Journal articles: 'Open-jet wind tunnel'

1

Cooper, Kevin R., Edzard Mercker, and Jürg Müller. "The necessity for boundary corrections in a standard practice for the open-jet wind tunnel testing of automobiles." Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering 231, no. 9 (April 26, 2017): 1245–73. http://dx.doi.org/10.1177/0954407017701287.

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This paper is intended to provide a summary of the necessary adjustments required for road-representative open-jet wind tunnel measurements on automobiles. The open-jet wind tunnel provides accurate measurements, but they are made in a finite-sized jet that differs from the unconfined open-road conditions. Furthermore, measurements on a given automobile made in different open-jet wind tunnels disagree with each other, and with measurements in closed-wall wind tunnels that were corrected for the influences of their solid boundaries. There appears to be reticence at some company levels to making ‘corrections’ to open-jet measurements. Perhaps non-specialist managers think that the need for a ‘correction’ means an erroneous measurement. It does not! Any high-quality wind tunnel measurement is accurate, but it needs to be ‘calibrated’ to on-road conditions through an appropriate set of procedures. Closed-wall wind tunnels measure higher drag coefficients, in comparison with those in an unconstrained on-road flow. Open-jet wind tunnels frequently measure a lower value. The closed-wall adjustments lower the drag coefficient to the unconstrained value. Open-jet adjustments should also adjust the drag coefficient to the same unconstrained value. This paper explores the range of effects from the finite jet and elucidates the effectiveness of a two-measurement correction procedure. It is shown that not every data point must be measured twice, only a small selected subset. Since approximately 20% of tunnel occupancy is in the fan-on condition, then the additional cost of correct accurate on-road-equivalent data is low.

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Du, Longhuan, Arganthaël Berson, and Robert G. Dominy. "Aerofoil behaviour at high angles of attack and at Reynolds numbers appropriate for small wind turbines." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 229, no. 11 (September 8, 2014): 2007–22. http://dx.doi.org/10.1177/0954406214550016.

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The aerodynamic characteristics of a NACA0018 aerofoil have been investigated experimentally for incidence angles ranging from [Formula: see text] to [Formula: see text] in closed-jet and open-jet wind tunnels with different blockage coefficients at Reynolds numbers from 60,000 to 140,000. The results provide a comprehensive data set for studying the performance of typical, small-scale Darrieus wind turbine blades which mainly operate at relatively low Reynolds number and experience extreme angles of attack, particularly during start-up. Measurements in both very high and very low blockage, open-jet wind tunnels capture a “second-stall” phenomenon at high angles of attack, but this behaviour is not observed in the closed-jet wind tunnel confirming the sensitivity of aerofoil performance at extreme incidence to wind tunnel configuration. Surface flow visualisation suggests that the “second-stall” occurs when the flow separation point near the leading edge of the aerofoil moves from the suction side to the pressure side which leads to a sudden change of wake structure. In the closed-jet wind tunnel, the tunnel walls constrain the wake and prevent the flow from switching from one regime to another. The measured data are also used to demonstrate that established wind tunnel blockage corrections break down under these extreme, post-stall angles of attack.

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Cheung, C. W., and G. J. Hancock. "Wind tunnel interference on unsteady two-dimensional aerofoil motions in low speed flows." Aeronautical Journal 92, no. 913 (March 1988): 115–21. http://dx.doi.org/10.1017/s0001924000022016.

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Summary The aerodynamic characteristics of two-dimensional transient aerofoil motions in low-speed flows in a wind tunnel with either closed wall or open (jet) walls, including the effect of a downstream closed wall diffuser, have been investigated. The mathematical formulation for the aerofoil and its unsteady wake is based on linear theory and is solved by a piecewise linear vorticity method; the wall boundaries are represented by distributions of sources. Numerical calculations have been made for various values of tunnel height to chord ratio. Interference effects on the rate of build up of lift to a steady state following a step change in incidence can be large, especially for open jet tunnels.

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Urbahs, Aleksandrs, Dmitrijs Titovs, Margarita Urbaha, Sergejs Luckinskis, and Andrejs Aleksandrovs. "Multipurpose Alpha Mechanism for the Open-jet Wind Tunnel." Transport and Aerospace Engineering 1 (May 8, 2014): 54. http://dx.doi.org/10.7250/tae.2014.010.

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Mikhailov, Yu S., and Yu G. Stepanov. "SIMULATION OF 2D FLOW AROUND OF AIRFOILS AT LOW-SPEED WIND TUNNEL WITH OPEN JET TEST-SECTION." Civil Aviation High TECHNOLOGIES 22, no. 1 (February 27, 2019): 51–62. http://dx.doi.org/10.26467/2079-0619-2019-22-1-51-62.

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At present, there is a great interest in the development of new airfoils for wind turbines and high-lift wings of unmanned aerial vehicles (UAV). The requirements for such airfoils differ from conventional aircraft airfoils, because of structural reasons and extreme operating conditions. So, wind turbine airfoils operate frequently under fully separated flow when stall is used for power regulation at high wind speeds. At the same time design of airfoils for wings UAV poses the problem of availability of high-lift at low Reynolds number. Modern airfoils are to a large extent developed from numerical methods. However, the complex flow conditions such as separation at high angles of attack, laminar separation bubbles and the transition from laminar to turbulent flow are difficult to predict accurately. Hence, testing of airfoils at a two-dimensional condition is an important phase in airfoil design. The development and validation of a 2D testing facility for investigation of single and multi-element airfoils in the wind tunnel Т-102 with open test section are considered in this article. T-102 is a continuous-operation, closed-layout wind tunnel with two reverse channels. The test section has an elliptical cross-section of 4 ×2,33 m and a length of 4 m. Two big flat panels of the L × H=3 ×3,9 m size installed upright on balance frame aligned with the free stream are used for simulating two-dimensional flow in the tunnel test section. The airfoil section in the layout of a rectangular wing is mounted horizontally between flat panels with minimum gaps to ensure 2D flow conditions. The aerodynamic forces and pitch moment acting on the model were measured by wind tunnel balance. To determine boundary corrections for a new test section of wind tunnel, the experimental investigation of three geometrically similar models has been executed. The use of boundary corrections has provided good correlation of the test data of airfoil NACA 6712 with the results obtained from the wind tunnel except for lift and drag coefficient values at high angles of attack.

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Wang, Yigng, Zhigng Yang, and Qilang Li. "Methods to control low frequency pulsation in open-jet wind tunnel." Applied Acoustics 73, no. 6-7 (June 2012): 666–72. http://dx.doi.org/10.1016/j.apacoust.2012.01.002.

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Underbrink, James R. "Pletharrays for aeroacoustic phased array applications." International Journal of Aeroacoustics 16, no. 4-5 (July 2017): 202–29. http://dx.doi.org/10.1177/1475472x17718884.

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“Pletharrays” are introduced, motivated, and presented for application to aeroacoustic phased array measurements. Pletharrays contain a plethora of arrays composed from a modest to high number of array elements to field a remarkably large number of high element count arrays for use in noise source imaging applications. Pletharrays that have been deployed for closed jet transonic wind tunnel, static engine ground, open jet wind tunnel, and flyover phased array tests are presented. Tremendous array element leverage to provide extensive measurement flexibility and fidelity are demonstrated.

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8

Al-Faruk, Abdullah, and Ahmad Sharifian. "Geometrical optimization of a swirling Savonius wind turbine using an open jet wind tunnel." Alexandria Engineering Journal 55, no. 3 (September 2016): 2055–64. http://dx.doi.org/10.1016/j.aej.2016.07.005.

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Funke, Stefan, Larisa Kim, and Henri Siller. "Acoustic Measurements of a Contra-Rotating Open Rotor in an Open Jet Wind-Tunnel." International Journal of Aeroacoustics 11, no. 2 (June 2012): 197–212. http://dx.doi.org/10.1260/1475-472x.11.2.197.

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10

Migliore, Paul, and Stefan Oerlemans. "Wind Tunnel Aeroacoustic Tests of Six Airfoils for Use on Small Wind Turbines*." Journal of Solar Energy Engineering 126, no. 4 (November 1, 2004): 974–85. http://dx.doi.org/10.1115/1.1790535.

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Aeroacoustic tests of seven airfoils were performed in an open jet anechoic wind tunnel. Six of the airfoils are candidates for use on small wind turbines operating at low Reynolds numbers. One airfoil was tested for comparison to benchmark data. Tests were conducted with and without boundary layer tripping. In some cases, a turbulence grid was placed upstream in the test section to investigate inflow turbulence noise. An array of 48 microphones was used to locate noise sources and separate airfoil noise from extraneous tunnel noise. Trailing-edge noise was dominant for all airfoils in clean tunnel flow. With the boundary layer untripped, several airfoils exhibited pure tones that disappeared after proper tripping was applied. In the presence of inflow turbulence, leading-edge noise was dominant for all airfoils.

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11

Rona, Aldo, Renato Paciorri, and Marco Geron. "Design and Testing of a Transonic Linear Cascade Tunnel With Optimized Slotted Walls." Journal of Turbomachinery 128, no. 1 (June 23, 2005): 23–34. http://dx.doi.org/10.1115/1.2101856.

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In linear cascade wind tunnel tests, a high level of pitchwise periodicity is desirable to reproduce the azimuthal periodicity in the stage of an axial compressor or turbine. Transonic tests in a cascade wind tunnel with open jet boundaries have been shown to suffer from spurious waves, reflected at the jet boundary, that compromise the flow periodicity in pitch. This problem can be tackled by placing at this boundary a slotted tailboard with a specific wall void ratio s and pitch angle α. The optimal value of the s-α pair depends on the test section geometry and on the tunnel running conditions. An inviscid two-dimensional numerical method has been developed to predict transonic linear cascade flows, with and without a tailboard, and quantify the nonperiodicity in the discharge. This method includes a new computational boundary condition to model the effects of the tailboard slots on the cascade interior flow. This method has been applied to a six-blade turbine nozzle cascade, transonically tested at the University of Leicester. The numerical results identified a specific slotted tailboard geometry, able to minimize the spurious reflected waves and regain some pitchwise flow periodicity. The wind tunnel open jet test section was redesigned accordingly. Pressure measurements at the cascade outlet and synchronous spark schlieren visualization of the test section, with and without the optimized slotted tailboard, have confirmed the gain in pitchwise periodicity predicted by the numerical model.

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12

Saddington, A. J., and K. Knowles. "Mutual interference between jets and intakes in STOVL aircraft." Aeronautical Journal 103, no. 1024 (June 1999): 281–86. http://dx.doi.org/10.1017/s0001924000064824.

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Abstract A series of experiments has been performed in an open-jet wind tunnel on a generic jet-lift STOVL aircraft in transition out of ground effect. In order to obtain information about the forces acting on the aircraft, static pressure measurements were made on the wing and intake lips. The model tested was equipped with a single vectored lift-jet and ‘powered’ intakes. Tests were conducted at a variety of nozzle pressure ratios and effective velocity ratios. The experiments conclude that a mutual interference exists between the jet and intake flows which generates non-linearly-additive loads on the airframe. This questions the validity of testing jets and intakes separately on a STOVL aircraft of this type.

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13

Tourn, Silvana, Jordi Pallarès, Ildefonso Cuesta, and Uwe Schmidt Paulsen. "Characterization of a new open jet wind tunnel to optimize and test vertical axis wind turbines." Journal of Renewable and Sustainable Energy 9, no. 3 (May 2017): 033302. http://dx.doi.org/10.1063/1.4982750.

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14

Ullah, Junaid, Aleš Prachař, Miroslav Šmíd, Avraham Seifert, Vitaly Soudakov, Thorsten Lutz, and Ewald Krämer. "Reynolds number and wind tunnel wall effects on the flow field around a generic UHBR engine high-lift configuration." CEAS Aeronautical Journal 11, no. 4 (August 31, 2020): 1009–23. http://dx.doi.org/10.1007/s13272-020-00463-w.

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Abstract RANS simulations of a generic ultra-high bypass ratio engine high-lift configuration were conducted in three different environments. The purpose of this study is to assess small scale tests in an atmospheric closed test section wind tunnel regarding transferability to large scale tests in an open-jet wind tunnel. Special emphasis was placed on the flow field in the separation prone region downstream from the extended slat cut-out. Validation with wind tunnel test data shows an adequate agreement with CFD results. The cross-comparison of the three sets of simulations allowed to identify the effects of the Reynolds number and the wind tunnel walls on the flow field separately. The simulations reveal significant blockage effects and corner flow separation induced by the test section walls. By comparison, the Reynolds number effects are negligible. A decrease of the incidence angle for the small scale model allows to successfully reproduce the flow field of the large scale model despite severe wind tunnel wall effects.

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15

Chong, T. P., P. F. Joseph, and P. O. A. L. Davies. "Design and performance of an open jet wind tunnel for aero-acoustic measurement." Applied Acoustics 70, no. 4 (April 2009): 605–14. http://dx.doi.org/10.1016/j.apacoust.2008.06.011.

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16

Wang, Yi Gang, Jia Shun Yang, Yang Yang, and Zhi Gang Yang. "The Effects of the Jet-Flow on Sound Propagation in Low-Speed Wind Tunnel." Applied Mechanics and Materials 226-228 (November 2012): 368–73. http://dx.doi.org/10.4028/www.scientific.net/amm.226-228.368.

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Based on the open-jet aero-acoustic wind tunnel, an experimental study was made to research the effects of the jet-flow on sound propagation. This study is focused on the changes of the direction of the sound propagation, the changes of the sound pressure level, the phenomenon of tone broadening and the availability of the existing prediction method for sound propagation in jet-flow. The results indicate that the influence of the jet-flow on the value of the noise source shift varies along the direction of the jet-flow and there is no regular influence on the sound pressure level. In addition, the flow around the test sample has affected the sound propagation, and the phenomenon of tone broadening exists when high frequency signal is used. The study also reveals the limitation of the application of the existing prediction method, because the model it used is too simple.

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Fei, Xiao, Christoph Jessing, Timo Kuthada, Jochen Wiedemann, and Andreas Wagner. "The Influence of Different Unsteady Incident Flow Environments on Drag Measurements in an Open Jet Wind Tunnel." Fluids 5, no. 4 (October 13, 2020): 178. http://dx.doi.org/10.3390/fluids5040178.

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Aerodynamic development for road vehicles is usually carried out in a uniform steady-state flow environment, either in the wind tunnel or in Computational Fluid Dynamics (CFD) simulations. However, out on the road, the vehicle experiences unsteady flow with fluctuating angles of incidence β, caused by natural wind, roadside obstacles, or traffic. In order to simulate such flow fields, the Forschungsinstitut für Kraftfahrwesen und Fahrzeugmotoren Stuttgart (FKFS) swing® system installed in the quarter scale model wind tunnel can create a variety of time-resolved signals with variable β. The static pressure gradient in the empty test section, as well as cD values of the Society of Automotive Engineers (SAE) body and the DrivAer model, have been measured under these transient conditions. The cD measurements have been corrected using the Two-Measurement Correction method in order to decouple the influence of the unsteady flow from that of the static pressure gradient. The investigation has determined that the static pressure gradient in the empty test section varies greatly with different excitation signals. Thus, it is imperative to apply a cD correction for unsteady wind tunnel measurements. The corrected cD values show that a higher signal amplitude, as in, signals with large β, lead to higher drag forces. The influence of the signal frequency on drag values varies depending on the vehicle geometry and needs to be investigated further in the future.

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18

Li, Q., W. Dai, L. Zhong, Z. Yang, K. Du, Y. Xu, and M. M. Rashidi. "Effects of Reinjection on Flow Field of Open Jet Automotive Wind Tunnel Test Section." Journal of Applied Fluid Mechanics 11, no. 1 (January 1, 2018): 43–53. http://dx.doi.org/10.29252/jafm.11.01.27715.

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Amandolese, X., and C. Vartanian. "Reduction of 3/4 open jet low-frequency fluctuations in the S2A wind tunnel." Journal of Wind Engineering and Industrial Aerodynamics 98, no. 10-11 (October 2010): 568–74. http://dx.doi.org/10.1016/j.jweia.2010.04.011.

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Quinn, Daniel B., Anthony Watts, Tony Nagle, and David Lentink. "A new low-turbulence wind tunnel for animal and small vehicle flight experiments." Royal Society Open Science 4, no. 3 (March 2017): 160960. http://dx.doi.org/10.1098/rsos.160960.

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Our understanding of animal flight benefits greatly from specialized wind tunnels designed for flying animals. Existing facilities can simulate laminar flow during straight, ascending and descending flight, as well as at different altitudes. However, the atmosphere in which animals fly is even more complex. Flow can be laminar and quiet at high altitudes but highly turbulent near the ground, and gusts can rapidly change wind speed. To study flight in both laminar and turbulent environments, a multi-purpose wind tunnel for studying animal and small vehicle flight was built at Stanford University. The tunnel is closed-circuit and can produce airspeeds up to 50 m s −1 in a rectangular test section that is 1.0 m wide, 0.82 m tall and 1.73 m long. Seamless honeycomb and screens in the airline together with a carefully designed contraction reduce centreline turbulence intensities to less than or equal to 0.030% at all operating speeds. A large diameter fan and specialized acoustic treatment allow the tunnel to operate at low noise levels of 76.4 dB at 20 m s −1 . To simulate high turbulence, an active turbulence grid can increase turbulence intensities up to 45%. Finally, an open jet configuration enables stereo high-speed fluoroscopy for studying musculoskeletal control in turbulent flow.

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Jia, Q., Y. Zhu, D. Bao, M. M. Rashidi, and Z. Yang. "On the Low Frequency Pressure Fluctuation in a 3/4 Open Jet Automotive Wind Tunnel." Journal of Applied Fluid Mechanics 12, no. 5 (September 1, 2019): 1359–69. http://dx.doi.org/10.29252/jafm.12.05.29530.

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22

Batura, N. I., Valery Viktorovich Vozhdaev, Gadzhi Gadzhimagomaevich Gadzhimagomedov, and Igor Ivanovich Lipatov. "MIXING LAYER STRUCTURE OF A JET IN A WIND TUNNEL WITH AN OPEN TEST SECTION." TsAGI Science Journal 48, no. 8 (2017): 711–22. http://dx.doi.org/10.1615/tsagiscij.2018026655.

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23

Moreau, Stéphane, Douglas Neal, and John Foss. "Hot-Wire Measurements Around a Controlled Diffusion Airfoil in an Open-Jet Anechoic Wind Tunnel." Journal of Fluids Engineering 128, no. 4 (2006): 699. http://dx.doi.org/10.1115/1.2201644.

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24

Kramer, C., H. J. Gerhardt, and L. J. Janssen. "Flow studies of an open jet wind tunnel and comparison with closed and slotted walls." Journal of Wind Engineering and Industrial Aerodynamics 22, no. 2-3 (June 1986): 115–27. http://dx.doi.org/10.1016/0167-6105(86)90078-4.

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Bao, Di, Qing Jia, and Zhigang Yang. "Effect of Vortex Generator on Flow Field Quality in 3/4 Open Jet Automotive Wind Tunnel." SAE International Journal of Passenger Cars - Mechanical Systems 10, no. 1 (March 28, 2017): 224–34. http://dx.doi.org/10.4271/2017-01-1530.

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Collin, Christopher, Steffen Mack, Thomas Indinger, and Joerg Mueller. "A Numerical and Experimental Evaluation of Open Jet Wind Tunnel Interferences using the DrivAer Reference Model." SAE International Journal of Passenger Cars - Mechanical Systems 9, no. 2 (April 5, 2016): 657–79. http://dx.doi.org/10.4271/2016-01-1597.

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27

Redonnet, S. "Investigation of the acoustic installation effects of an open-jet anechoic wind tunnel using computational aeroacoustics." Applied Acoustics 169 (December 2020): 107469. http://dx.doi.org/10.1016/j.apacoust.2020.107469.

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Jin, Ling, Haisheng Sun, Yubiao Jiang, Yong Liang, and Junlong Zhang. "Suppression of low-frequency pressure pulsations in an open jet wind tunnel by corner vortex generators." AIP Advances 11, no. 6 (June 1, 2021): 065306. http://dx.doi.org/10.1063/5.0056092.

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Shen, Zhe, Zhigang Yang, and Yigang Wang. "Unsteady correlation between shear layer vorticity and acoustic refraction in low speed open-jet wind tunnel." Applied Acoustics 182 (November 2021): 108202. http://dx.doi.org/10.1016/j.apacoust.2021.108202.

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Wang, Lican, Rongqian Chen, Yancheng You, Wenjun Wu, and Ruofan Qiu. "A Unified Correction Method for the Acoustic Refraction (UCMAR) Caused by a Three Dimensional Shear Layer." Acta Acustica united with Acustica 105, no. 5 (July 1, 2019): 732–42. http://dx.doi.org/10.3813/aaa.919353.

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The acoustic refraction induced by the shear layer in an open-jet wind tunnel causes a source shift when estimating the source location with beamforming. Traditional correction methods of the shear layer refraction are achieved through a computational eff ort or limited using one-dimensional or planar shear layer. In this paper, the unified correction method for acoustic refraction (UCMAR) is suitable for the three dimensions that covers several traditional forms. Meanwhile, the UCMAR can consider more general configurations, such as the temperature gradient on both sides of the shear layer and the off -axis source in a circular wind tunnel. These configurations are validated through a ray tracing technique and a benchmark example. In addition, the principle of time reverse is integrated with UCMAR. This results in a reverse UCMAR, which can quickly attain an acceptable solution.

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Mohan Kumar, Palanisamy, M. Mohan Ram Surya, Srikanth Narasimalu, and Teik-Cheng Lim. "Experimental and numerical investigation of novel Savonius wind turbine." Wind Engineering 43, no. 3 (June 6, 2018): 247–62. http://dx.doi.org/10.1177/0309524x18780392.

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Savonius wind turbines have distinct advantages in terms of simplicity, low noise, and ease of manufacturing, yet they are not preferred for large-scale power generation due to their lower aerodynamic performance and high wind loads. This study is aimed at reducing the thrust load with retractable type telescopic blades. This novel telescopic Savonius turbine is tested in an open jet wind tunnel to assess the performance in terms of torque, power, and thrust on the rotor. The dynamic and static characteristics are obtained for both extended and retracted configuration after correcting the experimental data for wind tunnel blockage. A preliminary numerical study is carried out in an effort to determine the variation of the drag coefficient in relation to the bucket thickness. The proposed telescopic turbine demonstrates a reduction in thrust load of 72.4% with a maximum power coefficient of 0.14 at the tip speed ratio of 0.7 compared to an extended operating configuration, similar to a conventional Savonius turbine. Thus, the telescopic Savonius turbine can be scaled up to higher kilowatt capacity with the cost comparable to other high-speed rotors such as Darrieus or horizontal axis wind turbines.

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Jin, Ling, Yunsong Gu, Xiao Bing Deng, Haisheng Sun, Tingrui Yue, and Junlong Zhang. "Standing wave and its impact on the low-frequency pressure fluctuation in an open jet wind tunnel." Journal of Wind Engineering and Industrial Aerodynamics 208 (January 2021): 104413. http://dx.doi.org/10.1016/j.jweia.2020.104413.

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Wetzel, Drew A., John Griffin, and Louis N. Cattafesta. "Experiments on an elliptic circulation control aerofoil." Journal of Fluid Mechanics 730 (July 30, 2013): 99–144. http://dx.doi.org/10.1017/jfm.2013.293.

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AbstractExperiments are performed on an elliptic circulation control aerofoil in an open-jet wind tunnel facility. The influence of blowing from a single trailing-edge slot on the external flow is assessed using two-component particle image velocimetry (PIV) and steady surface pressure measurements. The test section configuration (open jet or closed wall) significantly affects the leading-edge region of the flow field. PIV is also used to measure the curved wall jet and its interaction with the external flow near the trailing edge. PIV measurements of the curved wall jet reveal mean tangential velocity similarity in the outer region of the flow above the location where the tangential velocity reaches a local maximum. The length and velocity parameters required for similarity scale with the product of the chord Reynolds number and the momentum coefficient in accordance with the recent publication by Stalnov, Kribus & Seifert (J. Renew. Sustain. Energy, vol. 2, 2010, p. 063101). The separation location is also a function of the product of these parameters. The dataset is used to assemble equations to predict the similarity length scales, velocity scales and separation location. These equations compare well with the present measurements.

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Roberts, LS, MV Finnis, and K. Knowles. "Modelling boundary-layer transition on wings operating in ground effect at low Reynolds numbers." Proceedings of the Institution of Mechanical Engineers, Part D: Journal of Automobile Engineering 233, no. 11 (October 25, 2018): 2820–37. http://dx.doi.org/10.1177/0954407018804007.

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The transition-sensitive, three-equation k- kL- ω eddy-viscosity closure model was used for simulations of three-dimensional, single-element and multi-element wing configurations operating in close proximity to the ground. The aim of the study was to understand whether the model correctly simulated the transitional phenomena that occurred in the low Reynolds number operating conditions and whether it offered an improvement over the classical fully turbulent k-ω shear stress transport model. This was accomplished by comparing the simulation results to experiments conducted in a 2.7 m × 1.7 m closed-return, three-quarter-open-jet wind tunnel. The model was capable of capturing the presence of a laminar separation bubble on the wing and predicted sectional forces and surface-flow structures generated by the wings in wind tunnel testing to within 2.5% in downforce and 4.1% in drag for a multi-element wing. It was found, however, that the model produced insufficient turbulent kinetic energy during shear-layer reattachment, predicted turbulent trailing-edge separation prematurely in areas of large adverse pressure gradients, and was found to be very sensitive to inlet turbulence quantities. Despite these deficiencies, the model gave results that were much closer to wind-tunnel tests than those given by the fully turbulent k-ω shear stress transport model, which tended to underestimate downforce. Significant differences between the transitional and fully turbulent models in terms of pressure field, wake thickness and turbulent kinetic energy production were found and highlighted the importance of using transitional models for wings operating at low Reynolds numbers in ground effect. The k- kL- ω model has been shown to be appropriate for the simulation of separation-induced transition on a three-dimensional wing operating in ground effect at low Reynolds number.

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Lin, C. Y., and F. B. Hsiao. "Experimental Study of Flow Separation over NACA633018 Wing with Synthetic Jet Control at Low Reynolds Numbers." Journal of Mechanics 29, no. 1 (October 16, 2012): 45–52. http://dx.doi.org/10.1017/jmech.2012.120.

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AbstractThis paper experimentally studies flow separation and aerodynamic performance of a NACA633018 wing using a series of piezoelectric-driven disks, which are located at 12% chord length from the leading edge to generate a spanwise-distributed synthetic jets to excite the passing flow. The experiment is conducted in an open-type wind tunnel with Reynolds numbers (Re) of 8 × 104 and 1.2 × 105, respectively, based on the wing chord. The oscillations of the synthetic jet actuators (SJAs) disturb the neighboring passage flow on the upper surface of the wing before the laminar separation takes place. The disturbances of energy influence the downstream development of boundary layers to eliminate or reduce the separation bubble on the upper surface of the wing. Significant lift increase and drag decrease are found at the tested Reynolds number of 8 × 104 due to the actuators excitation. Furthermore, the effect of drag also reduces dominant with increasing Reynolds number, but the increase on lift is reduced with the Reynolds number increased.

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Wang, Meng, Stephane Moreau, Gianluca Iaccarino, and Michel Roger. "LES Prediction of Wall-Pressure Fluctuations and Noise of a Low-Speed Airfoil." International Journal of Aeroacoustics 8, no. 3 (May 2009): 177–97. http://dx.doi.org/10.1260/147547208786940017.

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This paper discusses the prediction of wall-pressure fluctuations and noise of a low-speed flow past a thin cambered airfoil using large-eddy simulation (LES). The results are compared with experimental measurements made in an open-jet anechoic wind-tunnel at Ecole Centrale de Lyon. To account for the effect of the jet on airfoil loading, a Reynolds-averaged Navier-Stokes calculation is first conducted in the full wind-tunnel configuration, and the mean velocities from this calculation are used to define the boundary conditions for the LES in a smaller domain within the potential core of the jet. The LES flow field is characterized by an attached laminar boundary layer on the pressure side of the airfoil and a transitional and turbulent boundary layer on the suction side, in agreement with experimental observations. An analysis of the unsteady surface pressure field shows reasonable agreement with the experiment in terms of frequency spectra and spanwise coherence in the trailing-edge region. In the nose region, characterized by unsteady separation and transition to turbulence, the wall-pressure fluctuations are highly sensitive to small perturbations and thus diffcult to predict or measure with certainty. The LES, in combination with the Ffowcs Williams and Hall solution to the Lighthill equation, also predicts well the radiated trailing-edge noise. A finite-chord correction is derived and applied to the noise prediction, which is shown to improve the overall agreement with the experimental sound spectrum.

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37

Merino-Martínez, Roberto, Alejandro Rubio Carpio, Lourenço Tércio Lima Pereira, Steve van Herk, Francesco Avallone, Daniele Ragni, and Marios Kotsonis. "Aeroacoustic design and characterization of the 3D-printed, open-jet, anechoic wind tunnel of Delft University of Technology." Applied Acoustics 170 (December 2020): 107504. http://dx.doi.org/10.1016/j.apacoust.2020.107504.

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38

Lei, Jiao, Pengcheng Huang, Linhe Zhang, Yukui Yuan, Wenyang Deng, Shaohua Mao, and Jun Zhang. "Experimental study on flow characteristics of a large-scale open jet wind tunnel for outdoor pool fire research." Journal of Wind Engineering and Industrial Aerodynamics 210 (March 2021): 104522. http://dx.doi.org/10.1016/j.jweia.2021.104522.

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39

Stoll, Daniel, and Jochen Wiedemann. "Active Crosswind Generation and Its Effect on the Unsteady Aerodynamic Vehicle Properties Determined in an Open Jet Wind Tunnel." SAE International Journal of Passenger Cars - Mechanical Systems 11, no. 5 (April 3, 2018): 429–46. http://dx.doi.org/10.4271/2018-01-0722.

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40

Madanahalli, A. V., and S. R. Gollahalli. "Effects of Nozzle Orientation on the Structure and Emissions of Spray Flames." Journal of Energy Resources Technology 115, no. 3 (September 1, 1993): 183–89. http://dx.doi.org/10.1115/1.2905991.

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An experimental study of the effects of the orientation of the liquid fuel stream relative to the air stream from a twin fluid atomizer located in an open-jet wind tunnel is presented. The orientation angle was set at 0 (concurrent), 45, 90, 135, and 180 deg (directly opposed). At 45 and 90 deg, the flame length, the radiation emission, and the concentrations of carbon monoxide, carbon dioxide, nitric oxide, and soot are higher than those at co-flow conditions. At 135 deg, all these quantities decrease markedly from their values at 90 deg and again increase when the fuel and air streams are directly opposed (180 deg). These changes are discussed in terms of the influx of air and recirculation of combustion products into the salient zones of the flame.

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Bernhammer, Lars O., Roeland De Breuker, and Moti Karpel. "Energy harvesting for actuators and sensors using free-floating flaps." Journal of Intelligent Material Systems and Structures 28, no. 2 (July 28, 2016): 163–77. http://dx.doi.org/10.1177/1045389x16645954.

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A novel configuration of an energy harvester for local actuation and sensing devices using limit cycle oscillations has been modeled, designed and tested. A wing section has been designed with two trailing-edge free-floating flaps. A free-floating flap is a flap that can freely rotate around a hinge axis and is driven by trailing edge tabs. In the rotational axis of each flap a generator is mounted that converts the vibrational energy into electricity. It has been demonstrated numerically how a simple electronic system can be used to keep such a system at stable limit cycle oscillations by varying the resistance in the electric circuit. Additionally, it was shown that the stability of the system is coupled to the charge level of the battery, with increasing charge level leading to a less stable system. The system has been manufactured and tested in the Open Jet Wind Tunnel Facility of the Technical University Delft. The numerical results could be validated successfully and voltage generation could be demonstrated at cost of a decrease in lift of 2%.

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Zhang, Minghui, and Tze Pei Chong. "Effects of porous trailing edge on aerodynamic noise characteristics." International Journal of Aeroacoustics 19, no. 3-5 (June 2020): 254–71. http://dx.doi.org/10.1177/1475472x20937941.

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The objective of this work is to investigate the effect of the porous trailing edge on the aeroacoustics performance of the NACA 65(12)-10 aerofoil. The motivation behind this study is to investigate the effect of the porous parameters to explore the noise control concepts. Experimental testing in an aeroacoustics open jet wind tunnel was performed at chord-based Reynolds numbers between 0.2 and 0.6 million, and effective angles of attack at ±1.7 degree, including at 0 degrees. The porous trailing edge at porosity 30% with different holes diameters and the length of these porous trailing edges are used in the acoustic experiments. The study reveals that the level of the reduction of the broadband noise becomes larger as the diameter of the holes decreases and the length of the porous trailing edge increases at lower Reynolds numbers. Bluntness-induced tone noise is produced at high Reynolds number. Meanwhile, the porous trailing edge can suppress the laminar instability noise at the middle and low frequency regions.

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Geyer, Thomas Fritz, and Ennes Sarradj. "Self Noise Reduction and Aerodynamics of Airfoils With Porous Trailing Edges." Acoustics 1, no. 2 (April 24, 2019): 393–409. http://dx.doi.org/10.3390/acoustics1020022.

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The application of open-porous materials is a possible method to effectively reduce the aerodynamic noise of an airfoil. However, the porous consistency may have a negative effect on the aerodynamic performance of the airfoil, since very often the lift is decreased while the drag increases. In a recent investigation, the generation of trailing edge noise of a set of airfoil models made from different porous materials was examined experimentally. The materials were characterized mainly by their airflow resistivity. Besides the material, the chordwise extent of the porous material was varied, which was done by covering the front part of the porous airfoil with a thin, impermeable adhesive foil. Acoustic measurements were performed in an open jet wind tunnel using microphone array technology, while the aerodynamic performance was measured simultaneously using a six-component balance. In general, both the airflow resistivity and the extent of the porous material have an influence on the trailing edge noise. However, if a suitable material is chosen, the results show that a noticeable reduction of trailing edge noise is possible even with only a small chordwise extent of the porous material.

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Amiri, M., AR Teymourtash, and M. Kahrom. "Experimental and numerical investigations on the aerodynamic performance of a pivoted Savonius wind turbine." Proceedings of the Institution of Mechanical Engineers, Part A: Journal of Power and Energy 231, no. 2 (November 4, 2016): 87–101. http://dx.doi.org/10.1177/0957650916677428.

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Savonius turbines have been the subject of various wind energy projects due to their good starting characteristics, easy installation, and independency of wind direction. However, the Savonius rotor suffers from low aerodynamic performance, which is mainly due to the adverse torque of the returning blade. A recently introduced design suggests using pivoted blades for the rotor to eliminate the negative torque of the returning blade. In this study, the aerodynamic performance of the newly proposed turbine has been investigated experimentally and numerically. The experimental measurements are performed in a subsonic open-jet type wind tunnel facility. The numerical simulations are performed using ANSYS-Fluent commercial software, by making use of the multiple reference frame model. The effects of the number of blades (3-, 4-, and 6-bladed) on the torque and power coefficients are examined in details, at several Reynolds numbers. Results show that the new rotor has no negative torque in one complete revolution and that the 3-bladed rotor has the best aerodynamic performance, in a manner that, it reaches a maximum power coefficient of 0.21 at TSR = 0.5. Although increasing the number of blades decreases the output torque oscillations, it also decreases the average power coefficient of the rotor. Results show that Reynolds number does not have a significant effect on the average power coefficient of the rotor in the studied range of 7.7 × 104 ≤ Re ≤ 1.2 × 105.

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Sandham, N. D., E. Schülein, A. Wagner, S. Willems, and J. Steelant. "Transitional shock-wave/boundary-layer interactions in hypersonic flow." Journal of Fluid Mechanics 752 (July 4, 2014): 349–82. http://dx.doi.org/10.1017/jfm.2014.333.

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AbstractStrong interactions of shock waves with boundary layers lead to flow separations and enhanced heat transfer rates. When the approaching boundary layer is hypersonic and transitional the problem is particularly challenging and more reliable data is required in order to assess changes in the flow and the surface heat transfer, and to develop simplified models. The present contribution compares results for transitional interactions on a flat plate at Mach 6 from three different experimental facilities using the same instrumented plate insert. The facilities consist of a Ludwieg tube (RWG), an open-jet wind tunnel (H2K) and a high-enthalpy free-piston-driven reflected shock tunnel (HEG). The experimental measurements include shadowgraph and infrared thermography as well as heat transfer and pressure sensors. Direct numerical simulations (DNS) are carried out to compare with selected experimental flow conditions. The combined approach allows an assessment of the effects of unit Reynolds number, disturbance amplitude, shock impingement location and wall cooling. Measures of intermittency are proposed based on wall heat flux, allowing the peak Stanton number in the reattachment regime to be mapped over a range of intermittency states of the approaching boundary layer, with higher overshoots found for transitional interactions compared with fully turbulent interactions. The transition process is found to develop from second (Mack) mode instabilities superimposed on streamwise streaks.

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Wang, Lican, Rongqian Chen, Yancheng You, Zhengwu Chen, and Ruofan Qiu. "Effects of Shear Layer Characteristics on Acoustic Propagation and Source Localization." Xibei Gongye Daxue Xuebao/Journal of Northwestern Polytechnical University 37, no. 6 (December 2019): 1148–57. http://dx.doi.org/10.1051/jnwpu/20193761148.

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The shear layer characteristics of an open-jet acoustic wind tunnel are of key importance on measurements of aeroacoustics. The effects of thickness, spreading angle and strength of shear layer on acoustic propagation and source localization are investigated through the mean/spreading shear layer with a self-similar velocity distribution. Based on the shear flow, the acoustic propagation is computed by the linearized Euler equations via a source term, and then source localization is obtained from beamforming technique combined with the theory of Amiet. Results show that the numerical method can precisely capture the refraction and reflection after sound traversing shear layer. The thickness, spreading angle and strength of the shear layer exerts little effects on the refracted region where sound wave nearly vertical incident, while mainly influence the corresponding up/downstream region in terms of phase change. Increment of thickness, spreading angle and strength of the shear layer increases the acoustic difference between the shear layer with and without thickness, and produces a larger error of source localization downstream of the actual position.

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Laratro, Alex, Maziar Arjomandi, Benjamin Cazzolato, and Richard Kelso. "Self-noise of NACA 0012 and NACA 0021 aerofoils at the onset of stall." International Journal of Aeroacoustics 16, no. 3 (April 2017): 181–95. http://dx.doi.org/10.1177/1475472x17709929.

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The aerodynamic noise of a NACA 0012 and NACA 0021 aerofoil is measured and compared in order to determine whether there are differences in their noise signatures with a focus on the onset of stall. Measurements of the self-noise of each aerofoil are measured in an open-jet Anechoic Wind Tunnel at Reynolds numbers of 64,000 and 96,000, at geometric angles of attack from −5° through 40° at a resolution of 1°. Further measurements are taken at Re = 96,000 at geometric angles of attack from −5 through 16° at a resolution of 0.5°. Results show that while the noise generated far into the stall regime is quite similar for both aerofoils the change in noise level at the onset of stall is significantly different between the two aerofoils with the NACA 0021 exhibiting a much sharper increase in noise levels below a chord-based Strouhal number of Stc = 1.1. This behaviour is consistent with the changes in lift of these aerofoils as well as the rate of collapse of the suction peak of a NACA 0012 aerofoil under these flow conditions.

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Smout, P. D., and P. C. Ivey. "Investigation of Wedge Probe Wall Proximity Effects: Part 2—Numerical and Analytical Modeling." Journal of Engineering for Gas Turbines and Power 119, no. 3 (July 1, 1997): 605–11. http://dx.doi.org/10.1115/1.2817027.

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An experimental study of wedge probe wall proximity effects is described in Part 1 of this paper. Actual size and large-scale model probes were tested to understand the mechanisms responsible for this effect, by which free-stream pressure near the outer wall of a turbomachine may be overindicated by up to 20 percent dynamic head. CFD calculations of the flow over two-dimensional wedge shapes and a three-dimensional wedge probe were made in support of the experiments, and are reported in this paper. Key flow structures in the probe wake were identified that control the pressures indicated by the probe in a given environment. It is shown that probe aerodynamic characteristics will change if the wake flow structures are modified, for example by traversing close to the wall, or by calibrating the probe in an open jet rather than in a closed section wind tunnel. A simple analytical model of the probe local flows was derived from the CFD results. It is shown by comparison with experiment that this model captures the dominant flow features.

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Lignarolo, L. E. M., D. Ragni, F. Scarano, C. J. Simão Ferreira, and G. J. W. van Bussel. "Tip-vortex instability and turbulent mixing in wind-turbine wakes." Journal of Fluid Mechanics 781 (September 23, 2015): 467–93. http://dx.doi.org/10.1017/jfm.2015.470.

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Kinetic-energy transport and turbulence production within the shear layer of a horizontal-axis wind-turbine wake are investigated with respect to their influence on the tip-vortex pairwise instability, the so-called leapfrogging instability. The study quantifies the effect of near-wake instability and tip-vortex breakdown on the process of mean-flow kinetic-energy transport within the far wake of the wind turbine, in turn affecting the wake re-energising process. Experiments are conducted in an open-jet wind tunnel with a wind-turbine model of 60 cm diameter at a diameter-based Reynolds number range $\mathit{Re}_{D}=150\,000{-}230\,000$. The velocity fields in meridian planes encompassing a large portion of the wake past the rotor are measured both in the unconditioned and the phase-locked mode by means of stereoscopic particle image velocimetry. The detailed topology and development of the tip-vortex interactions are discussed prior to a statistical analysis based on the triple decomposition of the turbulent flow fields. The study emphasises the role of the pairing instability as a precursor to the onset of three-dimensional vortex distortion and breakdown, leading to increased turbulent mixing and kinetic-energy transport across the shear layer. Quadrant analysis further elucidates the role of sweep and ejection events within the two identified mixing regimes. Prior to the onset of the instability, vortices shed from the blade appear to inhibit turbulent mixing of the expanding wake. The second region is dominated by the leapfrogging instability, with a sudden increase of the net entrainment of kinetic energy. Downstream of the latter, random turbulent motion characterises the flow, with a significant increase of turbulent kinetic-energy production. In this scenario, the leapfrogging mechanism is recognised as the triggering event that accelerates the onset of efficient turbulent mixing followed by the beginning of the wake re-energising process.

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Haans, Wouter, Tonio Sant, Gijs van Kuik, and Gerard van Bussel. "Stall in Yawed Flow Conditions: A Correlation of Blade Element Momentum Predictions With Experiments." Journal of Solar Energy Engineering 128, no. 4 (July 16, 2006): 472–80. http://dx.doi.org/10.1115/1.2349545.

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Yawed flow conditions introduce unsteady loads in a wind turbine that affect generated power quality and fatigue life. An unsteady phenomenon of special concern is dynamic stall, due to the significant load fluctuations associated with it. Although the assumptions underlying blade element momentum (BEM) models are totally inadequate in yawed flow conditions, these models, modified with engineering models, are still widely used in industry. It is therefore relevant to assess the capabilities of BEM models in predicting the location of dynamic stall on the blade for a rotor in yawed flow conditions. A rotor model is placed in an open jet wind tunnel and tested in yawed flow conditions. The locations of dynamic stall on the blade of a rotor model as a function of the blade position are observed. Two experimental techniques are used; tufts glued to the blade and hot-film anemometry in the near wake. The results from the two techniques are compared and possible causes for differences are identified. Furthermore, the rotor model in yaw is modeled with a simple BEM model, utilizing a Gormont dynamic stall model. The regions of dynamic stall on the blades predicted by the BEM model are compared with the experimental results. The BEM model seems capable of a crude prediction of the dynamic stall locations found for the rotor model in yawed flow conditions.

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Journal articles on the topic 'Open-jet wind tunnel'

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