Experimental investigations of controlled transition of a laminar separation bubble in an axisymmetric diffuser

Hoefener, Lars; Nitsche, W.

doi:10.1007/s00348-007-0377-0

Cited by 3 publications

(1 citation statement)

References 22 publications

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“…Understanding the characteristics of an LSB on an airfoil has been the subject of many investigations, both experimentally and numerically, over the last few decades [6,10,17], but the overall LSB dynamics are still not completely understood. The experimental approaches to LSBs have been discussed to understand the complex nature of this phenomenon.…”

Section: Introductionmentioning

confidence: 99%

Characteristics and Effects of Laminar Separation Bubbles on NREL S809 Airfoil Using the γ - R e θ Transition Model

Rho

2020

Applied Sciences

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Understanding the characteristics and effects of the laminar separation bubbles (LSBs) is important in the aerodynamic design of wind turbine airfoils for maximizing wind turbine efficiency. In the present study, numerical simulations using the γ-Reθ transition model were performed to analyze the flow structure of LSBs around a 21% thick NREL S809 airfoil. The simulation results obtained from the γ-Reθ transition model and the standard k-ε model for the aerodynamic coefficients at various angles of attack (AoAs) were compared with the wind tunnel data acquired from the Delft University 1.8 m × 1.25 m low-turbulence wind tunnel. When the AoA increased, the bubble on the suction airfoil surface was found to move closer to the leading edge owing to an earlier laminar separation (LS). Furthermore, the transition onset (TO) points were shown to occur right after separation, thus causing an abrupt increase in turbulence intensity (TI) and forming different bubble extents with increasing AoAs. Consequently, the transition model-based approaches can provide a clear understanding of the characteristics and effects of the LSB on airfoil aerodynamic performance. The findings of this study can provide important insights into redesigning an airfoil with a reduced bubble length causing the improved aerodynamic performance.

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Section: Introductionmentioning

confidence: 99%

Characteristics and Effects of Laminar Separation Bubbles on NREL S809 Airfoil Using the γ - R e θ Transition Model

Rho

2020

Applied Sciences

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Flow over a rounded backward-facing step, using a z-coordinate model and a σ-coordinate model

Rygg¹,

Alendal

Haugan

2011

Ocean Dynamics

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Homogeneous, nonrotating flow over a backward-facing rounded step is simulated using the 2D vertical version of two general circulation models, a z-coordinate model-the Massachusetts Institute of Technology general circulation model (MITgcm)-and a σ -coordinate model-the Bergen Ocean Model (BOM). The backward-facing step is a well-known testcase since it is geometrically simple but still embodies important flow characteristics such as separation point, reattachment length, and recirculation of the flow. The study compares the core of the two models and uses constant eddy viscosities and diffusivities. The Reynolds numbers ranges from 2·10 2 to 2·10 6 . The results correspond with previously published results having a relatively stationary separation point and a fluctuating reattachment length due to downslope propagating eddies released from the reattachment zone for Reynolds numbers higher than or equal to 2 · 10 4 . For Reynolds number within the laminar regime, the flow is stationary. The discrepancies between the models increase by enhancing Reynolds numbers. The σ -coordinate model experiences a reduction in eddy sizes with increasing resolution and Reynolds numbers in correspondence with published experiments, while the size of the eddies are independent of the Reynolds number using the MITgcm. Due to mixing generated by the staircase topography, the z-coordinate model gives a better convergence of the separation point and reattachment length compared with the BOM; however, this conclusion might change with the inclusion of a relevant turbulence scheme.

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Convective heat transfer increase in internal laminar flow using a vibrating surface

Ricci

Romagnoli

Montelpare

et al. 2014

International Journal of Thermal Sciences

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Experimental investigations of controlled transition of a laminar separation bubble in an axisymmetric diffuser

Cited by 3 publications

References 22 publications

Characteristics and Effects of Laminar Separation Bubbles on NREL S809 Airfoil Using the γ - R e θ Transition Model

Characteristics and Effects of Laminar Separation Bubbles on NREL S809 Airfoil Using the γ - R e θ Transition Model

Flow over a rounded backward-facing step, using a z-coordinate model and a σ-coordinate model

Convective heat transfer increase in internal laminar flow using a vibrating surface

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