Research Papers: Flows in Complex Systems

Experimental and Numerical Investigations on Withdrawal of Water-Capped Viscoplastic Fluid

[+] Author and Article Information
Amir H. Azimi

Department of Civil Engineering,
Lakehead University,
Thunder Bay, ON P7B 5E1, Canada
e-mail: azimi@lakeheadu.ca

Jianan Cai

Department of Civil and Environmental
University of Alberta,
Edmonton, AB T6G 2W2, Canada
e-mail: jianan@ualberta.ca

David Z. Zhu

Department of Civil and Environmental
University of Alberta,
Edmonton, AB T6G 2W2, Canada
e-mail: david.zhu@ualberta.ca

Nallamuthu Rajaratnam

Professor Emeritus
Department of Civil and Environmental
University of Alberta,
Edmonton, AB T6G 2W2, Canada
e-mail: nrajaratnam@ualberta.ca

Contributed by the Fluids Engineering Division of ASME for publication in the JOURNAL OF FLUIDS ENGINEERING. Manuscript received July 10, 2016; final manuscript received March 3, 2017; published online May 18, 2017. Assoc. Editor: Mhamed Boutaous.

J. Fluids Eng 139(8), 081102 (May 18, 2017) (14 pages) Paper No: FE-16-1434; doi: 10.1115/1.4036267 History: Received July 10, 2016; Revised March 03, 2017

Withdrawal of water-capped viscoplastic fluid was investigated using laboratory experimentation and numerical modeling. The viscoplastic fluid was modeled using a Laponite suspension, which was withdrawn by a vertical pipe intake. Variations of the Laponite–water interface and intake configurations were investigated in this study. The critical submergence, the depth of the intake in the Laponite layer when the upper water begins to withdraw, was studied under different experimental conditions, and the critical depths were measured for different flow rates. An empirical relationship was found between the withdrawal flow rate and the critical submergence. The averaged Laponite velocity was measured at different withdrawal stages to identify the critical stage. A series of numerical simulations were conducted to study the effect of intake structures so that a maximum amount of the Laponite suspension can be withdrawn before the water layer being withdrawn. It was found that a combination of a collar and a cone with an edge length to the intake diameter of 1.5 can increase the pumping duration by 16.7%. The installation of a collar or collar-cone setup can also decrease the disturbance in Laponite layer.

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Fig. 1

Schematic of experimental setup and computational domain. The top water layer, hw and the transparent bottom layer, ha + hb, is the Laponite suspension.

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Fig. 2

Schematic of computational boundary and local mesh resolution with intake element arrangement: (a) computational boundary and numerical coordinate system and (b) computational domain was simulated as a cylinder with a radius of 0.25 m and an angle of 3.6 deg

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Fig. 3

Variation of the Laponite–water interface with time for test E3: (a) t = 60 s, (b) t = 90 s, (c) tc = 119 s (the critical regime), (d) t = 180 s, (e) t = 210 s, and (f) t = 240 s

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Fig. 4

Images of Laponite suspension at different times during flow withdrawal of test E9 show the two-dimensional velocity fields developing at the vicinity of the pipe intake. The dark gray area at the top corner of most images shows the top water layer and the rest light gray area is the Laponite: (a) t = 40 s, (b) t = 80, (c) t = 90 s (critical regime, tc = 87 s), (d) t = 120 s, (e) t = 160 s, (f) t = 200 s, (g) t = 240 s, (h) t = 280 s, and (i) t = 320 s (see color figure online).

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Fig. 5

Effect of withdrawal velocity on the deformation of Laponite–water interface with time: (a) test E3 (uo = 4.27 m/s) and (b) test E9 (uo = 0.53 m/s); Δh is the interface drop at each time step

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Fig. 6

Laponite–water interface at the critical stage for tests E1, E3, E5, E6, E8, E9, and E10

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Fig. 7

Effects of withdrawal flow rate and pumping time on the variations of the Laponite–water interface level for tests E3, E8, and E10: (a) variations of h with time. Solid points indicate the time corresponding to the critical stage for each test. (b) Correlations of h with withdrawal flow rates of Laponite QL and water QW.

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Fig. 8

Variations of f(θ) with θ for test E9. Stable stage in subcritical regime at t = 48 s. Intermediate stage at t = 215 s, which both Laponite and water are withdrawing. Stable stage when all the water has been taken out by the pump and Laponite is withdrawing again (t = 256 s).

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Fig. 9

Deformation of the Laponite–water interface from the beginning of interface deformation at t = 100 s to the critical stage at tc = 108 s for test S3 (E8)

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Fig. 10

Schematic sketch of nozzle configuration for numerical experiments: (a) a collar with sharp edges for cases S4 and S5 and (b) a collar with a cone on the top corresponding to cases S6–S9

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Fig. 11

Variations of Lapotine–water interface profiles for different nozzle configurations. The flow condition is similar to the experimental test E8 (i.e., Q = 206 mL/s). Numbers on the interface profiles are the time from the onset of withdrawal in seconds: (a) case S4, (b) case S5, (c) case S6, (d) case S7, (e) case S8, and (f) case S9.

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Fig. 12

Contour plots of the water velocity at the onset of steady-state regime (critical time, tc) for different nozzle configurations: (a) case S3 (tc = 108 s), (b) case S4 (tc = 106 s), (c) case S5 (tc = 116 s), (d) case S6 (tc = 98 s), (e) case S7 (tc = 126 s), (f) case S8 (tc = 105 s), and (g) case S9 (tc = 85 s)

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Fig. 13

Variations of the computed shear rate of Laponite with radial distance from the virtual origin (1.4do below the intake) for different nozzle configurations: (a) θ = 30 deg, (b) θ = 60 deg, (c) θ = 90 deg, and (d) θ = 120 deg. The thick horizontal line shows the shear rate of 0.084 s − 1 as an indicator of the active flow region for τ/τo = 0.01%.




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