Advanced experimental and numerical methods for te prediction of complex gas liquid annular flows

建议的工作涉及垂直向下的气液环状流的实验和模拟调查。这些是各种工业应用中的关键部件，其中主要的例子是用于生产洗涤剂的冷凝器和化学反应器。在后一种情况下，将液体原料作为膜喷射到管束的内侧上，并通过与含有SO 3的空气接触而经历放热磺化，所述空气与管壁上的膜并流地沿管流下。为了获得所需质量的产物，必须严格控制反应液体的温度;否则，会形成不期望的副产物。工业界在模拟这些系统方面取得了良好的进展，但这种模拟受到基础物理复杂性的限制。首先，在界面上形成复杂的波图案，这些波图案影响气体和液体之间的相互作用以及反应和传热过程。其次，液滴从膜上脱落，并以不受控制的方式与气体中的SO 3反应。了解在哪些条件下出现哪种流动状态，并且能够以系统的方式预测流动状态对于利用向下环状气液流的反应器的有效和最佳操作是至关重要的。垂直向上的环形流在文献中已受到相当大的关注（例如，见休伊特和Hall Taylor 1a，Hewitt 1b，休伊特和Govan 1c以及巴博萨等人1d的工作），但垂直向下的环形流的研究却很少。这是令人惊讶的，因为Webb和Hewitt 1 e的早期研究表明，湍流气体核心和薄液膜之间的相互作用，特别是当重力和界面剪切都很重要时，会产生许多复杂的现象和丰富的动力学，这些都不是很清楚。一般来说，目前对向下环状流的建模是不够的。因此，有必要通过界面应力施加到液体上的气体是负责波的形成和液滴夹带的液体膜和气体湍流之间的耦合有一个大大改善的理解，实现这样的理解是所提出的工作的目的。这里提出的项目是一种平衡的协同方法，采用了最新的先进实验方法，在EPSRC资助的其他项目EP/D 031222和EP/E021468中进行的详细数值和分析研究的结果，在早期研究时无法获得，和先进的理论和建模方法，以开发有效和准确的方法，系统地预测流动界面行为和向下的环形流中的流态。

The proposed work involves an experimental and modelling investigation of vertically downwards gas-liquid annular flows. These are the key components in a wide variety of industrial applications, prime examples of which are, condensers and chemical reactors used in the production of detergents. In the latter case, a liquid feedstock is injected as a film onto the inside of a bundle of tubes and undergoes an exothermic sulphonation by contact with air containing SO3 which flows down the tubes co-currently with the films on the tube walls. To obtain the required quality of the product, the temperature of the reacting liquid must be rigidly controlled; otherwise, undesirable by-products are formed. Industry has made good progress in modelling these systems but such modelling is limited by the complexity of the underlying physics. First, a complex pattern of waves is formed on the interface and these affect the interaction between the gas and liquid and also the reaction and heat transfer processes. Secondly, liquid droplets are torn off the film and react with the SO3 in the gas in an uncontrolled way. Knowing which flow regime occurs under which conditions, and being able to predict the flow regimes in a systematic manner is crucial for the efficient and optimal operation of reactors that exploit downwards annular gas-liquid flows. Whereas vertically upwards annular flows have received considerable attention in the literature (see e.g. the work of Hewitt and Hall Taylor1a, Hewitt1b, Hewitt and Govan1c and Barbosa et al.1d), there has been very little work on vertically downwards annular flows. This is surprising given the early studies of Webb and Hewitt1e, whose work in this area has shown that the interactions between the turbulent gas core and the thin liquid film, particularly when both gravity and interfacial shear are significant, give rise to many complex phenomena and rich dynamics, which are not well-understood. The current state of modelling of downwards annular flows in general is insufficient. Hence, there is a need for a substantially improved understanding of the coupling between the liquid film and gas turbulence through the interfacial stress exerted by the gas onto the liquid which is responsible for wave formation and drop entrainment; achieving such an understanding is the aim of the proposed work. The project proposed here is a well-balanced synergistic approach adopting recent, advanced experimental methods, results of the detailed numerical and analytical studies conducted in other EPSRC-funded projects, EP/D031222 and EP/E021468, unavailable at the time of earlier studies, and advanced theoretical and modelling methodologies to develop efficient and accurate methods for the systematic prediction of flow interfacial behaviour and flow regimes in downwards annular flows.