scholarly journals A CFD-PBM coupled model under entire turbulent spectrum for simulating a bubble column with highly viscous media

2021 ◽  
Author(s):  
Huahai Zhang ◽  
Yuelin Wang ◽  
Ali Sayyar ◽  
Tiefeng Wang
Keyword(s):  
Bubble Column ◽  
Coupled Model ◽  
Turbulent Energy ◽  
Balance Model ◽  
Inertial Subrange ◽  
Liquid Viscosity ◽  
Bubble Breakup ◽  
Turbulent Spectrum ◽  
Hydrodynamic Behaviors ◽  
Breakup Model

To account for the effect of liquid viscosity, the bubble breakup model considering turbulent eddy collision based on the inertial subrange turbulent spectrum was extended to the entire turbulent spectrum that included the energy-containing, inertial, and energy-dissipation subranges. The computational fluid dynamics-population balance model (CFD-PBM) coupled model was modified to include this extended bubble breakup model for simulations of a bubble column. The effect of turbulent energy spectrum on the bubble breakup and hydrodynamic behaviors was studied in a bubble column under different liquid viscosities. The results showed that when the liquid viscosity was < 80 mPas, the bubble breakup and hydrodynamics were almost independent on the turbulent spectrum. At liquid viscosity > 80 mPas, the bubble breakup rate and gas holdup were significantly under-predicted when the inertial turbulent spectrum was used, and when using the entire turbulent spectrum the predictions were more consistent with experimental data.

scholarly journals Numerical Simulation Study on Distribution of Bubble in Flow near Aerator Based on CFD-PBM Coupled Model in Tunnel

2021 ◽  
Vol 2021 ◽  
pp. 1-24
Author(s):  
Jiaming Lei ◽  
Jianmin Zhang ◽  
Lifang Zhang
Keyword(s):  
Size Distribution ◽  
Bubble Size ◽  
Numerical Models ◽  
Coupled Model ◽  
Bubble Size Distribution ◽  
Balance Model ◽  
Main Process ◽  
Air Bubbles ◽  
Air Concentration ◽  
Aerated Flow

The aerator can reduce erosion by mixing a large amount of air into the water in the solid wall area. The effectiveness of erosion reduction is mainly based on air concentration and its bubble size distribution. However, simultaneous simulation of the air concentration and its bubble size distribution in numerical simulations is still a hot and difficult area of research. Aiming at the downstream aerated flow of hydraulic aeration facilities, several numerical models, such as VOF, mixture, Euler, and Population Balance Model (PBM), are compared and verified by experiments. The results show that the CFD-PBM coupled model performs well compared to other conventional multiphase models. It can not only obtain the evolution law of the bubble distribution downstream of the aerator but also accurately simulate the recombination and evolution process of bubble aggregation and breakage. The Sauter mean diameter of the air bubbles in the aerated flow decreases along the way and eventually reaches a stable value. The bubble breakage is the main process in the development of the bubbles. It reveals the aeration law that the small air bubbles are closer to the bottom plate, while the large bubbles float up along the aerated flow, which provides a powerful support for the basic research on the mechanism of aeration and erosion reduction.

An Ocean Refractometer: Resolving Millimeter-Scale Turbulent Density Fluctuations via the Refractive Index

2006 ◽  
Vol 23 (1) ◽  
pp. 121-137 ◽  
Author(s):  
Matthew H. Alford ◽  
David W. Gerdt ◽  
Charles M. Adkins
Keyword(s):  
Refractive Index ◽  
Density Fluctuations ◽  
Inertial Subrange ◽  
Conductivity Measurements ◽  
Velocity Fluctuations ◽  
Fiber Motion ◽  
Turbulent Spectrum ◽  
Ocean Measurements ◽  
Fiberoptic Sensor ◽  
Better Than

Abstract A fiberoptic sensor has been constructed to measure oceanic density fluctuations via their refractive index signature. The resolution (Δz = 1 mm, Δt = 0.2 ms) and precision (Δn &lt; 10−8, Δρ = 3.4 × 10−5 kg m−3) of the device are far better than other methods and are sufficient to resolve the entire turbulent spectrum. Spectra show the salinity Batchelor rolloff at levels undetectable via conductivity measurements. However, the low-wavenumber portion of the spectrum occupied by the turbulent inertial subrange (≈1 m–1 cm scales) is marred by noise resulting from fiber motion in response to turbulent velocity fluctuations. The technique is described, and the first ocean measurements are reported.

An improved bubble breakup model in turbulent flow

2020 ◽  
Vol 386 ◽  
pp. 121484 ◽  
Author(s):  
Huahai Zhang ◽  
Guangyao Yang ◽  
Ali Sayyar ◽  
Tiefeng Wang
Keyword(s):  
Turbulent Flow ◽  
Bubble Breakup ◽  
Breakup Model

Application of Population Balance Model in the Simulation of Slurry Bubble Column

2014 ◽  
Vol 53 (12) ◽  
pp. 4922-4930 ◽  
Author(s):  
Lijia Xu ◽  
Zihong Xia ◽  
Xiaofeng Guo ◽  
Caixia Chen
Keyword(s):  
Bubble Column ◽  
Population Balance ◽  
Balance Model ◽  
Population Balance Model ◽  
Slurry Bubble Column
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