Direct Numerical Simulation of Water Droplets in Turbulent Flow

Details on the fall speeds of raindrops are essential in both applications and natural events, such as rain-rate retrieval and soil erosion. Here, we examine the influence of turbulence on the terminal velocity of two water drops of different sizes. For the first time, computations of droplets in tu...

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Bibliographic Details
Published in:Fluids (Basel) 2020-09, Vol.5 (3), p.158
Main Authors: Ren, Weibo, Reutzsch, Jonathan, Weigand, Bernhard
Format: Article
Language:English
Subjects:
Computational fluid dynamics
Computer simulation
Deformation
Direct numerical simulation
Droplets
Erosion rates
Flow characteristics
Fluid flow
internal circulation
Kinetic energy
Markov analysis
Rain
raindrop
Raindrops
Reynolds number
Shear layers
Simulation
Soil erosion
Terminal velocity
turbulence
Turbulence intensity
Turbulent flow
Velocity
volume of fluid method (VOF)
wake recirculation
Water drops
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Summary:Details on the fall speeds of raindrops are essential in both applications and natural events, such as rain-rate retrieval and soil erosion. Here, we examine the influence of turbulence on the terminal velocity of two water drops of different sizes. For the first time, computations of droplets in turbulent surroundings are conducted with a direct numerical simulation code based on a volume of fluid method. Both the drop surface deformation and internal circulation are captured. The turbulence intensity at the inflow area, as well as the turbulence length scale are varied. In turbulent flow, we find a decline in the terminal velocities for both drops. Based on the study of the wake flow characteristics and drop surface deformation, the decrease in the terminal velocity is found to be directly linked to a shortening of the wake recirculation region resulting from an earlier and more drastic increase in the turbulence kinetic energy in the shear layer. The turbulent surroundings trigger substantial rises in the drop axis ratio amplitude and a slight increase in the drop oscillation frequency, but barely influence the time-averaged drop axis length.
ISSN:2311-5521
2311-5521
DOI:10.3390/fluids5030158