DOI: 10.5281/zenodo.18714123
title: Three-phase flow regimes and bed expansion in fluidized beds under low-density-ratio conditions

description: This dataset provides processed steady-state experimental measurements obtained in a laboratory-scale three-phase fluidized bed reactor (gas–liquid–solid system). The database has been generated to support detailed hydrodynamic analysis and to provide a reliable benchmark dataset for Computational Fluid Dynamics (CFD) model development and validation of low solid–liquid density contrast systems, such as Expanded Granular Sludge Bed (EGSB) and Upflow Anaerobic Sludge Blanket (UASB) reactors.

The experimental facility consists of a transparent cylindrical column with a total height of 1400 mm and an inner diameter of 68 mm, operated in co-current upward flow. The solid phase is composed of millimetric particles representative of granular sludge systems, while the liquid phase density was varied to reproduce low relative density difference conditions characteristic of anaerobic bioreactors. Gas was injected at the bottom of the column through a multi-point distributor to ensure uniform phase interaction,


The reported bed heights were determined using a non-intrusive optical image-processing methodology. Time-averaged grayscale images were computed, and vertical grayscale profiles were extracted from a central horizontal band of the column (605 vertical pixel positions). The contribution of gas-phase optical attenuation was removed using background recordings without solids. The bed interface position was identified as the axial location where the processed grayscale profile crossed a fixed threshold value corresponding to 70% of the grayscale range (g70 criterion). 

 

The dataset incudes two files:

 



File 01: FluidizedBed_ExperimentalDatabase.csv

Format: Comma-separated values (CSV)Variables: 




Column Name
 Description
 Units


CaseID
Sequential identifier of each experimental case.
        -


LiquidDensity 
 Liquid phase density
     kg·m⁻³


ParticleDiameter
Mean particle diameter
       m


jl
Superficial liquid velocity
      m·s⁻¹


jg
Superficial gas velocity
      m·s⁻¹


Ut
Particle terminal velocity
      m·s⁻¹


h
Measured bed heigh
      mm





 

 



Note: In order to exclude cases in which washout occurs and the grayscale level increases directly from the base of the reactor, resulting in non-physical bed height estimations, the following criterion was established to filter the valid range of cases considered in this study:  h>100 mm & h<600 mm


 



File 02: Greyscale.mat


Format:  MATLAB MAT-file (version 7.3)

Software: MATLAB R2023bVariables: 

 

 

 






ResCases.VAR
 Description
 Units


profile
Time-averaged vertical grayscale intensity profiles extracted from the central region of the reactor
     -


Jl
Superficial liquid velocity
       m·s⁻¹


Jg
Superficial gas velocity
       m·s⁻¹


D
Mean particle diameter
 mm


px2mm
900mm/605px
      mm/px


alphalim
0.70 (Threshold vale)
    -


L
900 (Effective measurement height of the column)
   mm





 

Type: 4-D double array -> (rho_index, D_index, Jl_index, Jg_index)



Type: 5-D double array -> (rho_index, D_index, Jl_index, Jg_index, vertical pixel profile)


 





rho_index: [1] -> 1000 kg·m⁻³ ; [2] -> 1025 kg·m⁻³.

D_index: [1] and [2]  empty of particles (background cases) ;[3] -> 2.5mm ; [4]-> 4mm.

Jl_index: 11 superficial liquid velocities for each case. 

Jg_index: 10 superficial gas velocities for each case. 

vertical pixel profile: 605 vertical pixel positions used to map grayscale intensity at each height level.