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Hydraulic gradient prediction for solid-water mixture flow through horizontal pipelines of different diameters and roughness and solids concentrations

Osra Faisal A.

Journal of Water and Land Development

2021

no. 49

267--272

In wastewater treatment plants, large pumps are often used to accommodate unknown hydraulic properties of solid-water mixture flow. The use of large pumps translates into higher purchasing and operating costs. Wastewater mixture is pumped with solids of different types and concentrations through pipelines. The design of these ducts is mainly based on the hydraulic laws of solid-water mixture which is represented by a corrected friction coefficient corresponding to the concentration of solids in water. This paper experimentally studies hydraulic properties of solid-water mixtures in pipelines by the varying Froude number (Fr), which represents the velocity mixture, solid concentration, pipeline diameter and pipeline material type-roughness coefficient. The experiments have been conducted in the wastewater treatment plant where six solid concentrations can be found ranging from 2 to 12% by weight. The pipe diameter ranges between 100 to 300 mm. It has been found that both the friction coefficient and the hydraulic gradient ameliorate with the increase of the pipeline roughness and the solids concentration in the water mixture, whereas the Fr drop with the diameter of the pipeline. The results are translated into curves and equations to predict the corrected pipeline friction coefficient and the hydraulic gradient of the solid-water mixture flow through horizontal pipelines at various solids concentrations, roughness and diameters.

Decreasing wall shear stress in hydromixture flow after deflocculant application

Jaworska-Jóźwiak Beata

TASK Quarterly : scientific bulletin of Academic Computer Centre in Gdansk

2018

Vol. 22, No 3

225--235

The aim of the paper is to present the influence of selected deflocculants on decreasing the hydromixture viscosity and as a consequence decreasing the wall shear stresses in a flowing medium. Adding deflocculants to improve the conditions encountered in a pipeline during the hydromixture flow is called chemical processing. The experimental studies presented in the article were performed for a hydromixture with a mass concentration of 20% and 43% consisting mostly of solids with the averaged diameter equal to 45.5μm. The measurements were performed for varied doses of deflocculants in three proportions in a wide range of shear rates. The results of experiments have confirmed that the influence of the deflocculant on the wall shear stress is complex as there is an opposing phenomenon strongly depending on the doses of deflocculant samples. The results of the experiments are discussed and major conclusions are drawn.