Low-Reynolds-number k-epsilon-tilde model with enhanced near-wall dissipation introduction

AIAA Journal ◽  
2002 ◽  
Vol 40 ◽  
pp. 1462-1464
Author(s):  
M. Rahman ◽  
T. Siikonen
Keyword(s):  
Reynolds Number ◽  
Low Reynolds Number ◽  
Low Reynolds ◽  
Near Wall

A Reynolds-Stress Model for Near-Wall and Low-Reynolds-Number Regions

1988 ◽  
Vol 110 (1) ◽  
pp. 38-44 ◽  
Author(s):  
Nobuyuki Shima
Keyword(s):  
Reynolds Number ◽  
Reynolds Stress ◽  
Present Model ◽  
Transport Model ◽  
Low Reynolds Number ◽  
Reynolds Stress Model ◽  
Turbulence Energy ◽  
Stress Model ◽  
Low Reynolds ◽  
Near Wall

The Reynolds stress model for high Reynolds numbers proposed by Launder et al. is extended to near-wall and low-Reynolds-number regions. In the development of the model, particular attention is given to the high anisotropy of turbulent stresses in the immediate vicinity of a wall and to the behavior of the exact stress equation at the wall. A transport model for the turbulence energy dissipation rate is also developed by taking into account its compatibility with the stress model at the wall. The model and the low-Reynolds-number model of Hanjali’c and Launder are applied to fully-developed pipe flow. Comparison of the numerical results with Laufer’s data shows that the present model gives significantly improved predictions. In particular, the present model is shown to reproduce the sharp peak in the distribution of the streamwise turbulence intensity in the immediate vicinity of the wall.

scholarly journals Numerical Predictions of Uniform CO2 Corrosion in Complex Fluid Domains Using Low Reynolds Number Models

Metals ◽  
2018 ◽  
Vol 8 (12) ◽  
pp. 1001
Author(s):  
Haijun Hu ◽  
Hao Xu ◽  
Changmeng Huang ◽  
Xing Chen ◽  
Xiufeng Li ◽  
...  
Keyword(s):  
Experimental Data ◽  
Mass Transfer ◽  
Reynolds Number ◽  
Low Reynolds Number ◽  
Co2 Corrosion ◽  
Aqueous Corrosion ◽  
Corrosion Rates ◽  
Complex Fluid ◽  
Low Reynolds ◽  
Near Wall

To get the knowledge of local corrosion, thinning is useful for developing targeted inspection plans for pipe components in the oil/gas industry. Aiming at this object, this work presents a computer fluid dynamics (CFD) method to predict CO2 aqueous corrosion in complex fluid domains. The processes involved in CO2 aqueous corrosion, including flow dynamics, mass transfer, chemical reactions, and electrochemical reactions, are modeled and simulated by a commercial CFD software of Fluent V15.0 (Version, manufacturer, city, country). Mass transfer in the straight pipe flow and jet impinging flow are simulated using three low-Reynolds-number turbulent models (Abe–Kondoh–Nagano k − ε model, Change–Hsieh–Chenk k − ε model, and k − ε shear stress transport model). The flow domains are meshed by grids with the first near-wall node at the position at y+ = 0.1. Comparisons between simulations and experimental data show the Abe–Kondoh–Nagano model provides the best predictions of near-wall flow and mass transfer. Thus, it is used to predict CO2 aqueous corrosion. Corrosion rates of dissolved CO2 in straight pipes and a jet impinging are predicted. The predicted corrosion rates are compared with experimental data and results derived from commercial software, Multicorp V5.2.105. The results show that predicted corrosion rates are reasonable. The locations of the highest corrosion rate for a jet impinging system are revealed.

Methods to Set Up and Investigate Low Reynolds Number, Fully Developed Turbulent Plane Channel Flows

1998 ◽  
Vol 120 (3) ◽  
pp. 496-503 ◽  
Author(s):  
F. Durst ◽  
M. Fischer ◽  
J. Jovanovic´ ◽  
H. Kikura
Keyword(s):  
Reynolds Number ◽  
Initial Conditions ◽  
Control Volume ◽  
Low Reynolds Number ◽  
Plane Channel ◽  
Finite Size ◽  
Wall Region ◽  
Turbulent Plane ◽  
Low Reynolds ◽  
Near Wall

The tripping of fully developed turbulent plane channel flow was studied at low Reynolds number, yielding unique flow properties independent of the initial conditions. The LDA measuring technique was used to obtain reliable mean velocities, rms values of turbulent velocity fluctuations and skewness and flatness factors over the entire cross-section with emphasis on the near-wall region. The experimental results were compared with the data obtained from direct numerical simulations available in the literature. The analysis of the data indicates the important role of the upstream conditions on the flow development. It is shown that the fully developed turbulent state at low Reynolds number can be reached only by significant tripping of the flow at the inlet of the channel. Effects related to the finite size of the LDA measuring control volume and an inaccuracy in the estimation of the wall shear stress from near-wall velocity measurements are discussed in detail since these can yield systematic discrepancies between the measured and simulated results.

A Low-Reynolds Number Explicit Algebraic Stress Model

2006 ◽  
Vol 128 (6) ◽  
pp. 1364-1376 ◽  
Author(s):  
M. M. Rahman ◽  
T. Siikonen
Keyword(s):  
Reynolds Number ◽  
Low Reynolds Number ◽  
Stress Model ◽  
Algebraic Stress Model ◽  
Numerical Instabilities ◽  
Low Reynolds ◽  
Prandtl Numbers ◽  
Dissipation Equation ◽  
Good Agreement ◽  
Near Wall

A low-Reynolds number extension of the explicit algebraic stress model, developed by Gatski and Speziale (GS) is proposed. The turbulence anisotropy Πb and production to dissipation ratio P∕ϵ are modeled that recover the established equilibrium values for the homogeneous shear flows. The devised (Πb, P∕ϵ) combined with the model coefficients prevent the occurrence of nonphysical turbulence intensities in the context of a mild departure from equilibrium, and facilitate an avoidance of numerical instabilities, involved in the original GS model. A new near-wall damping function fμ in the eddy viscosity relation is introduced. To enhance dissipation in near-wall regions, the model constants Cϵ(1,2) are modified and an extra positive source term is included in the dissipation equation. A realizable time scale is incorporated to remove the wall singularity. The turbulent Prandtl numbers σ(k,ϵ) are modeled to provide substantial turbulent diffusion in near-wall regions. The model is validated against a few flow cases, yielding predictions in good agreement with the direct numerical simulation and experimental data.

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