A new extension for k– turbulence models to account for wall roughness

Knopp, Tobias; Eisfeld, Bernhard; Calvo, Javier Bartolome

doi:10.1016/j.ijheatfluidflow.2008.09.009

Cited by 111 publications

(126 citation statements)

References 21 publications

(80 reference statements)

Supporting

Mentioning

115

Contrasting

Unclassified

Order By: Relevance

“…Thus the values of k w and ω w in this analysis are based on the roughness extension proposed by Knopp et al [13]. Since the atmospheric flow is always considered a fully rough turbulent regime [14], this roughness extension can be simplified to…”

Section: Roughness Extension and Meshingmentioning

confidence: 99%

See 1 more Smart Citation

Hybrid turbulence models for atmospheric flow: A proper comparison with RANS models

Bautista

Dufresne

Masson

2015

E3S Web of Conferences

View full text Add to dashboard Cite

Abstract.A compromise between the required accuracy and the need for affordable simulations for the wind industry might be achieved with the use of hybrid turbulence models. Detached-Eddy Simulation (DES) [1] is a hybrid technique that yields accurate results only if it is used according to its original formulation [2]. Due to its particular characteristics (i.e., the type of mesh required), the modeling of the atmospheric flow might always fall outside the original scope of DES. An enhanced version of DES called Simplify Improved Delayed Detached-Eddy Simulation (SIDDES) [3] can overcome this and other disadvantages of DES. In this work the neutrally stratified atmospheric flow over a flat terrain with homogeneous roughness will be analyzed using a Reynolds-Averaged Navier-Stokes (RANS) model called k − ω SST (shear stress transport) [4], and the hybrids k − ω SST-DES and k − ω SST-SIDDES models. An obvious test is to validate these hybrid approaches and asses their advantages and disadvantages over the pure RANS model. However, for several reasons the technique to drive the atmospheric flow is generally different for RANS and LES or hybrid models. The flow in a RANS simulation is usually driven by a constant shear stress imposed at the top boundary [5], therefore modeling only the atmospheric surface layer. On the contrary the LES and hybrid simulations are usually driven by a constant pressure gradient, thus a whole atmospheric boundary layer is simulated. Rigorously, this represents two different simulated cases making the model comparison not trivial. Nevertheless, both atmospheric flow cases are studied with the mentioned models. The results prove that a simple comparison of the time average turbulent quantities obtained by RANS and hybrid simulations is not easily achieved. The RANS simulations yield consistent results for the atmospheric surface layer case, while the hybrid model results are not correct. As for the atmospheric boundary layer case, no meaningful conclusion could be established for RANS, and the DES results are not satisfactory. However the SIDDES model is capable of reproducing accurately the atmospheric boundary layer over flat terrain.

show abstract

Section: Roughness Extension and Meshingmentioning

confidence: 99%

“…This roughness extension requires the first cell center to be located at a non-dimensional distance of z + 1 = u * z 1 /ν ≈ 0.3 regardless of the roughness height [13]. For high Reynolds number flows, such constrain results in extremely fine and high aspect-ratio cells close to the wall.…”

Section: Roughness Extension and Meshingmentioning

confidence: 99%

Hybrid turbulence models for atmospheric flow: A proper comparison with RANS models

Bautista

Dufresne

Masson

2015

E3S Web of Conferences

View full text Add to dashboard Cite

show abstract

“…Modifications are designed to predict the transition location moving upstream appropriately due to surface roughness. To correctly simulate the roughness effects on the skin friction and heat transfer coefficients in the fully turbulent regime, formula proposed by Knopp et al (2009) CHAPTER 2. REVIEW OF LITERATURE…”

Section: Introduction Of the Workmentioning

confidence: 99%

A bypass transition model based on the intermittency function

View full text Add to dashboard Cite

“…In 2009 Knopp et al [16] presented an extension for k-ω turbulence models, based on the equivalent sand grain approach, to account for wall roughness. Briefly, the grid requirements are the same for simulation of flows over both rough surfaces and smooth walls, the skin friction for transitional roughness Reynolds numbers prediction is improved and there is no need to modify the SST k-ω model.…”

Section: Introductionmentioning

confidence: 99%

“…Briefly, the grid requirements are the same for simulation of flows over both rough surfaces and smooth walls, the skin friction for transitional roughness Reynolds numbers prediction is improved and there is no need to modify the SST k-ω model. Knopp et al [16] indicate that this new method can be utilized to predict the aerodynamic effects of surface roughness on the flow past an airfoil in high lift conditions. Salem et al [17] have proposed a computational fluid dynamics (CFD) model coupled with a deposition model using the full two-dimensional Navier-Stokes equations and the SST k-ω turbulence model in order to assess the performance degradation of wind turbine NACA 63-215 airfoil operating in dusty regions.…”

Section: Introductionmentioning

confidence: 99%

Aerodynamic Performance of a NREL S809 Airfoil in an Air-Sand Particle Two-Phase Flow

2017

View full text Add to dashboard Cite

This paper opens up a new perspective on the aerodynamic performance of a wind turbine airfoil. More specifically, the paper deals with a steady, incompressible two-phase flow, consisting of air and two different concentrations of sand particles, over an airfoil from the National Renewable Energy Laboratory, NREL S809. The numerical simulations were performed on turbulence models for aerodynamic operations using commercial computational fluid dynamics (CFD) code. The computational results obtained for the aerodynamic performance of an S809 airfoil at various angles of attack operating at Reynolds numbers of Re = 1 × 10 6 and Re = 2 × 10 6 in a dry, dusty environment were compared with existing experimental data on air flow over an S809 airfoil from reliable sources. Notably, a structured mesh consisting of 80,000 cells had already been identified as the most appropriate for numerical simulations. Finally, it was concluded that sand concentration significantly affected the aerodynamic performance of the airfoil; there was an increase in the values of the predicted drag coefficients, as well as a decrease in the values of the predicted lift coefficients caused by increasing concentrations of sand particles. The region around the airfoil was studied by using contours of static pressure and discrete phase model (DPM) concentration.

show abstract

A new extension for k– turbulence models to account for wall roughness

Cited by 111 publications

References 21 publications

Hybrid turbulence models for atmospheric flow: A proper comparison with RANS models

Hybrid turbulence models for atmospheric flow: A proper comparison with RANS models

A bypass transition model based on the intermittency function

Aerodynamic Performance of a NREL S809 Airfoil in an Air-Sand Particle Two-Phase Flow

Contact Info

Product

Resources

About