Wind Tunnel Testing Airfoils at Low Reynolds Numbers

2011 ◽  
Author(s):  
Michael Selig ◽  
Robert Deters ◽  
Gregory Wiliamson
Keyword(s):  
Wind Tunnel ◽  
Reynolds Numbers ◽  
Wind Tunnel Testing ◽  
Low Reynolds Numbers ◽  
Low Reynolds ◽  
Tunnel Testing

Wind Tunnel Testing of Micro Air Vehicles at Low Reynolds Numbers

2004 ◽  
Author(s):  
Roberto Albertani ◽  
Paul Hubner ◽  
Peter Ifju ◽  
Rick Lind ◽  
Jason Jackowski
Keyword(s):  
Wind Tunnel ◽  
Micro Air Vehicles ◽  
Reynolds Numbers ◽  
Wind Tunnel Testing ◽  
Low Reynolds Numbers ◽  
Low Reynolds ◽  
Tunnel Testing ◽  
Air Vehicles

The influence of the flow separation bubble and transition location on the profile drag of three 4-digit NACA aerofoil profiles

2021 ◽  
pp. 0309524X2110550
Author(s):  
Moutaz Elgammi ◽  
Tonio Sant ◽  
Atiyah Abdulmajid Ateeah
Keyword(s):  
Wind Tunnel ◽  
Flow Separation ◽  
Separation Bubble ◽  
Reynolds Numbers ◽  
Force Balance ◽  
Navier Stokes ◽  
Separation Mechanism ◽  
Numerical Work ◽  
Low Reynolds Numbers ◽  
Low Reynolds

Modeling of the flow over aerofoil profiles at low Reynolds numbers is difficult due to the complex physics associated with the laminar flow separation mechanism. Two major problems arise in the estimation of profile drag: (1) the drag force at low Reynolds numbers is extremely small to be measured in a wind tunnel by force balance techniques, (2) the profile drag is usually calculated by pressure integration, hence the skin friction component of drag is excluded. In the present work, three different 4-digit NACA aerofoils are investigated. Measurements are conducted in an open-ended subsonic wind tunnel, while numerical work is performed by time Reynolds-averaged Navier Stokes (RANS) coupled with the laminar-kinetic-energy ( K-kl-w) turbulence model. The influence of the flow separation bubbles and transition locations on the profile drag is discussed and addressed. This paper gives important insights into importance of measurements at low Reynolds numbers for better aerodynamic loads predictions.

Static and Dynamic Analysis of a NACA 0021 Airfoil Section at Low Reynolds Numbers: Drag and Moment Coefficients

2019 ◽  
Author(s):  
David Holst ◽  
Francesco Balduzzi ◽  
Alessandro Bianchini ◽  
Christian Navid Nayeri ◽  
Christian Oliver Paschereit ◽  
...  
Keyword(s):  
Experimental Data ◽  
Wind Tunnel ◽  
Wind Turbines ◽  
Reynolds Numbers ◽  
Correction Method ◽  
Hysteresis Cycle ◽  
Low Reynolds Numbers ◽  
Static And Dynamic Analysis ◽  
Wide Range ◽  
Low Reynolds

Abstract Wind industry needs high quality airfoil data for a range of the angle of attack (AoA) much wider than that often provided by the technical literature, which often lacks data i.e. in deep- and post-stall region. Especially in case of vertical axis wind turbines (VAWTs), the blades operate at very large AoAs, which exceed the range of typical aviation application. In a previous study, some of the authors analyzed the trend of the lift coefficient of a NACA 0021 airfoil, using the suggestions provided by detailed CFD analyses to correct experimental data at low Reynolds numbers collected in an open-jet tunnel. In the present study, the correction method is extended in order to analyze even the drag and moment coefficients over a wide range of AoAs for two different Reynolds numbers (Re = 140k and Re = 180k) of particular interest for small wind turbines. The utility of these data is again specifically high in case of VAWTs, in which both the drag and the moment coefficient largely contribute to the torque. The investigation involves tunnel data regarding both static polars and dynamic sinusoidal pitching movements at multiple reduced frequencies. Concerning the numerical simulations, two different computational domains were considered, i.e. the full wind tunnel and the open field. Once experimental data have been purged by the influence of the wind tunnel by means of the proposed correction method, they were compared to existing data for similar Reynolds both for the NACA0021 and for similar airfoils. By doing so, some differences in the static stall angle and the extent of the hysteresis cycle are discussed. Overall, the present paper provides the scientific community with detailed analysis of low-Reynolds NACA 0021 data in multiple variations, which may enable, inter alia, a more effective VAWT design in the near future.

scholarly journals Experimental and Numerical Icing Penalties of an S826 Airfoil at Low Reynolds Numbers

Aerospace ◽  
2020 ◽  
Vol 7 (4) ◽  
pp. 46 ◽  
Author(s):  
Richard Hann ◽  
R. Jason Hearst ◽  
Lars Roar Sætran ◽  
Tania Bracchi
Keyword(s):  
Wind Tunnel ◽  
Turbulence Models ◽  
Reynolds Numbers ◽  
Low Reynolds Numbers ◽  
3D Printed ◽  
Numerical Tools ◽  
Low Reynolds ◽  
Performance Penalty ◽  
High Reynolds ◽  
Ice Shapes

Most icing research focuses on the high Reynolds number regime and manned aviation. Information on icing at low Reynolds numbers, as it is encountered by wind turbines and unmanned aerial vehicles, is less available, and few experimental datasets exist that can be used for validation of numerical tools. This study investigated the aerodynamic performance degradation on an S826 airfoil with 3D-printed ice shapes at Reynolds numbers Re = 2 × 105, 4 × 105, and 6 × 105. Three ice geometries were obtained from icing wind tunnel experiments, and an additional three geometries were generated with LEWICE. Experimental measurements of lift, drag, and pressure on the clean and iced airfoils have been conducted in the low-speed wind tunnel at the Norwegian University of Science and Technology. The results showed that the icing performance penalty correlated to the complexity of the ice geometry. The experimental data were compared to computational fluid dynamics (CFD) simulations with the RANS solver FENSAP. Simulations were performed with two turbulence models (Spalart Allmaras and Menter’s k-ω SST). The simulation data showed good fidelity for the clean and streamlined icing cases but had limitations for complex ice shapes and stall.

Visualization Of The Flow Around The Ekranoplan Model

2017 ◽  
Vol 12 (2) ◽  
pp. 5-10
Author(s):  
Dmitriy Nazarov ◽  
Alexandr Pavlenko ◽  
Boris Zanin
Keyword(s):  
Wind Tunnel ◽  
Flow Pattern ◽  
Reynolds Numbers ◽  
Vortex Structures ◽  
Attack Angle ◽  
Low Reynolds Numbers ◽  
Low Level ◽  
Subsonic Wind Tunnel ◽  
Flow Turbulence ◽  
Low Reynolds

The flow around the ekranoplan model was experimentally investigated in subsonic wind tunnel at low Reynolds numbers with a low level of flow turbulence. The method of carbon-oil visualization of surface streamlines was used in the experiments to obtain the flow pattern on the surface of the model. Different areas of separation and vortex structures on the fuselage and wing were discovered. The effect of varying of the attack angle on the flow pattern was demonstrated.

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