An integrative image measurement technique for dense bubbly flows with a wide size distribution

Karn, Ashish; Ellis, Christopher R.; Arndt, Roger E. A.; Hong, Jiarong

doi:10.1016/j.ces.2014.09.036

Cited by 89 publications

(49 citation statements)

References 35 publications

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“…Only projected bubble images could be obtained. This problem is well known and, despite some proposals (Bian et al, 2013;Sahagian and Proussevitch, 1998), a solution is far from being reached and the use of 2D projected images is a common way of processing bubble images (Karn et al, 2015;Lage and Espósito, 1999;Lau et al, 2013aLau et al, , 2013bWongsuchoto et al, 2003). However, the bubble shape data obtained by this approach are considered reliable: the bubble shape information allowed the extrapolation of correlations for the aspect ratio (Besagni, 2016; and flow regime transition criteria .…”

Section: Image Analysis: Uncertaintiesmentioning

confidence: 99%

The dual effect of viscosity on bubble column hydrodynamics

Besagni

Inzoli

Guido

et al. 2017

Chemical Engineering Science

110

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A B S T R A C TSome authors, in the last decades, have observed the dual effect of viscosity on gas holdup and flow regime transition in small-diameter and small-scale bubble columns. This work concerns the experimental investigation of the dual effect of viscosity on gas holdup and flow regime transition as well as bubble size distributions in a large-diameter and large-scale bubble column. The bubble column is 5.3 m in height, has an inner diameter of 0.24 m, and can be operated with gas superficial velocities in the range of 0.004-0.20 m/s. Air was used as the dispersed phase, and various water-monoethylene glycol solutions were employed as the liquid phase. The water-monoethylene glycol solutions that were tested correspond to a viscosity between 0.9 mPa s and 7.97 mPa s, a density between 997.086 kg/m 3 and 1094.801 kg/m 3 , a surface tension between 0.0715 N/m and 0.0502 N/m, and log 10 (Mo) between −10.77 and −6.55 (where Mo is the Morton number). Gas holdup measurements were used to investigate the global fluid dynamics and the flow regime transition between the homogeneous flow regime and the transition flow regime. An image analysis method was used to investigate the bubble size distributions and shapes for different gas superficial velocities, for different solutions of watermonoethylene glycol. In addition, based on the experimental data from the image analysis, a correlation between the bubble equivalent diameter and the bubble aspect ratio was proposed. The dual effect of viscosity, previously verified in smaller bubble columns, was confirmed not only with respect to the gas holdup and flow regime transition, but also for the bubble size distributions. Low viscosities stabilize the homogeneous flow regime and increase the gas holdup, and are characterized by a larger number of small bubbles. Conversely, higher viscosities destabilize the homogeneous flow regime and decrease the gas holdup, and the bubble size distribution moves toward large bubbles. The experimental results suggest that the stabilization/destabilization of the homogeneous regime is related to the changes in the bubble size distributions and a simple approach, based on the lift force, was proposed to explain this relationship. Finally, the experimental results were compared to the dual effect of organic compounds and inorganic compounds: future studies should propose a comprehensive theory to explain all the dual effects observed.

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Section: Image Analysis: Uncertaintiesmentioning

confidence: 99%

The dual effect of viscosity on bubble column hydrodynamics

Besagni

Inzoli

Guido

et al. 2017

Chemical Engineering Science

110

View full text Add to dashboard Cite

show abstract

“…In the present study, we have applied a method based on human recognition of the bubble edge Besagni and Inzoli, 2016b). This method was selected because, despite different image-processing algorithms that have been proposed, these techniques are still limited to resolve large bubble clusters, highly unsteady flows, and large void fractions (Karn et al, 2015). Additionally, at low holdup, there are problems associated with overlapping: if the holdup exceeds 1%, more than 40% of the bubbles are overlapping in the image (Lecuona et al, 2000;Rodríguez-Rodríguez et al, 2003).…”

Section: Introductionmentioning

confidence: 99%

Comprehensive experimental investigation of counter-current bubble column hydrodynamics: Holdup, flow regime transition, bubble size distributions and local flow properties

Besagni

Inzoli

2016

Chemical Engineering Science

113

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“…H was defined as the ratio of the particle perimeter to the perimeter of a circle having the same area. A perfect circle would have an H of 1 (Karn et al, 2014), while a lettuce area would have a circularity factor between 2 and 5, based on a preliminary investigation of 50 lettuce plants.…”

Section: Image Processing Methods and Regression Analysismentioning

confidence: 99%

Image Processing Methods for Measurement of Lettuce Fresh Weight

Park¹,

Han²,

Kim³

2015

Journal of Biosystems Engineering

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Purpose: Machine vision-based image processing methods can be useful for estimating the fresh weight of plants. This study analyzes the ability of two different image processing methods, i.e., morphological and pixel-value analysis methods, to measure the fresh weight of lettuce grown in a closed hydroponic system. Methods: Polynomial calibration models are developed to relate the number of pixels in images of leaf areas determined by the image processing methods to actual fresh weights of lettuce measured with a digital scale. The study analyzes the ability of the machine vision-based calibration models to predict the fresh weights of lettuce. Results: The coefficients of determination (> 0.93) and standard error of prediction (SEP) values (< 5 g) generated by the two developed models imply that the image processing methods could accurately estimate the fresh weight of each lettuce plant during its growing stage. Conclusions: The results demonstrate that the growing status of a lettuce plant can be estimated using leaf images and regression equations. This shows that a machine vision system installed on a plant growing bed can potentially be used to determine optimal harvest timings for efficient plant growth management.

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An integrative image measurement technique for dense bubbly flows with a wide size distribution

Cited by 89 publications

References 35 publications

The dual effect of viscosity on bubble column hydrodynamics

The dual effect of viscosity on bubble column hydrodynamics

Comprehensive experimental investigation of counter-current bubble column hydrodynamics: Holdup, flow regime transition, bubble size distributions and local flow properties

Image Processing Methods for Measurement of Lettuce Fresh Weight

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