Spatiotemporal Evolution Analysis of the 3-D Deformation Field of Land Subsidence in Beijing after the South-to-North Water Diversion Project

The implementation of the South-to-North Water Diversion Project (SNWDP) has alleviated groundwater resource pressure in North China to some extent, resulting in a gradual deceleration of land subsidence and even rebound in some areas. To investigate the spatiotemporal evolution characteristics of land subsidence in the eastern plain of Beijing following the SNWDP, this study employs Ascending (ASC) and Descending (DES) InSAR data combined with a Strain Model (SM) to obtain a Three-Dimensional (3-D) deformation field from 2016 to 2018. Through analysis of the 3-D deformation characteristics and spatiotemporal evolution of land subsidence in this region from 2016 to 2018, the results reveal a shift in the distribution of subsiding areas after the South-to-North Water Diversion, with a marked decrease in subsidence rates in certain areas. The maximum subsidence rate in the Beijing area has decreased to 110 mm/yr, accompanied by horizontal deformation at a rate of 12 mm/yr. Additionally, by examining the spatial relationship between major active faults and subsidence deformation in this region, the study further elucidates the influence of fault activity on the spatial distribution of subsidence deformation.

Assessment of the TFM in predicting the onset of turbulent fluidization

Accurate prediction of the onset of turbulent fluidization still remains elusive owing to the dependence of the transition velocity on several factors including measurement methods and interpretation of results. In this work, numerical simulations using the two fluid model (TFM) are performed in an attempt to predict the regime change reported by Gopalan etal.(2016) in a small scale pseudo-2D gas-solid fluidized bed containing Geldart D particles. Various time and frequency domain analyses were applied on predicted absolute and differential pressure time series data to reveal the bed dynamics. Numerical predictions of the transition velocity, Uc are in reasonably good agreement with experimental results from the small scale challenge problem. The literature correlations completely fail to predict the transition velocity for the system considered in this work. This work thus provides a different approach for validating the CFD model against experimental measurements.

Important mesoscale phenomena in gas phase fluidized bed ethylene polymerization

Gas phase fluidized bed processes have been widely applied to polyethylene production.In these processes,the flow,mass transfer,and reaction rate on the microscale and macroscale are strongly coupled because of the multiphase and multiscale nature of the fluidization system.Understanding mesoscale phenomena is therefore essential to the quantitative translation of the knowledge obtained from the microscale to the macroscale.This paper reviews the development of ethylene polymerization gas phase processes while focussing on studies regarding mesoscale phenomena.These include experimental characterizations,mathematical modelling and control strategies.Trends and future developments in this field are also discussed.