Direct Numerical Simulation of Mass Transfer in Turbulent Flow Around a Rotating Circular Cylinder (II) - Effect of Schmidt Number -

2005 ◽  
Vol 29 (7) ◽  
pp. 846-853
Author(s):  
Jong-Yeon Hwang ◽  
Kyung-Soo Yang
Keyword(s):  
Numerical Simulation ◽  
Mass Transfer ◽  
Circular Cylinder ◽  
Direct Numerical Simulation ◽  
Turbulent Flow ◽  
Schmidt Number ◽  
Rotating Circular Cylinder

Direct Numerical Simulation of Turbulent Flow and Mass Transfer Around a Rotating Circular Cylinder

2005 ◽  
Author(s):  
Jong-Yeon Hwang ◽  
Kyung-Soo Yang ◽  
Klaus Bremhorst
Keyword(s):  
Numerical Simulation ◽  
Mass Transfer ◽  
Reynolds Number ◽  
Circular Cylinder ◽  
Direct Numerical Simulation ◽  
Turbulent Flow ◽  
Friction Velocity ◽  
Concentration Field ◽  
Rotating Circular Cylinder ◽  
Instantaneous Concentration

Characteristics of turbulent flow and mass transfer around a rotating circular cylinder are investigated by Direct Numerical Simulation. Mass-transfer results are presented at a high Schmidt number (Sc = 1670). The concentration field is computed for three different cases of low Reynolds number, Re*R = 161, 348 and 623, based on the cylinder radius and friction velocity. Results confirm that the thickness of Nernst diffusion layer is very small compared with that of viscous sub-layer in the case of high Sc mass transfer. A strong correlation of the concentration field with streamwise and vertical velocity components is noticed. However, that is not the case with the spanwise velocity component. Visualization of instantaneous concentration reveals that the length scale of concentration fluctuation typically decreases as Reynolds number increases. The correlation between Sherwood number and Reynolds number is consistent with other experiments currently available.

Direct Numerical Simulation of Turbulent Flow Around a Rotating Circular Cylinder

2006 ◽  
Vol 129 (1) ◽  
pp. 40-47 ◽  
Author(s):  
Jong-Yeon Hwang ◽  
Kyung-Soo Yang ◽  
Klaus Bremhorst
Keyword(s):  
Numerical Simulation ◽  
Boundary Layer ◽  
Circular Cylinder ◽  
Direct Numerical Simulation ◽  
Turbulent Flow ◽  
Plane Channel ◽  
Outer Region ◽  
Wave Number ◽  
Boundary Layer Flows ◽  
Rotating Circular Cylinder

Turbulent flow around a rotating circular cylinder has numerous applications including wall shear stress and mass-transfer measurement related to the corrosion studies. It is also of interest in the context of flow over convex surfaces where standard turbulence models perform poorly. The main purpose of this paper is to elucidate the basic turbulence mechanism around a rotating cylinder at low Reynolds numbers to provide a better understanding of flow fundamentals. Direct numerical simulation (DNS) has been performed in a reference frame rotating at constant angular velocity with the cylinder. The governing equations are discretized by using a finite-volume method. As for fully developed channel, pipe, and boundary layer flows, a laminar sublayer, buffer layer, and logarithmic outer region were observed. The level of mean velocity is lower in the buffer and outer regions but the logarithmic region still has a slope equal to the inverse of the von Karman constant. Instantaneous flow visualization revealed that the turbulence length scale typically decreases as the Reynolds number increases. Wavelet analysis provided some insight into the dependence of structural characteristics on wave number. The budget of the turbulent kinetic energy was computed and found to be similar to that in plane channel flow as well as in pipe and zero pressure gradient boundary layer flows. Coriolis effects show as an equivalent production for the azimuthal and radial velocity fluctuations leading to their ratio being lowered relative to similar nonrotating boundary layer flows.

Effects of Schmidt Number on Turbulent Mass Transfer Around a Rotating Circular Cylinder

2011 ◽  
Vol 133 (8) ◽  
Author(s):  
Dong-Hyeog Yoon ◽  
Kyung-Soo Yang ◽  
Klaus Bremhorst
Keyword(s):  
Mass Transfer ◽  
Circular Cylinder ◽  
Diffusion Layer ◽  
Time Scale ◽  
Schmidt Number ◽  
Concentration Field ◽  
Limiting Behavior ◽  
Rotating Circular Cylinder ◽  
Scale Ratio ◽  
Turbulent Mass Transfer

Characteristics of turbulent mass transfer around a rotating circular cylinder have been investigated by Direct Numerical Simulation. The concentration field was computed for three different cases of Schmidt number, Sc = 1, 10 and 100 at ReR* = 336. Our results confirm that the thickness of the Nernst diffusion layer decreases as Sc increases. Wall-limiting behavior within the diffusion layer was examined and compared with that of channel flow. Concentration fluctuation time scale was found to scale with r+2, while the time scale ratio nearly equals the Schmidt number throughout the diffusion layer. Scalar modeling closure constants based on gradient diffusion models were found to vary considerably within the diffusion layer. Results of an octant analysis show the significant role played by the ejection and sweep events just as is found for flat plate, channel, and pipe flow boundary layers. Turbulence budgets revealed a strong Sc dependence of turbulent scalar transport.

Effects of Schmidt Number on Turbulent Mass Transfer Around a Rotating Circular Cylinder

2010 ◽  
Author(s):  
Dong-Hyeog Yoon ◽  
Kyung-Soo Yang ◽  
Kyongjun Lee ◽  
Klaus Bremhorst
Keyword(s):  
Mass Transfer ◽  
Circular Cylinder ◽  
Diffusion Layer ◽  
Schmidt Number ◽  
Concentration Field ◽  
Limiting Behavior ◽  
Rotating Circular Cylinder ◽  
Nernst Diffusion Layer ◽  
Scale Ratio ◽  
Turbulent Mass Transfer

Characteristics of turbulent mass transfer around a rotating circular cylinder have been investigated by Direct Numerical Simulation. The concentration field was computed for three different cases of Schmidt number, Sc = 1, 10 and 100 at Re* = 336. Our results confirm that the thickness of the Nernst diffusion layer decreases as Sc increases. Wall-limiting behavior within the Nernst diffusion layer was examined and compared with those of channel flow. Concentration fluctuation was found to be time-scaled with (r+)2 while the time scale ratio equals the Schmidt number throughout the Nernst diffusion layer. Scalar modeling closure constants were determined, and turned out to vary considerably within the diffusion layer.

scholarly journals Direct numerical simulation of turbulent mass transfer at the surface of an open channel flow

2022 ◽  
Vol 933 ◽  
Author(s):  
Michele Pinelli ◽  
H. Herlina ◽  
J.G. Wissink ◽  
M. Uhlmann
Keyword(s):  
Numerical Simulation ◽  
Mass Transfer ◽  
Reynolds Number ◽  
Direct Numerical Simulation ◽  
Channel Flow ◽  
Schmidt Number ◽  
Open Channel ◽  
Open Channel Flow ◽  
Reynolds Numbers ◽  
Transfer Velocity

We present direct numerical simulation results of turbulent open channel flow at bulk Reynolds numbers up to 12 000, coupled with (passive) scalar transport at Schmidt numbers up to 200. Care is taken to capture the very large-scale motions which appear already for relatively modest Reynolds numbers. The transfer velocity at the flat, free surface is found to scale with the Schmidt number to the power ‘ $-1/2$ ’, in accordance with previous studies and theoretical predictions for uncontaminated surfaces. The scaling of the transfer velocity with Reynolds number is found to vary, depending on the Reynolds number definition used. To compare the present results with those obtained in other systems, we define a turbulent Reynolds number at the edge of the surface-influenced layer. This allows us to probe the two-regime model of Theofanous et al. (Intl J. Heat Mass Transfer, vol. 19, 1976, pp. 613–624), which is found to correctly predict that small-scale vortices significantly affect the mass transfer for turbulent Reynolds numbers larger than 500. It is further established that the root mean square of the surface divergence is, on average, proportional to the mean transfer velocity. However, the spatial correlation between instantaneous surface divergence and transfer velocity tends to decrease with increasing Schmidt number and increase with increasing Reynolds number. The latter is shown to be caused by an enhancement of the correlation in high-speed regions, which in turn is linked to the spatial distribution of surface-parallel vortices.

scholarly journals Direct Numerical Simulation of Turbulent Flow in a Wavy Channel.

1998 ◽  
Vol 41 (2) ◽  
pp. 447-453 ◽  
Author(s):  
Takashi OHTA ◽  
Yutaka MIYAKE ◽  
Takeo KAJISHIMA
Keyword(s):  
Numerical Simulation ◽  
Direct Numerical Simulation ◽  
Turbulent Flow ◽  
Wavy Channel
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