Fractal dimension of cohesive sediment flocs at steady state under seven shear flow conditions
The morphological properties of kaolin flocs were investigated in a Couetteflow experiment at the steady state under seven shear flow conditions (shear rates of 5.36, 9.17, 14, 24, 31, 41 and 53 s ^{1}). These properties include a onedimensional (1D) fractal dimension (D _{1}), a twodimensional (2D) fractal dimension (D _{2}), a perimeterbased fractal dimension (D _{pf}) and an aspect ratio (AR). They were calculated based on the projected area (A), equivalent size, perimeter (P) and length (L) of the major axis of the floc determined through sample observation and an image analysis system. The parameter D _{2}, which characterizes the relationship between the projected area and the length of the major axis using a power function, A ∝ L ^{D2}, increased from 1.73 ± 0.03, 1.72 ± 0.03, and 1.75 ± 0.04 in the low shear rate group (G = 5.36, 9.17, and 14 s ^{1}) to 1.92 ± 0.03, 1.82 ± 0.02, 1.85 ± 0.02, and 1.81 ± 0.02 in the high shear rate group (24, 31, 41 and 53 s ^{1}), respectively. The parameter D _{1} characterizes the relationship between the perimeter and length of the major axis by the function P ∝ L ^{D1} and decreasedmore »
 Authors:

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 Beijing Normal University (China). College of Water Sciences.
 The Univ. of Tokyo, Kashiwa (Japan). Dept. of Natural Environmental Studies.
 Argonne National Lab. (ANL), Lemont, IL (United States)
 Publication Date:
 Grant/Contract Number:
 AC0206CH11357
 Type:
 Accepted Manuscript
 Journal Name:
 Water (Basel)
 Additional Journal Information:
 Journal Name: Water (Basel); Journal Volume: 7; Journal Issue: 8; Journal ID: ISSN 20734441
 Publisher:
 MDPI
 Research Org:
 Argonne National Lab. (ANL), Argonne, IL (United States)
 Sponsoring Org:
 USDOE Office of Science (SC)
 Country of Publication:
 United States
 Language:
 English
 Subject:
 37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; flocculation; fractal dimension; cohesive sediment; steady state; shear flow
 OSTI Identifier:
 1213671
Zhu, Zhongfan, Yu, Jingshan, Wang, Hongrui, Dou, Jie, and Wang, Cheng. Fractal dimension of cohesive sediment flocs at steady state under seven shear flow conditions. United States: N. p.,
Web. doi:10.3390/w7084385.
Zhu, Zhongfan, Yu, Jingshan, Wang, Hongrui, Dou, Jie, & Wang, Cheng. Fractal dimension of cohesive sediment flocs at steady state under seven shear flow conditions. United States. doi:10.3390/w7084385.
Zhu, Zhongfan, Yu, Jingshan, Wang, Hongrui, Dou, Jie, and Wang, Cheng. 2015.
"Fractal dimension of cohesive sediment flocs at steady state under seven shear flow conditions". United States.
doi:10.3390/w7084385. https://www.osti.gov/servlets/purl/1213671.
@article{osti_1213671,
title = {Fractal dimension of cohesive sediment flocs at steady state under seven shear flow conditions},
author = {Zhu, Zhongfan and Yu, Jingshan and Wang, Hongrui and Dou, Jie and Wang, Cheng},
abstractNote = {The morphological properties of kaolin flocs were investigated in a Couetteflow experiment at the steady state under seven shear flow conditions (shear rates of 5.36, 9.17, 14, 24, 31, 41 and 53 s1). These properties include a onedimensional (1D) fractal dimension (D1), a twodimensional (2D) fractal dimension (D2), a perimeterbased fractal dimension (Dpf) and an aspect ratio (AR). They were calculated based on the projected area (A), equivalent size, perimeter (P) and length (L) of the major axis of the floc determined through sample observation and an image analysis system. The parameter D2, which characterizes the relationship between the projected area and the length of the major axis using a power function, A ∝ LD2, increased from 1.73 ± 0.03, 1.72 ± 0.03, and 1.75 ± 0.04 in the low shear rate group (G = 5.36, 9.17, and 14 s1) to 1.92 ± 0.03, 1.82 ± 0.02, 1.85 ± 0.02, and 1.81 ± 0.02 in the high shear rate group (24, 31, 41 and 53 s1), respectively. The parameter D1 characterizes the relationship between the perimeter and length of the major axis by the function P ∝ LD1 and decreased from 1.52 ± 0.02, 1.48 ± 0.02, 1.55 ± 0.02, and 1.63 ± 0.02 in the low shear group (5.36, 9.17, 14 and 24 s1) to 1.45 ± 0.02, 1.39 ± 0.02, and 1.39 ± 0.02 in the high shear group (31, 41 and 53 s1), respectively. The results indicate that with increasing shear rates, the flocs become less elongated and that their boundary lines become tighter and more regular, caused by more breakages and possible restructurings of the flocs. The parameter Dpf, which is related to the perimeter and the projected area through the function , decreased as the shear rate increased almost linearly. The parameter AR, which is the ratio of the length of the major axis and equivalent diameter, decreased from 1.56, 1.59, 1.53 and 1.51 in the low shear rate group to 1.43, 1.47 and 1.48 in the high shear rate group. These changes in Dpf and AR show that the flocs become less convoluted and more symmetrical and that their boundaries become smoother and more regular in the high shear rate group than in the low shear rate group due to breakage and possible restructuring processes. To assess the effects of electrolyte and sediment concentration, 0.1 mol/L calcium chloride (CaCl2) and initial sediment concentration from 7.87 × 105 to 1.57 × 105 were used in this preliminary study. The addition of electrolyte and increasing sediment concentration could produce more symmetrical flocs with less convoluted and simpler boundaries. In addition, some new information on the temporal variation of the median size of the flocs during the flocculation process is presented.},
doi = {10.3390/w7084385},
journal = {Water (Basel)},
number = 8,
volume = 7,
place = {United States},
year = {2015},
month = {8}
}