Mass shedding rate of an isolated high-speed slug propagating in a pipeline

An isolated liquid slug in the pipeline can accelerate and achieve a high speed when subjected to a driving pressure. During the slug’s high-speed movement in a pipeline, part of the liquid will shed from it resulting in changes in the slug’s mass and length. To understand the mass shedding mechanism, the mass shedding rate is studied using three-dimensional computational-fluid-dynamics methodology, in which the volume-of-fluid technique is applied to track the water–air interface and the RNG (Formula presented.) model is used to describe the turbulence. The effects of driving pressure, initial slug length, pipe inclination angle, pipe wall roughness and gravity on the slug mass shedding rate are investigated. The results show that the slug mass shedding rate is independent of driving pressure, initial slug length, pipe inclination angle and gravity, and it increases as a power function with the increase in wall roughness. It is explained from the mass shedding rate that when the slug’s traveled distance exceeds six times the initial slug length, the slug will break up. This paper solves the problem that there is no standard to select a reliable mass shedding rate for modeling the isolated high-speed slug propagating in pipelines. Highlights: Simulate the movement of an isolated liquid slug propelled by pressurized air with 3D CFD model. Propose a model for calculating the slug mass shedding rate. Study three influence factors of the slug mass shedding rate.</p

Nonlinear Water Quality Response to Numerical Simulation of In Situ Phosphorus Control Approaches

The nonlinear and heterogeneous responses of nutrients to eutrophication control measures are a major challenge for in situ treatment engineering design, especially for large water bodies. Tackling the problem calls for a full understanding of potential water quality responses to various treatment schemes, which cannot be fulfilled by empirical-based methods or small-scale tests. This paper presents a methodology for Phoslock application based on the idea of object-oriented intelligent engineering design (OOID), which includes numerical simulation to explore the features of responses to numerous assumed schemes. A large plateau lake in Southwestern China was employed as a case study to illustrate the characteristics of the water quality response and demonstrate the applicability of this new approach. It was shown by the simulation and scenario analysis that the water quality response to Phoslock application always reflected nonlinearity and spatiotemporal heterogeneity, and always varied with objects, boundary conditions, and engineering design parameters. It was also found that some design parameters, like release position, had a significant impact on efficiency. Thus, a remarkable improvement could be obtained by cost-effective analysis based on scenarios using combinations of design parameters