An Improved Correction Method for Sound Source Drift in A Jet Flow and Its Application to A Wind Tunnel Measurement

2015 ◽  
Vol 101 (3) ◽  
pp. 642-649 ◽  
Author(s):  
Yigang Wang ◽  
Jiashun Yang ◽  
Qing Jia ◽  
Zhigang Yang ◽  
Zhe Shen
Keyword(s):  
Wind Tunnel ◽  
Sound Source ◽  
Jet Flow ◽  
Correction Method ◽  
Wind Tunnel Measurement

Effect on Sound Source Drift Caused by Angles Between Jet Flow Direction and Microphone Array or Sound Source Plane

2016 ◽  
Author(s):  
Zhe Shen ◽  
Yigang Wang ◽  
Zhigang Yang
Keyword(s):  
Wind Tunnel ◽  
Sound Source ◽  
Sound Propagation ◽  
Microphone Array ◽  
Flow Direction ◽  
Engineering Application ◽  
Jet Flow ◽  
Source Plane ◽  
Geometrical Acoustics ◽  
Beamforming Algorithm

When sound generated in jet flow propagates to outside of flow field, direction of sound propagation changes because of wave convection and refraction of shear layer. In wind tunnel, sound source drift appears when sound source is located with out-flow microphone array based on beamforming algorithm. In some cases, angles between jet flow direction and microphone array or sound source plane are inevitable due to geometric position, which increases the number of parameters affecting sound source drift distance. Geometrical acoustics and basic beamforming algorithm were used in this paper to deduce the relation between sound source drift and the angles. Equations for drift prediction and method for error reduction were given. Experimental verification was completed in a full-scale aero-acoustic wind tunnel with 2 loudspeakers set on an auto-body surface and microphone array with 120 channels. The experimental results prove that the equations for sound drift prediction in complicated geometric position relationship have a high accuracy, could help quick locating sound sources in engineering application.

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.

Synthetic Sound Source Generation for Acoustical Measurements in Turbomachines

2013 ◽  
Author(s):  
Michael Bartelt ◽  
Juan D. Laguna ◽  
Joerg R. Seume
Keyword(s):  
Wind Tunnel ◽  
Sound Source ◽  
Sound Propagation ◽  
Microphone Array ◽  
Sound Field ◽  
Acoustic Mode ◽  
Acoustic Excitation ◽  
Noise Emission ◽  
Noise Sources ◽  
Sound Fields

One of the greatest challenges in modern aircraft propulsion design is the reduction of the engine noise emission in order to develop quieter aircrafts. In the course of a current research project, the sound transport in low pressure turbines is investigated. For the corresponding experimental measurements, a specific acoustic excitation system is developed which can be implemented into the inlet of a turbine test rig and into an aeroacoustic wind tunnel. This allows for an acoustic mode generation and a synthesis of various sound source patterns to simulate typical turbomachinery noise sources such as rotor-stator interaction, etc. The paper presents the acoustical and technical design methodology in detail and addresses the experimental options of the system. Particular attention is paid to the design and the numerical optimization of the acoustic excitation units. To validate the sound generator during operation, measurements are performed in an aeroacoustic wind tunnel. For this purpose, an in-duct microphone array with a specific beamforming algorithm for hard-walled ducts is developed and applied to identify the source locations. The synthetically excited sound fields and the propagating acoustic modes are measured and analyzed by means of modal decomposition techniques. The measurement principles and the results are discussed in detail and it is shown that the intended sound source is produced and the intended sound field is excited. This paper shall contribute to help guide the development of excitation systems for aeroacoustic experiments to better understanding the physics of sound propagation within turbomachines.

Extensions to Maskell’s theory for blockage effects on bluff bodies in a closed wind tunnel

2001 ◽  
Vol 105 (1050) ◽  
pp. 409-418 ◽  
Author(s):  
J. E. Hackett ◽  
K. R. Cooper
Keyword(s):  
Wind Tunnel ◽  
Flat Plate ◽  
Correction Method ◽  
The Other ◽  
Bluff Bodies ◽  
Low Speed ◽  
Test Conditions ◽  
Lift And Drag ◽  
Low Speed Wind Tunnel

Abstract Extensions to Maskell’s original correction method, developed over several years, are consolidated and designated ‘Maskell III’. The procedures were applied to dedicated tests on a family of flat-plate wing models in a small, low-speed wind tunnel at NRC. Test conditions included angles of attack from -10° to 110° and models of up to 16% of tunnel area. Off-centre tests were included with model-to-wall distances down to 0.72 chords. Corrected lift and drag data correlated well between models of different sizes and at different offsets from the tunnel centreline. Comparisons are made with corrections using the pressure-signature and two-variable methods, emphasising post-stall conditions. These showed that the ‘Maskell III’ procedures, which require minimal input, correlated as well as the other methods for most model sizes and positions in the tunnel.

scholarly journals Wind tunnel measurement of flow and dispersion over urban area

2017 ◽  
Vol 143 ◽  
pp. 02074 ◽  
Author(s):  
Petr Michálek ◽  
David Zacho
Keyword(s):  
Wind Tunnel ◽  
Urban Area ◽  
Wind Tunnel Measurement

CFD Modeling of Flow Induced Vibration on a Mobile Cylinder for a 30 K-60 K Reynolds Number Comparison Between Simulation and Experimental Results

2009 ◽  
Author(s):  
Christophe Peyrard ◽  
Marco Belloli ◽  
Pierre Bousseau ◽  
Sara Muggiasca ◽  
Stefano Giappino ◽  
...  
Keyword(s):  
Wind Tunnel ◽  
Transmission Lines ◽  
Developed Countries ◽  
Flow Speed ◽  
Experimental Results ◽  
Cfd Modeling ◽  
Overhead Line ◽  
Rigid Cylinder ◽  
Wind Tunnel Measurement ◽  
Measurement Results

Fatigue and aging of electrical overhead transmission lines is a major concern nowadays in developed countries with ever increasing difficulties to build new lines and an already quite aged network. An important degradation phenomenon of overhead line cables is fretting fatigue close to the suspension clamps due to vortex induced vibrations (VIV). These VIV are generally observed for wind speeds in the range of 1 to 7 m/s. The existing industrial practice for predicting how prone cables are to VIV fatigue is based on a balance between the power generated by the wind and the power dissipated by the cable system. The power generated by the wind has been evaluated through measurements on real line spans and through wind tunnel experiments on rigid and flexible cylinders as a function of frequency and vibration amplitude. The wind tunnel measurement results are mainly performed for constant flow speed. Corresponding results show a scattering from simple to double. Furthermore, complementary investigations are required to better evaluate the power with wind speed variations across and along the overhead line span. EDF R&D (with Code_Saturne open source software) and Politecnico di Milano have evaluated CFD modeling on a mobile rigid cylinder with comparison to detailed wind tunnel measurement results performed by Politecnico di Milano on a 20 cm diameter rigid cylinder equipped with a pressure scanner. This paper presents the steps, the different questions raised, the difficulties and limitations for the setting and the realization of the CFD modeling approach. The comparison between experimental results and simulation results is presented for the mobile rigid cylinder with k-ω SST turbulence model.

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