Direct numerical simulation of rising bubble interaction with free surface using level contour reconstruction method

2012 ◽  
Vol 26 (10) ◽  
pp. 3141-3148 ◽  
Author(s):  
Seungwon Shin
Keyword(s):  
Numerical Simulation ◽  
Free Surface ◽  
Direct Numerical Simulation ◽  
Reconstruction Method ◽  
Rising Bubble ◽  
Contour Reconstruction ◽  
Bubble Interaction

scholarly journals Dissipation of shear-free turbulence near boundaries

2000 ◽  
Vol 422 ◽  
pp. 167-191 ◽  
Author(s):  
M. A. C. TEIXEIRA ◽  
S. E. BELCHER
Keyword(s):  
Numerical Simulation ◽  
Boundary Condition ◽  
Free Surface ◽  
Direct Numerical Simulation ◽  
Dissipation Rate ◽  
Solid Wall ◽  
Tangential Velocity ◽  
Main Role ◽  
Nonlinear Processes ◽  
Viscous Layer

The rapid-distortion model of Hunt & Graham (1978) for the initial distortion of turbulence by a flat boundary is extended to account fully for viscous processes. Two types of boundary are considered: a solid wall and a free surface. The model is shown to be formally valid provided two conditions are satisfied. The first condition is that time is short compared with the decorrelation time of the energy-containing eddies, so that nonlinear processes can be neglected. The second condition is that the viscous layer near the boundary, where tangential motions adjust to the boundary condition, is thin compared with the scales of the smallest eddies. The viscous layer can then be treated using thin-boundary-layer methods. Given these conditions, the distorted turbulence near the boundary is related to the undistorted turbulence, and thence profiles of turbulence dissipation rate near the two types of boundary are calculated and shown to agree extremely well with profiles obtained by Perot & Moin (1993) by direct numerical simulation. The dissipation rates are higher near a solid wall than in the bulk of the flow because the no-slip boundary condition leads to large velocity gradients across the viscous layer. In contrast, the weaker constraint of no stress at a free surface leads to the dissipation rate close to a free surface actually being smaller than in the bulk of the flow. This explains why tangential velocity fluctuations parallel to a free surface are so large. In addition we show that it is the adjustment of the large energy-containing eddies across the viscous layer that controls the dissipation rate, which explains why rapid-distortion theory can give quantitatively accurate values for the dissipation rate. We also find that the dissipation rate obtained from the model evaluated at the time when the model is expected to fail actually yields useful estimates of the dissipation obtained from the direct numerical simulation at times when the nonlinear processes are significant. We conclude that the main role of nonlinear processes is to arrest growth by linear processes of the viscous layer after about one large-eddy turnover time.

Advances in direct numerical simulation for MHD modeling of free surface flows

2002 ◽  
Vol 61-62 ◽  
pp. 95-102 ◽  
Author(s):  
Shin-ichi Satake ◽  
Tomoaki Kunugi ◽  
Sergey Smolentsev
Keyword(s):  
Numerical Simulation ◽  
Free Surface ◽  
Direct Numerical Simulation ◽  
Free Surface Flows ◽  
Surface Flows ◽  
Mhd Modeling

scholarly journals Direct Numerical Simulation of MHD Turbulent Free Surface Flow.

2002 ◽  
Vol 68 (667) ◽  
pp. 755-760
Author(s):  
Shin-ichi SATAKE ◽  
Tomoaki KUNUGI ◽  
Sergey SMOLENTSEV
Keyword(s):  
Numerical Simulation ◽  
Free Surface ◽  
Direct Numerical Simulation ◽  
Free Surface Flow ◽  
Surface Flow
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