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

通过管道运输核浆是一个重要的物理过程，但目前人们对此知之甚少，这是安全有效地清理和退役核设施内管道的关键。部分充满的管流通常由重力驱动，存在于一系列工业应用中，经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图形包含完整管道和明渠流动的特征。然而，与这些流动相比，对于部分充满的管道流动，科学文献仍然不够发达，工作往往局限于对水的研究。当输送含有固体颗粒的流体时，例如在浆料输送应用中，还有两个额外的重要注意事项。首先，流体(现在是两相非牛顿流体)不遵循为水流推导的传统流动关联式。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，因为在涉及核废料运输的应用中，沉积和堵塞具有潜在的破坏性和成本。CDT项目旨在解决部分填充的泥浆管道流动的以下重要挑战：(1)改进对流动的物理理解，(2)开发和验证准确可靠的流动关联，以及(3)预测输送行为(即固体沉淀的可能性)。这将通过流动的详细实验测量(帮助了解物理)和全面测试(经验发展和相关性和沉积测试)相结合来完成。工作液的特性将被认为是核废料泥浆的代表。因此，这项工作将在被动转移操作期间支持核电站内的操作和相关的部分填充的管道。在这些应用中，预计具有较差传输性能的流体将在未来变得普遍，因为最大限度地增加固体负荷可以最大限度地减少需要存储的废物量。目的：促进对复杂流体在部分填充管道中流动的物理理解，以便通过建立描述流动和沉降特性的传输关联式来安全、有效地清除核浆液。目的：1.利用激光诊断技术，全面描述模型复杂流体在部分填充管道(UOL)中的湍流流动。2.在全尺寸试验台(在NNL Workington)中调查非活性试验材料(浆料)的性能。3.利用目标1和目标2提供的信息，建立可用于设计核设施中安全有效的管道作业的输送关系(流量和沉降量)。方法和方法：为了实现目标1，实验将使用UOL超大规模管道流动(VLSPF)设施进行。模型聚合物溶液(如Carbopol和黄原胶)将用于模拟浆料的关键流变特性(屈服应力和剪切稀化)。与真正的泥浆不同，它们将是透明的，以便为高速立体粒子图像速度测量提供光学通道，从而在横截面平面上提供时间分辨率的三分量速度测量。雷诺数(Re)将是完全湍流的(Re=104左右)，填充高度将被调查，范围从30%到80%，涵盖核工业主要感兴趣的范围。这些实验的原理已经由CDT项目的牛顿流体项目主管建立，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