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Estimation of settling velocity using generalized reduced gradient (GRG) and hybrid generalized reduced gradient–genetic algorithm (hybrid GRG GA)

Shivashankar M., Pandey Manish, Zakwan Mohammad

Acta Geophysica

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2022

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Vol. 70, no 5

2487--2497

EN

This study describes the settling velocity phenomenon and deals with the methods for its estimation. The accuracy of three previously proposed settling velocity equations is also checked in this study. After graphical and statistical analysis, the authors proposed generalized reduced gradient (GRG) and hybrid generalized reduced gradient–genetic algorithm (hybrid GRG-GA) approaches for the estimation of settling velocity. Hybrid GRG-GA-based settling velocity approach showed more precise results than GRG approach. In addition, hybrid GRG-GA and GRG approaches were compared with previously proposed equations using 226 data points. The graphical and statistical analysis shows that the hybrid GRG-GA and GRG approaches give better agreement with observed data points as compared to previously proposed equations. Application of hybrid GRG-GA reduces the sum of square of error in fall velocity by over 70% and 30% on an average as compared to previous equations during training and testing, respectively. This study highlights that the hybrid GRG-GA approach could be efficiently used for calculating the settling velocity.

2

Reinvestigation on Mixing Length in an Open Channel Turbulent Flow

Kundu S., Kumbhakar M., Ghoshal K.

Acta Geophysica

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2018

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Vol. 66, no. 1

93--107

EN

The present study proposes a model on vertical distribution of streamwise velocity in an open channel turbulent flow through a newly proposed mixing length, which is derived for both clear water and sedimentladen turbulent flows. The analysis is based on a theoretical consideration which explores the effect of density stratification on the streamwise velocity profile. The derivation of mixing length makes use of the diffusion equation where both the sediment diffusivity and momentum diffusivity are taken as a function of height from the channel bed. The damping factor present in the mixing length of sediment-fluid mixture contains velocity and concentration gradients. This factor is capable of describing the dip-phenomenon of velocity distribution. From the existing experimental data of velocity, the mixing length data are calculated. The pattern shows that mixing length increases from bed to the dip-position, having a larger value at dip-position and then decreases up to the water surface with a zero value thereat. The present model agrees well with these data sets and this behavior cannot be described by any other existing model. Finally, the proposed mixing length model is applied to find the velocity distribution in wide and narrow open channels.The derived velocity distribution is compared with laboratory channel data of velocity, and the comparison shows good agreement.

3

Prędkość opadania zakłóconego cząstek stałych w emulsjach

Kawalec-Pietrenko B., Hołowacz I.

Inżynieria i Aparatura Chemiczna

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2006

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Nr 6s

112-113

EN

The sedimentation velocity of solid particles in 0/W emulsions has been measured. It was found that the settling velocity was an exponential function of the particle volume concentration for the low Reynolds number regime and emulsions exhibiting viscous Newtonian liquid behaviour.