scholarly journals Direct Numerical Simulation of Gas Transfer at Wind-Sheared Air-Water Interface

2014 ◽  
Vol 70 (2) ◽  
pp. I_46-I_50
Author(s):  
Ryosuke TERAOKA ◽  
Yuji SUGIHARA ◽  
Daisuke NAKAGAWA ◽  
Koji SHIONO
Keyword(s):  
Numerical Simulation ◽  
Direct Numerical Simulation ◽  
Gas Transfer ◽  
Water Interface ◽  
Air Water Interface

Blast Wave Mitigation from the Straight Tube by Using Water Part II - Numerical Simulation

2018 ◽  
Vol 910 ◽  
pp. 78-83 ◽  
Author(s):  
Yuta Sugiyama ◽  
Tomotaka Homae ◽  
Kunihiko Wakabayashi ◽  
Tomoharu Matsumura ◽  
Yoshio Nakayama
Keyword(s):  
Experimental Data ◽  
Numerical Simulation ◽  
Energy Transfer ◽  
Numerical Simulations ◽  
Blast Wave ◽  
Blast Waves ◽  
Straight Tube ◽  
Water Interface ◽  
Effect Of Water ◽  
Air Water Interface

This paper investigates explosions in a straight square tube in order to understand the mitigation effect of water on blast waves that emerge outside. Numerical simulations are used to assess the effect of water that is put inside the tube. The water reduces the peak overpressure outside, which agrees well with the experimental data. The increases in the kinetic and internal energies of the water are estimated, and the internal energy transfer at the air/water interface is shown to be an important factor in mitigating the blast wave in the present numerical method.

Dispersion of Particles on Liquid Surfaces

2011 ◽  
Author(s):  
Shriram B. Pillapakkam ◽  
Pushpendra Singh
Keyword(s):  
Numerical Simulation ◽  
Particle Size ◽  
Vertical Motion ◽  
Liquid Interface ◽  
Water Interface ◽  
Small Particles ◽  
Air Water Interface ◽  
Large Velocity ◽  
Simulation Results ◽  
Air Liquid Interface

In a recent study we have shown that when small particles, e.g., flour, pollen, glass, etc., contact an air-liquid interface, they disperse rapidly as if they were in an explosion. The rapid dispersion is due to the fact that the capillary force pulls particles into the interface causing them to accelerate to a large velocity. The vertical motion of a particle during its adsorption causes a radially-outward lateral (secondary) flow on the interface that causes nearby particles to move away. We present direct numerical simulation results for the adsorption of particles and show that the inertia of a particle plays an important role in its motion in the direction normal to a fluid-liquid interface. Although the importance of inertia diminishes with decreasing particle size, on an air-water interface the inertia continues to be important even when the size is as small as a few nanometers.

scholarly journals Influence of Turbulence Structure on Gas Transfer across Air-Water Interface

1999 ◽  
Vol 2 ◽  
pp. 673-684
Author(s):  
Iehisa NEZU ◽  
Tadanobu NAKAYAMA ◽  
Rie INOUE
Keyword(s):  
Gas Transfer ◽  
Turbulence Structure ◽  
Water Interface ◽  
Air Water Interface

scholarly journals Direct numerical simulation of gas transfer across the air–water interface driven by buoyant convection

2015 ◽  
Vol 787 ◽  
pp. 508-540 ◽  
Author(s):  
J. G. Wissink ◽  
H. Herlina
Keyword(s):  
Cold Water ◽  
Scaling Law ◽  
Numerical Code ◽  
Gas Transfer ◽  
Water Interface ◽  
Atmospheric Gases ◽  
Velocity Fluctuations ◽  
Air Water Interface ◽  
Schmidt Numbers ◽  
Time Accuracy

A series of direct numerical simulations of mass transfer across the air–water interface driven by buoyancy-induced convection have been carried out to elucidate the physical mechanisms that play a role in the transfer of heat and atmospheric gases. The buoyant instability is caused by the presence of a thin layer of cold water situated on top of a body of warm water. In time, heat and atmospheric gases diffuse into the uppermost part of the thermal boundary layer and are subsequently transported down into the bulk by falling sheets and plumes of cold water. Using a specifically designed numerical code for the discretization of scalar convection and diffusion, it was possible to accurately resolve this buoyant-instability-induced transport of atmospheric gases into the bulk at a realistic Prandtl number ($\mathit{Pr}=6$) and Schmidt numbers ranging from$\mathit{Sc}=20$to$\mathit{Sc}=500$. The simulations presented here provided a detailed insight into instantaneous gas transfer processes. The falling plumes with highly gas-saturated fluid in their core were found to penetrate deep inside the bulk. With an initial temperature difference between the water surface and the bulk of slightly above$2$ K, peaks in the instantaneous heat flux in excess of$1600~\text{W}~\text{m}^{-2}$were observed, proving the potential effectiveness of buoyant-convective heat and gas transfer. Furthermore, the validity of the scaling law for the ratio of gas and heat transfer velocities$K_{L}/H_{L}\propto (\mathit{Pr}/\mathit{Sc})^{0.5}$for the entire range of Schmidt numbers considered was confirmed. A good time-accurate approximation of$K_{L}$was found using surface information such as velocity fluctuations and convection cell size or surface divergence. A reasonable time accuracy for the$K_{L}$estimation was obtained using the horizontal integral length scale and the root mean square of the horizontal velocity fluctuations in the upper part of the bulk.

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