal energy. In all cases, the evaluation of appropriate design and control strategies requires understanding of how hot fluid and cold fluid interact to produce or destroy a stratification, which is an extremely challenging and open question at the forefront of current research in turbulence.This project will address the outstanding problem of predicting the thermal stratifications that are produced by non-uniform heating and cooling of a confined space and culminate in a design tool called [D*]stratify, which will enable the prediction and control of stratifications by identifying and using a limited number of key measurements. Our approach will transcend existing models by discovering and accounting for the energy behind turbulent plumes and thermal stratifications, coupling theory with real-time measurements. Utilising existing infrastructure, we will initiate a unique working laboratory for producing thermal stratifications, alongside direct numerical simulations of confined turbulent plumes. Our discoveries and modelling will facilitate the prediction, design and manipulation of thermal stratifications for both research and operation, whilst providing fundamental information about the underlying energy conversions.