Calculation of settling velocity of small solid particles in stratified suspension flows

1996 ◽  
Vol 22 ◽  
pp. 145
Author(s):  
Y Pyrkin
Keyword(s):  
Settling Velocity ◽  
Solid Particles ◽  
Suspension Flows

scholarly journals Can terminal settling velocity and drag of natural particles in water ever be predicted accurately?

2020 ◽  
Author(s):  
Onno J. I. Kramer ◽  
Peter J. de Moel ◽  
Shravan K. R. Raaghav ◽  
Eric T. Baars ◽  
Wim H. van Vugt ◽  
...  
Keyword(s):  
Drinking Water ◽  
Measurement Errors ◽  
Settling Velocity ◽  
Particle Density ◽  
Fixed Bed ◽  
Drinking Water Treatment ◽  
Liquid System ◽  
Solid Particles ◽  
Spherical Particles ◽  
Fluidised Bed

Abstract. Natural particles are frequently applied in drinking water treatment processes in fixed bed reactors, in fluidised bed reactors, and in sedimentation processes to clarify water and to concentrate solids. When particles settle, it has been found that in terms of hydraulics, natural particles behave differently when compared to perfectly round spheres. To estimate the terminal settling velocity of single solid particles in a liquid system, a comprehensive collection of equations is available. For perfectly round spheres, the settling velocity can be calculated quite accurately. However, for naturally polydisperse non-spherical particles, experimentally measured settling velocities of individual particles show considerable spread from the calculated average values. This work aimed to analyse and explain the different causes of this spread. To this end, terminal settling experiments were conducted in a quiescent fluid with particles varying in density, size and shape. For the settling experiments, opaque and transparent spherical polydisperse and monodisperse glass beads were selected. In this study, we also examined drinking water related particles, like calcite pellets and crushed calcite seeding material grains, both applied in drinking water softening. Polydisperse calcite pellets were sieved and separated to acquire more uniformly dispersed samples. In addition, a wide variety of grains with different densities, sizes and shapes were investigated for their terminal settling velocity and behaviour. The derived drag coefficient was compared with well-known models such as Brown–Lawler. A sensitivity analysis showed that the spread is caused to a lesser extent by variations in fluid properties, measurement errors and wall effects. Natural variations in specific particle density, path trajectory instabilities and distinctive multi-particle settling behaviour caused a slightly larger degree of spread. In contrast, greater spread is caused by variations in particle size, shape and orientation.

scholarly journals Effects of salinity on solid particle settling velocity in non-Newtonian Herschel–Bulkley fluids

2021 ◽  
Author(s):  
Robert Moukhametov ◽  
Anurag Srivastava ◽  
Syeda Akhter ◽  
Jerahmeel Bautista ◽  
Hicham Ferroudji ◽  
...  
Keyword(s):  
Oil And Gas ◽  
Settling Velocity ◽  
Terminal Velocity ◽  
Solid Particles ◽  
Accurate Estimation ◽  
Shear Stresses ◽  
Drilling Technology ◽  
Concentration Result ◽  
Oil And Natural Gas ◽  
Different Diameters

AbstractSettling velocity or depositional velocity is considered a key parameter to account for in the drilling technology of oil and gas wells as well as hydrocarbon processing since an accurate estimation of this parameter allows the transport of cuttings efficiently, avoids non-productive time, and helps avoid costly problems. Understanding the settling velocity in fluid with high salinity will help for the better separation of oil and natural gas streams in processing facilities. Although a great amount of effort was given to rheology and settling velocity measurements for power-law fluid and Bingham fluids, there are limited studies available in the literature for Herschel–Bulkley (H–B) fluid with salinity. The present study analyzes the fluid rheology of non-Newtonian fluids with, and without, salinity. Moreover, experiments have been conducted to measure the settling velocity of different diameters of solid particles through Herschel–Bulkley fluids with various salinity conditions. For the rheology analysis, it is found that higher weight percentages of NaCl lead to low values of shear stresses. As well, higher weight percentages of CaCl2 concentration result in a slight increase in shear stresses per a given shear rate. On the other hand, higher percentages of salt concentration cause an increase in the terminal velocity.

scholarly journals The characteristics and in-sewer transport potential of solids derived from domestic food waste disposers

2021 ◽  
Author(s):  
Abigail Legge ◽  
Andy Nichols ◽  
Henriette Jensen ◽  
Simon Tait ◽  
Richard Ashley
Keyword(s):  
Particle Size ◽  
Specific Gravity ◽  
Food Waste ◽  
Settling Velocity ◽  
Solid Particles ◽  
Size Distributions ◽  
Particle Size Distributions ◽  
Egg Shell ◽  
Shell Particles ◽  
Domestic Food

Abstract This study aims to assess the transportability of food waste disposer particles within a sewer system. A series of laboratory studies have examined the physical characteristics of solid particles derived from domestic food waste disposers. Particle size distributions and maximum settling velocity characteristics were measured for 18 common food types, and stored in a publicly accessible database. Particle size distributions are shown to fit well with a 2-parameter Gamma distribution. Settling velocity is generally higher for larger particles, except when particle density and sphericity changes. For most food types, particle specific gravity was close to unity. Egg shell particles had a significantly higher specific gravity. This information, combined with the particle size data has been used to show that there is a very low likelihood of food waste particle deposition in sewers during normal operational flows, other than temporary transient deposits of egg shell particles.

scholarly journals Can terminal settling velocity and drag of natural particles in water ever be predicted accurately?

2021 ◽  
Vol 14 (1) ◽  
pp. 53-71
Author(s):  
Onno J. I. Kramer ◽  
Peter J. de Moel ◽  
Shravan K. R. Raaghav ◽  
Eric T. Baars ◽  
Wim H. van Vugt ◽  
...  
Keyword(s):  
Drinking Water ◽  
Measurement Errors ◽  
Settling Velocity ◽  
Particle Density ◽  
Fixed Bed ◽  
Drinking Water Treatment ◽  
Solid Particles ◽  
Spherical Particles ◽  
Fluidised Bed ◽  
Natural Variations

Abstract. Natural particles are frequently applied in drinking water treatment processes in fixed bed reactors, fluidised bed reactors, and sedimentation processes to clarify water and to concentrate solids. When particles settle, it has been found that, in terms of hydraulics, natural particles behave differently when compared to perfectly round spheres. To estimate the terminal settling velocity of single solid particles in a liquid system, a comprehensive collection of equations is available. For perfectly round spheres, the settling velocity can be calculated quite accurately. However, for naturally polydisperse non-spherical particles, experimentally measured settling velocities of individual particles show considerable spread from the calculated average values. This work aims to analyse and explain the different causes of this spread. To this end, terminal settling experiments were conducted in a quiescent fluid with particles varying in density, size, and shape. For the settling experiments, opaque and transparent spherical polydisperse and monodisperse glass beads were selected. In this study, we also examined drinking-water-related particles, like calcite pellets and crushed calcite seeding material grains, which are both applied in drinking water softening. Polydisperse calcite pellets were sieved and separated to acquire more uniformly dispersed samples. In addition, a wide variety of grains with different densities, sizes, and shapes were investigated for their terminal settling velocity and behaviour. The derived drag coefficient was compared with well-known models such as the one of Brown and Lawler (2003). A sensitivity analysis showed that the spread is caused, to a lesser extent, by variations in fluid properties, measurement errors, and wall effects. Natural variations in specific particle density, path trajectory instabilities, and distinctive multi-particle settling behaviour caused a slightly larger degree of the spread. In contrast, a greater spread is caused by variations in particle size, shape, and orientation. In terms of robust process designs and adequate process optimisation for fluidisation and sedimentation of natural granules, it is therefore crucial to take into consideration the influence of the natural variations in the settling velocity when using predictive models of round spheres.

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