Simulation of the Transient Characteristics of Water Pipeline Leakage with Different Bending Angles

Numerical Investigation and Optimization of the Flow Characteristics of Bend Pipe with Different Bending Angles

The bend pipe with a circular section, which is widely used in hydropower, chemical industry and other fields, is a common form in pipeline systems. However, secondary flow occurs when the fluid flows through the bend pipe, thereby affecting the stability of the pipeline system. Different bending angles have various effects. Therefore, this paper establishes 3D models of a circular bend pipe with different bending angles. The influence of bending angle on flow field distribution and downstream flow is analyzed numerically. The larger the bending angle is, the more obvious the flow distribution and even the unevenness at the elbow will be, hence resulting in poor stability. The distance required to restore flow uniformity also increases. The pressure energy loss of the bend pipe with different bending angles is investigated. Results show that with the increase in bending angle, the global pressure loss presents a trend of “increase-decrease-increase.” The closer the bending angle is to 90°, the greater the influence of centrifugal force is on the flow, and the more obvious the secondary flow phenomenon will be. Aiming at the nonuniformity phenomenon, the structure optimization of a 90° bend pipe with the greatest influence is conducted. The improvement of the flow characteristics of bend pipe with different thick-diameter ratio and length-diameter ratio is compared. The deflector with a certain thickness can enhance the uniformity, safety and useful life of the bend pipe. The sharp-end length can improve the velocity uniformity to a certain extent but has minimal influence on flow characteristics compared with the thick-diameter ratio. This paper aims to study and improve the flow performance of a multi-structure bend pipe to make it suitable for more complex conditions.

Effect of Leak Geometry on Water Characteristics Inside Pipes

Water leaks from pipelines have large economic and ecological impacts. Minimizing water loss from supply pipelines has favorable effects on the environment as well as on energy consumption. This paper aims to understand the effect of the geometry of a leaking crack in a pipe wall by examining fluid flow characteristics, namely pressure and velocity distributions, inside the pipe. Practical observations show that the cause of wall rupture influences the geometry of cracks formed in a pipe wall, impacting aspects such as excessive pressure, corrosion. Knowledge of fluid flow characteristics could help in detecting and identifying leak characteristics at an early stage and assist in improving the energy and resource efficiency of water supply services. An experimental setup is developed to detect water leakage in a pipe when the leak is at an early stage and is difficult to detect by visual inspection. A computational fluid dynamic (CFD) model is developed using the COMSOL software. A comprehensive analysis of the effect of leak geometry on pressure and velocity distributions along the pipe is carried out while considering factors such as different pipe sizes, leak geometries, and steady-state flow conditions. It is observed that both velocity and pressure magnitudes rapidly fluctuate in the vicinity of leaks. Leaking cracks with slot, circle, and square shapes are found to generate distinguishing pressure and velocity distributions along the pipe. Thus, the geometry of the leaking crack and potentially its root cause(s) could be predicted by measuring velocity and pressure distributions.