Low-reynolds number approximation for turbulent eddy viscosity

1994 ◽  
Vol 9 (3) ◽  
pp. 283-292 ◽  
Author(s):  
A. Yakhot ◽  
S. Rakib ◽  
W. S. Flannery
Keyword(s):  
Reynolds Number ◽  
Eddy Viscosity ◽  
Low Reynolds Number ◽  
Turbulent Eddy ◽  
Low Reynolds

An Investigation Into the Potential of Low-Reynolds Number Eddy Viscosity Turbulent Flow Models to Predict Electronic Component Operational Temperature

2005 ◽  
Vol 127 (1) ◽  
pp. 67-75 ◽  
Author(s):  
Peter Rodgers ◽  
Vale´rie Eveloy ◽  
M. S. J. Hashmi
Keyword(s):  
Thermal Analysis ◽  
Reynolds Number ◽  
Eddy Viscosity ◽  
Predictive Accuracy ◽  
Low Reynolds Number ◽  
Turbulence Models ◽  
Thermal Design ◽  
Junction Temperature ◽  
Temperature Prediction ◽  
Low Reynolds

The flow modeling approaches employed in computational fluid dynamics (CFD) codes dedicated to the thermal analysis of electronic equipment are generally not specific for the analysis of forced airflows over populated electronic boards. This limitation has been previously highlighted (Eveloy, V. et al., 2004, IEEE Trans. Compon., Packag., Technol. 27, pp. 268–282), with component junction temperature prediction errors of up to 35% reported. This study evaluates the potential of three candidate low-Reynolds number eddy viscosity turbulence models to improve predictive accuracy. An array of fifteen board-mounted PQFPs is analyzed in a 4 m/s airflow. Using the shear stress transport k-ω model, significant improvements in component junction temperature prediction accuracy are obtained relative to the standard high-Reynolds number k-ε model, which are attributed to better prediction of both board leading edge heat transfer and component thermal interaction. Such improvements would enable parametric analysis of product thermal performance to be undertaken with greater confidence in the thermal design process, and the generation of more accurate temperature boundary conditions for use in Physics-of-Failure based reliability prediction methods. The case is made for vendors of CFD codes dedicated to the thermal analysis of electronics to consider the adoption of eddy viscosity turbulence models more suited to board-level analysis.

Calculation of High-Lift Cascades in Low Pressure Turbine Conditions Using a Three-Equation Model

2010 ◽  
Vol 133 (3) ◽  
Author(s):  
Roberto Pacciani ◽  
Michele Marconcini ◽  
Atabak Fadai-Ghotbi ◽  
Sylvain Lardeau ◽  
Michael A. Leschziner
Keyword(s):  
Reynolds Number ◽  
Kinetic Energy ◽  
Eddy Viscosity ◽  
Low Reynolds Number ◽  
Low Pressure ◽  
Equation Model ◽  
Bypass Transition ◽  
High Lift ◽  
Wide Range ◽  
Low Reynolds

A three-equation model has been applied to the prediction of separation-induced transition in high-lift low-Reynolds-number cascade flows. Classical turbulence models fail to predict accurately laminar separation and turbulent reattachment, and usually overpredict the separation length, the main reason for this being the slow rise of the turbulent kinetic energy in the early stage of the separation process. The proposed approach is based on solving an additional transport equation for the so-called laminar kinetic energy, which allows the increase in the nonturbulent fluctuations in the pretransitional and transitional region to be taken into account. The model is derived from that of Lardeau et al. (2004, “Modelling Bypass Transition With Low-Reynolds-Number Non-Linear Eddy-Viscosity Closure,” Flow, Turbul. Combust., 73, pp. 49–76), which was originally formulated to predict bypass transition for attached flows, subject to a wide range of freestream turbulence intensity. A new production term is proposed, based on the mean shear and a laminar eddy-viscosity concept. After a validation of the model for a flat-plate boundary layer, subjected to an adverse pressure gradient, the T106 and T2 cascades, recently tested at the von Kármán Institute, are selected as test cases to assess the ability of the model to predict the flow around high-lift cascades in conditions representative of those in low-pressure turbines. Good agreement with experimental data, in terms of blade-load distributions, separation onset, reattachment locations, and losses, is found over a wide range of Reynolds-number values.

Experimental Investigation on Blunt-Edged UTM Delta Wing VFE-2 Configurations at Low Reynolds Number

2018 ◽  
Vol 12 (3) ◽  
pp. 255
Author(s):  
Muhammad Zal Aminullah Daman Huri ◽  
Shabudin Bin Mat ◽  
Mazuriah Said ◽  
Shuhaimi Mansor ◽  
Md. Nizam Dahalan ◽  
...  
Keyword(s):  
Experimental Investigation ◽  
Reynolds Number ◽  
Delta Wing ◽  
Low Reynolds Number ◽  
Low Reynolds
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