Abstract: Blind tee, as an essential component in pipeline networks for transmission and distribution systems, plays a crucial role in ensuring stable pipeline operation. In this study, a model was established using Solidworks 2019 and Fluent to perform three-dimensional flow field calculations. The local resistance coefficient of the blind tee was analyzed by combining orthogonal analysis tests and SPSS software analysis. Empirical formulas were derived to explain the influence of each factor on local resistance coefficient. An optimal runner structure model was developed. The results indicate that the local resistance loss coefficient (ζ) decreases quadratically with increasing Reynolds number (Re) and branch pipe diameter (d), and increases quadratically with increasing included angle (θ) of the branch pipe. Furthermore, ζ decreases linearly with increasing blind end length (L₃). Through multivariate nonlinear regression, a correlation formula for the local resistance coefficient of the blind tee was derived. The fluid velocity near the right wall of branch pipe increases, and the distribution of turbulent kinetic energy at the bifurcation and branch pipe becomes more pronounced. Within the simulated range, the influence of each factor on ζ can be ranked as follows: Reynolds number > included angle > branch pipe diameter > blind end length. The smallest combination of local resistance loss coefficient was observed when the Reynolds number was 6.4×10⁵, the included angle was π/6, the branch pipe diameter was 0.9D, and the blind end length was 4.0D. The research findings provide a theoretical basis for blind tee structure design and engineering applications.

Key words: blind tee-junction, local resistance coefficient, hydraulic properties, numerical simulation, orthogonal test