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.

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 Computation of Turbulent Heat Transfer on the Walls of a 180 Degree Turn Channel With a Low Reynolds Number Reynolds Stress Model

2002 ◽  
Author(s):  
D. L. Rigby ◽  
A. A. Ameri ◽  
E. Steinthorsson
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Reynolds Stress ◽  
Low Reynolds Number ◽  
Reynolds Stress Model ◽  
Turbulent Heat Transfer ◽  
Turbulent Heat ◽  
Stress Model ◽  
Generalized Gradient ◽  
Low Reynolds

The Low Reynolds number version of the Stress-ω model and the two equation k-ω model of Wilcox were used for the calculation of turbulent heat transfer in a 180 degree turn simulating an internal coolant passage. The Stress-ω model was chosen for its robustness. The turbulent thermal fluxes were calculated by modifying and using the Generalized Gradient Diffusion Hypothesis. The results showed that using this Reynolds Stress model allowed better prediction of heat transfer compared to the k-ω two equation model. This improvement however required a finer grid and commensurately more CPU time.

scholarly journals Aerodynamic Performance of Micro Aerial Wing Structures at Low Reynolds Number

2019 ◽  
Vol 11 (1) ◽  
pp. 107-120 ◽  
Author(s):  
Y. D. DWIVEDI ◽  
Vasishta BHARGAVA ◽  
P. M. V. RAO ◽  
Donepudi JAGADEESH
Keyword(s):  
Reynolds Number ◽  
Low Reynolds Number ◽  
Lift Coefficient ◽  
Reynolds Numbers ◽  
Aerodynamic Performance ◽  
Panel Method ◽  
Experiment Data ◽  
Wing Structures ◽  
Low Reynolds ◽  
Good Agreement

Corrugations are folds on a surface as found on wings of dragon fly insects. Although they fly at relatively lower altitudes its wings are adapted for better aerodynamic and aero-elastic characteristics. In the present work, three airfoil geometries were studied using the 2-D panel method to evaluate the aerodynamic performance for low Reynolds number. The experiments were conducted in wind tunnel for incompressible flow regime to demonstrate the coefficients of lift drag and glide ratio at two Reynolds numbers 1.9x104 and 1.5x105 and for angles of attack ranging between 00 and 160. The panel method results have been validated using the current and existing experiment data as well as with the computational work from cited literature. A good agreement between the experimental and the panel methods were found for low angles of attack. The results showed that till 80 angle of attack higher lift coefficient and lower drag coefficient are obtainable for corrugated airfoils as compared to NACA 0010. The validation of surface pressure coefficients for all three airfoils using the panel method at 40 angles of attack was done. The contours of the non-dimensional pressure and velocity are illustrated from -100 to 200 angles of attack. A good correlation between the experiment data and the computational methods revealed that the corrugated airfoils exhibit better aerodynamic performance than NACA 0010.

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.

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