The Influence of Temperature on the Bulk Settling of Cohesive Sediment in Still Water with the Lattice Boltzmann Method

Guang-Quan Qiao,Xi Feng,Wei-Bing Feng,Jin-Feng Zhang,Yong-Chang Lu,Qing-He Zhang

doi:10.3390/w11050945

Abstract

Flocculation is very common and significant for cohesive sediment in coastal areas, and the influence of temperature on it cannot be neglected. The Lattice Boltzmann Method (LBM), combined with the extended Derjaguin‒Landau‒Verwey‒Overbeek (XDLVO) theory, which considers the micro-interaction forces between particles, was applied to simulate the settling and flocculation processes of cohesive sediment under various temperature conditions. The floc size, floc volume, suspended sediment concentration (SSC), and settling velocities were analyzed. The analyses revealed that with increasing temperature, both the mean floc diameter and floc volume grew, while the maximum floc diameter initially increased and then slightly decreased with its peak at 10 °C. During settling, the SSC change rate was exponentially related to the SSC, with an optimal fitting index of 0.3. The LBM sediment settling velocity was also compared with some formulas and physical model tests; the comparison results consistently demonstrated that the LBM was reasonable for modeling the bulk settling of cohesive sediment. Further discussions illustrated that the cohesive sediment is more difficult to flocculate at low temperatures due to the low aggregation frequency, while at high temperatures, some large flocs broke easily due to the effect of the short-distance force and macro force.

Highlights

IntroductionAs a result of its own physical properties and external environments, cohesive sediment can form flocs
Cohesive sediment is an important type of sediment in the near shore zone
During the same settling period, both both the floc floc sizes and floc volume increased with increasing temperature

Summary

Introduction

As a result of its own physical properties and external environments, cohesive sediment can form flocs . Temperature is one of many factors that influence flocculation [1,2,3]. Much research has been conducted to study the influence of temperature on cohesive sediment. Lau [8] studied temperature’s effects on the settling velocity and deposition of cohesive sediment in an annular channel of distilled water that was housed in a temperature-controlled chamber. He claimed that, as temperature increased, the repulsive forces between particles increased

Methods

Discussion

Conclusion