Turbulent structures in the near-wall region for a boundary layer over a d-type rough surface at a low Reynolds number.

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.

Download Full-text

Structure of a turbulent boundary layer over a d-type rough surface at low Reynolds number.

TRANSACTIONS OF THE JAPAN SOCIETY OF MECHANICAL ENGINEERS Series B ◽

10.1299/kikaib.51.3102 ◽

1985 ◽

Vol 51 (470) ◽

pp. 3102-3109

Author(s):

Hideo OSAKA ◽

Yoshiro KAGEYAMA ◽

Satoru OYAMA

Keyword(s):

Boundary Layer ◽

Reynolds Number ◽

Turbulent Boundary Layer ◽

Rough Surface ◽

Low Reynolds Number ◽

Low Reynolds

Download Full-text

Low-Reynolds Number Turbulence Models: An Approach for Reducing Mesh Sensitivity

Journal of Fluids Engineering ◽

10.1115/1.1638791 ◽

2004 ◽

Vol 126 (1) ◽

pp. 14-21 ◽

Cited By ~ 12

Author(s):

Jonas Bredberg ◽

Lars Davidson

Keyword(s):

Reynolds Number ◽

Low Reynolds Number ◽

Turbulence Models ◽

Wall Region ◽

Interior Node ◽

Modified Model ◽

Step Flow ◽

Flow And Heat Transfer ◽

Low Reynolds ◽

Near Wall

This study presents a new near-wall treatment for low-Reynolds number (LRN) turbulence models that maintains accuracy in ‘coarse’ mesh predictions. The method is based on a thorough examination of approximations made when integrating the discretized equations in the near-wall region. A number of modifications are proposed that counteract errors introduced when an LRN-model is used on meshes for which the first interior node is located at y+≈5. Here the methodology is applied to the k−ω turbulence model by Bredberg et al., although similar corrections are relevant for all LRN models. The modified model gives asymptotically, in the sense of mesh refinement, identical results to the baseline model. For coarser meshes y+⩽10, the present method improves numerical stability with less mesh-dependency than the non-modified model. Results are included for fully developed channel flow, a backward-facing step flow and heat transfer in a periodic rib-roughened channel.

Download Full-text