Blind tees are widely used in subsea pipelines to enhance the mixing conditions of oil and gas products, but their structural design still relies on experience. In this paper, a series of numerical investigations have been carried out on blind-tee pipes in order to develop an in-depth understanding of their mixing mechanism and clarify the effects of blind-tee structures on the pipe flow. Firstly, the three-dimensional flow conditions in a typical blind tee have been simulated under different Reynolds numbers to investigate the mixing mechanism. Two critical Reynolds numbers for the vortex generations in blind tees are determined in the laminar flow regime, and the fitting curves of blind-tee vorticity dissipations are obtained. Then, the geometrical parameters, including the radial size ϕ, axial length (BSL) and position of the blind section, are varied systematically to study their effects on the flow characteristics and mixing conditions. The results indicate that increasing ϕ and BSL in an appropriate range can strengthen the flow circulation and promote the fluid exchange. Finally, an optimal configuration is obtained, which can improve the mixing capacity of blind tee by 53% in terms of the volume average vorticity as compared to the typical structure.

盲三通广泛用于海底管道，以提高油气产品的混合条件，但其结构设计仍依赖经验。本文对盲三通管进行了一系列数值研究，以深入了解其混合机理并阐明盲三通结构对管道流动的影响。首先，在不同雷诺数下模拟了典型盲三通中的三维流动条件，以研究混合机制。在层流状态下确定了盲三通内涡流产生的两个临界雷诺数，得到了盲三通涡量耗散的拟合曲线。然后，几何参数，包括径向尺寸，轴向长度（BSL）和盲区位置，系统地变化，以研究它们对流动特性和混合条件的影响。结果表明，在适当的范围内增加φ和BSL可以加强流动循环，促进流体交换。最终得到了一种最佳配置，与典型结构相比，盲三通的体积平均涡量可提高53%的混合能力。