A New Low-Reynolds-Number k-ε Model for Turbulent Flow Over Smooth and Rough Surfaces

1996 ◽  
Vol 118 (2) ◽  
pp. 255-259 ◽  
Author(s):  
Hanzhong Zhang ◽  
Mohammad Faghri ◽  
Frank M. White
Keyword(s):  
Reynolds Number ◽  
Turbulent Flow ◽  
Dissipation Rate ◽  
Rough Surfaces ◽  
Low Reynolds Number ◽  
Friction Factors ◽  
Log Law ◽  
Low Reynolds ◽  
Flow Experiments ◽  
Grain Roughness

A new low-Reynolds-number k-ε model is proposed to simulate turbulent flow over smooth and rough surfaces by including the equivalent sand-grain roughness height into the model functions. The simulation of various flow experiments shows that the model can predict the log-law velocity profile and other properties such as friction factors, turbulent kinetic energy and dissipation rate for both smooth and rough surfaces.

Contribution towards a Reynolds-stress closure for low-Reynolds-number turbulence

1976 ◽  
Vol 74 (4) ◽  
pp. 593-610 ◽  
Author(s):  
K. Hanjalić ◽  
B. E. Launder
Keyword(s):  
Reynolds Number ◽  
Shear Stress ◽  
Reynolds Stress ◽  
Dissipation Rate ◽  
Numerical Solutions ◽  
Low Reynolds Number ◽  
Transport Processes ◽  
Turbulent Shear ◽  
Turbulent Shear Stress ◽  
Low Reynolds

The problem of closing the Reynolds-stress and dissipation-rate equations at low Reynolds numbers is considered, specific forms being suggested for the direct effects of viscosity on the various transport processes. By noting that the correlation coefficient$\overline{uv^2}/\overline{u^2}\overline{v^2} $is nearly constant over a considerable portion of the low-Reynolds-number region adjacent to a wall the closure is simplified to one requiring the solution of approximated transport equations for only the turbulent shear stress, the turbulent kinetic energy and the energy dissipation rate. Numerical solutions are presented for turbulent channel flow and sink flows at low Reynolds number as well as a case of a severely accelerated boundary layer in which the turbulent shear stress becomes negligible compared with the viscous stresses. Agreement with experiment is generally encouraging.

Application of Non-Linear k–ω Model to the Turbulent Flow Inside a Sharp U-Bend

2000 ◽  
Author(s):  
B. Song ◽  
R. S. Amano
Keyword(s):  
Reynolds Number ◽  
Turbulent Flow ◽  
Low Reynolds Number ◽  
Turbulence Models ◽  
Higher Order ◽  
Shear Stresses ◽  
Complex Flow ◽  
Streamline Curvature ◽  
Non Linear ◽  
Low Reynolds

Simulation of the complex flow inside a sharp U-bend needs both refined turbulence models and higher order numerical discretization schemes. In the present study, a nonlinear low-Reynolds number (low-Re) k–ω model including the cubic terms was employed to predict the turbulent flow through a square cross-sectioned U-bend with a sharp curvature, Rc/D = 0.65. In the turbulence model employed for the present study, the cubic terms are incorporated to represent the effect of extra strain-rates such as streamline curvature and three-dimensionality on both turbulence normal and shear stresses. In order to accurately predict such complex flowfields, a higher-order bounded interpolation scheme (Song, et al., 1999) has been used to discretize all the transport equations. The calculated results by using both the non-linear k–ω model and the linear low-Reynolds number k–ε model (Launder and Sharma, 1974) have been compared with experimental data. It is shown that the present model produces satisfactory predictions of the flow development inside the sharp U-bend and well captures the characteristics of the turbulence anisotropy within the duct core region and wall sub-layer.

scholarly journals Turbulent Flow Computations in Rotating Cavities Using Low-Reynolds-Number Models

1996 ◽  
Author(s):  
Hector Iacovides ◽  
Kostas S. Nikas ◽  
Marcel A. F. Te Braak
Keyword(s):  
Reynolds Number ◽  
Dissipation Rate ◽  
Correction Term ◽  
Low Reynolds Number ◽  
Moment Closure ◽  
Rotating Disc ◽  
Moment Coefficient ◽  
Second Moment Closure ◽  
Low Reynolds ◽  
Radial Outflow

This study is concerned with the use of low-Reynolds-number models of turbulence transport in the computation of flows through rotating cavities. The models tested are the Launder and Sharma low-Re k-ε (L-S) and a low-Re differential second-moment closure (DSM), first used by Iacovides and Toumpanakis, both with and without the Yap correction term to the dissipation rate equation. The cases examined include rotor-stator systems without throughflow, rotor-stator systems with radial outflow, contra-rotating disc systems without throughflow and also with radial outflow, co rotating discs with radial outflow and also rotor-stator systems with radial inflow. Earlier studies have shown that, when no throughflow or when radial outflow is involved, the L-S tends to over-estimate the size of the regions over which the boundary layers remain laminar, while the zonal k-ε/l-eqn model is unable to predict partially laminarized flows. A modification to the ε equation proposed here, which in regions of low turbulence reduces the dissipation rate when the fluid is in solid body rotation, provides a simple empirical way to significantly improve the L-S predictions of partially laminarized flows through rotating cavities, to acceptable levels. The DSM model used, in some cases led to some further predictive improvements and, for rotor-stator systems without throughflow, to a significant improvement in the predicted value of the moment coefficient. The Yap length scale correction term, while in most cases it has either a beneficial or a neutral effect on the flow predictions, in cases involving radial inflow it leads to poorer predictions. Models that do not rely on wall distance thus appear more likely to have a wider range of applicability.

2E1 Active Control of Reattaching Flow Field at Low Reynolds Number Turbulent Flow Region

2013 ◽  
Vol 2013 (0) ◽  
pp. 143-144
Author(s):  
Naoto YAMAGUCHI ◽  
Isao TERUYA ◽  
Masaaki ISHIKAWA ◽  
Yuta MURO
Keyword(s):  
Reynolds Number ◽  
Flow Field ◽  
Turbulent Flow ◽  
Active Control ◽  
Low Reynolds Number ◽  
Flow Region ◽  
Low Reynolds
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