Development of flow and settling correlations for the transport of nuclear slurries in partially-filled pipes

核浆液的管道输送是一个重要的物理过程，但目前对其了解甚少，它是核设施内管道安全高效清理和退役的关键。部分填充的管道流通常由重力驱动，存在于一系列工业应用中，通常用于输送含有沉积物或颗粒的流体，例如污水和废水，以及核或采矿作业中的泥浆。部分填充的管道几何形状包含了全管道和明渠流动的特征。然而，与这些流动相比，关于部分填充管道流动的科学文献仍然不够发达，其工作通常仅限于对水的研究。当输送含有固体颗粒的流体时，例如在泥浆输送应用中，还有两个重要的考虑因素。首先，流体（现在是两相和非牛顿流体）不遵循传统的水流相关关系。其次，了解悬浮颗粒的沉降行为（及其对流动条件的依赖）对于避免沉积和堵塞至关重要，这在涉及核废料运输的应用中是潜在的破坏性和昂贵的。CDT项目旨在解决部分填充浆体管道流动的以下重要挑战：(1)提高对流动的物理理解，(2)开发和验证准确可靠的流动相关性，以及(3)预测输运行为（即固体沉降的可能性）。这将通过详细的流动实验测量（有助于物理理解）和全面测试（用于经验开发和相关性和沉降的测试）相结合来完成。工作流体将具有被认为具有代表性的核废料浆料的特性。因此，这项工作将支持核电站和相关的部分填充管道在被动转移操作期间的操作。在这些应用中，由于最大限度地增加固体载荷可以最大限度地减少需要储存的废物量，因此预计未来运输性能较差的流体将变得普遍。目的：促进对复杂流体在部分填充管道中流动的物理理解，以便通过发展传输相关性来表征流动和沉降特性，从而为核浆液的安全有效清洗提供信息。目的:1。为了充分表征，使用激光诊断，模型复杂流体在湍流中部分填充管道（UoL）的流动。2. 研究非活性测试材料（浆料）在全尺寸测试平台（在NNL沃金顿）的行为。3. 利用目标1和目标2的信息发展可用于设计核设施中安全有效的管道操作的输送相关性（包括流动和沉降）。方法和方法：为了实现目标1，实验将使用UoL的超大规模管道流（VLSPF）设施进行。模型聚合物溶液（例如卡波醇和黄原胶）将用于模拟浆料的关键流变性能（屈服应力和剪切变薄）。与真实的浆料不同，它们将是透明的，为高速立体粒子图像测速提供光学通道，在横截面上提供时间分辨的三分量速度测量。雷诺数（Re）将是完全紊流的（Re =104左右），填充高度将在30%到80%之间进行研究，涵盖核工业主要感兴趣的范围。这些实验的原理是由牛顿流体CDT项目的主管建立的，现在将应用于非牛顿流体

The transport of nuclear slurry through pipelines is an important, but currently poorly understood, physical process which is key to the safe and efficient clean out and decommissioning of pipelines within nuclear facilities. Partially-filled pipe flows, often gravity-driven, are present in a range of industrial applications and are often used to transport fluids with sediments or particulates, for example sewage and waste-water, as well as slurries in nuclear or mining operations. The partially-filled pipe geometry contains features of a full pipe and an open channel flow. However, in comparison to these flows, the scientific literature remains under-developed for partially-filled pipe flow with work often restricted to studies of water. When transporting fluids that contain solid particles, such as in slurry transport applications, there are two additional important considerations. Firstly, the fluids (now two-phase and non-Newtonian) do not follow the traditional flow correlations that were derived for water flows. And secondly, understanding the settling behaviour of the suspended particles (and its dependence of flow conditions) is critically important to avoid deposition and blockages, which are potentially disruptive and costly in applications that involve the transport of nuclear waste. The CDT project aims to address the following important challenges for partially-filled pipe flow of slurries: (1) an improved physical understanding of the flow, (2) the development and validation of accurate and reliable flow correlations, and (3) predicting transport behaviour (i.e. the likelihood of solids settling). This will be done through a combination of detailed experimental measurements of the flow (to help with physical understanding) and full-scale testing (for the empirical development and testing of correlations and sedimentation). The working fluids will have characteristics that are considered representative of nuclear waste slurries. As such, the work will support operations within nuclear plants and associated partially-filled pipelines during passive transfer operations. In these applications it is expected that fluids with less favourable transport properties will become prevalent in the future, as maximising solids loading minimises the quantity of waste that needs to be stored. Aim: To advance the physical understanding of the flow of complex fluids in partially-filled pipes in order to inform the safe and efficient clean-out of nuclear slurries through the development of transport correlations to characterise both the flow and the settling properties. Objectives: 1. To fully characterise, using laser diagnostics, the flow of model complex fluids in turbulent flow in a partially-filled pipe (at UoL). 2. To investigate the behaviour of non-active test materials (slurries) in a full-scale test rig (at NNL Workington). 3. To use the information from objectives 1 and 2 to develop transport correlations (for both flow and sedimentation) that can be used to design safe and efficient pipeline operations in nuclear facilities. Methodology and Approach: To achieve objective 1, the experiments will be conducted using the UoL Very Large-Scale Pipe Flow (VLSPF) facility. Model polymeric solutions (e.g. Carbopol and xanthan gum) will be used which imitate the key rheological properties of slurries (yield stress and shear-thinning). Unlike real slurries they will be transparent to provide optical access for high-speed stereoscopic particle image velocimetry measurements providing time-resolved, three-component velocity measurements in the cross-sectional plane. Reynolds numbers (Re) will be fully turbulent (around Re=104) and fill-heights ranging from 30% to 80% will be investigated, covering the range of primary interest to the nuclear industry. The principles of these experiment have been established by the supervisors of the CDT project for Newtonian fluids and will now be applied to the non-Newtonian