This paper compares the results of force and moment measurements made on the same test article and with the same balance in three transonic wind tunnels. Comparisons are made for the same combination of Reynolds number, Mach number, sideslip angle, control surface configuration, and angle of attack range. Between-tunnel force and moment differences are quantified. An analysis of variance was performed at four unique sites in the design space to assess the statistical significance of between-tunnel variation and any interaction with angle of attack. Tunnel to tunnel differences too large to attribute to random error were detected were observed for all forces and moments. In some cases these differences were independent of angle of attack and in other cases they changed with angle of attack.
Kwon, Hyeok-Bin; Nam, Seong-Won; You, Won-Hee
This study is devoted to measure the aerodynamic forces acting on two railway trains, one of which is a high-speed train at 300km/h maximum operation speed, and the other is a conventional train at the operating speed 100km/h. The three-dimensional train shapes have been modeled as detailed as possible including the inter-car, the upper cavity for pantograph, and the bogie systems. The aerodynamic forces on each vehicle of the trains have been measured in the subsonic wind tunnel with 4m×3m test section of Korea Aerospace Research Institute at Daejeon, Korea. The aerodynamic forces and moments of the train models have been plotted for various yaw angles and the characteristics of the aerodynamic coefficients has been discussed relating to the experimental conditions.
Federal Laboratory Consortium — The Microsystem Aeromechanics Wind Tunnel advances the study of fundamental flow physics relevant to micro air vehicle (MAV) flight and assesses vehicle performance...
Full Text Available The paper discusses the results of wind tunnel tests of airfoils with additional active airflow applied to their upper surfaces. These studies were carried out for a range of velocities up to 28 m/s in an open wind tunnel. Several types of airfoils selected for the examination feature different geometries and are widely applied in today’s aviation industry. The changes in the lift and drag force generated by these airfoils were recorded during the study. The test bench for the tests was equipped with a compressor and a vacuum pump to enable airflow through some holes on the airfoil upper surface. A rapid prototyping method and a 3D printer based on a powder printing technique were applied to print the airfoils. All of their surfaces were subject to surface grinding to smooth their external surfaces. The wind tunnel tests with and without active airflow applied to airfoils are summarised in the paper.
Federal Laboratory Consortium — NASA Ames Research Center is pleased to offer the services of our premier wind tunnel facilities that have a broad range of proven testing capabilities to customers...
Federal Laboratory Consortium — This ARDEC facility consists of subsonic, transonic, and supersonic wind tunnels to acquire aerodynamic data. Full-scale and sub-scale models of munitions are fitted...
Thermal and Pressure Characterization of a Wind Tunnel Force Balance Using the Single Vector System. Experimental Design and Analysis Approach to Model Pressure and Temperature Effects in Hypersonic Wind Tunnel Research
Lynn, Keith C.; Commo, Sean A.; Johnson, Thomas H.; Parker, Peter A,
Wind tunnel research at NASA Langley Research Center s 31-inch Mach 10 hypersonic facility utilized a 5-component force balance, which provided a pressurized flow-thru capability to the test article. The goal of the research was to determine the interaction effects between the free-stream flow and the exit flow from the reaction control system on the Mars Science Laboratory aeroshell during planetary entry. In the wind tunnel, the balance was exposed to aerodynamic forces and moments, steady-state and transient thermal gradients, and various internal balance cavity pressures. Historically, these effects on force measurement accuracy have not been fully characterized due to limitations in the calibration apparatus. A statistically designed experiment was developed to adequately characterize the behavior of the balance over the expected wind tunnel operating ranges (forces/moments, temperatures, and pressures). The experimental design was based on a Taylor-series expansion in the seven factors for the mathematical models. Model inversion was required to calculate the aerodynamic forces and moments as a function of the strain-gage readings. Details regarding transducer on-board compensation techniques, experimental design development, mathematical modeling, and wind tunnel data reduction are included in this paper.
Full Text Available The 1.2 m x 1.2 m Trisonic Blowdown Wind Tunnel is the largest of the experimental facilities at the National Institute for Aerospace Research - I.N.C.A.S. "Elie Carafoli", Bucharest, Romania. The tunnel has been designed by the Canadian company DSMA (now AIOLOS and since its commissioning in 1978 has performed high speed aerodynamic tests for more than 120 projects of aircraft, missiles and other objects among which the twin jet fighter IAR-93, the jet trainer IAR-99, the MIG-21 Lancer, the Polish jet fighter YRYDA and others. In the last years the wind tunnel has been used mostly for experimental research in European projects such as UFAST. The high flow quality parameters and the wide range of testing capabilities ensure the competitivity of the tunnel at an international level.
Mattiello, E.; Eriksen, M. B.; Georgakis, Christos T.
/FORCE Technology Climatic Wind Tunnel facility. The measured aerodynamic damping of the twin-cable arrangement in dry conditions was compared to the values obtained from full-scale monitoring and from an analytical model using static force coefficients. The comparison revealed broad agreement in the investigated...... Re range, as did the force coefficients obtained from dynamic and static tests....
V. T. Bui
Full Text Available When planning and implementing an aerodynamic experiment, model sizes and its position in the test section of the wind tunnel (WT play very important role. The paper focuses on the value variations of the aerodynamic characteristics of a model through changing its position in the WT test section and on the attenuation of the velocity field disturbance in front of the model. Flow around aerodynamic model profile in the open test section of the low-speed WT T-500 is simulated at BMSTU Department SM3. The problem is solved in a two-dimensional case using the ANSYS Fluent package. The mathematical model of flow is based on the Reynolds equations closed by the SST turbulence model. The paper also presents the results of the experiment. Experiments conducted in WT T-500 well correlate with the calculated data and show the optimal position in the middle of the test section when conducting the weighing and drainage experiments. Disturbance of tunnel dynamic pressure (velocity head and flow upwash around the model profile and circular cylinder in the WT test section is analyzed. It was found that flow upstream from the front stagnation point on the body weakly depends on the Reynolds number and obtained results can be used to assess the level of disturbances in the flow around a model by incompressible airflow.
Kuznetsov, Sergeii; Pospíšil, Stanislav; Král, Radomil
Roč. 112, 2-B (2015), s. 303-316 ISSN 1897-628X R&D Projects: GA ČR(CZ) GA14-12892S Keywords : climatic tunnel * wind tunnel * atmospheric boundary layer * flow resistance * wind tunnel contraction Subject RIV: JM - Building Engineering https://suw.biblos.pk.edu.pl/resources/i5/i6/i6/i7/i6/r56676/KuznetsovS_ClimaticWind.pdf
Andersen, Ingrid Marie Vincent
An investigation of the wind forces acting on a 9,000+ TEU container ship has been carried out through a series of wind tunnel tests. It was investigated how the wind forces depend on the container configuration on the deck using a 1:450 scale model and a series of appropriate container...... are presented as nondimensional coefficients. It is concluded, that the measured forces and moment depend on the container configuration on deck, and the results may provide a general idea of how the magnitude of the wind forces is affected by a given container stacking configuration on a similar container ship....
This section presents the results obtained during the experimental campaign that was conducted in the wind tunnel at LM Wind Power in Lunderskov from August 16th to 26th, 2010. The goal of this study is to validate the so-called TNO trailing edge noise model through measurements of the boundary...... layer turbulence characteristics and the far-field noise generated by the acoustic scattering of the turbulent boundary layer vorticies as they convect past the trailing edge. This campaign was conducted with a NACA0015 airfoil section that was placed in the wind tunnel section. It is equipped with high...
Rhew, Ray D.
NASA's Aeronautics Test Program (ATP) chartered a team to examine the issues and risks associated with the lack of funding and focus on force measurement over the past several years, focusing specifically on strain-gage balances. NASA partnered with the U.S. Air Force's Arnold Engineering Development Center (AEDC) to exploit their combined capabilities and take a national level government view of the problem and established the National Force Measurement Technology Capability (NFMTC) project. This paper provides an update on the team's status for revitalizing the government's balance capability with respect to designing, fabricating, calibrating, and using the these critical measurement devices.
Rhew, Ray D.; Skelley, Marcus L.; Woike, Mark R.; Bader, Jon B.; Marshall, Timothy J.
Lack of funding and lack of focus on research over the past several years, coupled with force measurement capabilities being decentralized and distributed across the National Aeronautics and Space Administration (NASA) research centers, has resulted in a significant erosion of (1) capability and infrastructure to produce and calibrate force measurement systems; (2) NASA s working knowledge of those systems; and (3) the quantity of high-quality, full-capability force measurement systems available for use in aeronautics testing. Simultaneously, and at proportional rates, the capability of industry to design, manufacture, and calibrate these test instruments has been eroding primarily because of a lack of investment by the aeronautics community. Technical expertise in this technology area is a core competency in aeronautics testing; it is highly specialized and experience-based, and it represents a niche market for only a few small precision instrument shops in the United States. With this backdrop, NASA s Aeronautics Test Program (ATP) chartered a team to examine the issues and risks associated with the problem, focusing specifically on strain- gage balances. The team partnered with the U.S. Air Force s Arnold Engineering Development Center (AEDC) to exploit their combined capabilities and take a national level government view of the problem. This paper describes the team s approach, its findings, and its recommendations, and the current status for revitalizing the government s balance capability with respect to designing, fabricating, calibrating, and using the instruments.
Zilz, D. E.
A wind tunnel model of a supersonic V/STOL fighter configuration has been tested to measure the aerodynamic interaction effects which can result from geometrically close-coupled propulsion system/airframe components. The approach was to configure the model to represent two different test techniques. One was a conventional test technique composed of two test modes. In the Flow-Through mode, absolute configuration aerodynamics are measured, including inlet/airframe interactions. In the Jet-Effects mode, incremental nozzle/airframe interactions are measured. The other test technique is a propulsion simulator approach, where a sub-scale, externally powered engine is mounted in the model. This allows proper measurement of inlet/airframe and nozzle/airframe interactions simultaneously. This is Volume 2 of 2: Wind Tunnel Test Force and Moment Data Report.
Hunton, Lynn W.
A wind-tunnel investigation of the Boeing XB-47 full-scale empennage was conducted to provide, prior to flight tests, data required on the effectiveness of the elevator and rudder. The XB-47 airplane is a jet-propelled medium bomber having wing and tail surfaces swept back 35 degrees. The investigation included tests of the effectiveness of the elevator with normal straight sides, with a buldged trailing edge, and with a modified hinge-line gap and tests of the effectiveness of the rudder with a normal straight-sided tab and with a bulged tab.
Burns, Devin E.; Williams, Quincy L.; Phillips, Ben D.; Commo, Sean A.; Ponder, Jonathon D.
This manuscript reviews design, manufacture, materials, sensors, and data acquisition technologies that may benefit wind tunnel balances for the aerospace research community. Current state-of-the-art practices are used as the benchmark to consider advancements driven by researcher and facility needs. Additive manufacturing is highlighted as a promising alternative technology to conventional fabrication and has the potential to reduce both the cost and time required to manufacture force balances. Material alternatives to maraging steels are reviewed. Sensor technologies including piezoresistive, piezoelectric, surface acoustic wave, and fiber optic are compared to traditional foil based gages to highlight unique opportunities and shared challenges for implementation in wind tunnel environments. Finally, data acquisition systems that could be integrated into force balances are highlighted as a way to simplify the user experience and improve data quality. In summary, a rank ordering is provided to support strategic investment in exploring the technologies reviewed in this manuscript.
Haukka, Harri; Harri, Ari-Matti; Aleksashkin, Sergei; Koryanov, Valeri; Schmidt, Walter; Heilimo, Jyri; Finchenko, Valeri; Martynov, Maxim; Ponomarenko, Andrey; Kazakovtsev, Victor; Arruego, Ignazio
An atmospheric re-entry and descent and landing system (EDLS) concept based on inflatable hypersonic decelerator techniques is highly promising for the Earth re-entry missions. We developed such EDLS for the Earth re-entry utilizing a concept that was originally developed for Mars. This EU-funded project is called RITD - Re-entry: Inflatable Technology Development - and it was to assess the bene¬fits of this technology when deploying small payloads from low Earth orbits to the surface of the Earth with modest costs. The principal goal was to assess and develope a preliminary EDLS design for the entire relevant range of aerodynamic regimes expected to be encountered in Earth's atmosphere during entry, descent and landing. The RITD entry and descent system utilizes an inflatable hypersonic decelerator. Development of such system requires a combination of wind tunnel tests and numerical simulations. This included wind tunnel tests both in transsonic and subsonic regimes. The principal aim of the wind tunnel tests was the determination of the RITD damping factors in the Earth atmosphere and recalculation of the results for the case of the vehicle descent in the Mars atmosphere. The RITD mock-up model used in the tests was in scale of 1:15 of the real-size vehicle as the dimensions were (midsection) diameter of 74.2 mm and length of 42 mm. For wind tunnel testing purposes the frontal part of the mock-up model body was manufactured by using a PolyJet 3D printing technology based on the light curing of liquid resin. The tail part of the mock-up model body was manufactured of M1 grade copper. The structure of the mock-up model placed th center of gravity in the same position as that of the real-size RITD. The wind tunnel test program included the defining of the damping factor at seven values of Mach numbers 0.85; 0.95; 1.10; 1.20; 1.25; 1.30 and 1.55 with the angle of attack ranging from 0 degree to 40 degrees with the step of 5 degrees. The damping characteristics of
Caetano, J V; Percin, M; van Oudheusden, B W; Remes, B; de Wagter, C; de Croon, G C H E; de Visser, C C
An accurate knowledge of the unsteady aerodynamic forces acting on a bio-inspired, flapping-wing micro air vehicle (FWMAV) is crucial in the design development and optimization cycle. Two different types of experimental approaches are often used: determination of forces from position data obtained from external optical tracking during free flight, or direct measurements of forces by attaching the FWMAV to a force transducer in a wind-tunnel. This study compares the quality of the forces obtained from both methods as applied to a 17.4 gram FWMAV capable of controlled flight. A comprehensive analysis of various error sources is performed. The effects of different factors, e.g., measurement errors, error propagation, numerical differentiation, filtering frequency selection, and structural eigenmode interference, are assessed. For the forces obtained from free flight experiments it is shown that a data acquisition frequency below 200 Hz and an accuracy in the position measurements lower than ± 0.2 mm may considerably hinder determination of the unsteady forces. In general, the force component parallel to the fuselage determined by the two methods compares well for identical flight conditions; however, a significant difference was observed for the forces along the stroke plane of the wings. This was found to originate from the restrictions applied by the clamp to the dynamic oscillations observed in free flight and from the structural resonance of the clamped FWMAV structure, which generates loads that cannot be distinguished from the external forces. Furthermore, the clamping position was found to have a pronounced influence on the eigenmodes of the structure, and this effect should be taken into account for accurate force measurements.
Computational fluid dynamic (CFD) simulations of models tested in wind tunnels require a high level of fidelity and accuracy particularly for the purposes of CFD validation efforts. Considerable effort is required to ensure the proper characterization of both the physical geometry of the wind tunnel and recreating the correct flow conditions inside the wind tunnel. The typical trial-and-error effort used for determining the boundary condition values for a particular tunnel configuration are time and computer resource intensive. This paper describes a method for calculating and updating the back pressure boundary condition in wind tunnel simulations by using a proportional-integral-derivative controller. The controller methodology and equations are discussed, and simulations using the controller to set a tunnel Mach number in the NASA Langley 14- by 22-Foot Subsonic Tunnel are demonstrated.
Benson, Thomas J.; Galica, Carol A.; Vila, Anthony J.
The Beginner's Guide to Wind Tunnels is a Web-based, on-line textbook that explains and demonstrates the history, physics, and mathematics involved with wind tunnels and wind tunnel testing. The Web site contains several interactive computer programs to demonstrate scientific principles. TunnelSim is an interactive, educational computer program that demonstrates basic wind tunnel design and operation. TunnelSim is a Java (Sun Microsystems Inc.) applet that solves the continuity and Bernoulli equations to determine the velocity and pressure throughout a tunnel design. TunnelSys is a group of Java applications that mimic wind tunnel testing techniques. Using TunnelSys, a team of students designs, tests, and post-processes the data for a virtual, low speed, and aircraft wing.
User Fees Contact Information Dr. Surjatin Wiriadidjaja, UPT-LAGG, BPP Teknologi, Puspiptek, Serpong, Tangerang 15310, Indonesia. Tel: (62) 21 756...of the tunnel, FFA T1500 Transonic Wind Tunnel Circuit (Sweden) manufactured by The Swedish Defense Research Agency (FOI). 2.4 m Transonic Wind
National Aeronautics and Space Administration — Rotorcraft engineers traditionally use the wind tunnel to evaluate and finalize designs. Insufficient correlation between wind tunnel results and flight tests, have...
Jacobs, Derya, A.; Aasen, Curtis A.
Time, money, and, personnel are becoming increasingly scarce resources within government agencies due to a reduction in funding and the desire to demonstrate responsible economic efficiency. The ability of an organization to plan and schedule resources effectively can provide the necessary leverage to improve productivity, provide continuous support to all projects, and insure flexibility in a rapidly changing environment. Without adequate internal controls the organization is forced to rely on external support, waste precious resources, and risk an inefficient response to change. Management systems must be developed and applied that strive to maximize the utility of existing resources in order to achieve the goal of "faster, cheaper, better". An area of concern within NASA Langley Research Center was the scheduling, planning, and resource management of the Wind Tunnel Enterprise operations. Nine wind tunnels make up the Enterprise. Prior to this research, these wind tunnel groups did not employ a rigorous or standardized management planning system. In addition, each wind tunnel unit operated from a position of autonomy, with little coordination of clients, resources, or project control. For operating and planning purposes, each wind tunnel operating unit must balance inputs from a variety of sources. Although each unit is managed by individual Facility Operations groups, other stakeholders influence wind tunnel operations. These groups include, for example, the various researchers and clients who use the facility, the Facility System Engineering Division (FSED) tasked with wind tunnel repair and upgrade, the Langley Research Center (LaRC) Fabrication (FAB) group which fabricates repair parts and provides test model upkeep, the NASA and LARC Strategic Plans, and unscheduled use of the facilities by important clients. Expanding these influences horizontally through nine wind tunnel operations and vertically along the NASA management structure greatly increases the
Virmavirta, Mikko; Kivekäs, Juha; Komi, Paavo
The effect of skis on the force-time characteristics of the simulated ski jumping takeoff was examined in a wind tunnel. Takeoff forces were recorded with a force plate installed under the tunnel floor. Signals from the front and rear parts of the force plate were collected separately to examine the anteroposterior balance of the jumpers during the takeoff. Two ski jumpers performed simulated takeoffs, first without skis in nonwind conditions and in various wind conditions. Thereafter, the same experiments were repeated with skis. The jumpers were able to perform very natural takeoff actions (similar to the actual takeoff) with skis in wind tunnel. According to the subjective feeling of the jumpers, the simulated ski jumping takeoff with skis was even easier to perform than the earlier trials without skis. Skis did not much influence the force levels produced during the takeoff but they still changed the force distribution under the feet. Contribution of the forces produced under the rear part of the feet was emphasized probably because the strong dorsiflexion is needed for lifting the skis to the proper flight position. The results presented in this experiment emphasize that research on ski jumping takeoff can be advanced by using wind tunnels.
A wind tunnel test of the Adaptable Deployable Entry and Placement Technology (ADEPT) was conducted in April 2015 at the US Army's 7 by10 Foot Wind Tunnel located at NASA Ames Research Center. Key geometric features of the fabric test article were a 0.7 meter deployed base diameter, a 70 degree half-angle forebody cone angle, eight ribs, and a nose-to-base radius ratio of 0.7. The primary objective of this wind tunnel test was to obtain static deflected shape and pressure distributions while varying pretension at dynamic pressures and angles of attack relevant to entry conditions at Earth, Mars, and Venus. Other objectives included obtaining aerodynamic force and moment data and determining the presence and magnitude of any dynamic aeroelastic behavior (buzz/flutter) in the fabric trailing edge. All instrumentation systems worked as planned and a rich data set was obtained. This paper describes the test articles, instrumentation systems, data products, and test results. Four notable conclusions are drawn. First, test data support adopting a pre-tension lower bound of 10 foot pounds per inch for Nano-ADEPT mission applications in order to minimize the impact of static deflection. Second, test results indicate that the fabric conditioning process needs to be reevaluated. Third, no flutter/buzz of the fabric was observed for any test condition and should also not occur at hypersonic speeds. Fourth, translating one of the gores caused ADEPT to generate lift without the need for a center of gravity offset. At hypersonic speeds, the lift generated by actuating ADEPT gores could be used for vehicle control.
Federal Laboratory Consortium — This wind tunnel is used for basic and applied research in aeromechanics on advanced and unique technology rotorcraft. It supports research on advanced concepts and...
Fly higher, faster, preserve the life of test pilots and passengers, many challenges faced by man since the dawn of the twentieth century, with aviation pioneers. Contemporary of the first aerial exploits, wind tunnels, artificially recreating conditions encountered during the flight, have powerfully contributed to the progress of aeronautics. But the use of wind tunnels is not limited to aviation. The research for better performance, coupled with concern for energy saving, encourages manufacturers of ground vehicles to perform aerodynamic tests. Buildings and bridge structures are also concerned. This article deals principally with the wind tunnels built at ONERA during the last century. Somme wind tunnels outside ONERA, even outside France, are also evocated when their characteristics do not exist at ONERA.
Federal Laboratory Consortium — Description: This facility consists of a large-scale, low-speed open-loop induction wind tunnel which has been modified to house a linear turbine cascade. A 125-hp...
Maki, S; Sakai, J; Murata, E
A wind tunnel which permits estimates of atmospheric diffusion is described. Smoke from power plant smoke stacks, for example, can be simulated and traced to determine the manner of diffusion in the air as well as the grade of dilution. The wind tunnel is also capable of temperature controlled diffusion tests in which temperature distribution inside the wind tunnel is controlled. A minimum wind velocity of 10 cm can be obtained with accuracy within plus or minus 0.05 percent using a controlled direct current motor; diffusion tests are often made at low wind velocity. Fully automatic measurements can be obtained by using a minicomputer so that the operation and reading of the measuring instruments can be remotely controlled from the measuring chamber. (Air Pollut. Abstr.)
Jingping XIAO; Li CHEN; Qiang WANG; Qiao WANG
Based on the unsteady aerodynamics experiment (UAE) phase VI and the model experiment in controlled conditions (MEXICO) projects and the related research carried out in China Aerodynamic Research and Development Center (CARDC), the recent progress in the wind tunnel experimental techniques for the wind turbine is sum-marized. Measurement techniques commonly used for di?erent types of wind tunnel ex-periments for wind turbine are reviewed. Important research achievements are discussed, such as the wind tunnel disturbance, the equivalence of the airfoil in?ow condition, the three-dimensional (3D) e?ect, the dynamic in?ow in?uence, the ?ow ?eld structure, and the vortex induction. The corresponding research at CARDC and some ideas on the large wind turbine are also introduced.
Ross, James C.; Jorgenson, Charles C.; Norgaard, Magnus
The use of neural networks to minimize the amount of data required to completely define the aerodynamic performance of a wind tunnel model is examined. The accuracy requirements for commercial wind tunnel test data are very severe and are difficult to reproduce using neural networks. For the current work, multiple input, single output networks were trained using a Levenberg-Marquardt algorithm for each of the aerodynamic coefficients. When applied to the aerodynamics of a 55% scale model of a U.S. Air Force/ NASA generic fighter configuration, this scheme provided accurate models of the lift, drag, and pitching-moment coefficients. Using only 50% of the data acquired during, the wind tunnel test, the trained neural network had a predictive accuracy equal to or better than the accuracy of the experimental measurements.
Vuković Đorđe S.
Full Text Available During a supersonic run of a blowdown wind tunnel, temperature of air in the test section drops which can affect planned measurements. Adverse thermal effects include variations of the Mach and Reynolds numbers, variation of airspeed, condensation of moisture on the model, change of characteristics of the instrumentation in the model, et cetera. Available data on thermal effects on instrumentation are pertaining primarily to long-run-duration wind tunnel facilities. In order to characterize such influences on instrumentation in the models, in short-run-duration blowdown wind tunnels, temperature measurements were made in the wing-panel-balance and main-balance spaces of two wind tunnel models tested in the T-38 wind tunnel. The measurements showed that model-interior temperature in a run increased at the beginning of the run, followed by a slower drop and, at the end of the run, by a large temperature drop. Panel-force balance was affected much more than the main balance. Ways of reducing the unwelcome thermal effects by instrumentation design and test planning are discussed.
Geurts, C.P.W.; Bentum, van C.A.; Willemsen, E.
This paper addresses questions that arose during development and application of the Dutch guideline for wind tunnel testing to determine wind loads on buildings. This guideline (CUR 103) is being used since 2005, and a first revision is foreseen. Within this revision, the relation with Eurocode EN
...) of the test article in a wind tunnel test. The theory for such P&A determinations is developed and applied to data from a recent pressure sensitive paint test in AEDC's 16 ft transonic wind tunnel...
The physics and geological relationships of particles driven by the wind under near Martian conditions were examined in the Martian Surface Wind Tunnel. Emphasis was placed on aeolian activity as a planetary process. Threshold speeds, rates of erosion, trajectories of windblown particles, and flow fields over various landforms were among the factors considered. Results of experiments on particles thresholds, rates of erosion, and the effects of electrostatics on particles in the aeolian environment are presented.
Andersen, S.A.; Jensen, Vagn Orla; Nielsen, P.
The normal magnetic field configuration of a Q device has been modified to obtain a 'magnetic Laval nozzle'. Continuous supersonic plasma 'winds' are obtained with Mach numbers ~3. The magnetic nozzle appears well suited for the study of the interaction of supersonic plasma 'winds' with either...
Fischer, Andreas; Bertagnolio, Franck
In this section, the wind tunnel configuration used for aerodynamic and aeroacoustic measurement is described. Then, the validation of the method for evaluating far-field noise from surface microphones as described in Section 5 is presented. Finally, the design concept proposed in Section 6 is ve...
Visintini, L.; Murray, C.N.
C.C.R. Euratom Ispra are currently involved in studies on the possibility of storing radioactive wastes in deep ocean sediment beds. The report summarizes the results of wind tunnel tests performed in March 1985 on a 1:2.5 scale model of a European Standard Penetrator in Aermacchi low speed wind tunnel. Tests covered the measurement of overall fluid dynamic forces at varying angle of attack and measurement of unsteady pressures acting on the instrumentation head protruding in the penetrator's wake. Overall force coefficients were found to be in good agreement with predictions. Unsteady pressures were found to be much smaller than expected so that no mechanical damage to instrumentation is to be foreseen even at the high dynamic pressures typical of the penetrator moving into water. The present work has been undertaken under contract 2450-84-08 ED ISP I of C.C.R. EURATOM ISPRA
Inadequate Reynolds number similarity in testing of scaled models affects the quality of aerodynamic data from wind tunnels. This is due to scale effects of boundary-layer shock wave interaction which is likely to be severe at transonic speeds. The idea of operation of wind tunnels using test gas cooled to cryogenic temperatures has yielded a quantrum jump in the ability to realize full scale Reynolds number flow similarity in small transonic tunnels. In such tunnels, the basic flow control problem consists of obtaining and maintaining the desired test section flow parameters. Mach number, Reynolds number, and dynamic pressure are the three flow parameters that are usually required to be kept constant during the period of model aerodynamic data acquisition. The series of activity involved in modeling, control law development, mechanization of the control laws on a microcomputer, and the performance of a globally stable automatic control system for the 0.3-m Transonic Cryogenic Tunnel (TCT) are discussed. A lumped multi-variable nonlinear dynamic model of the cryogenic tunnel, generation of a set of linear control laws for small perturbation, and nonlinear control strategy for large set point changes including tunnel trajectory control are described. The details of mechanization of the control laws on a 16 bit microcomputer system, the software features, operator interface, the display and safety are discussed. The controller is shown to provide globally stable and reliable temperature control to + or - 0.2 K, pressure to + or - 0.07 psi and Mach number to + or - 0.002 of the set point value. This performance is obtained both during large set point commands as for a tunnel cooldown, and during aerodynamic data acquisition with intrusive activity like geometrical changes in the test section such as angle of attack changes, drag rake movements, wall adaptation and sidewall boundary-layer removal. Feasibility of the use of an automatic Reynolds number control mode with
Banks, D.; Cochran, B.
This presentation will describe the finding of an atmospheric boundary layer (ABL) wind tunnel study conducted as part of the Bolund Experiment. This experiment was sponsored by Risø DTU (National Laboratory for Sustainable Energy, Technical University of Denmark) during the fall of 2009 to enable a blind comparison of various air flow models in an attempt to validate their performance in predicting airflow over complex terrain. Bohlund hill sits 12 m above the water level at the end of a narrow isthmus. The island features a steep escarpment on one side, over which the airflow can be expected to separate. The island was equipped with several anemometer towers, and the approach flow over the water was well characterized. This study was one of only two only physical model studies included in the blind model comparison, the other being a water plume study. The remainder were computational fluid dynamics (CFD) simulations, including both RANS and LES. Physical modeling of air flow over topographical features has been used since the middle of the 20th century, and the methods required are well understood and well documented. Several books have been written describing how to properly perform ABL wind tunnel studies, including ASCE manual of engineering practice 67. Boundary layer wind tunnel tests are the only modelling method deemed acceptable in ASCE 7-10, the most recent edition of the American Society of Civil Engineers standard that provides wind loads for buildings and other structures for buildings codes across the US. Since the 1970’s, most tall structures undergo testing in a boundary layer wind tunnel to accurately determine the wind induced loading. When compared to CFD, the US EPA considers a properly executed wind tunnel study to be equivalent to a CFD model with infinitesimal grid resolution and near infinite memory. One key reason for this widespread acceptance is that properly executed ABL wind tunnel studies will accurately simulate flow separation
Permata, Robby; Andika, Matza Gusto; Syariefatunnisa, Risdhiawan, Eri; Hermawan, Budi; Noordiana, Indra
Musi VI Bridge is planned to cross the Musi River in Palembang City, South Sumatera Province, Indonesia. The main span is a steel arch type with 200 m length and side span length is 75 m. Finite element analysis results showed that the bridge has frequency ratio for torsional and heaving mode (torsional frequency/heaving frequency)=1.14. This close to unity value rises concern about aerodynamic behaviour and stability of the bridge deck under wind loading. Sectional static and free vibration wind tunnel test were performed to clarify this phenomena in B2TA3 facility in Serpong, Indonesia. The test followed the draft of Guide of Wind Tunnel Test for Bridges developed by Indonesian Ministry of Public Works. Results from wind tunnel testing show that the bridge is safe from flutter instability and no coupled motion vibration observed. Therefore, low value of frequency ratio has no effect to aerodynamic behaviour of the bridge deck. Vortex-induced vibration in heaving mode occurred in relatively low wind velocity with permissible maximum amplitude value.
Lo, Ching F.; Steinle, Frank W., Jr.
Report discusses potential use of artificial-intelligence systems to manage wind-tunnel test facilities at Ames Research Center. One of goals of program to obtain experimental data of better quality and otherwise generally increase productivity of facilities. Another goal to increase efficiency and expertise of current personnel and to retain expertise of former personnel. Third goal to increase effectiveness of management through more efficient use of accumulated data. System used to improve schedules of operation and maintenance of tunnels and other equipment, assignment of personnel, distribution of electrical power, and analysis of costs and productivity. Several commercial artificial-intelligence computer programs discussed as possible candidates for use.
Al-Asmi, K.; Castro, I. P.
A method for producing oscillatory flow in open-circuit wind tunnels driven by centrifugal fans is described. Performance characteristics of a new device installed on two such tunnels of greatly differing size are presented. It is shown that sinusoidal variations of the working section flow, having peak-to-peak amplitudes up to at least 30 percent of the mean flow speed and frequencies up to, typically, that corresponding to the acoustic quarter-wave-length frequency determined by the tunnel size, can be obtained with negligible harmonic distortion or acoustic noise difficulties. A brief review of the various methods that have been used previously is included, and the advantages and disadvantages of these different techniques are highlighted. The present technique seems to represent a significant improvement over many of them.
Liu, Tian-Shu; Cattafesta, L. N., III; Radeztsky, R. H.; Burner, A. W.
In image-based measurements, quantitative image data must be mapped to three-dimensional object space. Analytical photogrammetric methods, which may be used to accomplish this task, are discussed from the viewpoint of experimental fluid dynamicists. The Direct Linear Transformation (DLT) for camera calibration, used in pressure sensitive paint, is summarized. An optimization method for camera calibration is developed that can be used to determine the camera calibration parameters, including those describing lens distortion, from a single image. Combined with the DLT method, this method allows a rapid and comprehensive in-situ camera calibration and therefore is particularly useful for quantitative flow visualization and other measurements such as model attitude and deformation in production wind tunnels. The paper also includes a brief description of typical photogrammetric applications to temperature- and pressure-sensitive paint measurements and model deformation measurements in wind tunnels.
Young, C. P., Jr. (Compiler); Gloss, B. B. (Compiler)
The principal motivating factor was the National Transonic Facility (NTF). Since the NTF can achieve significantly higher Reynolds numbers at transonic speeds than other wind tunnels in the world, and will therefore occupy a unique position among ground test facilities, every effort is being made to ensure that model design and fabrication technology exists to allow researchers to take advantage of this high Reynolds number capability. Since a great deal of experience in designing and fabricating cryogenic wind tunnel models does not exist, and since the experience that does exist is scattered over a number of organizations, there is a need to bring existing experience in these areas together and share it among all interested parties. Representatives from government, the airframe industry, and universities are included.
amplifier and control system , and data acquisition, processing, and display systems . Boeing�s LRTS (Fig. 2), consists of a sled structure that...Support Test Stand Sled Tail Sting Outrigger Arm Figure 2: System integration test at whirl tower Port Rotor Balance Main Strut Flap Tail...demonstrated. Finally, the reliability of the flap actuation system was successfully proven in more than 60 hours of wind tunnel testing
Patterson AFB, AFFDL, Ohio, October 1964. 17. Brunk, James E. "Users Manual: Extended Capability Magnus Rotor and Ballistic Body 6-DOF Trajectory...measure "second-order" aerodynamic effects resulting, for example, from Reynolds number in- fluence. Consequently, all wind tunnel data systems are...sting-model interference effects , sting configurations normally consist of one or more linearly tapered sections combined with one or more untapered
Verelst, David Robert; Larsen, Torben J.; van Wingerden, Jan-Willem
. The discussed test cases show that the turbine is stable while operating in free yawing conditions. Further, the effect of the tower shadow passage on the blade flapwise strain measurement is evaluated. Finally, data from the experiment is compared with preliminary simulations using DTU Wind Energy......This research paper presents preliminary results on a behavioural study of a free yawing downwind wind turbine. A series of wind tunnel tests was performed at the TU Delft Open Jet Facility with a three bladed downwind wind turbine and a rotor radius of 0.8 meters. The setup includes an off...... the shelf three bladed hub, nacelle and generator on which relatively flexible blades are mounted. The tower support structure has free yawing capabilities provided at the base. A short overview on the technical details of the experiment is given as well as a brief summary of the design process...
National Aeronautics and Space Administration — During initial design studies, parametric variation of vehicle geometry is routine. In addition, rotorcraft engineers traditionally use the wind tunnel to evaluate...
Verelst, David Robert; Larsen, Torben J.; van Wingerden, J.W.
During February and April 2012 a series of wind tunnel tests were performed at the TU Delft Open Jet Facility (OJF) with a three bladed downwind wind turbine and a rotor radius of 0.8 meters. The setup includes an off the shelf three bladed hub, nacelle and generator on which relatively flexible ...... in free yawing conditions. Further, the effect of the tower shadow passage on the blade flapwise strain measurement is evaluated. Finally, data from the experiment is compared with preliminary simulations using DTU Wind Energy's aeroelastic simulation program HAWC2....... blades are mounted. The tower support structure has free yawing capabilities provided at the tower base. A short overview on the technical details of the experiment is provided as well as a brief summary of the design process. The discussed test cases show that the turbine is stable while operating...
December 1976 (University *AEDC-TR-79-55, November 1979 Microfilms No. 77-10777) 19. Sears, W.R. "Adaptive Wind Tunnels with 37. Ilrdelyi, A., Magnus , W...California Institute of Technology General Dynamics-CONVAIR Pasadena, CA 91109 P. O. Box 1128 San Diego, CA 92112 Mr. L. I. Chases , MUG-MD Lib. General...Electric Company Dr. R. Magnus Missile and Space Division General Dynamics-CONVAIR P. 0. Box 8555 Kearny Mesa Plant Philadelphia, PA 19101 P. 0. Box
U.S. Environmental Protection Agency — Wind tunnel evaluation of EPA's Hi-Vol TSP sampler for sampling effectiveness with regards to aerodynamic particle diameter (5 to 35 microns), wind speed (2, 8, 24...
Nakai, Masayuki; Sada, Koichi
A wind direction fluctuation vane was added to CRIEPI's large - scale atmospheric diffusion wind tunnel for the purpose of increasing and controlling turbulence intensity. When the wind direction fluctuation vane was operated lateral plume spread and lateral turbulence intersity became greater than for cases when it was not operated. Use of the vane improved the ability of the wind tunnel to simulate plane spread under natural conditions. (author)
Busan, Ronald C.; Rothhaar, Paul M.; Croom, Mark A.; Murphy, Patrick C.; Grafton, Sue B.; O-Neal, Anthony W.
Design of Experiment (DOE) testing methods were used to gather wind tunnel data characterizing the aerodynamic and propulsion forces and moments acting on a complex vehicle configuration with 10 motor-driven propellers, 9 control surfaces, a tilt wing, and a tilt tail. This paper describes the potential benefits and practical implications of using DOE methods for wind tunnel testing - with an emphasis on describing how it can affect model hardware, facility hardware, and software for control and data acquisition. With up to 23 independent variables (19 model and 2 tunnel) for some vehicle configurations, this recent test also provides an excellent example of using DOE methods to assess critical coupling effects in a reasonable timeframe for complex vehicle configurations. Results for an exploratory test using conventional angle of attack sweeps to assess aerodynamic hysteresis is summarized, and DOE results are presented for an exploratory test used to set the data sampling time for the overall test. DOE results are also shown for one production test characterizing normal force in the Cruise mode for the vehicle.
Pricop, M. V.; Cojocaru, M. G.; Stoica, C. I.; Niculescu, M. L.; Neculaescu, A. M.; Persinaru, A. G.; Boscoianu, M.
Affordable space access requires partial or ideally full launch vehicle reuse, which is in line with clean environment requirement. Although the idea is old, the practical use is difficult, requiring very large technology investment for qualification. Rocket gliders like Space Shuttle have been successfullyoperated but the price and correspondingly the energy footprint were found not sustainable. For medium launchers, finally there is a very promising platform as Falcon 9. For very small launchers the situation is more complex, because the performance index (payload to start mass) is already small, versus medium and heavy launchers. For partial reusable micro launchers this index is even smaller. However the challenge has to be taken because it is likely that in a multiyear effort, technology is going to enable the performance recovery to make such a system economically and environmentally feasible. The current paper is devoted to a small unitary glide back booster which is foreseen to be assembled in a number of possible configurations. Although the level of analysis is not deep, the solution is analyzed from the aerodynamic point of view. A wind tunnel model is designed, with an active canard, to enablea more efficient wind tunnel campaign, as a national level premiere.
Sjöholm, Mikael; Vignaroli, Andrea; Angelou, Nikolas
Measurement campaigns with continuous-wave Doppler Lidars (Light detection and ranging) developed at DTU Wind Energy in Denmark were performed in two very different wind tunnels. Firstly, a measurement campaign in a small icing wind tunnel chamber at VTT in Finland was performed with high frequency...... used in blind test comparisons for wind turbine wake modelers. These Lidar measurement activities constitute the Joint Experiment Project” L4WT - Lidars for Wind Tunnels, with applications to wakes and atmospheric icing in a prospective Nordic Network” with the aim of gaining and sharing knowledge...... about possibilities and limitations with lidar instrumentation in wind tunnels, which was funded by the IRPWind project within the community of the European Energy Research Alliance (EERA) Joint Programme on Wind Energy....
Sørensen, Jens Nørkær; Shen, Wen Zhong; Mikkelsen, Robert Flemming
, the corrections from the model are in very good agreement with the CFD computaions, demonstrating that one-dimensional momentum theory is a reliable way of predicting corrections for wall interference in wind tunnels with closed as well as open cross sections. Keywords: Wind tunnel correction, momentum theory...
As part of the technology education curriculum, the author's eighth-grade students design, build, test, and race CO2 vehicles. To help them in refining their designs, they use a wind tunnel to test for aerodynamic drag. In this article, the author describes how to build a wind tunnel using inexpensive, readily available materials. (Contains 1…
Britcher, Colin P.; Goodyer, Michael J.; Eskins, Jonathan; Parker, David; Halford, Robert J.
Digital controllers are being developed for wind tunnel magnetic suspension and balance systems, which in turn permit wind tunnel testing of aircraft models free from support interference. Hardware and software features of two existing digital control systems are reviewed. Some aspects of model position sensing and system calibration are also discussed.
A Vision in Aeronautics, a project within the NASA Lewis Research Center's Information Infrastructure Technologies and Applications (IITA) K-12 Program, employs small-scale, subsonic wind tunnels to inspire students to explore the world of aeronautics and computers. Recently, two educational K-12 wind tunnels were built in the Cleveland area. During the 1995-1996 school year, preliminary testing occurred in both tunnels.
Sørensen, Jens Nørkær; Shen, Wen Zhong; Mikkelsen, Robert Flemming
In the paper we present a correction model for wall interference on rotors of wind turbines or propellers in wind tunnels. The model, which is based on a one-dimensional momentum approach, is validated against results from CFD computations using a generalized actuator disc principle. In the model...... good agreement with the CFD computations, demonstrating that one-dimensional momentum theory is a reliable way of predicting corrections for wall interference in wind tunnels with closed as well as open cross sections....
Martínez Lacasa, Daniel; Moreno Blanc, Javier; Tresánchez, Marcel; Clotet Bellmunt, Eduard; Jiménez-Soto, Juan M.; Magrans, Rudys; Pardo Martínez, Antonio; Marco Colás, Santiago; Palacín Roca, Jordi
This paper presents themeasurement of gas concentration and wind intensity performed with amobile robot in a customturbulent wind tunnel designed for experimentation with customizable wind and gas leak sources.This paper presents the representation in different information layers of the measurements obtained in the turbulent wind tunnel under different controlled environmental conditions in order to describe the plume of the gas and wind intensities inside the experimentation chamber...
Wang, Jia-Ying; Meng, Qing-Hao; Luo, Bing; Zeng, Ming
This article presents a new type of active controlled multiple-fan wind tunnel. The wind tunnel consists of swivel plates and arrays of direct current fans, and the rotation speed of each fan and the shaft angle of each swivel plate can be controlled independently for simulating different kinds of outdoor wind fields. To measure the similarity between the simulated wind field and the outdoor wind field, wind speed and direction time series of two kinds of wind fields are recorded by nine two-dimensional ultrasonic anemometers, and then statistical properties of the wind signals in different time scales are analyzed based on the empirical mode decomposition. In addition, the complexity of wind speed and direction time series is also investigated using multiscale entropy and multivariate multiscale entropy. Results suggest that the simulated wind field in the multiple-fan wind tunnel has a high degree of similarity with the outdoor wind field.
Denham, Casey; Owens, D. Bruce
Flight dynamics research was conducted to collect and analyze rotary balance wind tunnel test data in order to improve the aerodynamic simulation and modeling of a low-cost small unmanned aircraft called FASER (Free-flying Aircraft for Sub-scale Experimental Research). The impetus for using FASER was to provide risk and cost reduction for flight testing of more expensive aircraft and assist in the improvement of wind tunnel and flight test techniques, and control laws. The FASER research aircraft has the benefit of allowing wind tunnel and flight tests to be conducted on the same model, improving correlation between wind tunnel, flight, and simulation data. Prior wind tunnel tests include a static force and moment test, including power effects, and a roll and yaw damping forced oscillation test. Rotary balance testing allows for the calculation of aircraft rotary derivatives and the prediction of steady-state spins. The rotary balance wind tunnel test was conducted in the NASA Langley Research Center (LaRC) 20-Foot Vertical Spin Tunnel (VST). Rotary balance testing includes runs for a set of given angular rotation rates at a range of angles of attack and sideslip angles in order to fully characterize the aircraft rotary dynamics. Tests were performed at angles of attack from 0 to 50 degrees, sideslip angles of -5 to 10 degrees, and non-dimensional spin rates from -0.5 to 0.5. The effects of pro-spin elevator and rudder deflection and pro- and anti-spin elevator, rudder, and aileron deflection were examined. The data are presented to illustrate the functional dependence of the forces and moments on angle of attack, sideslip angle, and angular rate for the rotary contributions to the forces and moments. Further investigation is necessary to fully characterize the control effectors. The data were also used with a steady state spin prediction tool that did not predict an equilibrium spin mode.
Kubo, Y. [Kyushu Inst. of Technology, Kitakyushu (Japan). Faculty of Engineering
This paper describes the wind tunnel test on a PC cable-stayed bridge. The aerodynamic force that acts on a building is represented by the drag that works in the wind direction, the lift that works perpendicularly to the wind direction, and the aerodynamic moment that causes rotation. In the measurement of wind load, a girder is partially extracted in the wind tunnel and set in a three-component balance, and the drag, lift, and aerodynamic moment are measured using a strain meter while blowing the wind. In a wind tunnel experiment, the similarity on Reynolds number, field number, rigidity, hydraulic force, structural attenuation, and reduced wind velocity is required. However, the wind velocity in the actual bridge uses the same air as that in an experiment. The similarity rule on the Reynolds is not thus satisfied. It is necessary to cause no self-excited vibration (galloping and flutter) as wind-resistant performance and suppress the eddy excitation to less than the allowable amplitude. Moreover, the three-dimensional experiment using an elastic model is conducted in addition to the two-dimensional experiment using a rigid model. In the three-dimensional experiment, various vibration modes that occur in the actual bridge appear. 12 refs., 15 figs.
Tests of wind erosion were performed in a controlled-environment wind tunnel to support the development of natural-material protective barriers for long-term isolation of radioactive waste. Barrier performance standards currently being developed for internal and external barrier performance are expected to mandate a surface layer that is resistant to wind erosion. The purpose of this study was to initiate a series of tests to determine suitable soil and gravel mixtures for such a barrier and to test worst-case surface layer conditions under the influence of high wind speeds. Six mixed soil and gravel surfaces were prepared, weathered to represent natural wind-blown desert areas, and subjected to controlled wind erosion forces in a wind tunnel. The applied erosive forces, including surface shear forces, were characterized to provide a means of relating wind tunnel results with actual field conditions. Soil particle losses from the surfaces caused by suspension, saltation, and surface creep were monitored by aerosol sample probes and mass balance measurements. 23 refs., 22 figs., 3 tabs
Agdrup, Kristian; Jensen, Andreas G.; Aage, Christian
Tests have been performed at the Danish Maritime Institute (DMI) to investigate the applicability of a new wind tunnel Planar Motion Mechanism (PMM) for the determination of hydrodynamic coefficients of ships. The method has been tested on a tanker with known towing tank data. The wind tunnel model...... data giving reasonable results. The dependency of amplitude and frequency is evaluated, and sources of inaccuracy are discussed. It is concluded that the wind tunnel method is a promising method to achieve a fast and cost-effective estimate of the hydrodynamic coefficients of a ship hull...
Full Text Available Wind tunnel test and computational fluid dynamics (CFD simulation are two main methods for the study of automotive aerodynamics. CFD simulation software solves the results in calculation by using the basic theory of aerodynamic. Calculation will inevitably lead to bias, and the wind tunnel test can effectively simulate the real driving condition, which is the most effective aerodynamics research method. This paper researches the aerodynamic characteristics of the wing of a racing car. Aerodynamic model of a racing car is established. Wind tunnel test is carried out and compared with the simulation results of computational fluid dynamics. The deviation of the two methods is small, and the accuracy of computational fluid dynamics simulation is verified. By means of CFD software simulation, the coefficients of six aerodynamic forces are fitted and the aerodynamic equations are obtained. Finally, the aerodynamic forces and torques of the racing car travel in bend are calculated.
Russell, Carl R.; Jung, Jaewoo; Willink, Gina; Glasner, Brett
There is currently a lack of published data for the performance of multicopter unmanned aircraft system (UAS) vehicles, such as quadcopters and octocopters, often referred to collectively as drones. With the rapidly increasing popularity of multicopter UAS, there is interest in better characterizing the performance of this type of aircraft. By studying the performance of currently available vehicles, it will be possible to develop models for vehicles at this scale that can accurately predict performance and model trajectories. This paper describes a wind tunnel test that was recently performed in the U.S. Army's 7- by 10-ft Wind Tunnel at NASA Ames Research Center. During this wind tunnel entry, five multicopter UAS vehicles were tested to determine forces and moments as well as electrical power as a function of wind speed, rotor speed, and vehicle attitude. The test is described here in detail, and a selection of the key results from the test is presented.
Kelley, P. B.; Beaufait, W. B.; Kitchens, L. L.; Pace, J. P.
The analysis and interpretation of wind tunnel pressure data from the Space Shuttle wind tunnel test IA300 are presented. The primary objective of the test was to determine the effects of the Space Shuttle Main Engine (SSME) and the Solid Rocket Booster (SRB) plumes on the integrated vehicle forebody pressure distributions, the elevon hinge moments, and wing loads. The results of this test will be combined with flight test results to form a new data base to be employed in the IVBC-3 airloads analysis. A secondary objective was to obtain solid plume data for correlation with the results of gaseous plume tests. Data from the power level portion was used in conjunction with flight base pressures to evaluate nominal power levels to be used during the investigation of changes in model attitude, eleveon deflection, and nozzle gimbal angle. The plume induced aerodynamic loads were developed for the Space Shuttle bases and forebody areas. A computer code was developed to integrate the pressure data. Using simplified geometrical models of the Space Shuttle elements and components, the pressure data were integrated to develop plume induced force and moments coefficients that can be combined with a power-off data base to develop a power-on data base.
Full Text Available A customized vertical wind tunnel has been built by the University of Canterbury Rocketry group (UC Rocketry. This wind tunnel has been critical for the success of UC Rocketry as it allows the optimization of avionics and control systems before flight. This paper outlines the construction of the wind tunnel and includes an analysis of flow quality including swirl. A minimal modelling methodology for roll dynamics is developed that can extrapolate wind tunnel behavior at low wind speeds to much higher velocities encountered during flight. The models were shown to capture the roll flight dynamics in two rocket launches with mean roll angle errors varying from 0.26° to 1.5° across the flight data. The identified model parameters showed consistent and predictable variations over both wind tunnel tests and flight, including canard–fin interaction behavior. These results demonstrate that the vertical wind tunnel is an important tool for the modelling and control of sounding rockets.
Tourn, Silvana; Pallarès, Jordi; Cuesta, Ildefonso
Based on the increasing interest in urban environmental technologies, the study of small scale vertical axis wind turbines shows motivating challenges. In this paper, we present the characteristics and potentials of a new open jet wind tunnel. It has a nozzle exit area of 1.5 × 1.5 m2, and it can......%. The detailed characterization of the flow carried out indicates that the wind tunnel can be used to test small scale models of wind turbines....
Federal Laboratory Consortium — The 1- by 1-Foot Supersonic Wind Tunnel (1x), located in the Engine Research Building, is one of the most active test facilities at the Glenn Research Center. Used...
Jørgensen, Jeppe Bjørn; Sørensen, Bent F.; Kildegaard, C.
A novel approach is presented and used in a generic tunneling crack tool for the prediction of crack growth rates for tunneling cracks propagating across a bond-line in a wind turbine blade under high cyclic loadings. In order to test and demonstrate the applicability of the tool, model predictions...
Andersen, Ingrid Marie Vincent
An investigation of the wind forces acting on a 9,000+ TEU container ship has been carried out through a series of wind tunnel tests. It was investigated how the wind forces depend on the container configuration on the deck using a 1:450 scale model and a series of appropriate container...... are presented as nondimensional coefficients. It is concluded, that the measured forces and moment depend on the container configuration on deck, and the results may provide a general idea of how the magnitude of the wind forces is affected by a given container stacking configuration on a similar container ship....
Kalvig, Siri; Hjertager, Bjørn; Manger, Eirik
The performance of a model wind turbine is simulated with three different CFD methods: actuator disk, actuator line and a fully resolved rotor. The simulations are compared with each other and with measurements from a wind tunnel experiment. The actuator disk is the least accurate and most cost-efficient, and the fully resolved rotor is the most accurate and least cost-efficient. The actuator line method is believed to lie in between the two ends of the scale. The fully resolved rotor produces superior wake velocity results compared to the actuator models. On average it also produces better results for the force predictions, although the actuator line method had a slightly better match for the design tip speed. The open source CFD tool box, OpenFOAM, was used for the actuator disk and actuator line calculations, whereas the market leading commercial CFD code, ANSYS/FLUENT, was used for the fully resolved rotor approach
Several comparisons of computational fluid dynamics to wind tunnel test data are shown for the purpose of code validation. The wind tunnel test, 05-CA, uses a 7.66% model of NASA's Multi-Purpose Crew Vehicle in the 11-foot test section of the Ames Unitary Plan Wind tunnel. A variety of freestream conditions over four Mach numbers and three angles of attack are considered. Test data comparisons include time-averaged integrated forces and moments, time-averaged static pressure ports on the surface, and Strouhal Number. The applicability of the US3D code to subsonic and transonic flow over a bluff body is assessed on a comprehensive data set. With close comparison, this work validates US3D for highly separated flows similar to those examined here.
Piatak, David J.; Sekula, Martin K.; Rausch, Russ D.
The Ares I-X Flight Test Vehicle (FTV), launched in October 2009, carried with it over 243 buffet verification pressure sensors and was one of the most heavily instrumented launch vehicle flight tests. This flight test represented a unique opportunity for NASA and its partners to compare the wind-tunnel derived buffet environment with that measured during the flight of Ares I-X. It is necessary to define the launch vehicle buffet loads to ensure that structural components and vehicle subsystems possess adequate strength, stress, and fatigue margins when the vehicle structural dynamic response to buffet forcing functions are considered. Ares I-X buffet forcing functions were obtained via wind-tunnel testing of a rigid buffet model (RBM) instrumented with hundreds of unsteady pressure transducers designed to measure the buffet environment across the desired frequency range. This paper discusses the comparison of RBM and FTV buffet environments, including fluctuating pressure coefficient and normalized sectional buffet forcing function root-mean-square magnitudes, frequency content of power-spectral density functions, and force magnitudes of an alternating flow phenomena. Comparison of wind-tunnel model and flight test vehicle buffet environments show very good agreement with root-mean-square magnitudes of buffet forcing functions at the majority of vehicle stations. Spectra proved a challenge to compare because of different wind-tunnel and flight test conditions and data acquisition rates. However, meaningful and promising comparisons of buffet spectra are presented. Lastly, the buffet loads resulting from the transition of subsonic separated flow to supersonic attached flow were significantly over-predicted by wind-tunnel results.
de Lucas, Manuela; Ferrer, Miguel; Janss, Guyonne F E
Wind farms have shown a spectacular growth during the last 15 years. Avian mortality through collision with moving rotor blades is well-known as one of the main adverse impacts of wind farms. In Spain, the griffon vulture incurs the highest mortality rates in wind farms. As far as we know, this study is the first attempt to predict flight trajectories of birds in order to foresee potentially dangerous areas for wind farm development. We analyse topography and wind flows in relation to flight paths of griffon vultures, using a scaled model of the wind farm area in an aerodynamic wind tunnel, and test the difference between the observed flight paths of griffon vultures and the predominant wind flows. Different wind currents for each wind direction in the aerodynamic model were observed. Simulations of wind flows in a wind tunnel were compared with observed flight paths of griffon vultures. No statistical differences were detected between the observed flight trajectories of griffon vultures and the wind passages observed in our wind tunnel model. A significant correlation was found between dead vultures predicted proportion of vultures crossing those cells according to the aerodynamic model. Griffon vulture flight routes matched the predominant wind flows in the area (i.e. they followed the routes where less flight effort was needed). We suggest using these kinds of simulations to predict flight paths over complex terrains can inform the location of wind turbines and thereby reduce soaring bird mortality.
Manuela de Lucas
Full Text Available BACKGROUND: Wind farms have shown a spectacular growth during the last 15 years. Avian mortality through collision with moving rotor blades is well-known as one of the main adverse impacts of wind farms. In Spain, the griffon vulture incurs the highest mortality rates in wind farms. METHODOLOGY/PRINCIPAL FINDINGS: As far as we know, this study is the first attempt to predict flight trajectories of birds in order to foresee potentially dangerous areas for wind farm development. We analyse topography and wind flows in relation to flight paths of griffon vultures, using a scaled model of the wind farm area in an aerodynamic wind tunnel, and test the difference between the observed flight paths of griffon vultures and the predominant wind flows. Different wind currents for each wind direction in the aerodynamic model were observed. Simulations of wind flows in a wind tunnel were compared with observed flight paths of griffon vultures. No statistical differences were detected between the observed flight trajectories of griffon vultures and the wind passages observed in our wind tunnel model. A significant correlation was found between dead vultures predicted proportion of vultures crossing those cells according to the aerodynamic model. CONCLUSIONS: Griffon vulture flight routes matched the predominant wind flows in the area (i.e. they followed the routes where less flight effort was needed. We suggest using these kinds of simulations to predict flight paths over complex terrains can inform the location of wind turbines and thereby reduce soaring bird mortality.
Kelly, Kathryn A.
The long-term objective of this research was an understanding of the wind-forced ocean circulation, particularly for the Pacific Ocean. To determine the ocean's response to the winds, we first needed to generate accurate maps of wind stress. For the ocean's response to wind stress we examined the sea surface height (SSH) both from altimeters and from numerical models for the Pacific Ocean.
Becker, Jeff; Biegel, Bryan (Technical Monitor)
The NASA Ames wind tunnel customers are one of the first users of the Information Power Grid (IPG) storage system at the NASA Advanced Supercomputing Division. We wanted to be able to store their data on the IPG so that it could be accessed remotely in a secure but timely fashion. In addition, incorporation into the IPG allows future use of grid computational resources, e.g., for post-processing of data, or to do side-by-side CFD validation. In this paper, we describe the integration of grid data access mechanisms with the existing DARWIN web-based system that is used to access wind tunnel test data. We also show that the combined system has reasonable performance: wind tunnel data may be retrieved at 50Mbits/s over a 100 base T network connected to the IPG storage server.
Lynn, Keith C.; Commo, Sean A.; Parker, Peter A.
Wind-tunnel research was recently conducted at the NASA Langley Research Center s 31-Inch Mach 10 Hypersonic Facility in support of the Mars Science Laboratory s aerodynamic program. Researchers were interested in understanding the interaction between the freestream flow and the reaction control system onboard the entry vehicle. A five-component balance, designed for hypersonic testing with pressurized flow-through capability, was used. In addition to the aerodynamic forces, the balance was exposed to both thermal gradients and varying internal cavity pressures. Historically, the effect of these environmental conditions on the response of the balance have not been fully characterized due to the limitations in the calibration facilities. Through statistical design of experiments, thermal and pressure effects were strategically and efficiently integrated into the calibration of the balance. As a result of this new approach, researchers were able to use the balance continuously throughout the wide range of temperatures and pressures and obtain real-time results. Although this work focused on a specific application, the methodology shown can be applied more generally to any force measurement system calibration.
Vanderpool, R.W.; Peters, T.M.
Wind tunnel tests of the Department of Energy RAAMP (Radioactive Atmospheric Aerosol Monitoring Program) monitor have been conducted at wind speeds of 2 km/hr and 24 km/hr. The RAAMP sampler was developed based on three specific performance objectives: (1) meet EPA PM10 performance criteria, (2) representatively sample and retain particles larger than 10 microm for later isotopic analysis, (3) be capable of continuous, unattended operation for time periods up to 2 months. In this first phase of the evaluation, wind tunnel tests were performed to evaluate the sampler as a potential candidate for EPA PM10 reference or equivalency status. As an integral part of the project, the EPA wind tunnel facility was fully characterized at wind speeds of 2 km/hr and 24 km/hr in conjunction with liquid test aerosols of 10 microm aerodynamic diameter. Results showed that the facility and its operating protocols met or exceeded all 40 CFR Part 53 acceptance criteria regarding PM10 size-selective performance evaluation. Analytical procedures for quantitation of collected mass deposits also met 40 CFR Part 53 criteria. Modifications were made to the tunnel's test section to accommodate the large dimensions of the RAAMP sampler's instrument case
de Ponte, JD
Full Text Available In order to meet the increasingly stringent requirements for wind tunnel balances, as expressed by the wind tunnel testing community, balance design philosophy needs to be further expanded to include alternative sensor, material, design...
De Ponte, JD
Full Text Available In order to meet the increasingly stringent requirements for wind tunnel balances, as expressed by the wind tunnel testing community, balance design philosophy needs to be further expanded to include alternative sensor, material, design...
Full Text Available The University of Defence in Brno has a new low-speed wind tunnel. In order to confirm the quality of the wind inside of the measurement section, several measurements of the dynamic pressure have been performed with the Pitot-static tube. The pressure fields are then analysed and quality of the field is evaluated. Measurement of a pressure drop on the body of a standing helicopter was conducted.
Dougherty, Christopher; Veismann, Marcel; Gharib, Morteza
The recent emergence of small unmanned aerial vehicles (UAVs) has reshaped the aerospace testing environment. Traditional closed-loop wind tunnels are not particularly suited nor easily retrofit to take advantage of these coordinated, controls-based rotorcraft. As such, a highly configurable, novel wind tunnel aimed at addressing the unmet technical challenges associated with single or formation flight performance of autonomous drone systems is presented. The open-loop fan array wind tunnel features 1296 individually controllable DC fans arranged in a 2.88m x 2.88m array. The fan array can operate with and without a tunnel enclosure and is able to rotate between horizontal and vertical testing configurations. In addition to standard variable speed uniform flow, the fan array can generate both unsteady and shear flows. Through the aid of smaller side fan array units, vortex flows are also possible. Conceptual design, fabrication, and validation of the tunnel performance will be presented, including theoretical and computational predictions of flow speed and turbulence intensity. Validation of these parameters is accomplished through standard pitot-static and hot-wire techniques. Particle image velocimetry (PIV) of various complex flows will also be shown. This material is based upon work supported by the Center for Autonomous Systems and Technologies (CAST) at the Graduate Aerospace Laboratories of the California Institute of Technology (GALCIT).
Jacobs, Eastman N
Tests were conducted on the 6-inch wind tunnel of the National Advisory Committee for Aeronautics to form a part of a research on open-throat wind tunnels. The primary object of this part of the research was to study a type of air pulsation which has been encountered in open-throat tunnels, and to find the most satisfactory means of eliminating such pulsations. In order to do this it was necessary to study the effects of different variable on all of the important characteristics of the tunnel. This paper gives not only the results of the study of air pulsations and methods of eliminating them, but also the effects of changing the exit-cone diameter and flare and the effects of air leakage from the return passage. It was found that the air pulsations in the 6-inch wind tunnel could be practically eliminated by using a moderately large flare on the exit cone in conjunction with leakage introduced by cutting holes in the exit cone somewhat aft of its minimum diameter.
Rolin, Vincent; Porté-Agel, Fernando
Vertical axis wind turbines (VAWTs) are in a relatively infant state of development when compared to their cousins the horizontal axis wind turbines. Very few studies have been carried out to characterize the wake flow behind VAWTs, and virtually none to observe the influence of the atmospheric boundary layer. Here we present results from an experiment carried out at the EPFL-WIRE boundary-layer wind tunnel and designed to study the interaction between a turbulent boundary layer flow and a VAWT. Specifically we use stereoscopic particle image velocimetry to observe and quantify the influence of the boundary layer flow on the wake generated by a VAWT, as well as the effect the VAWT has on the boundary layer flow profile downstream. We find that the wake behind the VAWT is strongly asymmetric, due to the varying aerodynamic forces on the blades as they change their position around the rotor. We also find that the wake adds strong turbulence levels to the flow, particularly on the periphery of the wake where vortices and strong velocity gradients are present. The boundary layer is also shown to cause greater momentum to be entrained downwards rather than upwards into the wake.
Hansen, Henriette I.; Thoft-Christensen, Palle
This paper describes preparation of wind tunnel testing of the principle of using flaps to control the motion of suspension bridges. The experiment will take place at the Instituto Superior Technico Lisbon, Portugal. The bridge section model is constructed of foam with an aluminium frame. The flaps...... are regulated by servo motors. Neural networks are used to position the flaps in the optimal positions....
Mccormick, B. W.; Zilliac, G. G.; Ballin, M. G.
Included is a summary of two studies related to the spinning of light aircraft. The first study was conducted to demonstrate that the aerodynamic forces and moments acting on a tail of a spinning aircraft can be obtained from static wind-tunnel tests. The second study analytically investigated spinning using a high angle-of-attack aerodynamic model derived from a static wind-tunnel data base. The validity of the aerodynamic model is shown by comparisons with rotary-balance data and forced-oscillation tests. The results of a six-degree-of-freedom analysis show that the dynamics and aerodynamics of the steep- and flat-spin modes of a modified Yankee have been properly modeled.
Bronkhorst, A.J.; Franke, J.; Geurts, C.P.W.; Bentum, van C.A.; Grepinet, F.
Design of solar energy mounting systems requires more knowledge on the wind patterns around these systems. To obtain more insight in the flow patterns, which cause the pressure distributions on the solar energy systems, a wind tunnel test and Computational Fluid Dynamics analysis have been
Full Text Available Preventing overloads in wind tunnel model supports is crucial to the integrity of the tested system. Results can only be interpreted as valid if the model support, conventionally called a sting remains sufficiently rigid during testing. Modeling and preliminary calculation can only give an estimate of the sting’s behavior under known forces and moments but sometimes unpredictable, aerodynamically caused model behavior can cause large transient overloads that cannot be taken into account at the sting design phase. To ensure model integrity and data validity an analog fast protection circuit was designed and tested. A post-factum analysis was carried out to optimize the overload detection and a short discussion on aeroelastic phenomena is included to show why such a detector has to be very fast. The last refinement of the concept consists in a fast detector coupled with a slightly slower one to differentiate between transient overloads that decay in time and those that are the result of aeroelastic unwanted phenomena. The decision to stop or continue the test is therefore conservatively taken preserving data and model integrity while allowing normal startup loads and transients to manifest.
Moers, M.H.P.; Moers, M.H.P.; Tack, R.G.; van Hulst, N.F.; Bölger, B.; Bölger, B.
The simultaneous operation of a photon scanning tunneling microscope with an atomic force microscope is presented. The use of standard atomic force silicon nitride cantilevers as near-field optical probes offers the possibility to combine the two methods. Vertical forces and torsion are detected
Wind tunnels have been used for several decades to study wind erosion processes. Portable wind tunnels offer the advantage of testing natural surfaces in the field, but they must be carefully designed to insure that a logarithmic boundary layer is formed and that wind erosion processes may develop ...
Instrumentation Wind tunnel speed was measured by two pitot probes mounted on opposite tunnel walls upstream of the model and above the ground...board. The pitot probes were connected differentially to Scanivalve 1-psi transducers. A secondary measurement of wind tunnel speed was made with the...Manf. Model Range 1 Tunnel Vel (south pitot ) Transducer Scanivalve CR24D 1 psi 2 Tunnel Vel (north pitot ) Transducer Scanivalve CR24D 1 psi 3
Biser, Aileen O.
To respond to the need for improved data base management and analysis capabilities for wind-tunnel data at the Langley 16-Foot Transonic Tunnel, research was conducted into current methods of managing wind-tunnel data and a method was developed as a solution to this need. This paper describes the development of the data base management and analysis method for wind-tunnel data. The design and implementation of the software system are discussed and examples of its use are shown.
Suzuki, Masahiro; Nakade, Koji; Ido, Atsushi
As the maximum speed of high-speed trains increases, flow-induced vibration of trains in tunnels has become a subject of discussion in Japan. In this paper, we report the result of a study on use of modifications of train shapes as a countermeasure for reducing an unsteady aerodynamic force by on-track tests and a wind tunnel test. First, we conduct a statistical analysis of on-track test data to identify exterior parts of a train which cause the unsteady aerodynamic force. Next, we carry out a wind tunnel test to measure the unsteady aerodynamic force acting on a train in a tunnel and examined train shapes with a particular emphasis on the exterior parts identified by the statistical analysis. The wind tunnel test shows that fins under the car body are effective in reducing the unsteady aerodynamic force. Finally, we test the fins by an on-track test and confirmed its effectiveness.
The nacelle shape of a mimic engine mounted on the wind tunnel test model for an STOL aircraft developed by the National Aerospace Laboratory has much larger length than in the nacelle of a scale reduced to 8% of an actual engine, and the shape below the nacelle is different. Therefore, in order to estimate the air force in the actual aircraft from the aerodynamic data obtained in a wind tunnel test, the data are corrected by using differences in aerodynamic loads (estimated values) applied on the mimic engine and the actual engine. For the purpose of discussing the reasonability of this correction, an 8%-scale flow through nacelle with the same shape as in the actual aircraft (the actual aircraft type) and a flow through nacelle for a wind tunnel testing model of the experimental STOL aircraft were fabricated and wind tunnel tests were performed. These results were compared with the corrected results of the mimic engine wind tunnel test. As a result, it was made clear that the force data have been corrected excessively, and the moments have been corrected considerably well. 7 refs., 32 figs., 7 tabs.
Huyer, S [Univ. of Colorado, Boulder, CO (US)
The wind turbine industry faces many problems regarding the construction of efficient and predictable wind turbine machines. Steady state, two-dimensional wind tunnel data are generally used to predict aerodynamic loads on wind turbine blades. Preliminary experimental evidence indicates that some of the underlying fluid dynamic phenomena could be attributed to dynamic stall, or more specifically to generation of forced unsteady separated flow fields. A collaborative research effort between the University of Colorado and the National Renewable Energy Laboratory was conducted to systematically categorize the local and global effects of three- dimensional forced unsteady flow fields.
Buehrle, Ralph David
The research investigates the effect of wind tunnel model system dynamics on measured aerodynamic data. During wind tunnel tests designed to obtain lift and drag data, the required aerodynamic measurements are the steady-state balance forces and moments, pressures, and model attitude. However, the wind tunnel model system can be subjected to unsteady aerodynamic and inertial loads which result in oscillatory translations and angular rotations. The steady-state force balance and inertial model attitude measurements are obtained by filtering and averaging data taken during conditions of high model vibrations. The main goals of this research are to characterize the effects of model system dynamics on the measured steady-state aerodynamic data and develop a correction technique to compensate for dynamically induced errors. Equations of motion are formulated for the dynamic response of the model system subjected to arbitrary aerodynamic and inertial inputs. The resulting modal model is examined to study the effects of the model system dynamic response on the aerodynamic data. In particular, the equations of motion are used to describe the effect of dynamics on the inertial model attitude, or angle of attack, measurement system that is used routinely at the NASA Langley Research Center and other wind tunnel facilities throughout the world. This activity was prompted by the inertial model attitude sensor response observed during high levels of model vibration while testing in the National Transonic Facility at the NASA Langley Research Center. The inertial attitude sensor cannot distinguish between the gravitational acceleration and centrifugal accelerations associated with wind tunnel model system vibration, which results in a model attitude measurement bias error. Bias errors over an order of magnitude greater than the required device accuracy were found in the inertial model attitude measurements during dynamic testing of two model systems. Based on a theoretical modal
Full Text Available The wind-induced vibration of stay cables of cable-stayed bridges, which includes rain-wind-induced vibration (RWIV and dry galloping (DG, has been studied for a considerable amount of time. In general, mechanical dampers or surface modification are applied to suppress the vibration. In particular, several types of surface-modification cable, including indentation, longitudinally parallel protuberance, helical fillet, and U-shaped grooving, have been developed. Recently, a new type of aerodynamically stable cable with spiral protuberances was developed. It was confirmed that the cable has a low drag force coefficient, like an indented cable, and that it prevented the formation of water rivulets on the cable surface. In this study, the stability for RWIV of this cable was investigated with various flow angles and protuberance dimensions in a wind-tunnel test. It was found that the spiral protuberance cable is aerodynamically stable against both RWIV and DG for all test wind angles. The effects of the protuberance dimensions were also clarified. Keywords: Rain-wind-induced vibration, Dry galloping, Stay cable, Wind-tunnel test
Gable roof buildings are widely used in industrial buildings. Based on wind tunnel tests with rigid models, wind pressure distributions on gable roof buildings with different aspect ratios were measured simultaneously. Some characteristics of the measured wind pressure field on the surfaces of the models were analyzed, including mean wind pressure, fluctuating wind pressure, peak negative wind pressure, and characteristics of proper orthogonal decomposition results of the measured wind pressure field. The results show that extremely high local suctions often occur in the leading edges of longitudinal wall and windward roof, roof corner, and roof ridge which are the severe damaged locations under strong wind. The aspect ratio of building has a certain effect on the mean wind pressure coefficients, and the effect relates to wind attack angle. Compared with experimental results, the region division of roof corner and roof ridge from AIJ2004 is more reasonable than those from CECS102:2002 and MBMA2006.The contributions of the first several eigenvectors to the overall wind pressure distributions become much bigger. The investigation can offer some basic understanding for estimating wind load distribution on gable roof buildings and facilitate wind-resistant design of cladding components and their connections considering wind load path. PMID:24082851
Li, Qing'an; Kamada, Yasunari; Maeda, Takao; Murata, Junsuke; Iida, Kohei; Okumura, Yuta
Wind turbines mounted on floating platforms are subjected to completely different and soft foundation properties, rather than onshore wind turbines. Due to the flexibility of their mooring systems, floating offshore wind turbines are susceptible to large oscillations such as aerodynamic force of the wind and hydrodynamic force of the wave, which may compromise their performance and structural stability. This paper focuses on the evaluation of aerodynamic forces depending on suppressing undesired turbine's motion by a rotor thrust control which is controlled by pitch changes with wind tunnel experiments. In this research, the aerodynamic forces of wind turbine are tested at two kinds of pitch control system: steady pitch control and cyclic pitch control. The rotational speed of rotor is controlled by a variable speed generator, which can be measured by the power coefficient. Moment and force acts on model wind turbine are examined by a six-component balance. From cyclic pitch testing, the direction and magnitude of moment can be arbitrarily controlled by cyclic pitch control. Moreover, the fluctuations of thrust coefficient can be controlled by collective pitch control. The results of this analysis will help resolve the fundamental design of suppressing undesired turbine's motion by cyclic pitch control. - Highlights: • Offshore wind offers additional options in regions with low onshore potential. • Two kinds of pitch control system: Steady pitch control and Cyclic pitch control. • Performance curves and unsteady aerodynamics are investigated in wind tunnel. • Fluctuations of thrust coefficient can be controlled by collective pitch control.
The basic principle of adaptable wind tunnel walls is explained. First results of an investigation carried out at the Aero-Space Institute of Berlin Technical University are presented for two dimensional flexible walls and a NACA 0012 airfoil. With five examples exhibiting very different flow conditions it is demonstrated that it is possible to reduce wall interference and to avoid blockage at transonic speeds by wall adaptation.
Rtishcheva, A. S.
As part of the component development of TsAGI’s new subsonic wind tunnel where the air flow velocity in the closed test section is up to 160 m/sec hydraulic and thermal characteristics of air cooler are calculated. The air cooler is one of the most important components due to its highest hydraulic resistance in the whole wind tunnel design. It is important to minimize its hydraulic resistance to ensure the energy efficiency of wind tunnel fans and the cost-cutting of tests. On the other hand the air cooler is to assure the efficient cooling of air flow in such a manner as to maintain the temperature below 40 °C for seamless operation of measuring equipment. Therefore the relevance of this project is driven by the need to develop the air cooler that would demonstrate low hydraulic resistance of air and high thermal effectiveness of heat exchanging surfaces; insofar as the cooling section must be given up per unit time with the amount of heat Q=30 MW according to preliminary evaluations. On basis of calculation research some variants of air cooler designs are proposed including elliptical tubes, round tubes, and lateral plate-like fins. These designs differ by the number of tubes and plates, geometrical characteristics and the material of finned surfaces (aluminium or cooper). Due to the choice of component configurations a high thermal effectiveness is achieved for finned surfaces. The obtained results form the basis of R&D support in designing the new subsonic wind tunnel.
Berry, Scott A.; Merski, N. Ronald; Blanchard, Robert C.
An aerothermodynamic database of global heating images was acquired of the Shuttle Orbiter in the NASA Langley Research Center 20-Inch Mach 6 Air Tunnel. These results were obtained for comparison to the global infrared images of the Orbiter in flight from the infrared sensing aeroheating flight experiment (ISAFE). The most recent ISAFE results from STS-103, consisted of port side images, at hypersonic conditions, of the surface features that result from the strake vortex scrubbing along the side of the vehicle. The wind tunnel results were obtained with the phosphor thermography system, which also provides global information and thus is ideally suited for comparison to the global flight results. The aerothermodynamic database includes both windward and port side heating images of the Orbiter for a range of angles of attack (20 to 40 deg), freestream unit Reynolds number (1 x 10(exp 6))/ft to 8 x 10(exp 6)/ft, body flap deflections (0, 5, and 10 deg), speed brake deflections (0 and 45 deg), as well as with boundary layer trips for forced transition to turbulence heating results. Sample global wind tunnel heat transfer images were extrapolated to flight conditions for comparison to Orbiter flight data. A windward laminar case for an angle of attack of 40 deg was extrapolated to Mach 11.6 flight conditions for comparison to STS-2 flight thermocouple results. A portside wind tunnel image for an angle of attack of 25 deg was extrapolated for Mach 5 flight conditions for comparison to STS-103 global surface temperatures. The comparisons showed excellent qualitative agreement, however the extrapolated wind tunnel results over-predicted the flight surface temperatures on the order of 5% on the windward surface and slightly higher on the portside.
Holmquist, L.J.; Harden, P.A.; Muraida, J.E.
Recent concerns at Palisades about control room habitability in the event of a loss-of-coolant accident have led to an extensive effort to increase control room habitability margin. The heating, ventilating and air-conditioning (HVAC) system servicing the control room has the potential for unfiltered in-leakage through its normal outside air intake louvered isolation dampers during emergency mode. The current limiting control room habitability analysis allows for 1.2 x 10 -2 m 3 /s (25 ft 3 /min) unfiltered in-leakage into the control room envelope. This leakage value was not thought to be achievable with the existing as-built configuration. Repairing the system was considered as a potential solution; however, this would be costly and could negatively affect plant operation. In addition, the system would still be required to meet the low specified unfiltered in-leakage. A second approach to this problem was to determine the atmospheric dispersion factors (x/Q's) through a wind tunnel test using a scale model of Palisades. The results of the wind tunnel testing could yield more realistic x/Q's for control room habitability than previously employed methods. Palisades selected the wind tunnel study option based on its ease of implementation, realistic results, and low cost. More importantly, the results of the study could increase the allowable unfiltered in-leakage
Ericsson, L. E.
Among the many problems the test engineer faces when trying to simulate full-scale vehicle dynamics in a wind tunnel test is the fact that the test usually will be performed at Reynolds numbers far below those existing on the full-scale vehicle. It is found that a severe scaling problem may exist even in the case of attached flow. The strong coupling existing between boundary layer transition and vehicle motion can cause the wind tunnel results to be very misleading, in some cases dangerously so. For example, the subscale test could fail to show a dynamic stability problem existing in full-scale flight, or, conversely, show one that does not exist. When flow separation occurs together with boundary layer transition, the scaling problem becomes more complicated, and the potential for dangerously misleading subscale test results increases. The existing literature is reviewed to provide examples of the different types of dynamic simulation problems that the test engineer is likely to face. It should be emphasized that the difficulties presented by transition effects in the case of wind tunnel simulation of vehicle dynamics apply to the same extent to numeric simulation methods.
Lammert, Michael P. [National Renewable Energy Lab. (NREL), Golden, CO (United States); Kelly, Kenneth J. [National Renewable Energy Lab. (NREL), Golden, CO (United States); Yanowitz, Janet [Ecoengineering, Sharonville, OH (United States)
In this report, the National Renewable Energy Laboratory analyzed results from multiple, independent truck platooning projects to compare and contrast track test results with wind tunnel test results conducted by Lawrence Livermore National Laboratory (LLNL). Some highlights from the report include compiled data, and results from four independent SAE J1321 full-size track test campaigns that were compared to LLNL wind tunnel testing results. All platooning scenarios tested demonstrated significant fuel savings with good correlation relative to following distances, but there are still unanswered questions and clear opportunities for system optimization. NOx emissions showed improvements from NREL tests in 2014 to Auburn tests in 2015 with respect to J1321 platooning track testing of Peloton system. NREL evaluated data from Volpe's Naturalistic Study of Truck Following Behavior, which showed minimal impact of naturalistic background platooning. We found significant correlation between multiple track studies, wind tunnel tests, and computational fluid dynamics, but also showed that there is more to learn regarding close formation and longer-distance effects. We also identified potential areas for further research and development, including development of advanced aerodynamic designs optimized for platooning, measurement of platoon system performance in traffic conditions, impact of vehicle lateral offsets on platooning performance, and characterization of the national potential for platooning based on fleet operational characteristics.
Hoffmann, Kristoffer; Tophøj Rasmussen, Johannes; Hansen, Svend Ole; Reiso, Marit; Isaksen, Bjørn; Egeberg Aasland, Tale
Experimental laboratory testing of vortex-induced structural oscillations in flowing water is an expensive and time-consuming procedure, and the testing of high Reynolds number flow regimes is complicated due to the requirement of either a large-scale or high-speed facility. In most cases, Reynolds number scaling effects are unavoidable, and these uncertainties have to be accounted for, usually by means of empirical rules-of-thumb. Instead of performing traditional hydrodynamic measurements, wind tunnel testing in an appropriately designed experimental setup may provide an alternative and much simpler and cheaper framework for estimating the structural behavior under water current and wave loading. Furthermore, the fluid velocities that can be obtained in a wind tunnel are substantially higher than in a water testing facility, thus decreasing the uncertainty from scaling effects. In a series of measurements, wind tunnel testing has been used to investigate the static response characteristics of a circular and a rectangular section model. Motivated by the wish to estimate the vortex-induced in-line vibration characteristics of a neutrally buoyant submerged marine structure, additional measurements on extremely lightweight, helium-filled circular section models were conducted in a dynamic setup. During the experiment campaign, the mass of the model was varied in order to investigate how the mass ratio influences the vibration amplitude. The results show good agreement with both aerodynamic and hydrodynamic experimental results documented in the literature.
Rivas, J. A., Jr.; Gill, T. E.; Van Pelt, R. S.; Walsh, E.
Ephemeral wetlands are ideal sources for dust emission, as well as repositories for dormant stages of aquatic invertebrates. An important component of invertebrate dispersal and colonization to new areas is the ability to be entrained into the atmosphere. Aquatic invertebrate eggs fall within the size of dust and sand grains (30-600μm), are less dense and aerodynamically shaped. We have shown previously that aquatic invertebrates can be dispersed long distances in dust storms but the extent of transport of taxa based on diapausing egg size/morphology has not been investigated. Here, we control the wind erosion process in a wind tunnel to test entrainment of diapausing stages of brine shrimp, clam shrimp, tadpole shrimp, fairy shrimp, Daphnia, and the rotifers Brachionus plicatilis and B. calyciflorus into the air by saltation. Diapausing eggs were mixed with sterilized wind-erodible soil. The soil/egg mixture was moistened with distilled water and air dried to form a crust. Dust was generated in a wind tunnel by releasing sand grains that act as saltator material similar to wind-entrained natural sands. Maximum wind velocity was 10m/s and entrained particles were sampled through an isokinetic horizontal intake opening. Aeolian sediment was collected from three points in the system; transfer section for coarse sediment, the pan subtending a settling chamber for finer saltation-sized sediment, and two paper filters for suspension-sized sediment. Samples were then passed through 250 and 350 μm sieves to remove abrader sand and rehydrated with various sterile media depending on the type of organism. We retrieved viable brine, fairy, and tadpole shrimp, ostracods, Daphnia, and diapausing eggs of the rotifers after hydration. This experiment demonstrates that resting stages of many invertebrates can be wind-eroded due to size and egg morphology and remain viable under controlled conditions mimicking dust emission.
Bagheri, Maryam; Araya, Daniel
It is hypothesized that blade curvature can serve as a passive means to control fluid entrainment and wake recovery in vertical-axis wind turbine (VAWT) arrays. We test this experimentally in a wind tunnel using two different VAWT configurations, one with straight blades and another with helical blades, keeping all other experimental parameters fixed. A small-scale, commercially available VAWT (15W max power) is used as the baseline wind tunnel model in each case. The commercial VAWT blades are replaced with either straight or helical blades that are 3D-printed extrusions of the same airfoil cross-section. Results from smoke flow visualization, three-component wake velocity measurements, and turbine power data are presented. These results give insight into the potential use of VAWTs with curved blades in utility-scale wind farms.
Suzuki, Masahiro; Nakade, Koji
A basic study of flow controls using air blowing was conducted to reduce unsteady aerodynamic force acting on trains running in tunnels. An air blowing device is installed around a model car in a wind tunnel. Steady and periodic blowings are examined utilizing electromagnetic valves. Pressure fluctuations are measured and the aerodynamic force acting on the car is estimated. The results are as follows: a) The air blowing allows reducing the unsteady aerodynamic force. b) It is effective to blow air horizontally at the lower side of the car facing the tunnel wall. c) The reduction rate of the unsteady aerodynamic force relates to the rate of momentum of the blowing to that of the uniform flow. d) The periodic blowing with the same frequency as the unsteady aerodynamic force reduces the aerodynamic force in a manner similar to the steady blowing.
Battistia, L.; Benini, E.; Brighenti, A.
The DeepWind Project aims at investigating the feasibility of a new floating vertical-axis wind turbine (VAWT) concept, whose purpose is to exploit wind resources at deep-water offshore sites. The results of an extensive experimental campaign on the DeepWind reduced scale demonstrator are here...... was installed on a high precision test bench, whose axis was suitable to be inclined up to 15° with respect to the design (i.e. upright) operating condition. The experiments were performed at the large scale, high speed wind tunnel of the Politecnico di Milano (Italy), using a “free jet” (open channel...... presented for different wind speeds and rotor angular velocities, including also skewed flow operation due to a tilted rotor arrangement. To accomplish this, after being instrumented to measure aerodynamic power and thrust (both in streamwise and transversal directions), a troposkien three-bladed rotor...
Iungo, Giacomo; Wu, Ting; Cöeffé, Juliette; Porté-Agel, Fernando; WIRE Team
An investigation on the interaction between atmospheric boundary layer flow and wind turbines is carried out with wind tunnel and LIDAR measurements. The former were carried out using hot-wire anemometry and multi-hole pressure probes in the wake of a three-bladed miniature wind turbine. The wind turbine wake is characterized by a strong velocity defect in the proximity of the rotor, and its recovery is found to depend on the characteristics of the incoming atmospheric boundary layer (mean velocity and turbulence intensity profiles). Field experiments were performed using three wind LIDARs. Bi-dimensional scans are performed in order to analyse the wake wind field with different atmospheric boundary layer conditions. Furthermore, simultaneous measurements with two or three LIDARs allow the reconstruction of multi-component velocity fields. Both LIDAR and wind tunnel measurements highlight an increased turbulence level at the wake boundary for heights comparable to the top-tip of the blades; this flow feature can produce dangerous fatigue loads on following wind turbines.
Verelst, David Robert; Larsen, Torben J.; van Wingerden, Jan-Willem
A series of free yawing wind tunnel experiments was held in the Open Jet Facility (OJF) of the TU Delft. The ≈ 300 W turbine has three blades in a downwind configuration and is optionally free to yaw. Different 1.6m diameter rotor configurations are tested such as blade flexibility and sweep...
Morse, S. F.; Roper, A. T.
The results of the cryogenic wind tunnel program conducted at NASA Langley Research Center are presented to provide a starting point for the design of an instructional/research wind tunnel facility. The advantages of the cryogenic concept are discussed, and operating envelopes for a representative facility are presented to indicate the range and mode of operation. Special attention is given to the design, construction and materials problems peculiar to cryogenic wind tunnels. The control system for operation of a cryogenic tunnel is considered, and a portion of a linearized mathematical model is developed for determining the tunnel dynamic characteristics.
Barlas, Emre; Buckingham, Sophia; Glabeke, Gertjan
Scaled wind turbine models have been installed in the VKI L1-B atmospheric boundary layer wind tunnel at offshore and onshore conditions. Time-resolved measurements were carried out with three component hot wire anemometry and stereo-PIV in the middle vertical plane of the wake up to eleven turbine...... diameter downstream. The results show an earlier wake recovery for the onshore case. The effect of inflow conditions and the wind turbine’s working conditions on wake meandering was investigated. Wake meandering was detected by hot wire anemometry through a low frequency peak in the turbulent power...
Makino, Yoshikazu; Ohira, Keisuke; Makimoto, Takuya; Mitomo, Toshiteru; 牧野, 好和; 大平, 啓介; 牧本, 卓也; 三友, 俊輝
Effects of static aeroelastic deformation of a wind-tunnel test model on the aerodynamic characteristics are discussed in wind-tunnel tests in the preliminary design phase of the silent supersonic technology demonstrator (S3TD). The static aeroelastic deformation of the main wing is estimated for JAXA 2m x 2m transonic wind-tunnel and 1m x 1m supersonic wind-tunnel by a finite element method (FEM) structural analysis in which its structural model is tuned with the model deformation calibratio...
Wind erosion tests were performed in a wind tunnel in support of the development of long-term protective barriers to cap stabilized waste sites at the Hanford Site. Controlled wind and saltating sand erosive stresses were applied to physical models of barrier surface layers to simulate worst-case eolian erosive stresses. The goal of these tests was to provide information useful to the design and evaluation of the surface layer composition of an arid-region waste site barrier concept that incorporates a deep fine-soil reservoir. A surface layer composition is needed that will form an armor resistant to eolian erosion during periods of extreme dry climatic conditions, especially when such conditions result in the elimination or reduction of vegetation by water deprivation or wildfire. Because of the life span required of Hanford waste barriers, it is important that additional work follow these wind tunnel studies. A modeling effort is planned to aid the interpretation of test results with respect to the suitability of pea gravel to protect the finite-soil reservoir during long periods of climatic stress. It is additionally recommended that wind tunnel tests be continued and field data be obtained at prototype or actual barrier sites. Results wig contribute to barrier design efforts and provide confidence in the design of long-term waste site caps for and regions
Funded by NASA grants for four years, the Brown Computer Graphics Group has developed novel 3D user interfaces for desktop and immersive scientific visualization applications. This past grant period supported the design and development of a software library, the 3D Widget Library, which supports the construction and run-time management of 3D widgets. The 3D Widget Library is a mechanism for transferring user interface technology from the Brown Graphics Group to the Virtual Wind Tunnel system at NASA Ames as well as the public domain.
In a series of measurements, wind tunnel testing has been used to investigate the static response characteristics of a circular and a rectangular section model. Motivated by the wish to estimate the vortex-induced in-line vibration characteristics of a neutrally buoyant submerged marine structure, additional measurements on extremely lightweight, helium-filled circular section models were conducted in a dynamic setup. During the experiment campaign, the mass of the model was varied in order to investigate how the mass ratio influences the vibration amplitude. The results show good agreement with both aerodynamic and hydrodynamic experimental results documented in the literature.
Favre, A; Gaviglio, J; Dumas, R
Results are presented of research obtained by means of an apparatus for measurement of time and space correlation and of a spectral analyzer in the study of the longitudinal component of turbulence velocities in a wind tunnel downstream of a grid of meshes. Application to the case of a flat-plate boundary layer is illustrated. These researches were made at the Laboratoire de Mecanique de l'Atmosphere de l'I.M.F.M. for the O.N.E.R.A.
Full Text Available This paper presents preliminary results concerning the design and aerodynamic calculations of a light sport aircraft (LSA. These were performed for a new lightweight, low cost, low fuel consumption and long-range aircraft. The design process was based on specific software tools as Advanced Aircraft Analysis (AAA, XFlr 5 aerodynamic and dynamic stability analysis, and Catia design, according to CS-LSA requirements. The calculations were accomplished by a series of tests performed in the wind tunnel in order to assess experimentally the aerodynamic characteristics of the airplane.
Hosoya, N.; Peterka, J. A.; Gee, R. C.; Kearney, D.
Conducted extensive wind-tunnel tests on parabolic trough solar collectors to determine practical wind loads applicable to structural design for stress and deformation, and local component design for concentrator reflectors.
Sørensen, Jens Nørkær; Sørensen, Dan Nørtoft
small, since important properties of the blade boundary layer otherwise cannot be captured correctly. On the other hand, severe problems with wind tunnel blockage may be the result if the ratio between the areas of the rotor and the wind tunnel cross section is too big. In all cases, wind tunnel...... wallcorrections are needed in order that measured data corresponds to unconstrained flow conditions. The present work is based on a model for ducted axial fans by Sørensen and Sørensen , modified to account for free (unbounded) turbines . Here, we extend the model to acount for wind turbines placed in wind...
Castelli, M. Raciti; Masi, M.; Battisti, L.; Benini, E.; Brighenti, A.; Dossena, V.; Persico, G.
Computational Fluid Dynamics (CFD) based on the Unsteady Reynolds Averaged Navier Stokes (URANS) equations have long been widely used to study vertical axis wind turbines (VAWTs). Following a comprehensive experimental survey on the wakes downwind of a troposkien-shaped rotor, a campaign of bi-dimensional simulations is presented here, with the aim of assessing its reliability in reproducing the main features of the flow, also identifying areas needing additional research. Starting from both a well consolidated turbulence model (k-ω SST) and an unstructured grid typology, the main simulation settings are here manipulated in a convenient form to tackle rotating grids reproducing a VAWT operating in an open jet wind tunnel. The dependence of the numerical predictions from the selected grid spacing is investigated, thus establishing the less refined grid size that is still capable of capturing some relevant flow features such as integral quantities (rotor torque) and local ones (wake velocities). (paper)
Raciti Castelli, M.; Masi, M.; Battisti, L.; Benini, E.; Brighenti, A.; Dossena, V.; Persico, G.
Computational Fluid Dynamics (CFD) based on the Unsteady Reynolds Averaged Navier Stokes (URANS) equations have long been widely used to study vertical axis wind turbines (VAWTs). Following a comprehensive experimental survey on the wakes downwind of a troposkien-shaped rotor, a campaign of bi-dimensional simulations is presented here, with the aim of assessing its reliability in reproducing the main features of the flow, also identifying areas needing additional research. Starting from both a well consolidated turbulence model (k-ω SST) and an unstructured grid typology, the main simulation settings are here manipulated in a convenient form to tackle rotating grids reproducing a VAWT operating in an open jet wind tunnel. The dependence of the numerical predictions from the selected grid spacing is investigated, thus establishing the less refined grid size that is still capable of capturing some relevant flow features such as integral quantities (rotor torque) and local ones (wake velocities).
Full Text Available This paper presents the measurement of gas concentration and wind intensity performed with a mobile robot in a custom turbulent wind tunnel designed for experimentation with customizable wind and gas leak sources. This paper presents the representation in different information layers of the measurements obtained in the turbulent wind tunnel under different controlled environmental conditions in order to describe the plume of the gas and wind intensities inside the experimentation chamber. The information layers have been generated from the measurements gathered by individual onboard gas and wind sensors carried out by an autonomous mobile robot. On the one hand, the assumption was that the size and cost of these specialized sensors do not allow the creation of a net of sensors or other measurement alternatives based on the simultaneous use of several sensors, and on the other hand, the assumption is that the information layers created will have application on the development and test of automatic gas source location procedures based on reactive or nonreactive algorithms.
Rumple, Christopher; Welch, Matthew; Naughton, Jonathan
The rise of industries like wind energy have provided motivation for generating realistic turbulent inflows in wind tunnels. Facilities with the ability to produce such inflows can study the interaction between the inflow turbulence and the flow of interest such as a wind turbine wake. An active grid - a system of actively driven elements - has gained increasing acceptance in turbulence research over the last 20 years. The ability to tailor the inflow turbulence quantities (e.g. turbulence intensities, integral length scale, and turbulence spectrum) is a driving reason for the growing use of active grids. An active grid with 40 independent axes located within the forward contraction of a low speed wind tunnel is used to explore the range of turbulent inflows possible using hot-wire anemometry to characterize the turbulence. Motor control algorithms (i.e. user waveform inputs) used to produce various turbulent inflows will be presented. Wind data available from meteorological towers are used to develop relevant inflows for wind turbines to demonstrate the usefulness of the active grid. This work was supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, under Award # DE-SC0012671.
Wutscher, Thorsten; Weymouth, Alfred J.; Giessibl, Franz J.
The phantom force is an apparently repulsive force, which can dominate the atomic contrast of an AFM image when a tunneling current is present. We described this effect with a simple resistive model, in which the tunneling current causes a voltage drop at the sample area underneath the probe tip. Because tunneling is a highly local process, the areal current density is quite high, which leads to an appreciable local voltage drop that in turn changes the electrostatic attraction between tip and sample. However, Si(111)-7×7 has a metallic surface state and it might be proposed that electrons should instead propagate along the surface state, as through a thin metal film on a semiconducting surface, before propagating into the bulk. In this paper, we first measure the phantom force on a sample that displays a metallic surface state [here, Si(111)-7×7] using tips with various radii. If the metallic surface state would lead to a constant electrostatic potential on the surface, we would expect a direct dependence of the phantom force with tip radius. In a second set of experiments, we study H/Si(100), a surface that does not have a metallic surface state. We conclude that a metallic surface state does not suppress the phantom force, but that the local resistance Rs has a strong effect on the magnitude of the phantom force.
Hiraki, K.; Zaitsu, D.; Yanaga, Y.; Kleine, H.
The rotational behavior of capsule-shaped models is investigated in the transonic wind tunnel of JAXA. A special support is developed to allow the model to rotate around the pitch, yaw and roll axes. This 3-DOF free rotational mounting apparatus achieves the least frictional torque from the support and the instruments. Two types of capsule models are prepared, one is drag type (SPH model) and the other is lift type (HTV-R model). The developed mounting apparatus is used in the wind tunnel tests with these capsule models. In a flow of Mach 0.9, the SPH model exhibits oscillations in pitch and yaw, and it rolls half a turn during the test. Similarly, the HTV-R model exhibits pitch and yaw oscillations in a flow of Mach 0.5. Moreover, it rolls multiple times during the test. In order to investigate the flow field around the capsule, the combined technique of color schlieren and surface tufts is applied. This visualization clearly shows the flow reattachment on the back surface of a capsule, which is suspected to induce the rapid rolling motion.
Nguyen Van Bang
Full Text Available The paper deals with the determination of the performance parameters of a small vertical axis wind turbines (VAWT, which operate by the utilization of drag forces acting on the blades of the turbine. The performance was evaluated by investigating the electrical power output and torque moment of the wind machine. Measurements were performed on the full-scale model and the experimental data are assessed and compared to other types of wind turbines, with respect to its purpose.
Leonardo P. Chamorro
Full Text Available Wind-tunnel experiments were carried out to better understand boundary layer effects on the flow pattern inside and above a model wind farm under thermally neutral conditions. Cross-wire anemometry was used to characterize the turbulent flow structure at different locations around a 10 by 3 array of model wind turbines aligned with the mean flow and arranged in two different layouts (inter-turbine separation of 5 and 7 rotor diameters in the direction of the mean flow by 4 rotor diameters in its span. Results suggest that the turbulent flow can be characterized in two broad regions. The first, located below the turbine top tip height, has a direct effect on the performance of the turbines. In that region, the turbulent flow statistics appear to reach equilibrium as close as the third to fourth row of wind turbines for both layouts. In the second region, located right above the first one, the flow adjusts slowly. There, two layers can be identified: an internal boundary layer where the flow is affected by both the incoming wind and the wind turbines, and an equilibrium layer, where the flow is fully adjusted to the wind farm. An adjusted logarithmic velocity distribution is observed in the equilibrium layer starting from the sixth row of wind turbines. The effective surface roughness length induced by the wind farm is found to be higher than that predicted by some existing models. Momentum recovery and turbulence intensity are shown to be affected by the wind farm layout. Power spectra show that the signature of the tip vortices, in both streamwise and vertical velocity components, is highly affected by both the relative location in the wind farm and the wind farm layout.
In wind tunnel tests, the problems arise of determining the wall pressure distribution, calculating the wall contour, and controlling adjustment of the walls. This report shows how these problems have been solved for the high speed wind tunnel of the Technical University of Berlin.
Moonen, P.; Blocken, B.J.E.; Roels, S.; Carmeliet, J.E.
A methodology for numerically simulating the flow conditions in closed-circuit wind tunnels is developed as a contribution to the general philosophy of incorporating Computational Fluid Dynamics (CFD) in wind tunnel design and testing and to CFD validation studies. The methodology is applied to the
Lee, Sam; Barnhart, Billy; Ratvasky, Thomas P.
The effect of ice accretion on a 1/12-scale complete aircraft model of S-3B Viking was studied in a rotary-balance wind tunnel. Two types of ice accretions were considered: ice protection system failure shape and runback shapes that form downstream of the thermal ice protection system. The results showed that the ice shapes altered the stall characteristics of the aircraft. The ice shapes also reduced the control surface effectiveness, but mostly near the stall angle of attack. There were some discrepancies with the data with the flaps deflected that were attributed to the low Reynolds number of the test. Rotational and forced-oscillation studies showed that the effects of ice were mostly in the longitudinal forces, and the effects on the lateral forces were relatively minor.
The Data Acquisition System in the Low Speed Wind Tunnel at the Aeronautical and Maritime Research Laboratory is responsible for the measurement, recording, processing and displaying of wind tunnel test data...
Bastankhah, Majid; Porté-Agel, Fernando
Wind-turbine wakes have negative effects on wind-farm performance. They are associated with: (a) the velocity deficit, which reduces the generated power of downwind turbines; and (b) the turbulence level, which increases the fatigue loads on downwind turbines. Controlling the yaw angle of turbines can potentially improve the performance of wind farms by deflecting the wake away from downwind turbines. However, except for few studies, wakes of yawed turbines still suffer from the lack of systematic research. To fill this research gap, we performed wind-tunnel experiments in the recirculating boundary-layer wind tunnel at the WIRE Laboratory of EPFL to better understand the wakes of yawed turbines. High-resolution stereoscopic particle image-velocimetry (S-PIV) was used to measure three velocity components in a horizontal plane located downwind of a horizontal-axis, three-blade model turbine. A servo-controller was connected to the DC generator of the turbine, which allowed us to apply different loadings. The power and thrust coefficients of the turbine were also measured for each case. These power and thrust measurements together with the highly-resolved flow measurements enabled us to study different wake characteristics such as the energy entrainment from the outer flow into the wake, the wake deflection and the helicoidal tip vortices for yawed turbines.
van Dooren, M F; Kühn, M.; Petrovic, V.
This paper combines the currently relevant research methodologies of scaled wind turbine model experiments in wind tunnels with remote-sensing short-range WindScanner Lidar measurement technology. The wind tunnel of the Politecnico di Milano was equipped with three wind turbine models and two short...... compared to hot wire probe measurements commonly used in wind tunnels. This yielded goodness of fit coefficients of 0.969 and 0.902 for the 1 Hz averaged u- and v-components of the wind speed, respectively, validating the 2D measurement capability of the Lidar scanners. Subsequently, the measurement...... for accurately measuring small scale flow structures in a wind tunnel....
John Kaiser Calautit
Full Text Available The data presented in this article were the basis for the study reported in the research articles entitled ‘A validated design methodology for a closed loop subsonic wind tunnel’ (Calautit et al., 2014 , which presented a systematic investigation into the design, simulation and analysis of flow parameters in a wind tunnel using Computational Fluid Dynamics (CFD. The authors evaluated the accuracy of replicating the flow characteristics for which the wind tunnel was designed using numerical simulation. Here, we detail the numerical and experimental set-up for the analysis of the closed-loop subsonic wind tunnel with an empty test section.
Doroshenko Sergey Aleksandrovich
Full Text Available The authors discuss wind loads applied to a set of two buildings. The wind load is simulated with the help of the wind tunnel. In the Russian Federation, special attention is driven to the aerodynamics of high-rise buildings and structures. According to the Russian norms, identification of aerodynamic coefficients for high-rise buildings, as well as the influence of adjacent buildings and structures, is performed on the basis of models of structures exposed to wind impacts simulated in the wind tunnel. This article deals with the results of the wind tunnel test of buildings. The simulation was carried out with the involvement of a model of two twenty-three storied buildings. The experiment was held in a wind tunnel of the closed type at in the Institute of Mechanics of Moscow State University. Data were compared at the zero speed before and after the experiment. LabView software was used to process the output data. Graphs and tables were developed in the Microsoft Excel package. GoogleSketchUp software was used as a visualization tool. The three-dimensional flow formed in the wind tunnel can't be adequately described by solving the two-dimensional problem. The aerodynamic experiment technique is used to analyze the results for eighteen angles of the wind attack.
Lucernoni, F.; Capelli, L.; Busini, V.; Sironi, S.
Waste Water Treatment Plants are known to have significant emissions of several pollutants and odorants causing nuisance to the near-living population. One of the purposes of the present work is to study a suitable model to evaluate odour emissions from liquid passive area sources. First, the models describing volatilization under a forced convection regime inside a wind tunnel device, which is the sampling device that typically used for sampling on liquid area sources, were investigated. In order to relate the fluid dynamic conditions inside the hood to the open field and inside the hood a thorough study of the models capable of describing the volatilization phenomena of the odorous compounds from liquid pools was performed and several different models were evaluated for the open field emission. By means of experimental tests involving pure liquid acetone and pure liquid butanone, it was verified that the model more suitable to describe precisely the volatilization inside the sampling hood is the model for the emission from a single flat plate in forced convection and laminar regime, with a fluid dynamic boundary layer fully developed and a mass transfer boundary layer not fully developed. The proportionality coefficient for the model was re-evaluated in order to account for the specific characteristics of the adopted wind tunnel device, and then the model was related with the selected model for the open field thereby computing the wind speed at 10 m that would cause the same emission that is estimated from the wind tunnel measurement furthermore, the field of application of the proposed model was clearly defined for the considered models during the project, discussing the two different kinds of compounds commonly found in emissive liquid pools or liquid spills, i.e. gas phase controlled and liquid phase controlled compounds. Lastly, a discussion is presented comparing the presented approach for emission rates recalculation in the field, with other approaches
Daileda, J. J.
Plotted and tabulated aerodynamic coefficient data from a wind tunnel test of the integrated space shuttle vehicle are presented. The primary test objective was to determine proximity force and moment data for the orbiter/external tank and solid rocket booster (SRB) with and without separation rockets firing for both single and dual booster runs. Data were obtained at three points (t = 0, 1.25, and 2.0 seconds) on the nominal SRB separation trajectory.
Drouard, A.; Vernazza, P.; Loehle, S.; Gattacceca, J.; Zander, T.; Eberhart, M.; Meindl, A.; Oefele, R.; Vaubaillon, J.; Colas, F.
Recently and for the very first time, experiments simulating vaporization of a meteorite sample were performed in a wind tunnel near Stuttgart with the specific aim to record emission spectra of the vaporized material. Using a high enthalpy air plasma flow for modeling an equivalent air friction of an entry speed of about 10 km/s, three meteorite types (H, CM and HED) and two meteoritical analogues (basalt and argillite) were ablated and high resolution spectra were recorded simultaneously. After the identification of all atomic lines, we per- formed a detailed study of our spectra using two approaches: (i) by direct comparison of multiplet in- tensities between the samples and (ii) by computation of a synthetic spectrum to constrain some physical parameters (temperature, elemental abundance). Finally, we compared our results to the elemental composition of our samples and we determined how much compositional information can be retrieved for a given meteor using visible sectroscopy.
Jaňour, Zbyněk; Jurčáková, Klára; Brych, Karel; Dittrt, František; Dittrich, F.
Roč. 88, č. 3 (2010), s. 185-190 ISSN 0957-5820 R&D Projects: GA MŠk(CZ) OC 113 Institutional research plan: CEZ:AV0Z20760514; CEZ:AV0Z20600510 Keywords : atmospheric turbulence * flow visualization * wind tunnel modeling Subject RIV: DG - Athmosphere Sciences, Meteorology Impact factor: 1.453, year: 2010 http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B8JGG-4Y7P8YF-1&_user=640952&_coverDate=05%2F31%2F2010&_rdoc=1&_fmt=high&_orig=search&_sort=d&_docanchor=&view=c&_searchStrId=1433050901&_rerunOrigin= google &_acct=C000034318&_version=1&_urlVersion=0&_userid=640952&md5=b036d2c5d747eadc03ff5697ea45e6a2
Full Text Available Contours in the CSIR Supersonic Wind Tunnel B Vallabha,b and BW Skewsa Received 17 February 2017, in revised form 23 June 2017 and accepted 25 June 2017 R & D Journal of the South African Institution of Mechanical Engineering 2017, 33, 32-41 http... with the Sivellsâ nozzle design method and the method of characteristics technique to design the nozzle profiles for the full supersonic Mach number range ðð â€ ðŽðŽ â€ ðð.5 of the facility. Automatic computation was used for the profile...
Full Text Available Enabling the full life cycle of scientific and engineering workflows requires robust middleware and services that support effective data management, near-realtime data movement and custom data processing. Many existing solutions exploit the database as a passive metadata catalog. In this paper, we present an approach that makes use of federation of databases to host data-centric wind tunnel application workflows. The user is able to compose customized application workflows based on database services. We provide a reference implementation that leverages typical business tools and technologies: Microsoft SQL Server for database services and Windows Workflow Foundation for workflow services. The application data and user's code are both hosted in federated databases. With the growing interest in XML Web Services in scientific Grids, and with databases beginning to support native XML types and XML Web services, we can expect the role of databases in scientific computation to grow in importance.
Taeschner, M.; Bunnenberg, C.
Future fusion plants and tritium handling facilities will contain large amounts of tritium. Following chronical or accidental releases to the atmosphere a secondary HTO source is established in the downwind sector of the tritium release point as a result of deposition processes. To investigate HTO reemission rates, experiments were performed with a special wind tunnel, in which the air flows across the surface of soil columns under controlled conditions. In order to measure the HTO content of an air sample that was experimentally contaminated by reemission of HTO from a labeled soil column, a fast method is used. The air sample is bubbled through a flask filled with a definite volume of low-tritium water. At the end of the sampling period, the volume and the specific activity of the flask water are measured. With the help of a simple mathematical formula, that is presented in this report, the HTO activity of the air sample can be calculated. (orig.) [de
Slater, J. W.; Saunders, J. D.
Computational simulations and wind tunnel testing were conducted to explore the operation of the Abe Silverstein Supersonic Wind Tunnel at the NASA Glenn Research Center at test section Mach numbers above the current limit of Mach 3.5. An increased Mach number would enhance the capability for testing of supersonic and hypersonic propulsion systems. The focus of the explorations was on understanding the flow within the second throat of the tunnel, which is downstream of the test section and is where the supersonic flow decelerates to subsonic flow. Methods of computational fluid dynamics (CFD) were applied to provide details of the shock boundary layer structure and to estimate losses in total pressure. The CFD simulations indicated that the tunnel could be operated up to Mach 4.0 if the minimum width of the second throat was made smaller than that used for previous operation of the tunnel. Wind tunnel testing was able to confirm such operation of the tunnel at Mach 3.6 and 3.7 before a hydraulic failure caused a stop to the testing. CFD simulations performed after the wind tunnel testing showed good agreement with test data consisting of static pressures along the ceiling of the second throat. The CFD analyses showed increased shockwave boundary layer interactions, which was also observed as increased unsteadiness of dynamic pressures collected in the wind tunnel testing.
Wolf, S. W. D.
Work was continued with the low speed self streamlining wind tunnel (SSWT) using the NACA 0012-64 airfoil in an effort to explain the discrepancies between the NASA Langley low turbulence pressure tunnel (LTPT) and SSWT results obtained with the airfoil stalled. Conventional wind tunnel corrections were applied to straight wall SSWT airfoil data, to illustrate the inadequacy of standard correction techniques in circumstances of high blockage. Also one SSWT test was re-run at different air speeds to investigate the effects of such changes (perhaps through changes in Reynold's number and freestream turbulence levels) on airfoil data and wall contours. Mechanical design analyses for the transonic self-streamlining wind tunnel (TSWT) were completed by the application of theoretical airfoil flow field data to the elastic beam and streamline analysis. The control system for the transonic facility, which will eventually allow on-line computer operation of the wind tunnel, was outlined.
渡辺, 重哉; WATANABE, Shigeya; 加藤, 裕之; KATO, Hiroyuki
Large-scale wind tunnels at NAL have been utilized to acquire data on aerodynamic characteristics for the development of various types of airplane and aerospace vehicle. Although in most cases measurements concentrate on the information needed directly for vehicle design, such as aerodynamic force and moment, surface pressure, and aerodynamic heating, the need for detailed spatial information on flows around vehicles is gradually increasing as the result of advancements in vehicle design tech...
He, Ji-Jun; Cai, Qiang-Guo; Tang, Ze-Jun
In recent years, high-molecular-weight anionic polyacrylamide (PAM) have been widely tested on a variety of soils, primarily in water erosion control. However, little information is available regarding the effectiveness of PAM on preventing soil loss from wind erosion. The research adopted room wind tunnel experiment, two kinds of soils were used which were from the agro-pastoral area of Inner Mongolia, the northwest of China, the clay content of soils were 22.0 and 13.7%, respectively. For these tests, all the treatments were performed under the condition of wind velocity of 14 m s(-1) and a blown angle of 8.75%, according to the actual situation of experimented area. The study results indicated that using PAM on the soil surface could enhance the capability of avoiding the wind erosion, at the same time, the effect of controlling wind soil erosion with 4 g m(-2) PAM was better than 2 g m(-2) PAM's. Economically, the 2 g m(-2) PAM used in soil surface can control wind erosion effectively in this region. The prophase PAM accumulated in soil could not improve the capability of avoiding the wind erosion, owing to the degradation of PAM in the soil and the continual tillage year after year. The texture of soil is a main factor influencing the capability of soil avoiding wind erosion. Soil with higher clay content has the higher capability of preventing soil from wind erosion than one with the opposite one under the together action of PAM and water.
Langston, L. S.
Progress is reported in an effort to study the three dimensional separation of fluid flow around two isolated cylinders mounted on an endwall. The design and performance of a hydrogen bubble generator for water tunnel tests to determine bulk flow properties and to measure main stream velocity and boundary layer thickness are described. Although the water tunnel tests are behind schedule because of inlet distortion problems, tests are far enough along to indicate cylinder spacing, wall effects and low Reynolds number behavior, all of which impacted wind tunnel model design. The construction, assembly, and operation of the wind tunnel and the check out of its characteristics are described. An off-body potential flow program was adapted to calculate normal streams streamwise pressure gradients at the saddle point locations.
Brown, Kenneth Alexander
The aerodynamic behavior of wind tunnels with porous, flexible walls formed from tensioned Kevlar has been characterized and new measurement techniques in such wind tunnels explored. The objective is to bring the aerodynamic capabilities of so-called Kevlar-wall test sections in-line with those of traditional solid-wall test sections. The primary facility used for this purpose is the 1.85-m by 1.85-m Stability Wind Tunnel at Virginia Tech, and supporting data is provided by the 2-m by 2-m L...
Romere, Paul O.; Brown, Steve Wesley
Development of the space shuttle necessitated an extensive wind tunnel test program, with the cooperation of all the major wind tunnels in the United States. The result was approximately 100,000 hours of space shuttle wind tunnel testing conducted for aerodynamics, heat transfer, and structural dynamics. The test results were converted into Chrysler DATAMAN computer program format to facilitate use by analysts, a very cost effective method of collecting the wind tunnel test results from many test facilities into one centralized location. This report provides final documentation of the space shuttle wind tunnel program. The two-volume set covers evolution of space shuttle aerodynamic configurations and gives wind tunnel test data, titles of wind tunnel data reports, sample data sets, and instructions for accessing the digital data base.
Maeda, Takao; Kamada, Yasunari; Murata, Junsuke; Suzuki, Daiki; Kaga, Norimitsu; Kagisaki, Yosuke
Wind turbines generate electricity due to extracting energy from the wind. The rotor aerodynamics strongly depends on the flow around blade. The surface flow on the rotating blade affects the sectional performance. The wind turbine surface flow has span-wise component due to span-wise change of airfoil section, chord length, twisted angle of blade and centrifugal force on the flow. These span-wise flow changes the boundary layer on the rotating blade and the sectional performance. Hence, the thorough understanding of blade surface flow is important to improve the rotor performance. For the purpose of clarification of the flow behaviour around the rotor blade, the velocity in the boundary layer on rotating blade surface of an experimental HAWT was measured in a wind tunnel. The velocity measurement on the blade surface was carried out by a laser Doppler velocimeter (LDV). As the results of the measurement, characteristics of surface flow are clarified. In optimum tip speed operation, the surface flow on leading edge and r/R=0.3 have large span-wise velocity which reaches 20% of sectional inflow velocity. The surface flow inboard have three dimensional flow patterns. On the other hand, the flow outboard is almost two dimensional in cross sectional plane.
De Wit, S.
In the design of low-rise buildings, wind tunnel experiments are scarcely employed to assess the wind-induced pressures, which are required e.g. for the simulation of ventilation flows or for the evaluation of the structural integrity. Instead, techniques are used, which predominandy rely on inter-
João Batista P. Falcão Filho
Full Text Available The Pilot Transonic Wind Tunnel of Institute of Aeronautics and Space (PTT Pilot Transonic Wind Tunnel is an important result of a tremendous effort to install a high speed wind tunnel complex (TTS acronyms for Transonic and Supersonic Tunnels, in Portuguese at the IAE, to support Brazilian aerospace research. Its history is described below, starting from the moment the TTS project was first conceived, highlighting each successive phase, mentioning the main difficulties encountered, and the solutions chosen, up until the final installation of the Pilot facility. A brief description of the tunnel's shakedown and calibration phases is also given, together with the present campaigns and proposed activities for the near future.
Littera, D.; Cozzolini, A.; Besch, M.; Carder, D.; Gautam, M.
Stringent emission regulations have forced drastic technological improvements in diesel aftertreatment systems, particularly in reducing Particulate Matter (PM) emissions. The formation and evolution of PM from modern engines are more sensitive to overall changes in the dilution process, such as rapidity of mixing, background PM present in the air. These technological advancements were made in controlled laboratory environments compliant with measurement standards (i.e. Code of Federal Regulation CFR in the USA) and are not fully representative of real-world emissions from these engines or vehicles. In light of this, a specifically designed and built wind tunnel by West Virginia University (WVU) is used for the study of the exhaust plume of a heavy-duty diesel vehicle, providing a better insight in the dilution process and the representative nanoparticles emissions in a real-world scenario. The subsonic environmental wind tunnel is capable of accommodating a full-sized heavy-duty truck and generating wind speeds in excess of 50mph. A three-dimensional gantry system allows spanning the test section and sample regions in the plume with accuracy of less than 5 mm. The gantry system is equipped with engine exhaust gas analyzers and PM sizing instruments. The investigation involves three different heavy-duty Class-8 diesel vehicles representative of three emission regulation standards, namely a US-EPA 2007 compliant, a US-EPA 2010 compliant, and a baseline vehicle without any aftertreatment technologies as a pre US-EPA 2007, respectively. The testing procedure includes three different vehicle speeds: idling, 20mph, and 35mph. The vehicles were tested on WVU's medium-duty chassis dynamometer, with the load applied to the truck reflecting the road load equation at the corresponding vehicle test speeds. Wind tunnel wind speed and vehicle speed were maintained in close proximity to one another during the entire test. Results show that the cross-sectional plume area
National Aeronautics and Space Administration — Closed wind tunnel beamforming for aeroacoustics has become more and more prevalent in recent years. Still, there are major drawbacks as current microphone arrays...
Spedding, Geoffrey; Browand, Frederick; McArthur, John
.... The flows are complex and almost always involve significant spanwise components. The results are being used to guide current wind-tunnel based quantitative flow investigations in selected two-dimensional planes.
Lysenkov, A. V.; Bosnyakov, S. M.; Glazkov, S. A.; Gorbushin, A. R.; Kuzmina, S. I.; Kursakov, I. A.; Matyash, S. V.; Ishmuratov, F. Z.
To obtain accurate data of calculation method error requires detailed simulation of the experiment in wind tunnel with keeping all features of the model, installation and gas flow. Two examples of such detailed data comparison are described in this paper. The experimental characteristics of NASA CRM model obtained in the ETW wind tunnel (Cologne, Germany), and CFD characteristics of this model obtained with the use of EWT-TsAGI application package are compared. Following comparison is carried out for an airplane model in the T-128 wind tunnel (TsAGI, Russia). It is seen that deformation influence on integral characteristics grows with increasing Re number and, accordingly, the dynamic pressure. CFD methods application for problems of experimental research in the wind tunnel allows to separate viscosity and elasticity effects.
Guezguez, Mohamed Sadok
Preserving the environment is a major challenge for today's aviation industry. Within this context, the CRIAQ MDO 505 project started, where a multidisciplinary approach was used to improve aircraft fuel efficiency. This international project took place between several Canadian and Italian teams. Industrial teams are Bombardier Aerospace, Thales Canada and Alenia Aermacchi. The academic partners are from Ecole de Technologie Superieure, Ecole Polytechnique de Montreal and Naples University. Teams from 'CIRA' and IAR-NRC research institutes had, also, contributed on this project. The main objective of this project is to improve the aerodynamic performance of a morphing wing prototype by reducing the drag. This drag reduction is achieved by delaying the flow transition (from laminar to turbulent) by performing shape optimization of the flexible upper skin according to different flight conditions. Four linear axes, each one actuated by a 'BLDC' motor, are used to morph the skin. The skin displacements are calculated by 'CFD' numerical simulation based on flow parameters which are Mach number, the angle of attack and aileron's angle of deflection. The wing is also equipped with 32 pressure sensors to experimentally detect the transition during aerodynamic testing in the subsonic wind tunnel at the IAR-NRC in Ottawa. The first part of the work is dedicated to establishing the necessary fieldbus communications between the control system and the wing. The 'CANopen' protocol is implemented to ensure real time communication between the 'BLDC' drives and the real-time controller. The MODBUS TCP protocol is used to control the aileron drive. The second part consists of implementing the skin control position loop based on the LVDTs feedback, as well as developing an automated calibration procedure for skin displacement values. Two 'sets' of wind tunnel tests were carried out to, experimentally, investigate the morphing wing controller effect; these tests also offered the
... of the data analysis techniques is given. Emphasis is placed on the scaling arguments used to compare data between a wind tunnel and full-scale study, and on methods of uncertainty analysis to provide a rigorous underpinning to the dataset. The report serves as a complete documentation for users of the MUST wind tunnel simulation dataset, which can be obtained by contacting the author.
Gillespie, V. P.
Factors to be considered in the design and fabrication of models for cryogenic wind tunnels include high model loads imposed by the high operating pressures, the mechanical and thermodynamic properties of materials in low temperature environments, and the combination of aerodynamic loads with the thermal environment. Candidate materials are being investigated to establish criteria for cryogenic wind tunnel models and their installation. Data acquired from these tests will be provided to users of the National Transonic Facility.
Koenig, D. G.; Falarski, M. D.
Tests were made in the Ames 40- by 80-foot wind tunnel to determine the forward speed effects on wing-mounted thrust augmentors. The large-scale model was powered by the compressor output of J-85 driven viper compressors. The flap settings used were 15 deg and 30 deg with 0 deg, 15 deg, and 30 deg aileron settings. The maximum duct pressure, and wind tunnel dynamic pressure were 66 cmHg (26 in Hg) and 1190 N/sq m (25 lb/sq ft), respectively. All tests were made at zero sideslip. Test results are presented without analysis.
Full Text Available In addition to the well-known soil factors which control wind erosion on flat, unridged surfaces, two specific processes affect the susceptibility of tillage ridged surfaces to wind erosion: ridge-induced roughness and ridge- trapping efficiency. In order to parameterize horizontal soil fluxes produced by wind over tillage ridges, eight-ridge configurations composed of sandy soil and exhibiting ridge heights to ridge spacing (RH/RS ratios ranging from 0.18 to 0.38 were experimented in a wind tunnel. These experiments are used to develop a parameterization of the horizontal fluxes over tillage ridged surfaces based only on the geometric characteristics of the ridges. Indeed, the key parameters controlling the horizontal flux, namely the friction velocity, threshold friction velocity and the adjustment coefficient, are derived through specific expressions, from ridge heights (RH and ridge spacing (RS. This parameterization was evaluated by comparing the results of the simulations to an additional experimental data set and to the data set obtained by Hagen and Armbrust (1992. In both cases, predicted and measured values are found to be in a satisfying agreement. This parameterization was used to evaluate the efficiency of ridges in reducing wind erosion. The results show that ridged surfaces, when compared to a loose, unridged soil surface, lead to an important reduction in the horizontal fluxes (exceeding 60%. Moreover, the effect of ridges in trapping particles contributes for more than 90% in the flux reduction while the ridge roughness effect is weak and decreases when the wind velocity increases.
Full Text Available In addition to the well-known soil factors which control wind erosion on flat, unridged surfaces, two specific processes affect the susceptibility of tillage ridged surfaces to wind erosion: ridge-induced roughness and ridge- trapping efficiency.
In order to parameterize horizontal soil fluxes produced by wind over tillage ridges, eight-ridge configurations composed of sandy soil and exhibiting ridge heights to ridge spacing (RH/RS ratios ranging from 0.18 to 0.38 were experimented in a wind tunnel. These experiments are used to develop a parameterization of the horizontal fluxes over tillage ridged surfaces based only on the geometric characteristics of the ridges. Indeed, the key parameters controlling the horizontal flux, namely the friction velocity, threshold friction velocity and the adjustment coefficient, are derived through specific expressions, from ridge heights (RH and ridge spacing (RS. This parameterization was evaluated by comparing the results of the simulations to an additional experimental data set and to the data set obtained by Hagen and Armbrust (1992. In both cases, predicted and measured values are found to be in a satisfying agreement.
This parameterization was used to evaluate the efficiency of ridges in reducing wind erosion. The results show that ridged surfaces, when compared to a loose, unridged soil surface, lead to an important reduction in the horizontal fluxes (exceeding 60%. Moreover, the effect of ridges in trapping particles contributes for more than 90% in the flux reduction while the ridge roughness effect is weak and decreases when the wind velocity increases.
Rotors, SAND76-0131. Albuquerque: July 1977. 10. Oliver, R.C. and P.R. Nixon. "Design Procedure for Coupling Savonius and Darrieus Wind Turbines ", Air...May 17-20, 1976. -65- 16. Blackwell, B.F., R.E. Sheldahl, and L.V. Feltz. Wind Tunnel Performance Data for the Darrieus Wind Turbine with NACA 0012...a 5.8 m/s (13 mph) wind . At 100 rpm, the Darrieus turbine would be fully self-sustaining and acceleration would continue to an operating tip speed
Downwind sound propagation over a noise screen is investigated by numerical computations and scale model experiments in a wind tunnel. For the computations, the parabolic equation method is used, with a range-dependent sound-speed profile based on wind-speed profiles measured in the wind tunnel and
Theodore, Colin R.; Willink, Gina C.; Russell, Carl R.; Amy, Alexander R.; Pete, Ashley E.
In April 2012 and October 2013, NASA and the U.S. Army jointly conducted a wind tunnel test program examining two notional large tilt rotor designs: NASA's Large Civil Tilt Rotor and the Army's High Efficiency Tilt Rotor. The approximately 6%-scale airframe models (unpowered) were tested without rotors in the U.S. Army 7- by 10-foot wind tunnel at NASA Ames Research Center. Measurements of all six forces and moments acting on the airframe were taken using the wind tunnel scale system. In addition to force and moment measurements, flow visualization using tufts, infrared thermography and oil flow were used to identify flow trajectories, boundary layer transition and areas of flow separation. The purpose of this test was to collect data for the validation of computational fluid dynamics tools, for the development of flight dynamics simulation models, and to validate performance predictions made during conceptual design. This paper focuses on the results for the Large Civil Tilt Rotor model in an airplane mode configuration up to 200 knots of wind tunnel speed. Results are presented with the full airframe model with various wing tip and nacelle configurations, and for a wing-only case also with various wing tip and nacelle configurations. Key results show that the addition of a wing extension outboard of the nacelles produces a significant increase in the lift-to-drag ratio, and interestingly decreases the drag compared to the case where the wing extension is not present. The drag decrease is likely due to complex aerodynamic interactions between the nacelle and wing extension that results in a significant drag benefit.
Carpentieri, Matteo; Hayden, Paul; Robins, Alan G.
Wind tunnel experiments have been carried out at the EnFlo laboratory to measure mean and turbulent tracer fluxes in geometries of real street canyon intersections. The work was part of the major DAPPLE project, focussing on the area surrounding the intersection between Marylebone Road and Gloucester Place in Central London, UK. Understanding flow and dispersion in urban streets is a very important issue for air quality management and planning, and turbulent mass exchange processes are important phenomena that are very often neglected in urban modelling studies. The adopted methodology involved the combined use of laser Doppler anemometry and tracer concentration measurements. This methodology was applied to quantify the mean and turbulent flow and dispersion fields within several street canyon intersections. Vertical profiles of turbulent tracer flux were also measured. The technique, despite a number of limitations, proved reliable and allowed tracer balance calculations to be undertaken in the selected street canyon intersections. The experience gained in this work will enable much more precise studies in the future as issues affecting the accuracy of the experimental technique have been identified and resolved.
Heidorn, K.; Davies, A.E.; Murphy, M.C.
The assessment of air quality impacts from roadways is a major concern to urban planners. In order to assess future road and building configurations, a number of techniques have been developed including mathematical models, which simulate traffic emissions and atmospheric dispersion through a series of mathematical relationships and physical models. The latter models simulate emissions and dispersion through scaling of these processes in a wind tunnel. Two roadway mathematical models, HIWAY-2 and CALINE-4, were applied to a proposed development in a large urban area. Physical modeling procedures developed by Rowan Williams Davies and Irwin Inc. (RWDI) in the form of line source simulators were also applied, and the resulting carbon monoxide concentrations were compared. The results indicated a factor of two agreement between the mathematical and physical models. The physical model, however, reacted to change in building massing and configuration. The mathematical models did not, since no provision for such changes was included in the mathematical models. In general, the RWDI model resulted in higher concentrations than either HIWAY-2 or CALINE-4. Where there was underprediction, it was often due to shielding of the receptor by surrounding buildings. Comparison of these three models with the CALTRANS Tracer Dispersion Experiment showed good results although concentrations were consistently underpredicted
Smith, Zachary; Jones, Anya; Hrynuk, John
Gust response of MAVs is a fundamental problem for flight stability and control of such aircraft. Current knowledge about the gust response of these vehicles is limited and gust interaction often results in damage to vehicles. Studying isolated gust effects on simple airfoil models in a controlled environment is a necessity for the further development of MAV control laws. Gusts have typically been generated by oscillating an airfoil causing the shedding of vortices to propagate through the system. While effective, this method provides only a transient up and downdraft behavior with small changes in angle of attack, not suitable for studying MAV scale gust interactions. To study these interactions, a gust that creates a change in flow angle larger than the static stall angle of typical airfoils was developed. This work was done in a low speed, low turbulence wind tunnel at base operating speed of 1.5 m/s, generating a Reynolds number of 12,000 on a NACA 0012 wing. It describes the fundamental mechanisms of how this gust was generated and the results obtained from the gust generator. The gust, which can alter the flow field in less than 1 second, was characterized using PIV and the interactions with a stationary airfoil at several angles of attack are evaluated.
Bahr, Christopher J.; Horne, William C.
An advanced form of background subtraction is presented and applied to aeroacoustic wind tunnel data. A variant of this method has seen use in other fields such as climatology and medical imaging. The technique, based on an eigenvalue decomposition of the background noise cross-spectral matrix, is robust against situations where isolated background auto-spectral levels are measured to be higher than levels of combined source and background signals. It also provides an alternate estimate of the cross-spectrum, which previously might have poor definition for low signal-to-noise ratio measurements. Simulated results indicate similar performance to conventional background subtraction when the subtracted spectra are weaker than the true contaminating background levels. Superior performance is observed when the subtracted spectra are stronger than the true contaminating background levels. Experimental results show limited success in recovering signal behavior for data where conventional background subtraction fails. They also demonstrate the new subtraction technique's ability to maintain a proper coherence relationship in the modified cross-spectral matrix. Beam-forming and de-convolution results indicate the method can successfully separate sources. Results also show a reduced need for the use of diagonal removal in phased array processing, at least for the limited data sets considered.
Larson, William E.
A computer program has been developed that improves the efficiency of wind tunnel model leak checking. The program uses a voice recognition unit to relay a technician's commands to the computer. The computer, after receiving a command, can respond to the technician via a voice response unit. Information about the model pressure orifice being checked is displayed on a gas-plasma terminal. On command, the program records up to 30 seconds of pressure data. After the recording is complete, the raw data and a straight line fit of the data are plotted on the terminal. This allows the technician to make a decision on the integrity of the orifice being checked. All results of the leak check program are stored in a database file that can be listed on the line printer for record keeping purposes or displayed on the terminal to help the technician find unchecked orifices. This program allows one technician to check a model for leaks instead of the two or three previously required.
Cobian-Iñiguez, Jeanette; Aminfar, AmirHessam; Chong, Joey; Burke, Gloria; Zuniga, Albertina; Weise, David R; Princevac, Marko
The present protocol presents a laboratory technique designed to study chaparral crown fire ignition and spread. Experiments were conducted in a low velocity fire wind tunnel where two distinct layers of fuel were constructed to represent surface and crown fuels in chaparral. Chamise, a common chaparral shrub, comprised the live crown layer. The dead fuel surface layer was constructed with excelsior (shredded wood). We developed a methodology to measure mass loss, temperature, and flame height for both fuel layers. Thermocouples placed in each layer estimated temperature. A video camera captured the visible flame. Post-processing of digital imagery yielded flame characteristics including height and flame tilt. A custom crown mass loss instrument developed in-house measured the evolution of the mass of the crown layer during the burn. Mass loss and temperature trends obtained using the technique matched theory and other empirical studies. In this study, we present detailed experimental procedures and information about the instrumentation used. The representative results for the fuel mass loss rate and temperature filed within the fuel bed are also included and discussed.
Huang, Junji; Duan, Lian; Choudhari, Meelan; Missouri Univ of Sci; Tech Team; NASA Langley Research Center Team
Direct numerical simulations (DNS) are used to examine the acoustic noise generation from the turbulent boundary layer on the nozzle wall of a Mach 6 Ludwieg Tube. The emphasis is on characterizing the freestream acoustic pressure disturbances radiated from the nozzle-wall turbulent boundary layer and comparing it with acoustic noise generated from a single, flat wall in an unconfined setting at a similar freestream Mach number to assess the effects of noise reverberation. In particular, the numerical database is used to provide insights into the pressure disturbance spectrum and amplitude scaling with respect to the boundary-layer parameters as well as to understand the acoustic source mechanisms. Such information is important for characterizing the freestream disturbance environment in conventional (i.e., noisy) hypersonic wind tunnels. Air Force Office of Scientific Research Award No. FA9550-14-1-0170.
McLennan, Anthony William
Two-dimensional aerodynamic characteristics of several thick blunt trailing edge airfoils are presented. These airfoils are not only directly applicable to the root section of wind turbine blades, where they provide the required structural strength at a fraction of the material and weight of an equivalent sharp trailing edge airfoil, but are also applicable to the root sections of UAVs having high aspect ratios, that also encounter heavy root bending forces. The Reynolds averaged Navier-Stokes code, ARC2D, was the primary numerical tool used to analyze each airfoil. The UCD-38-095, referred to as the Pareto B airfoil in this thesis, was also tested in the University of California, Davis Aeronautical Wind Tunnel. The Pareto B has an experimentally determined maximum lift coefficient of 1.64 at 14 degrees incidence, minimum drag coefficient of 0.0385, and maximum lift over drag ratio of 35.9 at a lift coefficient of 1.38, 10 degrees incidence at a Reynolds number of 666,000. Zig-zag tape at 2% and 5% of the chord was placed on the leading edge pressure and suction side of the Pareto B model in order to determine the aerodynamic performance characteristics at turbulent flow conditions. Experimental Pareto B wind tunnel data and previous FB-3500-0875 data is also presented and used to validate the ARC2D results obtained in this study. Additionally MBFLO, a detached eddy simulation Navier-Stokes code, was used to analyze the Pareto B airfoil for comparison and validation purposes.
Huang, Ju-Chrong; Weber, A.H.
All industrial complexes must be able to demonstrate that air pollutant concentrations from normal and accidental releases are within the bounds of stringent acceptance criteria. The offsite concentrations are comparatively easy to compute with the standard Gaussian models. By contrast, the onsite (in particular, near-field) concentrations can be more complex since the wind flows can interact with various structures in complex ways to create regions of relatively high local concentrations. Three methods can be used to predict the air pollutant concentrations: (1) mathematical models, (2) field experiments, and (3) fluid models (wind-tunnel testing). The complex flow in the vicinity of buildings is not amenable to simple mathematical generalizations. Field experiments cannot encompass the wind spectrum of meteorological conditions in the time generally allotted. Wind tunnel testing works best where numerical models fail and field testing is not applicable. This paper covers the following aspects related to the wind-tunnel modeling studies: (1) planning strategies; (2) types of wind-tunnel modeling studies flow visualization and concentration measurement experiments; (3) highlights (video tape show) of the wind tunnel experiments; (4) technical challenges; and (5) various applications
Kim, Dong Keon; Keum, Jong Yoon; Yoon, Soon Hyun
Experiments were conducted to estimate the performance of drag force type vertical axis wind turbine with an opening-shutting rotor. It was operated by the difference in drag force generated on both sides of the blades. The rotational speed was measured by a tachometer in a wind tunnel and the tunnel wind speed was measured by using a pitot-static tube and a micro manometer. The performance test for a prototype was accomplished by calculating power, power coefficient, torque coefficient from the measurement of torque and rpm by a dynamometer controller. Various design parameters, such as the number of blades(B), blade aspect ratio(W/R), angle of blades(α) and drag coefficient acting on a blade, were considered for optimal conditions. At the experiment of miniature model, maximum efficiency was found at N=15, α=60 .deg. and W/R=0.32. The measured test variables were power, torque, rotational speed, and wind speeds. The data presented are in the form of power and torque coefficients as a function of tip-speed ratio V/U. Maximum power was found in case of Ω=0.33, when the power and torque coefficient were 0.14 and 0.37 respectively. Comparing model test with prototype test, similarity law by advance ratio for vertical axis wind turbine was confirmed
Rolin, Vincent; Porté-Agel, Fernando
A vertical axis wind turbine is placed in a boundary layer flow in a wind tunnel, and its wake is investigated. Measurements are performed using an x-wire to measure two components of velocity and turbulence statistics in the wake of the wind turbine. The study is performed at various heights and crosswind positions in order to investigate the full volume of the wake for a range of tip speed ratios. The velocity deficit and levels of turbulence in the wake are related to the performance of the turbine. The asymmetric incoming boundary layer flow causes the rate of recovery in the wake to change as a function of height. Higher shear between the wake and unperturbed flow occurs at the top edge of the wake, inducing stronger turbulence and mixing in this region. The difference in flow relative to the blades causes the velocity deficit and turbulence level to change as a function of crosswind position behind the rotor. The relative difference diminishes with increasing tip speed ratio. Therefore, the wake becomes more homogeneous as tip speed ratio increases.
Hand, M. M.; Simms, D. A.; Fingersh, L. J.; Jager, D. W.; Cotrell, J. R.; Schreck, S.; Larwood, S. M.
The primary objective of the insteady aerodynamics experiment was to provide information needed to quantify the full-scale, three-dimensional aerodynamic behavior of horizontal-axis wind turbines. This report is intended to familiarize the user with the entire scope of the wind tunnel test and to support the use of the resulting data.
Ricci, A.; Burlando, M.; Freda, A.; Repetto, M.P.
This paper presents the results of an experimental study aimed at investigating the urban boundary layer in a district of Livorno city, in Tuscany. The wind flow over this area has been measured in the wind tunnel of the University of Genova using a physical model in scale 1:300. Two sets of
Full Text Available of evaluating wind loads of high-rise structures. The second part provides a description of the research, conducted at the wind-tunnel of the Council for Scientific and Industrial Research, in Pretoria, South Africa. The aim of this research was to determine...
Nutt, K. W.
Previous aerodynamic heating tests have been conducted in the AEDC/VKF Supersonic Wind Tunnel (A) to aid in defining the design thermal environment for the space shuttle external tank. The quality of these data has been under discussion because of the effects of low tunnel enthalpy and slow model injection rates. Recently the AEDC/VKF Hypersonic Wind Tunnel (C) has been modified to provide a Mach 4 capability that has significantly higher tunnel enthalpy with more rapid model injection rates. Tests were conducted in Tunnel C at Mach 4 to obtain data on the external tank for comparison with Tunnel A results. Data were obtained on a 0.0175 scale model of the Space Shuttle Integrated Vehicle at Re/ft = 4 x 10 to the 6th power with the tunnel stagnation temperature varying from 740 to 1440 R. Model attitude varied from an angle of attack of -5 to 5 deg and an angle of sideslip of -3 to 3 deg. One set of data was obtained in Tunnel C at Re/ft = 6.9 x 10 to the 6th for comparison with flight data. Data comparisons between the two tunnels for numerous regions on the external tank are given.
Full Text Available Background and Aims: This survey studies the wind tunnel performance by a two- componentlaser Doppler Anemometer, so some experiments were carried out to assess the performance of awind tunnel.Method: The tunnel was capable to produce air velocity of up to 40 m/s.. Measurements ofvelocity profiles have been made actors the test section of wind tunnel through the using a twocomponentfiber optic Laser Doppler anemometer. Measurements of velocity profiles andturbulence intensities have been made across the test section of the wind tunnel using a twocomponentfiber optic Laser Doppler anemometer (I.D.A for wind speeds ranging from 1 to3m/s.Results: Performance rests of velocity profiles at a given flow rate and various position of aerosolgenerator showed that although uniformity of flow dependent to the place of an atomizer (asaerosol generator but the variation of wind speed across the test section meets the wind speedrequirements, as specified by US EPAfor 3m/s only.Conclusion:At time which particles velocity reach to less than one micron, the air velocity relateson the similarity of particles and
Zhang, Ning; Du, Yunsong; Miao, Shiguang; Fang, Xiaoyi
The simulation performance over complex building clusters of a wind simulation model (Wind Information Field Fast Analysis model, WIFFA) in a micro-scale air pollutant dispersion model system (Urban Microscale Air Pollution dispersion Simulation model, UMAPS) is evaluated using various wind tunnel experimental data including the CEDVAL (Compilation of Experimental Data for Validation of Micro-Scale Dispersion Models) wind tunnel experiment data and the NJU-FZ experiment data (Nanjing University-Fang Zhuang neighborhood wind tunnel experiment data). The results show that the wind model can reproduce the vortexes triggered by urban buildings well, and the flow patterns in urban street canyons and building clusters can also be represented. Due to the complex shapes of buildings and their distributions, the simulation deviations/discrepancies from the measurements are usually caused by the simplification of the building shapes and the determination of the key zone sizes. The computational efficiencies of different cases are also discussed in this paper. The model has a high computational efficiency compared to traditional numerical models that solve the Navier-Stokes equations, and can produce very high-resolution (1-5 m) wind fields of a complex neighborhood scale urban building canopy (~ 1 km ×1 km) in less than 3 min when run on a personal computer.
Sitek, M. A. [Argonne National Lab. (ANL), Argonne, IL (United States). Transportation Research and Analysis Computing Center (TRACC) Energy Systems Division; Lottes, S. A. [Argonne National Lab. (ANL), Argonne, IL (United States). Transportation Research and Analysis Computing Center (TRACC) Energy Systems Division; Bojanowski, C. [Argonne National Lab. (ANL), Argonne, IL (United States). Transportation Research and Analysis Computing Center (TRACC) Energy Systems Division
Computational fluid dynamics (CFD) modeling is widely used in industry for design and in the research community to support, compliment, and extend the scope of experimental studies. Analysis of transportation infrastructure using high performance cluster computing with CFD and structural mechanics software is done at the Transportation Research and Analysis Computing Center (TRACC) at Argonne National Laboratory. These resources, available at TRACC, were used to perform advanced three-dimensional computational simulations of the wind tunnel laboratory at the Turner-Fairbank Highway Research Center (TFHRC). The goals were to verify the CFD model of the laboratory wind tunnel and then to use versions of the model to provide the capability to (1) perform larger parametric series of tests than can be easily done in the laboratory with available budget and time, (2) to extend testing to wind speeds that cannot be achieved in the laboratory, and (3) to run types of tests that are very difficult or impossible to run in the laboratory. Modern CFD software has many physics models and domain meshing options. Models, including the choice of turbulence and other physics models and settings, the computational mesh, and the solver settings, need to be validated against measurements to verify that the results are sufficiently accurate for use in engineering applications. The wind tunnel model was built and tested, by comparing to experimental measurements, to provide a valuable tool to perform these types of studies in the future as a complement and extension to TFHRC’s experimental capabilities. Wind tunnel testing at TFHRC is conducted in a subsonic open-jet wind tunnel with a 1.83 m (6 foot) by 1.83 m (6 foot) cross section. A three component dual force-balance system is used to measure forces acting on tested models, and a three degree of freedom suspension system is used for dynamic response tests. Pictures of the room are shown in Figure 1-1 to Figure 1-4. A detailed CAD
Rehman, Khurram; Malik, Afzaal M.; Khan, I. J.; Hassan, Jehangir
The range of flow velocities of high speed wind tunnels varies from Mach 1.0 to hypersonic order. In order to achieve such high speed flows, a high expansion nozzle is employed in the converging-diverging section of wind tunnel nozzle. The air for flow is compressed and stored in pressure vessels at temperatures close to ambient conditions. The stored air is dried and has minimum amount of moisture level. However, when this air is expanded rapidly, its temperature drops significantly and liquefaction conditions can be encountered. Air at near room temperature will liquefy due to expansion cooling at a flow velocity of more than Mach 4.0 in a wind tunnel test section. Such liquefaction may not only be hazardous to the model under test and wind tunnel structure; it may also affect the test results. In order to avoid liquefaction of air, a pre-heater is employed in between the pressure vessel and the converging-diverging section of a wind tunnel. A number of techniques are being used for heating the flow in high speed wind tunnels. Some of these include the electric arc heating, pebble bed electric heating, pebble bed natural gas fired heater, hydrogen burner heater, and the laser heater mechanisms. The most common are the pebble bed storage type heaters, which are inefficient, contaminating and time consuming. A well designed electrically heating system can be efficient, clean and simple in operation, for accelerating the wind tunnel flow up to Mach 10. This paper presents CFD analysis of electric preheater for different configurations to optimize its design. This analysis has been done using ANSYS 12.1 FLUENT package while geometry and meshing was done in GAMBIT.
Xavier Ortiz; David Rival; David Wood
To improve knowledge of the wind loads on photovoltaic structures mounted on flat roofs at the high angles required in high latitudes, and to study starting flow on low aspect ratio wind turbine blades, a series of wind tunnel tests were undertaken. Thin flat plates of aspect ratios between 0.4 and 9.0 were mounted on a sensitive three-component instantaneous force and moment sensor. The Reynolds numbers varied from 6 × 10 4 to 2 × 10 5 . Measurements were made for angles of attack between 0°...
Chougule, Prasad; Nielsen, Søren R.K.
been made to utilize high lift technology for vertical axis wind turbines in order to improve power efficiency. High lift is obtained by double-element airfoil mainly used in aeroplane wing design. In this current work a low Reynolds number airfoil is selected to design a double-element airfoil blade...... for use in vertical axis wind turbine to improve the power efficiency. Double-element airfoil blade design consists of a main airfoil and a slat airfoil. Orientation of slat airfoil is a parameter of investigation in this paper and air flow simulation over double-element airfoil. With primary wind tunnel...... that there is an increase in the lift coefficient by 26% for single-element airfoil at analysed conditions. The CFD simulation results were validated with wind tunnel tests. It is also observe that by selecting proper airfoil configuration and blade sizes an increase in lift coefficient can further be achieved....
Culler, Ethan; Farnsworth, John; Fagley, Casey; Seidel, Jurgen
Stall flutter and dynamic stall have received a significant amount of attention over the years. To experimentally study this problem, the body undergoing stall flutter is typically driven at a characteristic, single frequency sinusoid with a prescribed pitching amplitude and mean angle of attack offset. This approach allows for testing with repeatable kinematics, however it effectively decouples the structural motion from the aerodynamic forcing. Recent results suggest that this driven approach could misrepresent the forcing observed in a "free" stall flutter scenario. Specifically, a dynamically pitched rigid NACA 0018 wing section was tested in the wind tunnel under two modes of operation: (1) Cyber-Physical where "free" stall flutter was physically simulated through a custom motor-control system modeling a torsional spring and (2) Direct Motor-Driven Dynamic Pitch at a single frequency sinusoid representative of the cyber-physical motion. The time-resolved pitch angle and moment were directly measured and compared for each case. It was found that small deviations in the pitch angle trajectory between these two operational cases generate significantly different aerodynamic pitching moments on the wing section, with the pitching moments nearly 180o out of phase in some cases. This work is supported by the Air Force Office of Scientific Research through the Flow Interactions and Control Program and by the National Defense Science and Engineering Graduate Fellowship Program.
Dodson, R. O., Jr.
One of the objectives of the KC-135 Winglet Flight Research and Demonstration Program was to obtain experimental flight test data to verify the theoretical and wind tunnel winglet aerodynamic performance prediction methods. Good agreement between analytic, wind tunnel and flight test performance was obtained when the known differences between the tests and analyses were accounted for. The flight test measured fuel mileage improvements for a 0.78 Mach number was 3.1 percent at 8 x 10(5) pounds W/delta and 5.5 percent at 1.05 x 10(6) pounds W/delta. Correcting the flight measured data for surface pressure differences between wind tunnel and flight resulted in a fuel mileage improvement of 4.4 percent at 8 x 10(5) pounds W/delta and 7.2 percent at 1.05 x 10(6) pounds W/delta. The performance improvement obtained was within the wind tunnel test data obtained from two different wind tunnel models. The buffet boundary data obtained for the baseline configuration was in good agreement with previous established data. Buffet data for the 15 deg cant/-4 deg incidence configuration showed a slight improvement, while the 15 deg cant/-2 deg incidence and 0 deg cant/-4 deg incidence data showed a slight deterioration.
Gorbushin, A. R.
A review of foreign and Russian sources is given mentioning the pioneering wind tunnels built in Russia at the turn of 19th and 20th centuries. The first wind tunnel in Russia was constructed by V.A. Pashkevich at the Mikhailovsky Artillery Academy in St. Petersburg in 1871. In total from 1871 through 1915, 18 wind tunnels were constructed in Russia: 11 in Moscow, 5 in St. Petersburg and 2 in Kaluga. An overview of the pioneering Russian wind tunnels built by V.A. Pashkevich, K.E. Tsiolkovsky, prof. N.E. Zhukovsky, D.P. Ryabushinsky and prof. K.P. Boklevsky is given. Schemes, photographs, formulas, description of the research and test results taken from the original papers published by the wind tunnel designers are given. Photographs from the N.E. Zhukovsky Scientific and Memorial Museum and the Archive of the Russian Academy of Sciences are used in the article. Methods of flow visualization and results of their application are presented. The Russian scientists and researchers' contribution to the development of techniques and methods of aerodynamic experiment is shown, including one of the most important aspects - the wall interference problem.
Full Text Available The presented research validates the capability of a loosely coupled computational fluid dynamics (CFD and comprehensive rotorcraft analysis (CRA code to calculate the flowfield around a rotor and test stand mounted inside a wind tunnel. The CFD/CRA predictions for the Full-Scale UH-60A Airloads Rotor inside the National Full-Scale Aerodynamics Complex (NFAC 40- by 80-Foot Wind Tunnel at NASA Ames Research Center are compared with the latest measured airloads and performance data. The studied conditions include a speed sweep at constant lift up to an advance ratio of 0.4 and a thrust sweep at constant speed up to and including stall. For the speed sweep, wind tunnel modeling becomes important at advance ratios greater than 0.37 and test stand modeling becomes increasingly important as the advance ratio increases. For the thrust sweep, both the wind tunnel and test stand modeling become important as the rotor approaches stall. Despite the beneficial effects of modeling the wind tunnel and test stand, the new models do not completely resolve the current airload discrepancies between prediction and experiment.
cost approach for evaluation of wind effects in comparison to wind-tunnel experiments, using the ... edges of the hip-roof building in their wind-tunnel experiments. ..... choice of turbulence model depends on considerations such as the physics ...
Comprehensive control of odors, hydrogen sulfide (H2S), ammonia (NH3) and odorous volatile organic compound (VOC) emissions associated with animal production is a critical need. Current methods utilizing wind tunnels and flux chambers for measurements of gaseous emissions from area sources such as f...
Henriksen, Lars Christian; Natarajan, Anand; Kim, Taeseong
-principles derived state space model of the floating wind turbine. The ability to estimate aero- and hydrodynamic states could prove crucial for the performance of model-based control methods applied on floating wind turbines. Furthermore, two types of water kinematics have been compared two determine whether......In this work, the basic model for a spar buoy floating wind turbine , used by an extended Kalman filter, is presented and results concerning wind speed and wave force estimations are shown. The wind speed and aerodynamic forces are estimated using an extended Kalman filter based on a first...... or not linear and nonlinear water kinematics lead to significantly different loads....
Koehler, Kirsten A; Anthony, T Renee; van Dyke, Michael; Volckens, John
A rotating bluff-body disc (RBD) was developed to reduce spatiotemporal variability associated with sampling supermicron aerosol in low-velocity wind tunnels. The RBD is designed to rotate eight personal aerosol samplers around a circular path in a forward-facing plane aligned with the wind tunnel cross section. Rotation of the RBD allows each sampler to traverse an identical path about the wind tunnel cross section, which reduces the effects of spatial heterogeneity associated with dispersing supermicron aerosol in low-velocity wind tunnels. Samplers are positioned on the face of the RBD via sampling ports, which connect to an air manifold on the back of the disc. Flow through each sampler was controlled with a critical orifice or needle valve, allowing air to be drawn through the manifold with a single pump. A metal tube, attached to this manifold, serves as both the axis of rotation and the flow conduction path (between the samplers and the vacuum source). Validation of the RBD was performed with isokinetic samplers and 37-mm cassettes. For facing-the-wind tests, the rotation of the RBD significantly decreased intra-sampler variability when challenged with particle diameters from 1 to 100 μm. The RBD was then employed to determine the aspiration efficiency of Institute of Occupational Medicine (IOM) personal samplers under a facing-the-wind condition. Operation of IOM samplers on the RBD reduced the between-sampler variability for all particle sizes tested.
Lee, Min Hyung; Song, Hyun Wook
The force-dependent tunneling transport in metal/alkanethiol/metal junctions was examined using CAFM. Tunneling current and current density through alkanethiol SAMs increased with increasing tip-loading force in CAFM, which suggests that a potential change in geometry of the molecules under the tip loads influences the transport properties of alkanethiol SAMs. Enhanced intermolecular tunneling transport in the tilted molecular configuration under tip-loading effect is likely responsible for such an increase in tunneling current density. We also demonstrated that through-bond tunneling is a more efficient pathway in alkanethiol SAMs than are intermolecular chain-to-chain pathways, by demonstrating a dependence of current density on the associated tunneling distances. We report a tip-loading, force-dependent tunneling behavior in alkanethiol SAMs using CAFM. A variable tip-loading force applies to alkanethiol SAMs with a standard AFM feedback, and current(I)-voltage(V) characteristics are simultaneously measured while varying the loading forces. In particular, we observe how a tip-loading force in CAFM influences the transport properties of alkanethiol SAMs
Tourn, S.; Gilabert, R.; Sánchez, V.
Characterize a new open jet wind tunnel and define the uniform test section where performance studies of small VAWTs will be carried out.......Characterize a new open jet wind tunnel and define the uniform test section where performance studies of small VAWTs will be carried out....
Kmak, Frank J.; Hudgins, M.; Hergert, D.; George, Michael W. (Technical Monitor)
The 11-By 11-Foot Transonic leg of the Unitary Plan Wind Tunnel (UPWT) was modernized to improve tunnel performance, capability, productivity, and reliability. Wind tunnel tests to demonstrate the readiness of the tunnel for a return to production operations included an Integrated Systems Test (IST), calibration tests, and airplane validation tests. One of the two validation tests was a 0.037-scale Boeing 777 model that was previously tested in the 11-By 11-Foot tunnel in 1991. The objective of the validation tests was to compare pre-modernization and post-modernization results from the same airplane model in order to substantiate the operational readiness of the facility. Evaluation of within-test, test-to-test, and tunnel-to-tunnel data repeatability were made to study the effects of the tunnel modifications. Tunnel productivity was also evaluated to determine the readiness of the facility for production operations. The operation of the facility, including model installation, tunnel operations, and the performance of tunnel systems, was observed and facility deficiency findings generated. The data repeatability studies and tunnel-to-tunnel comparisons demonstrated outstanding data repeatability and a high overall level of data quality. Despite some operational and facility problems, the validation test was successful in demonstrating the readiness of the facility to perform production airplane wind tunnel%, tests.
Shabudin Mat; I. S. Ishak; Tholudin Mat Lazim; Shuhaimi Mansor; Mazuriah Said; Abdul Basid Abdul Rahman; Ahmad Shukeri Mohd. Kamaludim; Romain Brossay
This paper presents wind tunnel experiment on two delta wing configurations which are differentiated by their leading edge profiles: sharp and round-edged wings. The experiments were performed as a part of the delta wing aerodynamics research development in Universiti Teknologi Malaysia, low speed tunnel (UTM-LST). Steady load balance and flow visualization tests were conducted at Reynolds numbers of 0.5, 1, and 1.5 × 106, respectively. The flow measurement at low Reynolds number was also per...
Jaeger, Stephen M.; Allen, Christopher S.; Soderman, Paul T.; Olson, Larry E. (Technical Monitor)
Background noise in both open-jet and closed wind tunnels adversely affects the signal-to-noise ratio of acoustic measurements. To measure the noise of increasingly quieter aircraft models, the background noise will have to be reduced by physical means or through signal processing. In a closed wind tunnel, such as the NASA Ames 40- by 80- Foot Wind Tunnel, the principle background noise sources can be classified as: (1) fan drive noise; (2) microphone self-noise; (3) aerodynamically induced noise from test-dependent hardware such as model struts and junctions; and (4) noise from the test section walls and vane set. This paper describes the steps taken to minimize the influence of each of these background noise sources in the 40 x 80.
Full Text Available To improve knowledge of the wind loads on photovoltaic structures mounted on flat roofs at the high angles required in high latitudes, and to study starting flow on low aspect ratio wind turbine blades, a series of wind tunnel tests were undertaken. Thin flat plates of aspect ratios between 0.4 and 9.0 were mounted on a sensitive three-component instantaneous force and moment sensor. The Reynolds numbers varied from 6 × 104 to 2 × 105. Measurements were made for angles of attack between 0° and 90° both in the free stream and in wall proximity with increased turbulence and mean shear. The ratio of drag to lift closely follows the inverse tangent of the angle of incidence for virtually all measurements. This implies that the forces of interest are due largely to the instantaneous pressure distribution around the plate and are not significantly influenced by shear stresses. The instantaneous forces appear most complex for the smaller aspect ratios but the intensity of the normal force fluctuations is between 10% and 20% in the free-steam but can exceed 30% near the wall. As the wind tunnel floor is approached, the lift and drag reduce with increasing aspect ratio, and there is a reduction in the high frequency components of the forces. It is shown that the centre of pressure is closer to the centre of the plates than the quarter-chord position for nearly all cases.
Beck, J. W.
The goals, design, problems, and value of cryogenic transonic wind tunnels being developed in Europe are discussed. The disadvantages inherent in low-Reynolds-number (Re) wind tunnel simulations of aircraft flight at high Re are reviewed, and the cryogenic tunnel is shown to be the most practical method to achieve high Re. The design proposed for the European Transonic Wind tunnel (ETW) is presented: parameters include cross section. DISPLAY 83A46484/2 = 4 sq m, operating pressure = 5 bar, temperature = 110-120 K, maximum Re = 40 x 10 to the 6th, liquid N2 consumption = 40,000 metric tons/year, and power = 39,5 MW. The smaller Cologne subsonic tunnel being adapted to cryogenic use for preliminary studies is described. Problems of configuration, materials, and liquid N2 evaporation and handling and the research underway to solve them are outlined. The benefits to be gained by the construction of these costly installations are seen more in applied aerodynamics than in basic research in fluid physics. The need for parallel development of both high Re tunnels and computers capable of performing high-Re numerical analysis is stressed.
Leenders, J.K.; van Boxel, J.H.; Sterk, G.
The effect of several wind characteristics on sand transport was studied in three experiments in north Burkina Faso, West Africa. The first experiment is used to analyse the relation between wind speed and shear stress fluctuations across height. The second experiment is used to study the relation
Blumenthal, Philip Z.
A new high response on-line measurement system has been developed to continuously display and record the air stream dew point in the NASA Lewis 10 x 10 supersonic wind tunnel. Previous instruments suffered from such problems as very slow response, erratic readings, and high susceptibility to contamination. The system operates over the entire pressure level range of the 10 x 10 SWT, from less than 2 psia to 45 psia, without the need for a vacuum pump to provide sample flow. The system speeds up tunnel testing, provides large savings in tunnel power costs and provides the dew point input for the data-reduction subroutines which calculate test section conditions.
Muirhead, V. U.
A wind tunnel investigation was conducted to determine the influence of several physical variables on the aerodynamic drag of a trailer model. The physical variables included: a cab mounted wind deflector, boattail on trailer, flow vanes on trailer front, forced transition on trailer, and decreased gap between tractor and trailer. Tests were conducted at yaw angles (relative wind angles) of 0, 5, 10, 20, and 30 degrees and Reynolds numbers of 3.58 x 10 to the 5th power 6.12 x 10 to the 5th power based upon the equivalent diameter of the vehicles. The wind deflector on top of the cab produced a calculated reduction in fuel consumption of about 5 percent of the aerodynamic portion of the fuel budget for a wind speed of 15.3 km/hr (9.5 mph) over a wind angle range of 0 deg to 180 deg and for a vehicle speed of 88.5 km/hr (55 mph). The boattail produced a calculated 7 percent to 8 percent reduction in fuel consumption under the same conditions. The decrease in gap reduced the calculated fuel consumption by about 5 percent of the aerodynamic portion of the fuel budget.
Yeager, W. T., Jr.; Young, W. H., Jr.; Mantay, W. R.
An investigation was conducted in the Langley full-scale tunnel to measure the performance of several helicopter tail-rotor/fin configurations with regard to directional control problems encountered at low speeds in ground effect. Tests were conducted at wind azimuths of 0 deg to 360 deg in increments of 30 deg and 60 deg and at wind speeds from 0 to 35 knots. The results indicate that at certain combinations of wind speed and wind azimuth, large increases in adverse fin force require correspondingly large increases in the tail-rotor thrust, collective pitch, and power required to maintain yaw trim. Changing the tail-rotor direction of rotation to top blade aft for either a pusher tail rotor (tail-rotor wake blowing away from fin) or a tractor tail rotor (tail-rotor wake blowing against fin) will alleviate this problem. For a pusher tail rotor at 180 deg wind azimuth, increases in the fin/tail-rotor gap were not found to have any significant influence on the overall vehicle directional control capability. Changing the tail rotor to a higher position was found to improve tail-rotor performance for a fin-off configuration at a wind azimuth of 180 deg. A V-tail configuration with a pusher tail rotor with top blade aft direction of rotation was found to be the best configuration with regard to overall directional control capability.
Najafi, Nadia; Schmidt Paulsen, Uwe
This paper is about development and use of a research based stereo vision system for vibration and operational modal analysis on a parked, 1-kW, 3-bladed vertical axis wind turbine (VAWT), tested in a wind tunnel at high wind. Vibrations were explored experimentally by tracking small deflections...... of the markers on the structure with two cameras, and also numerically, to study structural vibrations in an overall objective to investigate challenges and to prove the capability of using stereo vision. Two high speed cameras provided displacement measurements at no wind speed interference. The displacement...
Sugimoto, Yoshiaki; Ueda, Keiichi; Abe, Masayuki; Morita, Seizo
We simultaneously measured the force and tunneling current in three-dimensional (3D) space on the Si(111)-(7 × 7) surface using scanning force/tunneling microscopy at room temperature. The observables, the frequency shift and the time-averaged tunneling current were converted to the physical quantities of interest, i.e. the interaction force and the instantaneous tunneling current. Using the same tip, the local density of states (LDOS) was mapped on the same surface area at constant height by measuring the time-averaged tunneling current as a function of the bias voltage at every lateral position. LDOS images at negative sample voltages indicate that the tip apex is covered with Si atoms, which is consistent with the Si-Si covalent bonding mechanism for AFM imaging. A measurement technique for 3D force/current mapping and LDOS imaging on the equivalent surface area using the same tip was thus demonstrated. (paper)
Romanowski, R. F.; Steinberg, I. H.
The apparatus and technique for measuring the thermophysical properties of models used with the phase-change paint method for obtaining wind tunnel heat transfer data are described. The method allows rapid measurement of the combined properties in a transient manner similar to an actual wind tunnel test. An effective value of the thermophysical properties can be determined which accounts for changes in thermal properties with temperature or with depth into the model surface. The apparatus was successfully tested at various heating rates between 19,000 and 124,000 watts per square meter.
Latorre Iglesias, E.; Thompson, D.; Smith, M.; Kitagawa, T.; Yamazaki, N.
Aerodynamic noise becomes a significant noise source at speeds normally reached by high-speed trains. The train bogies are identified as important sources of aerodynamic noise. Due to the difficulty to assess this noise source carrying out field tests, wind tunnel tests offer many advantages. Tests were performed in the large-scale low-noise anechoic wind tunnel at Maibara, Japan, using a 1/7 scale train car and bogie model for a range of flow speeds between 50, 76, 89 and 100 m/s. The depend...
Sasaki, Glen E.
The 12 Foot Pressure Wind Tunnel is a variable density, low turbulence wind tunnel that operates at subsonic speeds, and up to six atmospheres total pressure. The restoration of this facility is of critical importance to the future of the U.S. aerospace industry. As part of this project, several state of the art model support systems are furnished to provide an optimal balance between aerodynamic and operational efficiency parameters. Two model support systems, the Rear Strut Model Support, and the High Angle of Attack Model Support are discussed. This paper covers design parameters, constraints, development, description, and component selection.
Full Text Available Wind tunnel tests to measure unsteady cavity flow pressure measurements can be expensive, lengthy, and tedious. In this work, the feasibility of an active machine learning technique to design wind tunnel runs using proxy data is tested. The proposed active learning scheme used scattered data approximation in conjunction with uncertainty sampling (US. We applied the proposed intelligent sampling strategy in characterizing cavity flow classes at subsonic and transonic speeds and demonstrated that the scheme has better classification accuracies, using fewer training points, than a passive Latin Hypercube Sampling (LHS strategy.
Ulbrich, Norbert Manfred; Bridge, Thomas M.; Amaya, Max A.
A new global regression analysis method is discussed that predicts wind tunnel model weight corrections for strain-gage balance loads during a wind tunnel test. The method determines corrections by combining "wind-on" model attitude measurements with least squares estimates of the model weight and center of gravity coordinates that are obtained from "wind-off" data points. The method treats the least squares fit of the model weight separate from the fit of the center of gravity coordinates. Therefore, it performs two fits of "wind- off" data points and uses the least squares estimator of the model weight as an input for the fit of the center of gravity coordinates. Explicit equations for the least squares estimators of the weight and center of gravity coordinates are derived that simplify the implementation of the method in the data system software of a wind tunnel. In addition, recommendations for sets of "wind-off" data points are made that take typical model support system constraints into account. Explicit equations of the confidence intervals on the model weight and center of gravity coordinates and two different error analyses of the model weight prediction are also discussed in the appendices of the paper.
Leble, V.; Barakos, G.
The possibility of a wind turbine entering vortex ring state during pitching oscillations is explored in this paper. The aerodynamic performance of the rotor was computed using the Helicopter Multi-Block flow solver. This code solves the Navier-Stokes equations in integral form using the arbitrary Lagrangian-Eulerian formulation for time-dependent domains with moving boundaries. A 10-MW wind turbine was put to perform yawing and pitching oscillations suggesting the partial vortex ring state during pitching motion. The results also show the strong effect of the frequency and amplitude of oscillations on the wind turbine performance.
Leble, V; Barakos, G
The possibility of a wind turbine entering vortex ring state during pitching oscillations is explored in this paper. The aerodynamic performance of the rotor was computed using the Helicopter Multi-Block flow solver. This code solves the Navier-Stokes equations in integral form using the arbitrary Lagrangian-Eulerian formulation for time-dependent domains with moving boundaries. A 10-MW wind turbine was put to perform yawing and pitching oscillations suggesting the partial vortex ring state during pitching motion. The results also show the strong effect of the frequency and amplitude of oscillations on the wind turbine performance. (paper)
Full Text Available The paper presents a study on modelling the wind drifting of the snow deposited on the flat roofs of buildings in wind tunnel. The physical model of snow drifting in wind tunnel simulating the urban exposure to wind action is not frequently reported in literature, but is justified by the serious damages under accidental important snow falls combined with strong wind actions on the roofs of various buildings. A uniform layer of snow deposited on the flat roof was exposed to wind action in order to obtain the drifting. The parameters involved in the modelling at reduced scale, with particles of glass beads, of the phenomenon of transportation of the snow from the roof were analysed, particularly the roughness length and the friction wind speed. A numerical simulation in ANSYS CFX program was developed in parallel, by which a more accurate visualization of the particularities of the wind flow over the roof was possible, in the specific areas where the phenomenon of snow transportation was more susceptible to occur. Modified roughness length and friction wind speed were determined through methods used in the literature, an attempt being made in this work to analyse the factors that influence their values.
Castner, Raymond; Shaw, Stephen; Adamson, Eric; Simerly, Stephanie
In an effort to identify test facilities that offer sonic boom measurement capabilities, an exploratory test program was initiated using wind tunnels at NASA research centers. The subject of this report is the sonic boom pressure rail data collected in the Glenn Research Center 8- by 6-Foot Supersonic Wind Tunnel. The purpose is to summarize the lessons learned based on the test activity, specifically relating to collecting sonic boom data which has a large amount of spatial pressure variation. The wind tunnel background pressure profiles are presented as well as data which demonstrated how both wind tunnel Mach number and model support-strut position affected the wind tunnel background pressure profile. Techniques were developed to mitigate these effects and are presented.
National Aeronautics and Space Administration — Advances in computational capabilities for modeling the performance of advanced flight vehicles depend on verification measurements made in ground-based wind...
Eppers, Oliver; Mayer, Amelie; Diehl, Karoline; Mitra, Subir; Borrmann, Stephan; Szakáll, Miklós
Immersion and contact freezing are of outmost important ice nucleation processes in mixed phase clouds. Experimental studies are carried out in the Mainz vertical wind tunnel laboratory in order to characterize these nucleation processes for different ice nucleating particles (INP), such as for mineral dust or biological particles. Immersion freezing is investigated in our laboratory with two different experimental techniques, both attaining contact-free levitation of liquid droplets and cooling of the surrounding air down to about -25 °C. In an acoustic levitator placed in the cold room of our laboratory, drops with diameters of 2 mm are investigated. In the vertical air stream of the wind tunnel droplets with diameter of 700 micron are freely floated at their terminal velocities, simulating the flow conditions of the free atmosphere. Furthermore, the wind tunnel offers a unique platform for contact freezing experiments. Supercooled water droplets are floated in the vertical air stream at their terminal velocities and INP are injected into the tunnel air stream upstream of them. As soon as INP collides with the supercooled droplet the contact freezing is initiated. The first results of immersion and contact freezing experiments with cellulose particles both in the acoustic levitator and in the wind tunnel will be presented. Cellulose is considered as typical INP of biological origin and a macrotracer for plant debris. Nucleating properties of cellulose will be provided, mainly focusing on the temperature, INP concentration, and specific surface area dependences of the freezing processes. Direct comparison between the different experimental techniques (acoustic levitator and wind tunnel), as well as between nucleation modes (immersion and contact freezing) will be presented. The work is carried out within the framework of the German research unit INUIT.
Chougule, Prasad; Nielsen, Søren R K
Nowadays, small vertical axis wind turbines are receiving more attention due to their suitability in micro-electricity generation. There are few vertical axis wind turbine designs with good power curve. However, the efficiency of power extraction has not been improved. Therefore, an attempt has been made to utilize high lift technology for vertical axis wind turbines in order to improve power efficiency. High lift is obtained by double-element airfoil mainly used in aeroplane wing design. In this current work a low Reynolds number airfoil is selected to design a double-element airfoil blade for use in vertical axis wind turbine to improve the power efficiency. Double-element airfoil blade design consists of a main airfoil and a slat airfoil. Orientation of slat airfoil is a parameter of investigation in this paper and air flow simulation over double-element airfoil. With primary wind tunnel test an orientation parameter for the slat airfoil is initially obtained. Further a computational fluid dynamics (CFD) has been used to obtain the aerodynamic characteristics of double-element airfoil. The CFD simulations were carried out using ANSYS CFX software. It is observed that there is an increase in the lift coefficient by 26% for single-element airfoil at analysed conditions. The CFD simulation results were validated with wind tunnel tests. It is also observe that by selecting proper airfoil configuration and blade sizes an increase in lift coefficient can further be achieved
Weymouth, A J; Wutscher, T; Welker, J; Hofmann, T; Giessibl, F J
Simultaneous measurements of tunneling current and atomic forces provide complementary atomic-scale data of the electronic and structural properties of surfaces and adsorbates. With these data, we characterize a strong impact of the tunneling current on the measured force on samples with limited conductivity. The effect is a lowering of the effective gap voltage through sample resistance which in turn lowers the electrostatic attraction, resulting in an apparently repulsive force. This effect is expected to occur on other low-conductance samples, such as adsorbed molecules, and to strongly affect Kelvin probe measurements when tunneling occurs.
The U.S. Department of Energy, working through the National Renewable Energy Laboratory, is engaged in a comprehensive research effort to improve our understanding of wind turbine aeroacoustics. Quiet wind turbines are an inducement to widespread deployment, so the goal of NREL's aeroacoustic research is to develop tools that the U.S. wind industry can use in developing and deploying highly efficient, quiet wind turbines at low wind speed sites. NREL's National Wind Technology Center is implementing a multifaceted approach that includes wind tunnel tests, field tests, and theoretical analyses in direct support of low wind speed turbine development by its industry partners. To that end, wind tunnel aerodynamic tests and aeroacoustic tests have been performed on six airfoils that are candidates for use on small wind turbines. Results are documented in this report.
Mo, Ziwei; Fu, Hui-Zhen; Ho, Yuh-Shan
Wind tunnels have been widely employed in aerodynamic research. To characterize the high impact research, a bibliometric analysis was conducted on highly cited articles related to wind tunnel based on the Science Citation Index Expanded (SCI-EXPANDED) database from 1900 to 2014. Articles with at least 100 citations from the Web of Science Core Collection were selected and analyzed in terms of publication years, authors, institutions, countries/territories, journals, Web of Science categories, and citation life cycles. The results show that a total of 77 highly cited articles in 37 journals were published between 1959 and 2008. Journal of Fluid Mechanics published the most of highly cited articles. The USA was the most productive country and most frequent partner of internationally collaboration. The prolific institutions were mainly located in the USA and UK. The authors who were both first author and corresponding author published 88% of the articles. The Y index was also deployed to evaluate the publication characteristics of authors. Moreover, the articles with high citations in both history and the latest year with their citation life cycles were examined to provide insights for high impact research. The highly cited articles were almost earliest wind tunnel experimental data and reports on their own research specialty, and thus attracted high citations. It was revealed that classic works of wind tunnel research was frequently occurred in 1990s but much less in 2000s, probably due to the development of numerical models of computational fluid dynamic (CFD) in recent decades.
Kukačka, Libor; Nosek, Štěpán; Kellnerová, Radka; Jurčáková, Klára; Jaňour, Zbyněk
Roč. 2012, č. 381357 (2012), s. 1-13 ISSN 1537-744X Institutional research plan: CEZ:AV0Z20760514 Keywords : air pollution * atmospheric boundary layer * wind tunnel modelling * contaminant spreading * street canyon Subject RIV: DG - Athmosphere Sciences, Meteorology Impact factor: 1.730, year: 2012 http://www.tswj.com/2012/381357/
... the sampler inlet opening centered in the sampling zone. To meet the maximum blockage limit of § 53.62(c)(1) or for convenience, part of the test sampler may be positioned external to the wind tunnel... = reference method sampler volumetric flow rate; and t = sampling time. (iii) Remove the reference method...
Fluctuation Cone The Pressure-Fluctuation Cone was used for all wind-tunnel tests (Figure 3.7). The model is a 7◦ half-angle stainless - steel cone. It...analysis as a medium for fault detection: A review. Journal of Tribology , 130, January 2008.  L. M. Mack. Boundary layer linear stability theory. In
Stoughton, J. W.
Application of digital signal processing techniques to improve the non-linear dynamic characteristics of a sonar-type mercury manometer is described. The dynamic enhancement strategy quasi-linearizes the manometer characteristics and improves the effective bandwidth in the context of a wind-tunnel pressure regulation system. Model identification data and real-time hybrid simulation data demonstrate feasibility of approach.
Full Text Available Aerodynamic parameters obtained from separation experiments of internal stores in a wind tunnel are significant in aircraft designs. Accurate wind tunnel tests can help to improve the release stability of the stores and in-flight safety of the aircrafts in supersonic environments. A simulative system for free drop experiments of internal stores based on a practical project is provided in this paper. The system contains a store release mechanism, a control system and an attitude measurement system. The release mechanism adopts a six-bar linkage driven by a cylinder, which ensures the release stability. The structure and initial aerodynamic parameters of the stores are also designed and adjusted. A high speed vision measurement system for high speed rolling targets is utilized to measure the pose parameters of the internal store models and an optimizing method for the coordinates of markers is presented based on a priori model. The experimental results show excellent repeatability of the system, and indicate that the position measurement precision is less than 0.13 mm, and the attitude measurement precision for pitch and yaw angles is less than 0.126°, satisfying the requirements of practical wind tunnel tests. A separation experiment for the internal stores is also conducted in the FL-3 wind tunnel of China Aerodynamics Research Institute.
Radestock, M.; Riemenschneider, J.; Monner, H.P.; Huxdorf, O.; Werter, N.P.M.; De Breuker, R.
In a wind tunnel experiment a morphing wing with span extension and camber morphing was investigated. The considered aircraft is an unmanned aerial vehicle (UAV) with a span of 4 m. During the investigations a half wing model was analysed with pressure and structural measurement. The half wing model
Zahle, Frederik; Gaunaa, Mac; Sørensen, Niels N.
In this work a 2D CFD solver has been used to optimize the shape of a leading edge slat with a chord length of 30% of the main airfoil which was 40% thick. The airfoil configuration was subsequently tested in a wind tunnel and compared to numerical predictions. The multi-element airfoil was predi...
NASAs Environmentally Responsible Aviation (ERA) Project explores enabling technologies to reduce aviations impact on the environment. One research challenge area for the project has been to study advanced airframe and engine integration concepts to reduce community noise and fuel burn. In order to achieve this, complex wind tunnel experiments at both the NASA Langley Research Centers (LaRC) 14x22 and the Ames Research Centers 40x80 low-speed wind tunnel facilities were conducted on a Boeing Hybrid Wing Body (HWB) configuration. These wind tunnel tests entailed various entries to evaluate the propulsion airframe interference effects including aerodynamic performance and aeroacoustics. In order to assist these tests in producing high quality data with minimal hardware interference, extensive Computational Fluid Dynamic (CFD) simulations were performed for everything from sting design and placement for both the wing body and powered ejector nacelle systems to the placement of aeroacoustic arrays to minimize its impact on the vehicles aerodynamics. This paper will provide a high level summary of the CFD simulations that NASA performed in support of the model integration hardware design as well as some simulation guideline development based on post-test aerodynamic data. In addition, the paper includes details on how multiple CFD codes (OVERFLOW, STAR-CCM+, USM3D, and FUN3D) were efficiently used to provide timely insight into the wind tunnel experimental setup and execution.
Davis, J.M.; Eisner, A.D.; Wiener, R.W.; Main, C.E.
A phase Doppler anemometry system in combination with a laser light sheet was used in a low-speed recirculating wind tunnel to examine the flow field around an individual leaf. Turbulence similar to that encountered near the surface of the earth in a neutral stability boundary layer was generated using a grid at the upwind end of the wind tunnel test section. Individual healthy and diseased plant leaves were introduced into the tunnel with the leaf tip pointing downwind. The Mie-scattered radiation from the spores departing the diseased leaf was captured on videotape. Image processing software was used to enhance the visual quality of the individual frames from the videotape and to make spore velocity calculations. Three main vortex regions around the leaf were identified. The importance of these regions to the separation of the spores from the leaf surface and their subsequent downwind movement was analyzed
... ADMINISTRATION, DEPARTMENT OF TRANSPORTATION (CONTINUED) PIPELINE SAFETY LIQUEFIED NATURAL GAS FACILITIES... confining, structure; and (3) In the case of impounding systems for LNG storage tanks, impact forces and...
Soeder, Ronald H.
This manual describes the 10- by 10-Foot Supersonic Wind Tunnel at the NASA Lewis Research Center and provides information for users who wish to conduct experiments in this facility. Tunnel performance operating envelopes of altitude, dynamic pressure, Reynolds number, total pressure, and total temperature as a function of test section Mach number are presented. Operating envelopes are shown for both the aerodynamic (closed) cycle and the propulsion (open) cycle. The tunnel test section Mach number range is 2.0 to 3.5. General support systems, such as air systems, hydraulic system, hydrogen system, fuel system, and Schlieren system, are described. Instrumentation and data processing and acquisition systems are also described. Pretest meeting formats and schedules are outlined. Tunnel user responsibility and personnel safety are also discussed.
Phelps, A. E., III
A wind tunnel investigation of a full scale remotely piloted vehicle (RPV) armed with rocket launchers was conducted. The model had unacceptable longitudinal stability characteristics at negative angles of attack in the original design configuration. The addition of a pair of fins mounted in a V arrangement on the propeller shroud resulted in a configuration with acceptable longitudinal stability characteristics. The addition of wing mounted external stores to the modified configuration resulted in a slight reduction in the longitudinal stability. The lateral directional characteristics of the model were generally good, but the model had low directional stability at low angles of attack. Aerodynamic control power was very strong around all three axes.
Soriano, J. Francisco; Coquilla, Rachael V.; Wilson, Gregory R.; Seiff, Alvin; Rivell, Tomas
The primary focus of this study was to determine the accuracy of the Mars Pathfinder lander local pressure readings in accordance with the actual ambient atmospheric pressures of Mars during parachute descent. In order to obtain good measurements, the plane of the lander pressure sensor opening should ideally be situated so that it is parallel to the freestream. However, due to two unfavorable conditions, the sensor was positioned in locations where correction factors are required. One of these disadvantages is due to the fact that the parachute attachment point rotated the lander's center of gravity forcing the location of the pressure sensor opening to be off tangent to the freestream. The second and most troublesome factor was that the lander descends with slight oscillations that could vary the amplitude of the sensor readings. In order to accurately map the correction factors required at each sensor position, an experiment simulating the lander descent was conducted in the Martian Surface Wind Tunnel at NASA Ames Research Center. Using a 115 scale model at Earth ambient pressures, the test settings provided the necessary Reynolds number conditions in which the actual lander was possibly subjected to during the descent. In the analysis and results of this experiment, the readings from the lander sensor were converted to the form of pressure coefficients. With a contour map of pressure coefficients at each lander oscillatory position, this report will provide a guideline to determine the correction factors required for the Mars Pathfinder lander descent pressure sensor readings.
Van der Male, P.; Van Dalen, K.N.; Metrikine, A.
In determining wind forces on wind turbine blades, and subsequently on the tower and the foundation, the blade response velocity cannot be neglected. This velocity alters the wind force, which depends on the wind velocity relative to that of the blades This blade response velocity component of the
Creel, T. R.; Beckwith, I. E.
A method of shielding a wind-tunnel model from noise radiated by the tunnel-wall boundary layer has been developed and tested at the Langley Research Center. The shield consists of a rectangular array of longitudinal rods with boundary-layer suction through gaps between the rods. Tests were conducted at Mach 5 over a unit Reynolds number range of 1.0-3.5 x 10 to the 7th/m. Hot-wire measurements indicated the freestream noise, expressed in terms of the rms pressure fluctuations normalized by the mean pressure, was reduced from about 1.4 percent just upstream of the shielded region of a minimum level of about 0.4 percent in the forward portion of the shielded flow.
Peenemünde and Cape Canaveral mark cornerstones of space history. Kochel in Southern Germany and Tullahoma in Tennessee, USA also belong in this category. The technically unique Kochel wind tunnel was part of the German long-distance missile development strategy, planned and prepared in secret before the beginning of World War II. A 57 MW closed-circuit wind tunnel facility with 1 × 1 m measuring section was planned for continuous-flow simulation at high Mach numbers Ma 7-10. In the early 1940 s a site beside the Walchensee Power Station at Kochel am See in Upper Bavaria, Germany was chosen to provide the required altitude difference of 200 m for the hydraulic turbine drives. The preparatory activities for the erection of this impressive hypersonic wind tunnel facility were pushed ahead until an enforced temporary pause in September 1944. In early May 1945 US troops occupied the area and, in due course, scientists of General Arnold's Scientific Advisory Group, the `von Kármán team', ordered the transfer to the USA of available equipment, design materials and other paperwork. Here, at the Arnold Engineering Development Center (AEDC) Tullahoma, TN this `Tunnel A' was built to begin operation around 1957. The testing was conducted on the Mach 7 experimental aircraft X-15, space shuttle developments and still secret investigations on unmanned hypersonic vehicles.
Alter, Stephen J.; Brauckmann, Gregory J.; Kleb, Bil; Streett, Craig L; Glass, Christopher E.; Schuster, David M.
Using the Fully Unstructured Three-Dimensional (FUN3D) computational fluid dynamics code, an unsteady, time-accurate flow field about a Space Launch System configuration was simulated at a transonic wind tunnel condition (Mach = 0.9). Delayed detached eddy simulation combined with Reynolds Averaged Naiver-Stokes and a Spallart-Almaras turbulence model were employed for the simulation. Second order accurate time evolution scheme was used to simulate the flow field, with a minimum of 0.2 seconds of simulated time to as much as 1.4 seconds. Data was collected at 480 pressure taps at locations, 139 of which matched a 3% wind tunnel model, tested in the Transonic Dynamic Tunnel (TDT) facility at NASA Langley Research Center. Comparisons between computation and experiment showed agreement within 5% in terms of location for peak RMS levels, and 20% for frequency and magnitude of power spectral densities. Grid resolution and time step sensitivity studies were performed to identify methods for improved accuracy comparisons to wind tunnel data. With limited computational resources, accurate trends for reduced vibratory loads on the vehicle were observed. Exploratory methods such as determining minimized computed errors based on CFL number and sub-iterations, as well as evaluating frequency content of the unsteady pressures and evaluation of oscillatory shock structures were used in this study to enhance computational efficiency and solution accuracy. These techniques enabled development of a set of best practices, for the evaluation of future flight vehicle designs in terms of vibratory loads.
Coder, D. W.
Representation of the flow around full-scale ships was sought in the subsonic wind tunnels in order to a Hain Reynolds numbers as high as possible. As part of the quest to attain the largest possible Reynolds number, large models with high blockage are used which result in significant wall interference effects. Some experiences with such a high blockage model tested in the NASA Ames 12-foot pressure wind tunnel are summarized. The main results of the experiment relating to wind tunnel wall interference effects are also presented.
Romere, Paul O.; Brown, Steve Wesley
Development of the Space Shuttle necessitated an extensive wind tunnel test program, with the cooperation of all the major wind tunnels in the United States. The result was approximately 100,000 hours of Space Shuttle wind tunnel testing conducted for aerodynamics, heat transfer, and structural dynamics. The test results were converted into Chrysler DATAMAN computer program format to facilitate use by analysts, a very cost effective method of collecting the wind tunnel test results from many test facilities into one centralized location. This report provides final documentation of the Space Shuttle wind tunnel program. The two-volume set covers the evolution of Space Shuttle aerodynamic configurations and gives wind tunnel test data, titles of wind tunnel data reports, sample data sets, and instructions for accessing the digital data base.
Murman, E. M.
The capability for calculating transonic flows for realistic configurations and conditions is discussed. Various phenomena which were modeled are shown to have the same order of magnitude on the influence of predicted results. It is concluded that CFD can make the following contributions to the task of correlating wind tunnel and flight test data: some effects of geometry differences and aeroelastic distortion can be predicted; tunnel wall effects can be assessed and corrected for; and the effects of model support systems and free stream nonuniformities can be modeled.
Usry, J. W.; Wallace, J. W.
The forebody drag of a supercritical body of revolution was measured in free flight over a Mach number range of 0.85 to 1.05 and a Reynolds number range of 11.5 x 10 to the 6th power to 19.4 x 10 to the 6th power and was compared with wind-tunnel data. The forebody drag coefficient for a Mach number less than 0.96 was 0.111 compared with the wind-tunnel value of 0.103. A gradual increase in the drag occurred in the Langley 8-foot transonic pressure tunnel at a lower Mach number than in the Langley 16-foot transonic tunnel or in the free-flight test. The sharp drag rise occurred near Mach 0.98 in free flight whereas the rise occurred near Mach 0.99 in the Langley 16-foot transonic tunnel. The sharp rise was not as pronounced in the Langley 8-foot transonic pressure tunnel and was probably affected by tunnel-wall-interference effects. The increase occurred more slowly and at a higher Mach number. These results indicate that the drag measurements made in the wind tunnels near Mach 1 were significantly affected by the relative size of the model and the wind tunnel.
Shafer, Jaclyn A.
Warning category winds can adversely impact day-to-day space lift operations at Vandenberg Air Force Base (VAFB) in California. NASA's Launch Services Program and other programs at VAFB use wind forecasts issued by the 30 Operational Support Squadron Weather Flight (30 OSSWF) to determine if they need to limit activities or protect property such as a launch vehicle. The 30 OSSWF tasked the AMU to develop an automated Excel graphical user interface that includes pressure gradient thresholds between specific observing stations under different synoptic regimes to aid forecasters when issuing wind warnings. This required the AMU to determine if relationships between the variables existed.
Li, Feng; Lu, Zhixing; Lan, Yann-Wen; Jiao, Liying; Xu, Minxuan; Zhu, Xiaoyang; Zhang, Xiankun; Wu, Hualin; Qi, Junjie
In this work, the vertical electrical transport behavior of bilayer MoS 2 under the coupling of force and light was explored by the use of conductive atomic force microscopy. We found that the current-voltage behavior across the tip-MoS 2 -Pt junction is a tunneling current that can be well fitted by a Simmons approximation. The transport behavior is direct tunneling at low bias and Fowler-Nordheim tunneling at high bias, and the transition voltage and tunnel barrier height are extracted. The effect of force and light on the effective band gap of the junction is investigated. Furthermore, the source-drain current drops surprisingly when we continually increase the force, and the dropping point is altered by the provided light. This mechanism is responsible for the tuning of tunneling barrier height and width by force and light. These results provide a new way to design devices that take advantage of ultrathin two-dimensional materials. Ultrashort channel length electronic components that possess tunneling current are important for establishing high-efficiency electronic and optoelectronic systems.
Marroquin, J.; Lemoine, P.
An experimental Aerodynamic and Aero-Acoustic loads data base was obtained at transonic Mach numbers for the Space Shuttle Launch Vehicle configured with the ASRM Solid Rocket Boosters as an increment to the current flight configuration (RSRB). These data were obtained during transonic wind tunnel tests (IA 613A) conducted in the Arnold Engineering Development Center 16-Foot transonic propulsion wind tunnel from March 27, 1991 through April 12, 1991. This test is the first of a series of two tests covering the Mach range from 0.6 to 3.5. Steady state surface static and fluctuating pressure distributions over the Orbiter, External Tank and Solid Rocket Boosters of the Shuttle Integrated Vehicle were measured. Total Orbiter forces, Wing forces and Elevon hinge moments were directly measured as well from force balances. Two configurations of Solid Rocket Boosters were tested, the Redesigned Solid Rocket Booster (RSRB) and the Advanced Solid Rocket Motor (ASRM). The effects of the position (i.e. top, bottom, top and bottom) of the Integrated Electronics Assembly (IEA) box, mounted on the SRB attach ring, were obtained on the ASRM configured model. These data were obtained with and without Solid Plume Simulators which, when used, matched as close as possible the flight derived pressures on the Orbiter and External Tank base. Data were obtained at Mach numbers ranging from 0.6 to 1.55 at a Unit Reynolds Number of 2.5 million per foot through model angles of attack from -8 to +4 degrees at sideslip angles of 0, +4 and -4 degrees.
Marroquin, J.; Lemoine, P.
An experimental Aerodynamic and Aero-Acoustic loads data base was obtained at transonic Mach numbers for the Space Shuttle Launch Vehicle configured with the ASRM Solid Rocket Boosters as an increment to the current flight configuration (RSRB). These data were obtained during transonic wind tunnel tests (IA 613A) conducted in the Arnold Engineering Development Center 16-Foot transonic propulsion wind tunnel from March 27, 1991 through April 12, 1991. This test is the first of a series of two tests covering the Mach range from 0.6 to 3.5. Steady state surface static and fluctuating pressure distributions over the Orbiter, External Tank and Solid Rocket Boosters of the Shuttle Integrated Vehicle were measured. Total Orbiter forces, Wing forces and Elevon hinge moments were directly measured as well from force balances. Two configurations of Solid Rocket Boosters were tested, the Redesigned Solid Rocket Booster (RSRB) and the Advanced Solid Rocket Motor (ASRM). The effects of the position (i.e., top, bottom, top and bottom) of the Integrated Electronics Assembly (IEA) box, mounted on the SRB attach ring, were obtained on the ASRM configured model. These data were obtained with and without Solid Plume Simulators which, when used, matched as close as possible the flight derived pressures on the Orbiter and External Tank base. Data were obtained at Mach numbers ranging from 0.6 to 1.55 at a Unit Reynolds Number of 2.5 million per foot through model angles of attack from -8 to +4 degrees at sideslip angles of 0, +4 and -4 degrees.
Caridi, Giuseppe Carlo Alp; Ragni, Daniele; Sciacchitano, Andrea; Scarano, Fulvio
A new system for large-scale tomographic particle image velocimetry in low-speed wind tunnels is presented. The system relies upon the use of sub-millimetre helium-filled soap bubbles as flow tracers, which scatter light with intensity several orders of magnitude higher than micron-sized droplets. With respect to a single bubble generator, the system increases the rate of bubbles emission by means of transient accumulation and rapid release. The governing parameters of the system are identified and discussed, namely the bubbles production rate, the accumulation and release times, the size of the bubble injector and its location with respect to the wind tunnel contraction. The relations between the above parameters, the resulting spatial concentration of tracers and measurement of dynamic spatial range are obtained and discussed. Large-scale experiments are carried out in a large low-speed wind tunnel with 2.85 × 2.85 m2 test section, where a vertical axis wind turbine of 1 m diameter is operated. Time-resolved tomographic PIV measurements are taken over a measurement volume of 40 × 20 × 15 cm3, allowing the quantitative analysis of the tip-vortex structure and dynamical evolution.
Full Text Available Considering the characteristics of wind tunnel tests, a position measurement system that can minimize the effects on the flow of simulated wind must be established. In this study, a motion-capture camera was used to measure the displacement responses of structures in a wind tunnel test, and the applicability of the system was tested. A motion-capture system (MCS could output 3D coordinates using two-dimensional image coordinates obtained from the camera. Furthermore, this remote sensing system had some flexibility regarding lab installation because of its ability to measure at relatively long distances from the target structures. In this study, we performed wind tunnel tests on a pylon specimen and compared the measured responses of the MCS with the displacements measured with a laser displacement sensor (LDS. The results of the comparison revealed that the time-history displacement measurements from the MCS slightly exceeded those of the LDS. In addition, we confirmed the measuring reliability of the MCS by identifying the dynamic properties (natural frequency, damping ratio, and mode shape of the test specimen using system identification methods (frequency domain decomposition, FDD. By comparing the mode shape obtained using the aforementioned methods with that obtained using the LDS, we also confirmed that the MCS could construct a more accurate mode shape (bending-deflection mode shape with the 3D measurements.
Asensio, Carlos; Lozano, Francisco Javier; Gallardo, Pedro; Giménez, Antonio
Wind erosion is a key component of the soil degradation processes. The purpose of this study is to find out the influence of material loss from wind on soil properties for different soil types and changes in soil properties in olive groves when they are tilled. The study area is located in the north of the Tabernas Desert, in the province of Almería, southeastern Spain. It is one of the driest areas in Europe, with a semiarid thermo-Mediterranean type of climate. We used a new wind tunnel model over three different soil types (olive-cropped Calcisol, Cambisol and Luvisol) and studied micro-plot losses and deposits detected by an integrated laser scanner. We also studied the image processing possibilities for examining the particles attached to collector plates located at the end of the tunnel to determine their characteristics and whether they were applicable to the setup. Samples collected in the traps at the end of the tunnel were analyzed. We paid special attention to the influence of organic carbon, carbonate and clay contents because of their special impact on soil crusting and the wind-erodible fraction. A principal components analysis (PCA) was carried out to find any relations on generated dust properties and the intensity and behavior of those relationships. Component 1 separated data with high N and OC contents from samples high in fine silt, CO3= and available K content. Component 2 separated data with high coarse silt and clay contents from data with high fine sand content. Component 3 was an indicator of available P2O5 content. Analysis of variance (ANOVA) was carried out to analyze the effect of soil type and sampling height on different properties of trapped dust. Calculations based on tunnel data showed overestimation of erosion in soil types and calculation of the fraction of soil erodible by wind done by other authors for Spanish soils. As the highest loss was found in Cambisols, mainly due to the effect on soil crusting and the wind
Ben Mosbah, Abdallah
In order to improve the qualities of wind tunnel tests, and the tools used to perform aerodynamic tests on aircraft wings in the wind tunnel, new methodologies were developed and tested on rigid and flexible wings models. A flexible wing concept is consists in replacing a portion (lower and/or upper) of the skin with another flexible portion whose shape can be changed using an actuation system installed inside of the wing. The main purpose of this concept is to improve the aerodynamic performance of the aircraft, and especially to reduce the fuel consumption of the airplane. Numerical and experimental analyses were conducted to develop and test the methodologies proposed in this thesis. To control the flow inside the test sections of the Price-Paidoussis wind tunnel of LARCASE, numerical and experimental analyses were performed. Computational fluid dynamics calculations have been made in order to obtain a database used to develop a new hybrid methodology for wind tunnel calibration. This approach allows controlling the flow in the test section of the Price-Paidoussis wind tunnel. For the fast determination of aerodynamic parameters, new hybrid methodologies were proposed. These methodologies were used to control flight parameters by the calculation of the drag, lift and pitching moment coefficients and by the calculation of the pressure distribution around an airfoil. These aerodynamic coefficients were calculated from the known airflow conditions such as angles of attack, the mach and the Reynolds numbers. In order to modify the shape of the wing skin, electric actuators were installed inside the wing to get the desired shape. These deformations provide optimal profiles according to different flight conditions in order to reduce the fuel consumption. A controller based on neural networks was implemented to obtain desired displacement actuators. A metaheuristic algorithm was used in hybridization with neural networks, and support vector machine approaches and their
Yu, Xinting; Hörst, Sarah M.; He, Chao; Bridges, Nathan T.; Burr, Devon M.; Sebree, Joshua A.; Smith, James K.
Saltation threshold, the minimum wind speed for sediment transport, is a fundamental parameter in aeolian processes. Measuring this threshold using boundary layer wind tunnels, in which particles are mobilized by flowing air, for a subset of different planetary conditions can inform our understanding of physical processes of sediment transport. The presence of liquid, such as water on Earth or methane on Titan, may affect the threshold values to a great extent. Sediment density is also crucial for determining threshold values. Here we provide quantitative data on density and water content of common wind tunnel materials (including chromite, basalt, quartz sand, beach sand, glass beads, gas chromatograph packing materials, walnut shells, iced tea powder, activated charcoal, instant coffee, and glass bubbles) that have been used to study conditions on Earth, Titan, Mars, and Venus. The measured density values for low density materials are higher compared to literature values (e.g., ∼30% for walnut shells), whereas for the high density materials, there is no such discrepancy. We also find that low density materials have much higher water content and longer atmospheric equilibration timescales compared to high density sediments. We used thermogravimetric analysis (TGA) to quantify surface and internal water and found that over 80% of the total water content is surface water for low density materials. In the Titan Wind Tunnel (TWT), where Reynolds number conditions similar to those on Titan can be achieved, we performed threshold experiments with the standard walnut shells (125-150 μm, 7.2% water by mass) and dried walnut shells, in which the water content was reduced to 1.7%. The threshold results for the two scenarios are almost the same, which indicates that humidity had a negligible effect on threshold for walnut shells in this experimental regime. When the water content is lower than 11.0%, the interparticle forces are dominated by adsorption forces, whereas at
Roy, Sukanta; Saha, Ujjwal K.
Highlights: • Significance of the blockage correction in wind tunnel experiments of Savonius-style wind turbine. • Adaptation of blockage factor correlations under open type test sections for blockage ratio of 21.16%. • Effectiveness of adapted correlations for smaller blockage ratios (BRs) of 16% and 12.25%. • Estimate the magnitude of the blockage correction under various loading conditions for each BR. • Variation of blockage correction factor with respect to tip speed ratio and BR. - Abstract: An investigation into the blockage correction effects in wind tunnel experiments of a small-scale wind energy conversion system in an open type test section is carried out. The energy conversion system includes a Savonius-style wind turbine (SSWT) and a power measurement assembly. As the available correlations for the closed type test sections may not be appropriate for the open test section under dynamic loading conditions, new correlations are adapted for the blockage correction factors with free stream wind speed, turbine rotational speed and variable load applied to the turbine to quantify the energy conversion coefficients more precisely. These are obtained for a blockage ratio of 21.16% through a comparison of present experimental data with those of established experimental data under dynamic loading conditions. Further, the accuracy of the adapted correlations is substantiated into the experiments with smaller blockage ratios of 16% and 12.25%. The relationships of the tip speed ratios and blockage ratios with the blockage correction factor are also discussed. Using these correlations, this study provides evidence of increase of blockage correction in the range 1–10% with the increase of both tip speed ratio and blockage ratio. The results also indicate that for blockage ratios approaching 10 and tip speed ratios below 0.5, the blockage effects are almost negligible in the open type test sections
Full Text Available The knowledge of unsteady forces is necessary when designing vertical axis wind turbines (VAWTs. Measurement data for turbines operating at an open site are still very limited. The data obtained from wind tunnels or towing tanks can be used, but have limited applicability when designing large-scale VAWTs. This study presents experimental data on the normal forces of a 12-kW straight-bladed VAWT operated at an open site north of Uppsala, Sweden. The normal forces are measured with four single-axis load cells. The data are obtained for a wide range of tip speed ratios: from 1.7 to 4.6. The behavior of the normal forces is analyzed. The presented data can be used in validations of aerodynamic models and the mechanical design for VAWTs.
de Lucas, Manuela; Ferrer, Miguel; Janss, Guyonne F. E.
Background: Wind farms have shown a spectacular growth during the last 15 years. Avian mortality through collision with moving rotor blades is well-known as one of the main adverse impacts of wind farms. In Spain, the griffon vulture incurs the highest mortality rates in wind farms. Methodology/Principal Findings: As far as we know, this study is the first attempt to predict flight trajectories of birds in order to foresee potentially dangerous areas for wind farm development. We analyse topo...
National Aeronautics and Space Administration — ZONA Technology, Inc. (ZONA) proposes to develop an on-line flutter prediction tool for wind tunnel model using the parameter varying estimation (PVE) technique to...
The patterns of stimulus available to moths flying along pheromone plumes in a 3-m-long wind tunnel were characterized using a high frequency photoionization detector in conjunction with an inert tracer gas...
Schutzenhofer, L. A.; Howard, P. W.
Some exploratory tests were recently performed in the transonic test section of the NASA Marshall Space Flight Center 14-in. wind tunnel to suppress the background noise. In these tests, the perforated walls of the test section were covered with fine wire screens. The screens eliminated the edge tones generated by the holes in the perforated walls and significantly reduced the tunnel background noise. The tunnel noise levels were reduced to such a degree by this simple modification at Mach numbers 0.75, 0.9, 1.1, 1.2, and 1.46 that the fluctuating pressure levels of a turbulent boundary layer could be measured on a 5-deg half-angle cone.
Daryanto, Yanto; Purwono, Joko; Subagyo
Control surface of an Unmanned Aircraft Vehicle (UAV) consists of flap, aileron, spoiler, rudder, and elevator. Every control surface has its own special functionality. Some particular configurations in the flight mission often depend on the wing configuration. Configuration wing within flap deflection for takeoff setting deflection of flap 20° but during landing deflection of flap set on the value 40°. The aim of this research is to get the ultimate CLmax for take-off flap deflection setting. It is shown from Wind Tunnel Testing result that the 20° flap deflection gives optimum CLmax with moderate drag coefficient. The results of Wind Tunnel Testing representing by graphic plots show good performance as well as the stability of UAV.
Aljabri, Abdullah S.
Wind tunnel tests have been conducted on a one-foot diameter model of the SR-7L propfan in the Langley 16-Foot and 4 x 7 Meter Wind Tunnels as part of the Propfan Test Assessment (PTA) Program. The model propfan was sized to be used on a 1/9-scale model of the PTA testbed aircraft. The model propeller was tested in isolation and wing-mounted on the aircraft configuration at various Mach numbers and blade pitch angles. Agreement between data obtained from these tests and data from Hamilton Standard validate that the 1/9-scale propeller accurately simulates the aerodynamics of the SR-7L propfan. Predictions from an analytical computer program are presented and show good agreement with the experimental data.
A study of a force detected single-spin magnetic resonance measurement concept with atomic spatial resolution is presented. The method is based upon electrostatic force detection of spin-selection rule controlled single electron tunneling between two electrically isolated paramagnetic states. Single-spin magnetic resonance detection is possible by measuring the force detected tunneling charge noise on and off spin resonance. Simulation results of this charge noise, based upon physical models of the tunneling and spin physics, are directly compared to measured atomic force microscopy (AFM) system noise. The results show that the approach could provide single-spin measurement of electrically isolated defect states with atomic spatial resolution at room temperature.
Payne, A.; Ambal, K.; Boehme, C.; Williams, C. C.
A study of a force detected single-spin magnetic resonance measurement concept with atomic spatial resolution is presented. The method is based upon electrostatic force detection of spin-selection rule controlled single-electron tunneling between two electrically isolated paramagnetic states. Single-spin magnetic resonance detection is possible by measuring the force detected tunneling charge noise on and off spin resonance. Simulation results of this charge noise, based upon physical models of the tunneling and spin physics, are directly compared to measured atomic force microscopy system noise. The results show that the approach could provide single-spin measurement of electrically isolated qubit states with atomic spatial resolution at room temperature.
Butbul, Jonathan; MacPhee, David; Beyene, Asfaw
Highlights: • A novel flexible VAWT has been experimentally tested alongside numerically simulations. • Using FEA and CFD, direction of blade bending was predicted from inertial and aerodynamic forces. • High-speed camera footage has been used to validate the model. • The flexible VAWT was found to self-start in the majority of tests, while the rigid one did not. • It is suggested that flexible VAWTs can have improved performance in part-load applications. - Abstract: A novel flexible blade concept with the ability to morph and geometrically adapt to changing flow conditions has been proposed to improve part-load performance of horizontal-axis wind turbines. The extension of these benefits to a vertical axis wind turbine would make wind technology a more competitive player in the energy market. Both flexible and rigid wind turbine rotor blades for vertical axis application were modeled, designed, manufactured and tested. Their performances were tested in a low speed wind tunnel. The predicted magnitude and direction of blade morph was validated using a high speed camera as well as finite element analysis. The comparative results of straight rigid and straight morphing blades show that the coefficient of performance greatly depends on the tip speed ratio. Overall, the morphing blade has better performance at low RPMs, but the rigid blade performed better at high RPMs. It was observed that the flexible blade self-started in the majority of the experiments. At high RPM, the centrifugal force overwhelmed the lift force, bending the flexible blade out of phase in an undesired direction increasing drag and therefore reducing the coefficient of performance
Hudişteanu Sebastian Valeriu
Full Text Available The paper presents a wind tunnel experimental analysis of a small-scale building model (1:30. The objective of the study is to determine the wind influence on the ventilation of a double skin façade channel (DSF and the cooling effect over integrated photovoltaic panels. The tests were achieved by conceiving and implementation of an experimental program using a wind tunnel with atmospheric boundary layer. The effect of the wind over the ventilation of the horizontal channels of double skin façades is evaluated for different incident velocities. The results are generalized for the average steady state values of the velocities analysed. The experimental results put in evidence the correlation between the reference wind velocity and the dynamics of the air movement inside the double skin façade. These values are used to determine the convective heat transfer and the cooling effect of the air streams inside the channel upon the integrated photovoltaic panels. The decrease of the photovoltaic panels temperature determines a raise of 11% in efficiency and power generated.
Hudişteanu, Sebastian Valeriu; Popovici, Cătălin George; Cherecheş, Nelu-Cristian
The paper presents a wind tunnel experimental analysis of a small-scale building model (1:30). The objective of the study is to determine the wind influence on the ventilation of a double skin façade channel (DSF) and the cooling effect over integrated photovoltaic panels. The tests were achieved by conceiving and implementation of an experimental program using a wind tunnel with atmospheric boundary layer. The effect of the wind over the ventilation of the horizontal channels of double skin façades is evaluated for different incident velocities. The results are generalized for the average steady state values of the velocities analysed. The experimental results put in evidence the correlation between the reference wind velocity and the dynamics of the air movement inside the double skin façade. These values are used to determine the convective heat transfer and the cooling effect of the air streams inside the channel upon the integrated photovoltaic panels. The decrease of the photovoltaic panels temperature determines a raise of 11% in efficiency and power generated.
Cagle, Christopher M.; Jones, Gregory S.
Circulation Control airfoils have been demonstrated to provide substantial improvements in lift over conventional airfoils. The General Aviation Circular Control model is an attempt to address some of the concerns of this technique. The primary focus is to substantially reduce the amount of air mass flow by implementing unsteady flow. This paper describes a wind tunnel model that implements unsteady circulation control by pulsing internal pneumatic valves and details some preliminary results from the first test entry.
Wiggs, G. F. S.
There are few empirical measurements of velocity, shear velocity, sand transport, morphological change on the windward slopes of dunes.This thesis compares field measurements on a barchan dune in Oman with calculations using a mathematical model (FLOWSTAR) and measurements in a wind tunnel. All three techniques demonstrate similar patterns of velocity, confirming the acceleration of flow up the windward slope, deceleration between the crest and brink and significant flow decele...
Chaloupecká, Hana; Jaňour, Zbyněk; Mikšovský, J.; Jurčáková, Klára; Kellnerová, Radka
Roč. 111, October (2017), s. 194-210 ISSN 0957-5820 R&D Projects: GA ČR GA15-18964S Institutional support: RVO:61388998 Keywords : wind tunnel * short-term gas leakage * puff Subject RIV: DG - Athmosphere Sciences, Meteorology OBOR OECD: Meteorology and atmospheric sciences Impact factor: 2.905, year: 2016 https://www.sciencedirect.com/science/article/pii/S0957582017302203
Wiggs, Giles F. S.; Livingstone, Ian; Warren, Andrew
Field measurements on an unvegetated, 10 m high barchan dune in Oman are compared with measurements over a 1:200 scale fixed model in a wind tunnel. Both the field and wind tunnel data demonstrate similar patterns of wind and shear velocity over the dune, confirming significant flow deceleration upwind of and at the toe of the dune, acceleration of flow up the windward slope, and deceleration between the crest and brink. This pattern, including the widely reported upwind reduction in shear velocity, reflects observations of previous studies. Such a reduction in shear velocity upwind of the dune should result in a reduction in sand transport and subsequent sand deposition. This is not observed in the field. Wind tunnel modelling using a near-surface pulse-wire probe suggests that the field method of shear velocity derivation is inadequate. The wind tunnel results exhibit no reduction in shear velocity upwind of or at the toe of the dune. Evidence provided by Reynolds stress profiles and turbulence intensities measured in the wind tunnel suggest that this maintenance of upwind shear stress may be a result of concave (unstable) streamline curvature. These additional surface stresses are not recorded by the techniques used in the field measurements. Using the occurrence of streamline curvature as a starting point, a new 2-D model of dune dynamics is deduced. This model relies on the establishment of an equilibrium between windward slope morphology, surface stresses induced by streamline curvature, and streamwise acceleration. Adopting the criteria that concave streamline curvature and streamwise acceleration both increase surface shear stress, whereas convex streamline curvature and deceleration have the opposite effect, the relationships between form and process are investigated in each of three morphologically distinct zones: the upwind interdune and concave toe region of the dune, the convex portion of the windward slope, and the crest-brink region. The
Kanazaki, Masahiro; Yokokawa, Yuzuru; Murayama, Mitsuhiro; Ito, Takeshi; Jeong, Shinkyu; Yamamoto, Kazuomi
Design exploration of a nacelle chine installation was carried out. The nacelle chine improves stall performance when deploying multi-element high-lift devices. This study proposes an efficient design process using a Kriging surrogate model to determine the nacelle chine installation point in wind-tunnel tests. The design exploration was conducted in a wind-tunnel using the JAXA high-lift aircraft model at the JAXA Large-scale Low-speed Wind Tunnel. The objective was to maximize the maximum lift. The chine installation points were designed on the engine nacelle in the axial and chord-wise direction, while the geometry of the chine was fixed. In the design process, efficient global optimization (EGO) which includes Kriging model and genetic algorithm (GA) was employed. This method makes it possible both to improve the accuracy of the response surface and to explore the global optimum efficiently. Detailed observations of flowfields using the Particle Image Velocimetry method confirmed the chine effect and design results.
Smith, Stephen C.; Shirakata, Norm; Moes, Timothy R.; Cobleigh, Brent R.; Conners, Timothy H.
A flight experiment has been proposed to investigate the performance of an aerospike rocket motor installed in a lifting body configuration. An SR-71 airplane would be used to carry the aerospike configuration to the desired flight test conditions. Wind-tunnel tests were completed on a 4-percent scale SR-71 airplane with the aerospike pod mounted in various locations on the upper fuselage. Testing was accomplished using sting and blade mounts from Mach 0.6 to Mach 3.2. Initial test objectives included assessing transonic drag and supersonic lateral-directional stability and control. During these tests, flight simulations were run with wind-tunnel data to assess the acceptability of the configurations. Early testing demonstrated that the initial configuration with the aerospike pod near the SR-71 center of gravity was unsuitable because of large nosedown pitching moments at transonic speeds. The excessive trim drag resulting from accommodating this pitching moment far exceeded the excess thrust capability of the airplane. Wind-tunnel testing continued in an attempt to find a configuration suitable for flight test. Multiple configurations were tested. Results indicate that an aft-mounted model configuration possessed acceptable performance, stability, and control characteristics.
Alter, Stephen J.; Brauckmann, Gregory J.; Kleb, William L.; Glass, Christopher E.; Streett, Craig L.; Schuster, David M.
A transonic flow field about a Space Launch System (SLS) configuration was simulated with the Fully Unstructured Three-Dimensional (FUN3D) computational fluid dynamics (CFD) code at wind tunnel conditions. Unsteady, time-accurate computations were performed using second-order Delayed Detached Eddy Simulation (DDES) for up to 1.5 physical seconds. The surface pressure time history was collected at 619 locations, 169 of which matched locations on a 2.5 percent wind tunnel model that was tested in the 11 ft. x 11 ft. test section of the NASA Ames Research Center's Unitary Plan Wind Tunnel. Comparisons between computation and experiment showed that the peak surface pressure RMS level occurs behind the forward attach hardware, and good agreement for frequency and power was obtained in this region. Computational domain, grid resolution, and time step sensitivity studies were performed. These included an investigation of pseudo-time sub-iteration convergence. Using these sensitivity studies and experimental data comparisons, a set of best practices to date have been established for FUN3D simulations for SLS launch vehicle analysis. To the author's knowledge, this is the first time DDES has been used in a systematic approach and establish simulation time needed, to analyze unsteady pressure loads on a space launch vehicle such as the NASA SLS.
Smith, Mark S.
Wind tunnel oscillatory tests in pitch, roll, and yaw were performed on a 19%-scale model of the X-31A aircraft. These tests were used to study the aerodynamic characteristics of the X-31A in response to harmonic oscillations at six frequencies. In-phase and out-of-phase components of the aerodynamic coefficients were obtained over a range of angles of attack from 0 to 90 deg. To account for the effect of frequency on the data, mathematical models with unsteady terms were formulated by use of two different indicial functions. Data from a reduced set of frequencies were used to estimate model parameters, including steady-state static and dynamic stability derivatives. Both models showed good prediction capability and the ability to accurately fit the measured data. Estimated static stability derivatives compared well with those obtained from static wind tunnel tests. The roll and yaw rate derivative estimates were compared with rotary-balanced wind tunnel data and theoretical predictions. The estimates and theoretical predictions were in agreement at small angles of attack. The rotary-balance data showed, in general, acceptable agreement with the steady-state derivative estimates.
Full Text Available Micro fine sized palm oil fuel ash (POFA is a new supplementary cementitious material that can increase the strength, durability, and workability of concrete. However, production of this material incurs high cost and is not practical for the construction industry. This paper investigates a simple methodology of producing micro fine sized POFA by means of a laboratory scale wind tunnel system. The raw POFA obtained from an oil palm factory is first calcined to remove carbon residue and then grinded in Los Angeles abrasion machine. The grinded POFA is then blown in the fabricated wind tunnel system for separation into different ranges of particle sizes. The physical, morphological, and chemical properties of the micro fine sized POFA were then investigated using Laser Particle Size Analyser (PSA, nitrogen sorption, and Scanning Electron Microscopy with Energy Dispersive X-Ray (SEM-EDX. A total of 32.1% micro fine sized POFA were collected from each sample blown, with the size range of 1–10 micrometers. The devised laboratory scale of wind tunnel production system is successful in producing micro fine sized POFA and, with modifications, this system is envisaged applicable to be used to commercialize micro fine sized POFA production for the construction industry.
Alexandru Marius PANAIT
Full Text Available A supersonic and high speed transonic Pitot Prandtl is described as it can be implemented in the Trisonic Wind Tunnel for calibration and verification of Mach number precision. A new calculation method for arbitrary precision Mach numbers is proposed and explained. The probe is specially designed for the Trisonic wind tunnel and would greatly simplify obtaining a precise Mach calibration in the critical high transonic and low supersonic regimes, where typically wind tunnels exhibit poor performance. The supersonic Pitot Prandtl combined probe is well known in the aerospace industry, however the proposed probe is a derivative of the standard configuration, combining a stout cone-cylinder probe with a supersonic Pitot static port which allows this configuration to validate the Mach number by three methods: conical flow method – using the pressure ports on a cone generatrix, the Schlieren-optical method of shock wave angle photogrammetry and the Rayleigh supersonic Pitot equation, while having an aerodynamic blockage similar to that of a scaled rocket model commonly used in testing. The proposed probe uses an existing cone-cylinder probe forebody and support, adding only an afterbody with a support for a static port.
Markova, T. V.; Aksenov, A. A.; Zhluktov, S. V.; Savitsky, D. V.; Gavrilov, A. D.; Son, E. E.; Prokhorov, A. N.
A prospective hypersonic HEXAFLY aircraft is considered in the given paper. In order to obtain the aerodynamic characteristics of a new construction design of the aircraft, experiments with a scaled model have been carried out in a wind tunnel under different conditions. The runs have been performed at different angles of attack with and without hydrogen combustion in the scaled propulsion engine. However, the measured physical quantities do not provide all the information about the flowfield. Numerical simulation can complete the experimental data as well as to reduce the number of wind tunnel experiments. Besides that, reliable CFD software can be used for calculations of the aerodynamic characteristics for any possible design of the full-scale aircraft under different operation conditions. The reliability of the numerical predictions must be confirmed in verification study of the software. The given work is aimed at numerical investigation of the flowfield around and inside the scaled model of the HEXAFLY-CIAM module under wind tunnel conditions. A cold run (without combustion) was selected for this study. The calculations are performed in the FlowVision CFD software. The flow characteristics are compared against the available experimental data. The carried out verification study confirms the capability of the FlowVision CFD software to calculate the flows discussed.
Full Text Available The measurement of position and attitude parameters for the isolated target from a high-speed aircraft is a great challenge in the field of wind tunnel simulation technology. In this paper, firstly, an image acquisition method for small high-speed targets with multi-dimensional movement in wind tunnel environment is proposed based on laser-aided vision technology. Combining with the trajectory simulation of the isolated model, the reasonably distributed laser stripes and self-luminous markers are utilized to capture clear images of the object. Then, after image processing, feature extraction, stereo correspondence and reconstruction, three-dimensional information of laser stripes and self-luminous markers are calculated. Besides, a pose solution method based on projected laser stripes and self-luminous markers is proposed. Finally, simulation experiments on measuring the position and attitude of high-speed rolling targets are conducted, as well as accuracy verification experiments. Experimental results indicate that the proposed method is feasible and efficient for measuring the pose parameters of rolling targets in wind tunnels.
Mudford, Neil R.; O'Byrne, Sean B.; Neely, Andrew J.; Buttsworth, David R.; Balage, Sudantha
Hypersonic wind-tunnel testing with "free-flight" models unconnected to a sting ensures that sting/wake flow interactions do not compromise aerodynamic coefficient measurements. The development of miniaturized electronics has allowed the demonstration of a variant of a new method for the acquisition of hypersonic model motion data using onboard accelerometers, gyroscopes, and a microcontroller. This method is demonstrated in a Mach 6 wind-tunnel flow, whose duration and pitot pressure are sufficient for the model to move a body length or more and turn through a significant angle. The results are compared with those obtained from video analysis of the model motion, the existing method favored for obtaining aerodynamic coefficients in similar hypersonic wind-tunnel facilities. The results from the two methods are in good agreement. The new method shows considerable promise for reliable measurement of aerodynamic coefficients, particularly because the data obtained are in more directly applicable forms of accelerations and rates of turn, rather than the model position and attitude obtained from the earlier visualization method. The ideal may be to have both methods operating together.
Full Text Available High-precision wind tunnel simulation tests play an important role in aircraft design and manufacture. In this study, a high-speed pose vision measurement method is proposed for high-speed and rolling targets in a supersonic wind tunnel. To obtain images with high signal-to-noise ratio and avoid impacts on the aerodynamic shape of the rolling targets, a high-speed image acquisition method based on ultrathin retro-reflection markers is presented. Since markers are small-sized and some of them may be lost when the target is rolling, a novel markers layout with which markers are distributed evenly on the surface is proposed based on a spatial coding method to achieve highly accurate pose information. Additionally, a pose acquisition is carried out according to the mentioned markers layout after removing mismatching points by Case Deletion Diagnostics. Finally, experiments on measuring the pose parameters of high-speed targets in the laboratory and in a supersonic wind tunnel are conducted to verify the feasibility and effectiveness of the proposed method. Experimental results indicate that the position measurement precision is less than 0.16 mm, the pitching and yaw angle precision less than 0.132° and the roll angle precision 0.712°.
Full Text Available The measurement of position and attitude parameters for the isolated target from a high-speed aircraft is a great challenge in the field of wind tunnel simulation technology. This paper proposes a remote-controlled flexible pose measurement system in wind tunnel conditions for the separation of a target from an aircraft. The position and attitude parameters of a moving object are obtained by utilizing a single camera with a focal length and camera orientation that can be changed based on different measurement conditions. Using this proposed system and method, both the flexibility and efficiency of the pose measurement system can be enhanced in wind tunnel conditions to meet the measurement requirements of different objects and experiments, which is also useful for the development of an intelligent position and attitude measurement system. The position and the focal length of the camera also can be controlled remotely during measurements to enlarge both the vertical and horizontal measurement range of this system. Experiments are conducted in the laboratory to measure the position and attitude of moving objects with high flexibility and efficiency, and the measurement precision of the measurement system is also verified through experiments.
Jia, Zhenyuan; Ma, Xin; Liu, Wei; Lu, Wenbo; Li, Xiao; Chen, Ling; Wang, Zhengqu; Cui, Xiaochun
High-precision wind tunnel simulation tests play an important role in aircraft design and manufacture. In this study, a high-speed pose vision measurement method is proposed for high-speed and rolling targets in a supersonic wind tunnel. To obtain images with high signal-to-noise ratio and avoid impacts on the aerodynamic shape of the rolling targets, a high-speed image acquisition method based on ultrathin retro-reflection markers is presented. Since markers are small-sized and some of them may be lost when the target is rolling, a novel markers layout with which markers are distributed evenly on the surface is proposed based on a spatial coding method to achieve highly accurate pose information. Additionally, a pose acquisition is carried out according to the mentioned markers layout after removing mismatching points by Case Deletion Diagnostics. Finally, experiments on measuring the pose parameters of high-speed targets in the laboratory and in a supersonic wind tunnel are conducted to verify the feasibility and effectiveness of the proposed method. Experimental results indicate that the position measurement precision is less than 0.16 mm, the pitching and yaw angle precision less than 0.132° and the roll angle precision 0.712°.
Springer, A. M.
This study was undertaken in MSFC's 14-Inch Trisonic Wind Tunnel to determine if rapid prototyping methods could be used in the design and manufacturing of high speed wind tunnel models in direct testing applications, and if these methods would reduce model design/fabrication time and cost while providing models of high enough fidelity to provide adequate aerodynamic data, and of sufficient strength to survive the test environment. Rapid prototyping methods utilized to construct wind tunnel models in a wing-body-tail configuration were: fused deposition method using both ABS plastic and PEEK as building materials, stereolithography using the photopolymer SL-5170, selective laser sintering using glass reinforced nylon, and laminated object manufacturing using plastic reinforced with glass and 'paper'. This study revealed good agreement between the SLA model, the metal model with an FDM-ABS nose, an SLA nose, and the metal model for most operating conditions, while the FDM-ABS data diverged at higher loading conditions. Data from the initial SLS model showed poor agreement due to problems in post-processing, resulting in a different configuration. A second SLS model was tested and showed relatively good agreement. It can be concluded that rapid prototyping models show promise in preliminary aerodynamic development studies at subsonic, transonic, and supersonic speeds.
Kilgore, R. A.; Dress, D. A.
During the time which has passed since the construction of the first wind tunnel in 1870, wind tunnels have been developed to a high degree of sophistication. However, their development has consistently failed to keep pace with the demands placed on them. One of the more serious problems to be found with existing transonic wind tunnels is their inability to test subscale aircraft models at Reynolds numbers sufficiently near full-scale values to ensure the validity of using the wind tunnel data to predict flight characteristics. The Reynolds number capability of a wind tunnel may be increased by a number of different approaches. However, the best solution in terms of model, balance, and model support loads, as well as in terms of capital and operating cost appears to be related to the reduction of the temperature of the test gas to cryogenic temperatures. The present paper has the objective to review the evolution of the cryogenic wind tunnel concept and to describe its more important advantages.
C. J. Farrugia
Full Text Available The Earth's magnetosphere was very strongly disturbed during the passage of the strong shock and the following interacting ejecta on 21–25 October 2001. These disturbances included two intense storms (Dst*≈−250 and −180 nT, respectively. The cessation of this activity at the start of 24 October ushered in a peculiar state of the magnetosphere which lasted for about 28 h and which we discuss in this paper. The interplanetary field was dominated by the sunward component [B=(4.29±0.77, −0.30±0.71, 0.49±0.45 nT]. We analyze global indicators of geomagnetic disturbances, polar cap precipitation, ground magnetometer records, and ionospheric convection as obtained from SuperDARN radars. The state of the magnetosphere is characterized by the following features: (i generally weak and patchy (in time low-latitude dayside reconnection or reconnection poleward of the cusps; (ii absence of substorms; (iii a monotonic recovery from the previous storm activity (Dst corrected for magnetopause currents decreasing from ~−65 to ~−35 nT, giving an unforced decreased of ~1.1 nT/h; (iv the probable absence of viscous-type interaction originating from the Kelvin-Helmholtz (KH instability; (v a cross-polar cap potential of just 20–30 kV; (vi a persistent, polar cap region containing (vii very weak, and sometimes absent, electron precipitation and no systematic inter-hemisphere asymmetry. Whereas we therefore infer the presence of a moderate amount of open flux, the convection is generally weak and patchy, which we ascribe to the lack of solar wind driver. This magnetospheric state approaches that predicted by Cowley and Lockwood (1992 but has never yet been observed.
Luciana P. Bassi Marinho
Full Text Available The Alcântara Space Center (ASC region has a peculiar topography due to the existence of a coastal cliff, which modifies the atmospheric boundary layer characteristic in a way that can affect rocket launching operations. Wind tunnel measurements can be an important tool for the understanding of turbulence and wind flow pattern characteristics in the ASC neighborhood, along with computational fluid dynamics and observational data. The purpose of this paper is to describe wind tunnel experiments that have been carried out by researchers from the Brazilian Institutions IAE, ITA and INPE. The technologies of Hot-Wire Anemometer and Particle Image Velocimetry (PIV have been used in these measurements, in order to obtain information about wind flow patterns as velocity fields and vorticity. The wind tunnel measurements are described and the results obtained are presented.
Rondeau, Anthony; Sabroux, Jean-Christophe; Chassefière, Eric
thanks to a photovoltaic cell on which the alumina dust was deposited, taking advantage of the well-known loss of efficiency of dusty solar panels (e.g., Spirit Mars Rover before and after a "cleaning event"). The short circuit intensity of the cell being a function of the amount (mg/cm2) of dust deposited, it is possible to determine directly on-line the fraction of dust re-suspended during an experiment in the wind tunnel. Thus, we highlighted two kinds of mechanisms, with a transition region. Above a threshold and at each step increase of airflow velocity, a fraction of the deposit is quickly mobilised (in a few seconds). After a transition gap (approximately two minutes), a low linear increase of the re-suspension fraction is observed. This phenomenon is likely due to random bursts characterizing turbulent airflows. In addition, we brought to light a dust mobilisation mechanism by particle clustering, likely due to the adhesion forces between particles outmatching the adhesion forces between particles and the panel surface. These experimental data will allow to validate a re-suspension model for multi-layer deposits taking into account the effect of low pressure and of dust mobilisation by particles clustering. Reeks, M.W. and Hall, D., 2001. Kinetic models for particle resuspension in turbulent flows: theory and measurement. J. Aerosol Sci., 32: 1-31.
Bui, V. T.; Kalugin, V. T.; Lapygin, V. I.; Khlupnov, A. I.
With the use of ANSYS Fluent software and ANSYS ICEM CFD calculation grid generator, the flows past a wing airfoil, an infinite cylinder, and 3D blunted bodies located in the open and closed test sections of low-speed wind tunnels were calculated. The mathematical model of the flows included the Reynolds equations and the SST model of turbulence. It was found that the ratios between the aerodynamic coefficients in the test section and in the free (unbounded) stream could be fairly well approximated with a piecewise-linear function of the blockage factor, whose value weakly depended on the angle of attack. The calculated data and data gained in the analysis of previously reported experimental studies proved to be in a good agreement. The impact of the extension of the closed test section on the airfoil lift force is analyzed.
Ulbrich, N.; Volden, T.
A new approach is presented that uses a weighted least squares fit to analyze wind tunnel strain-gage balance calibration data. The weighted least squares fit is specifically designed to increase the influence of single-component loadings during the regression analysis. The weighted least squares fit also reduces the impact of calibration load schedule asymmetries on the predicted primary sensitivities of the balance gages. A weighting factor between zero and one is assigned to each calibration data point that depends on a simple count of its intentionally loaded load components or gages. The greater the number of a data point's intentionally loaded load components or gages is, the smaller its weighting factor becomes. The proposed approach is applicable to both the Iterative and Non-Iterative Methods that are used for the analysis of strain-gage balance calibration data in the aerospace testing community. The Iterative Method uses a reasonable estimate of the tare corrected load set as input for the determination of the weighting factors. The Non-Iterative Method, on the other hand, uses gage output differences relative to the natural zeros as input for the determination of the weighting factors. Machine calibration data of a six-component force balance is used to illustrate benefits of the proposed weighted least squares fit. In addition, a detailed derivation of the PRESS residuals associated with a weighted least squares fit is given in the appendices of the paper as this information could not be found in the literature. These PRESS residuals may be needed to evaluate the predictive capabilities of the final regression models that result from a weighted least squares fit of the balance calibration data.
would use the low sweep for carrier landing and subsonic cruise, and use the high sweep for 12 supersonic flight . According to Raymer [19...Wright-Patterson AFB, Ohio: Air Force Institute of Technology, 2005. 12. Katz, Joseph, Shaun Byrne, and Robert Hahl. "Stall Resistance Features of...Lifting-Body Airplane Configurations." Journal of Aircraft 2nd ser. 36 (1999): 471-474. 13. Kress, Robert W. "Variable Sweep Wing Design." AIAA 83
Ashby, George C.
An experimental investigation of the design of pitot probes for flowfield surveys in hypersonic wind tunnels is reported. The results show that a pitot-pressure probe can be miniaturized for minimum interference effects by locating the transducer in the probe support body and water-cooling it so that the pressure-settling time and transducer temperature are compatible with hypersonic tunnel operation and flow conditions. Flowfield surveys around a two-to-one elliptical cone model in a 20-inch Mach 6 wind tunnel using such a probe show that probe interference effects are essentially eliminated.
Accurate control of wind-tunnel test conditions can be dramatically enhanced using feedforward control architectures which allow operating conditions to be maintained at a desired setpoint through the use of mathematical models as the primary source of prediction. However, as the desired accuracy of the feedforward prediction increases, the model complexity also increases, so that an ever increasing computational load is incurred. This drawback can be avoided by employing a neural network that is trained offline using the output of a high fidelity wind-tunnel mathematical model, so that the neural network can rapidly reproduce the predictions of the model with a greatly reduced computational overhead. A novel neural network database generation method, developed through the use of fractional factorial arrays, was employed such that a neural network can accurately predict wind-tunnel parameters across a wide range of operating conditions whilst trained upon a highly efficient database. The subsequent network was incorporated into a Neural Network Model Predictive Control (NNMPC) framework to allow an optimised output schedule capable of providing accurate control of the wind-tunnel operating parameters. Facilitation of an optimised path through the solution space is achieved through the use of a chaos optimisation algorithm such that a more globally optimum solution is likely to be found with less computational expense than the gradient descent method. The parameters associated with the NNMPC such as the control horizon are determined through the use of a Taguchi methodology enabling the minimum number of experiments to be carried out to determine the optimal combination. The resultant NNMPC scheme was employed upon the Hessert Low Speed Wind Tunnel at the University of Notre Dame to control the test-section temperature such that it follows a pre-determined reference trajectory during changes in the test-section velocity. Experimental testing revealed that the
Wang, R.; Williams, C. C., E-mail: email@example.com [Department of Physics and Astronomy, University of Utah, Salt Lake City, Utah 84112 (United States)
Dynamic tunneling force microscopy (DTFM) is a scanning probe technique for real space mapping and characterization of individual electronic trap states in non-conductive films with atomic scale spatial resolution. The method is based upon the quantum mechanical tunneling of a single electron back and forth between a metallic atomic force microscopy tip and individual trap states in completely non-conducting surface. This single electron shuttling is measured by detecting the electrostatic force induced on the probe tip at the shuttling frequency. In this paper, the physical basis for the DTFM method is unfolded through a physical model and a derivation of the dynamic tunneling signal as a function of several experimental parameters is shown. Experimental data are compared with the theoretical simulations, showing quantitative consistency and verifying the physical model used. The experimental system is described and representative imaging results are shown.
Ho, Y. K.; Liu, C. H.
Urban morphology affects the near-ground atmospheric boundary layer that in turn modifies the wind flows and pollutant dispersion over urban areas. A number of numerical models (large-eddy simulation, LES and k-ɛ turbulence models) have been developed to elucidate the transport processes in and above urban street canyons. To complement the modelling results, we initiated a wind tunnel study to examine the influence of idealized urban roughness on the flow characteristics and pollutant dispersion mechanism over 2D idealized street canyons placed in cross flows. Hot-wire anemometry (HWA) was employed in this study to measure the flows over 2D street canyons in the wind tunnel in our university. Particular focus in the beginning stage was on the fabrication of hot-wire probes, data acquisition system, and signal processing technique. Employing the commonly adopted hot-wire universal function, we investigated the relationship in between and developed a scaling factor which could generalize the output of our hot-wire probes to the standardized one as each hot-wire probes has its unique behaviour. Preliminary experiments were performed to measure the wind flows over street canyons of unity aspect ratio. Vertical profiles of the ensemble average velocity and fluctuations at three different segments over the street canyons were collected. The results were then compared with our LES that show a good argument with each other. Additional experiments are undertaken to collect more data in order to formulate the pollutant dispersion mechanism of street canyons and urban areas.
Monbureau, E. M.; Heist, D. K.; Perry, S. G.; Brouwer, L. H.; Foroutan, H.; Tang, W.
Knowing the fate of effluent from an industrial stack is important for assessing its impact on human health. AERMOD is one of several Gaussian plume models containing algorithms to evaluate the effect of buildings on the movement of the effluent from a stack. The goal of this study is to improve AERMOD's ability to accurately model important and complex building downwash scenarios by incorporating knowledge gained from a recently completed series of wind tunnel studies and complementary large eddy simulations of flow and dispersion around simple structures for a variety of building dimensions, stack locations, stack heights, and wind angles. This study presents three modifications to the building downwash algorithm in AERMOD that improve the physical basis and internal consistency of the model, and one modification to AERMOD's building pre-processor to better represent elongated buildings in oblique winds. These modifications are demonstrated to improve the ability of AERMOD to model observed ground-level concentrations in the vicinity of a building for the variety of conditions examined in the wind tunnel and numerical studies.
Safaei Pirooz, Amir A.; Flay, Richard G. J.
We evaluate the accuracy of the speed-up provided in several wind-loading standards by comparison with wind-tunnel measurements and numerical predictions, which are carried out at a nominal scale of 1:500 and full-scale, respectively. Airflow over two- and three-dimensional bell-shaped hills is numerically modelled using the Reynolds-averaged Navier-Stokes method with a pressure-driven atmospheric boundary layer and three different turbulence models. Investigated in detail are the effects of grid size on the speed-up and flow separation, as well as the resulting uncertainties in the numerical simulations. Good agreement is obtained between the numerical prediction of speed-up, as well as the wake region size and location, with that according to large-eddy simulations and the wind-tunnel results. The numerical results demonstrate the ability to predict the airflow over a hill with good accuracy with considerably less computational time than for large-eddy simulation. Numerical simulations for a three-dimensional hill show that the speed-up and the wake region decrease significantly when compared with the flow over two-dimensional hills due to the secondary flow around three-dimensional hills. Different hill slopes and shapes are simulated numerically to investigate the effect of hill profile on the speed-up. In comparison with more peaked hill crests, flat-topped hills have a lower speed-up at the crest up to heights of about half the hill height, for which none of the standards gives entirely satisfactory values of speed-up. Overall, the latest versions of the National Building Code of Canada and the Australian and New Zealand Standard give the best predictions of wind speed over isolated hills.
Suen-Lewis, Emma M.; Barbano, Luke J.; Shrock, Jaron E.; Kaur, Manjit; Schaffner, David A.; Brown, Michael R.
We characterize fluctuations of the line averaged electron density of Taylor states produced by the magnetized coaxial plasma gun of the SSX device using a 632.8 nm HeNe laser interferometer. The analysis method uses the electron density dependence of the refractive index of the plasma to determine the electron density of the Taylor states. Typical magnetic field and density values in the SSX device approach about B ≅ 0.3 T and n = 0 . 4 ×1016 cm-3 . Analysis is improved from previous density measurement methods by developing a post-processing method to remove relative phase error between interferometer outputs and to account for approximately linear phase drift due to low-frequency mechanical vibrations of the interferometer. Precision density measurements coupled with local measurements of the magnetic field will allow us to characterize the wave composition of SSX plasma via density vs. magnetic field correlation analysis, and compare the wave composition of SSX plasma with that of the solar wind. Preliminary results indicate that density and magnetic field appear negatively correlated. Work supported by DOE ARPA-E ALPHA program.
Diepeveen, N.F.B.; Jarquin-Laguna, A.
In this paper the results are presented of experiments to prove an innovative concept for passive torque control of variable speed wind turbines using fluid power technology. It is demonstrated that by correctly configuring the hydraulic drive train, the wind turbine rotor operates at or near
downstream of the nozzle contraction. We used two different hot wire probes: a dual sensor miniature wire probe (Dantec 55P61) and a triple sensor fiber film probe (Dantec 55R91). The turbulence intensity measured with the dual sensor probe in the empty tunnel section was significantly lower than the one...
Klein, Vladislav; Murphy, Patrick C.
Aerodynamic equations were formulated for an aircraft in one-degree-of-freedom large amplitude motion about each of its body axes. The model formulation based on indicial functions separated the resulting aerodynamic forces and moments into static terms, purely rotary terms and unsteady terms. Model identification from experimental data combined stepwise regression and maximum likelihood estimation in a two-stage optimization algorithm that can identify the unsteady term and rotary term if necessary. The identification scheme was applied to oscillatory data in two examples. The model identified from experimental data fit the data well, however, some parameters were estimated with limited accuracy. The resulting model was a good predictor for oscillatory and ramp input data.
Kawakatsu, H. (The University of Tokyo, Tokyo (Japan). Institute of Industrial Science)
It is now about ten years since the scanning tunnel microscope (STM) and the atomic force microscope (AFM) were invented. These microscopes are used very importantly today as a surface analyzer capable of atomic order analysis for their very high resolution. The STM and AFM obtain images of atomic orders by means of mechanical scanning of the probes. This means that the microscopes can control positioning, force detection and displacement in regions of sub-nanometer orders. Examples of researches may include detection of acceleration, length measurement, positioning, force detection, nano-tripology, processing and gravitational wave detection. As described above, this paper notes the researches derived from the operational principles of the STM and AFM, rather than the researches on the observation objects. The great diversity of the researches taken up and the greatness in the number of researches in the STM and AFM gather how superbly germinative these were. 34 refs.
Aoyagi, K.; Aiken, T. N.
Tests were conducted in the Ames 40 by 80 foot wind tunnel to determine the aerodynamic characteristics of a large-scale V/STOL aircraft model with thrust augmentors. The model had a double-delta wing of aspect ratio 1.65 with augmentors located in the wing root and the wing trailing edge. The supply air for the augmentor primary nozzles was provided by the YJ-97 turbojet engine. The airflow was apportioned approximately 74 percent to the wing root augmentor and 24 percent to wing augmentor. Results were obtained at several trailing-edge flap deflections with the nozzle jet-momentum coefficients ranging from 0 to 7.9. Three-component longitudinal data are presented with the agumentor operating with and without the horizontal tail. A limited amount of six component data are also presented.
Full Text Available Wind tunnels usually use long cantilever stings to support aerodynamic models in order to reduce support system flow interference on experimental data. However, such support systems are a potential source of vibration problems which limit the test envelope and affect data quality due to the inherently low structural damping of the systems. When exposed to tunnel flow, turbulence and model flow separation excite resonant Eigenmodes of a sting structure causing large vibrations due to low damping. This paper details the development and experimental evaluation of an active damping system using piezoelectric devices with balance signal feedback both in a lab and a low speed acoustic wind tunnel and presents the control algorithm verification tests with a simple cantilever beam. It is shown that the active damper, controlled separately by both PID and BP neural network, has effectively attenuated the vibration. For sting mode only, 95% reduction of displacement response under exciter stimulation and 98% energy elimination of sting mode frequency have been achieved.
Bossuyt, Juliaan; Meyers, Johan; Howland, Michael F.; Meneveau, Charles
Instrumented small-scale porous disk models are used to study the spectrum of a surrogate for the power output in a micro wind farm with 100 models of wind turbines. The power spectra of individual porous disk models in the first row of the wind farm show the expected -5/3 power law at higher frequencies. Downstream models measure an increased variance due to wake effects. Conversely, the power spectrum of the sum of the power over the entire wind farm shows a peak at the turbine-to-turbine travel frequency between the model turbines, and a near -5/3 power law region at a much wider range of lower frequencies, confirming previous LES results. Comparison with the spectrum that would result when assuming that the signals are uncorrelated, highlights the strong effects of correlations and anti-correlations in the fluctuations at various frequencies. (paper)
Tchatchueng Kammegne, Michel Joel
In order to leave a cleaner environmental space to future generations, the international community has been mobilized to find green solutions that are effective and feasible in all sectors. The CRIAQ MDO505 project was initiated to test the morphing wingtip (wing and aileron) technology as one of these possible solutions. The main objectives of this project are: the design and manufacturing of a morphing wing prototype, the extension and control of the laminar region over the extrados, and to compare the effects of morphing and rigid aileron in terms of lift, drag and pressure distributions. The advantage of the extension of the laminar region over a wing is the drag reduction that results by delaying the transition towards its trailing edge. The location of the transition region depends on the flight case and it is controlled, for a morphing wing, via the actuators positions and displacements. Therefore, this thesis work focuses on the control of the actuators positions and displacements. This thesis presents essentially the modeling, instrumentation and wind tunnel testing results. Three series of wind tunnel tests with different values of aileron deflection angle, angle of attack and Mach number have been performed in the subsonic wind tunnel of the IAR-NRC. The used wing airfoil consisted of stringers, ribs, spars and a flexible upper surface mad of composite materials (glass fiber carbon), a rigid aileron and flexible aileron. The aileron was able to move between +/-6 degrees. The demonstrator's span measures 1.5 m and its chord measures 1.5 m. Structural analyses have been performed to determine the plies orientation, and the number of fiberglass layers for the flexible skin. These analyses allowed also to determine the actuator's forces to push and pull the wing upper surface. The 2D XFoil and 3D solvers Fluent were used to find the optimized airfoil and the optimal location of the transition for each flight case. Based on the analyses done by the
Wind engineering problems are commonly studied by wind tunnel experiments at a reduced scale. This introduces several limitations and calls for a careful planning of the tests and the interpretation of the experimental results. The talk first revisits the similitude laws and discusses how they are actually applied in wind engineering. It will also remind readers why different scaling laws govern in different wind engineering problems. Secondly, the paper focuses on the ways to simplify a detailed structure (bridge, building, platform) when fabricating the downscaled models for the tests. This will be illustrated by several examples from recent engineering projects. Finally, under the most severe weather conditions, manmade structures and equipment should remain operational. What “recreating the climate” means and aims to achieve will be illustrated through common practice in climatic wind tunnel modelling.
Full Text Available This paper presents wind tunnel experiment on two delta wing configurations which are differentiated by their leading edge profiles: sharp and round-edged wings. The experiments were performed as a part of the delta wing aerodynamics research development in Universiti Teknologi Malaysia, low speed tunnel (UTM-LST. Steady load balance and flow visualization tests were conducted at Reynolds numbers of 0.5, 1, and 1.5 × 106, respectively. The flow measurement at low Reynolds number was also performed at as low as speed of 5 m/s. During the experiments, laser with smoke flow visualizations test was performed on both wings. The study has identified interesting features of the interrelationship between the conventional leading edge primary vortex and the occurrence and development of the vortex breakdown above the delta wings. The results conclude the vortex characteristics are largely dependent on the Reynolds number, angle of attack, and leading-edge radii of the wing.
Frink, Neal T.; Allison, Dennis O.; Parikh, Paresh C.
The aim of this work is to demonstrate a simple technique which accounts for aeroelastic deformations experienced by HSR wind-tunnel models within CFD computations. With improved correlations, CFD can become a more effective tool for augmenting the post-test understanding of experimental data. The present technique involves the loose coupling of a low-level structural representation within the ELAPS code, to an unstructured Navier-Stokes flow solver, USM3Dns. The ELAPS model is initially calibrated against bending characteristics of the wind-tunnel model. The strength of this method is that, with a single point calibration of a simple structural representation, the static aeroelastic effects can be accounted for in CFD calculations across a range of test conditions. No prior knowledge of the model deformation during the wind-on test is required. This approach has been successfully applied to the high aspect-ratio planforms of subsonic transports. The current challenge is to adapt the procedure to low aspect-ratio planforms typical of HSR configurations.
Although genetically modified (GM) soybean has never been cultivated commercially in Japan, it is essential to set up the isolation distance required to prevent out-crossing between GM and conventional soybean in preparation for any future possibility of pollen transfer. The airborne soybean pollen was sampled using some Durham pollen samplers located in the range of 20 m from the field edge. In addition, the dispersal distance was assessed in a wind tunnel under constant air flow and then it was compared with the anticipated distances based on the pollen diameter. In the field, the maximum pollen density per day observed was 1.235 grains cm(-2) day(-1) at three observation points within 2.5 m from the field and inside the field the mean density did not reach the rate of 1 grain cm(-2 )day(-1) during 19 flowering days. The results of the wind tunnel experiment also showed that the plants had almost no airborne release of pollen and the dispersal distance was shorter than theoretical value due to clustered dispersal. This study showed little airborne pollen in and around the soybean field and the dispersal is restricted to a small area. Therefore, wind-mediated pollination appears to be negligible.
the modeling of the stall phenomenon which involves very complex aerodynamics. The NREL wind tunnel results were further scrutinized in term of the root flapwise and edgewise bending moments. This allowed to study the dynamics of the NREL blades, at the same time as verifying the consistency between these moments and different loads measured in these tests. Measurements of these moments at the root of the rigid NREL blades in head-on flow showed vibrations corresponding to the two first oscillation modes of the blades, in respectively the flapwise and edgewise directions. These features observed in both an upwind and a downwind configuration were presumed to follow from the presence of the tower. In the downwind configuration, dynamic effects affecting one blade when going through the shadow of the tower were found to be transmitted to the other blade in both the teetered and the rigid configurations. Modelling of the root edgewise and flapwise bending moments was performed by calculating two dynamic estimates based on forces measured respectively along the blade and in the hub region. The simulations generally reproduced the dynamic effects well, and they suggested a systematic error in the measurement of the root flapwise bending moment in the upwind configuration. Inaccuracies in measuring the tangential forces on the blade at high wind speeds were also detected. Offshore wind energy, that is expected to soon lead the development of the wind energy technology, was thereafter studied, where downwind turbines that were given special attention in the dynamic analysis above might reveal themselves as a more adapted solution. The many advantages as well as challenges related to this technology were acknowledged. The status of this technology was investigated in both Europe and North America, and it revealed that Europe is in advance regarding all aspects of wind energy over North America, where it still is at a planning stage. Important plans were however found to exist
Munk, Max M
This report contains the results of a series of tests with three wing models. By changing the section of one of the models and painting the surface of another, the number of models tested was increased to five. The tests were made in order to obtain some general information on the air forces on wing sections at a high Reynolds number and in particular to make sure that the Reynolds number is really the important factor, and not other things like the roughness of the surface and the sharpness of the trailing edge. The few tests described in this report seem to indicate that the air forces at a high Reynolds number are not equivalent to respective air forces at a low Reynolds number (as in an ordinary atmospheric wind tunnel). The drag appears smaller at a high Reynolds number and the maximum lift is increased in some cases. The roughness of the surface and the sharpness of the trailing edge do not materially change the results, so that we feel confident that tests with systematic series of different wing sections will bring consistent results, important and highly useful to the designer.
Propstra, K.; Propstra, K.; van Hulst, N.F.
Photon scanning tunnelling microscopy combined with atomic force microscopy allows simultaneous acquisition and direct comparison of optical and topographical images, both with a lateral resolution of about 30 nm, far beyond the optical diffraction limit. The probe consists of a modified
Borgonjen, E.G.; Borgonjen, E.G.; Moers, M.H.P.; Moers, M.H.P.; Ruiter, A.G.T.; van Hulst, N.F.
A 'stand-alone' Photon Scanning Tunneling Microscope combined with an Atomic force Microscope, using a micro-fabricated silicon-nitride probe, is applied to the imaging of field distribution in integrated optical ridge waveguides. The electric field on the waveguide is locally probed by coupling to
A new vegetation modeling concept for Building and Environmental Aerodynamics wind tunnel investigations was developed. The modeling concept is based on fluid dynamical similarity aspects and allows the small-scale modeling of various kinds of vegetation, e.g. field crops, shrubs, hedges, single trees and forest stands. The applicability of the modeling concept was validated in wind tunnel pollutant dispersion studies. Avenue trees in urban street canyons were modeled and their implications on traffic pollutant dispersion were investigated. The dispersion experiments proved the modeling concept to be practicable for wind tunnel studies and suggested to provide reliable concentration results. Unfavorable effects of trees on pollutant dispersion and natural ventilation in street canyons were revealed. Increased traffic pollutant concentrations were found in comparison to the tree-free reference case. - Highlights: → A concept for aerodynamic modelling of vegetation in small scale wind tunnel studies is presented. → The concept was applied to study pollutant dispersion in urban street canyons with avenue tress. → The wind tunnel studies show that modelling the aerodynamic effects of vegetation is important. → Avenue trees give rise to increased pollutant concentrations in urban street canyons. - Avenue trees in urban street canyons affect the pollutant dispersion and result in increased traffic exhaust concentrations.
Mo, Ziwei; Liu, Chun-Ho
Gaussian plume model is commonly adopted for pollutant concentration prediction in the atmospheric boundary layer (ABL). However, it has a number of limitations being applied to pollutant dispersion over complex land-surface morphology. In this study, the friction factor (f), as a measure of aerodynamic resistance induced by rough surfaces in the engineering community, was proposed to parameterize the vertical dispersion coefficient (σz) in the Gaussian model. A series of wind tunnel experiments were carried out to verify the mathematical hypothesis and to characterize plume dispersion as a function of surface roughness as well. Hypothetical urban areas, which were assembled in the form of idealized street canyons of different aspect (building-height-to-street-width) ratios (AR = 1/2, 1/4, 1/8 and 1/12), were fabricated by aligning identical square aluminum bars at different separation apart in cross flows. Pollutant emitted from a ground-level line source into the turbulent boundary layer (TBL) was simulated using water vapour generated by ultrasonic atomizer. The humidity and the velocity (mean and fluctuating components) were measured, respectively, by humidity sensors and hot-wire anemometry (HWA) with X-wire probes in streamwise and vertical directions. Wind tunnel results showed that the pollutant concentration exhibits the conventional Gaussian distribution, suggesting the feasibility of using water vapour as a passive scalar in wind tunnel experiments. The friction factor increased with decreasing aspect ratios (widening the building separation). It was peaked at AR = 1/8 and decreased thereafter. Besides, a positive correlation between σz/xn (x is the distance from the pollutant source) and f1/4 (correlation coefficient r2 = 0.61) was observed, formulating the basic parameterization of plume dispersion over urban areas.
Fuglsang, P.; Antoniou, I.; Soerensen, N.N.; Madsen, H.A.
This report concerns development and validation of a 2d testing facility for airfoil pressure measurements. The VELUX open jet wind tunnel was used with a test stand inserted. Reynolds numbers until 1.3 million were achieved with an airfoil chord of 0.45 m. The aerodynamic load coefficients were found from pressure distribution measurements and the total drag coefficient was calculated from wake rake measurements. Stationary inflow as well as dynamic inflow through pitching motion was possible. Wind tunnel corrections were applied for streamline curvature and down-wash. Even though the wind tunnel is not ideal for 2d testing, the overall quality of the flow was acceptable with a uniform flow field at the test stand position and a turbulence intensity of 1 % at the inlet of the test section. Reference values for free stream static and total pressure were found upstream of the test stand. The NACA 63-215 airfoil was tested and the results were compared with measurements from FFA and NACA. The measurements agreed well except for lift coefficient values at high angles of attack and the drag coefficient values at low angles of attack, that were slightly high. Comparisons of the measured results with numerical predictions from the XFOIL code and the EllipSys2D code showed good agreement. Measurements with the airfoil in pitching motion were carried out to study the dynamic aerodynamic coefficients. Steady inflow measurements at high angles of attack were used to investigate the double stall phenomenon. (au) EFP-94; EFP-95; EFP-97. 8 tabs., 82 ills., 16 refs.
Fischer, Andreas; Bertagnolio, Franck; Shen, Wen Zhong
A new CFD RANS based method to predict the far field sound pressure emitted from an aerofoil with serrated trailing edge has been developed. The model was validated by comparison to measurements conducted in the Virginia Tech Stability Wind Tunnel. The model predicted 3 dB lower sound pressure...... levels, but the tendencies for the different configurations were predicted correctly. Therefore the model can be used to optimise the serration geometry. A disadvantage of the new model is that the computational costs are significantly higher than for the Amiet model for a straight trailing edge. However...
Full Text Available This paper investigates the temperature control of the heat air-flow wind tunnel for sensor temperature-calibration and heat strength experiment. Firstly, a mathematical model was established to describe the dynamic characteristics of the fuel supplying system based on a variable frequency driving pump. Then, based on the classical cascade control, an improved control law with the Smith predictive estimate and the fuzzy proportional-integral-derivative was proposed. The simulation result shows that the control effect of the proposed control strategy is better than the ordinary proportional-integral-derivative cascade control strategy.
Boom, R.W.; Abdelsalam, M.K.; Bakerek, K.
This paper presents a new design study of a Magnetic Suspension and Balance System (MSBS) for airplane models in a large 8 ft x 8 ft wind tunnel. New developments in the design include: use of a superconducting solenoid as a model core instead of magnetized iron; combination of permanent magnet material in the model wings along with four race-track coils to produce the required roll torque; and mounting of all the magnets in an integral cold structure instead of in separate cryostats. Design of superconducting solenoid model cores and practical experience with a small-scale prototype are discussed
Kuznetsov, Sergeii; Ribičić, Mihael; Pospíšil, Stanislav; Plut, Mihael; Trush, Arsenii; Kozmar, H.
Roč. 41, č. 6 (2017), s. 643-661 ISSN 0732-8818 R&D Projects: GA ČR(CZ) GA14-12892S; GA MŠk(CZ) LO1219 Keywords : turbulent flow * atmospheric boundary layer * wind-tunnel simulation * castellated barrier wall * Counihan vortex generators * surface roughness elements * hot-wire measurements Subject RIV: JM - Building Engineering OBOR OECD: Construction engineering, Municipal and structural engineering Impact factor: 0.932, year: 2016 https://link.springer.com/article/10.1007/s40799-017-0196-z
The background noise level in the 9x15 foot wind tunnel at NASA Glenn has been documented, and the results compare favorably with historical measurements. A study of recessed microphone mounting techniques was also conducted, and a recessed cavity with a micronic wire mesh screen reduces hydrodynamic noise by around 10 dB. A three-microphone signal processing technique can provide additional benefit, rejecting up to 15 dB of noise contamination at some frequencies. The screen and cavity system offers considerable benefit to test efficiency, although there are additional calibration requirements.
Martin, R. M.; Brooks, T. F.; Hoad, D. R.
The NASA-Langley 4 x 7 m wind tunnel develops low frequency flow pulsations at certain velocity ranges during open throat mode operation, affecting the aerodynamics of the flow and degrading the resulting model test data. Triangular vanes attached to the trailing edge of flat steel rails, mounted 10 cm from the inside of the jet exit walls, have been used to reduce this effect; attention is presently given to methods used to reduce the inherent noise generation of the vanes while retaining their pulsation reduction features.
Correaltion of full-scale drag predictions with flight measurements on the C-141A aircraft. Phase 2: Wind tunnel test, analysis, and prediction techniques. Volume 1: Drag predictions, wind tunnel data analysis and correlation
Macwilkinson, D. G.; Blackerby, W. T.; Paterson, J. H.
The degree of cruise drag correlation on the C-141A aircraft is determined between predictions based on wind tunnel test data, and flight test results. An analysis of wind tunnel tests on a 0.0275 scale model at Reynolds number up to 3.05 x 1 million/MAC is reported. Model support interference corrections are evaluated through a series of tests, and fully corrected model data are analyzed to provide details on model component interference factors. It is shown that predicted minimum profile drag for the complete configuration agrees within 0.75% of flight test data, using a wind tunnel extrapolation method based on flat plate skin friction and component shape factors. An alternative method of extrapolation, based on computed profile drag from a subsonic viscous theory, results in a prediction four percent lower than flight test data.
Atencio, A., Jr.; Mckie, J.
A cooperative program between the Royal Aircraft Establishment (RAE), England, and the NASA Ames Research Center was initiated to compare acoustic measurements made in the RAE 24-foot wind tunnel and in the Ames 40- by 80-foot wind tunnel. The acoustic measurements were made in both facilities using the same 102 mm conical nozzle supplied by the RAE. The nozzle was tested by each organization using its respective jet test rig. The mounting hardware and nozzle exit conditions were matched as closely as possible. The data from each wind tunnel were independently analyzed by the respective organization. The results from these tests show good agreement. In both facilities, interference with acoustic measurement is evident at angles in the forward quadrant.
An experiment has been conducted in the NSRDC 7- x 10-foot transonic tunnel for the Sandia Corporation to evaluate various parachute parameters. The experiment consisted of three main parts: the first phase evaluated the disreefing characteristics of the various parachutes as well as the drag forces before, during, and after disreefing; the second phase measured the pressure distribution around the chute as well as the drag forces; and the final phase evaluated the disreefing and drag characteristics of gliding type parachutes. The free stream dynamic pressure varied from 65 to 500 psf. 12 figures, 1 table. (auth)
This thesis investigates particular concepts and technologies that can alleviate fatigue loads on wind turbines by using distributed active aerodynamic devices on the blades, a concept briefly referred to as `smart blades'. Firstly, published research work on smart control devices is reviewed, and
Chassany, J.Ph.; Salaun-Penquer, G.
The tests were carried out in the 3.30 x 2.20 subsonic elliptical wind-tunnel of the Marseille Institute of fluid mechanics, on a 1/1000 scale model measuring 3 m x 3 m. The aerodynamic field developing above the site, made visible by ammonium, hydro-chlorate fumes, and the residues were observed and filmed by means of a synchronised cine-camera with stroboscopic lighting for 4 wind directions. The fall-out from the various waste products was obtained from a spraying of lead acetate solution on the model and hydrogen sulphide emissions. The zones of maximum pollution can be determined from a study of the film taken during the blackening of the spots. (author) [fr
Michel Joël Tchatchueng Kammegne
wing for a specified flight condition. The feasibility and effectiveness of the developed control system by use of a proportional fuzzy feed-forward methodology are demonstrated experimentally through bench and wind tunnel tests of the morphing wing model.
Parajuli, Sagar Prasad; Zobeck, Ted M.; Kocurek, Gary; Yang, Zong-Liang; Stenchikov, Georgiy L.
Numerous parameterizations have been developed for predicting wind erosion, yet the physical mechanism of dust emission is not fully understood. Sandblasting is thought to be the primary mechanism, but recent studies suggest that dust emission by direct aerodynamic entrainment can be significant under certain conditions. In this work, using wind tunnel experiments, we investigated some of the lesser understood aspects of dust emission in sandblasting and aerodynamic entrainment for three soil types, namely clay, silty clay loam, and clay loam. First, we explored the role of erodible surface roughness on dust emitted by aerodynamic entrainment. Second, we compared the emitted dust concentration in sandblasting and aerodynamic entrainment under a range of wind friction velocities. Finally, we explored the sensitivity of emitted dust particle size distribution (PSD) to soil type and wind friction velocity in these two processes. The dust concentration in aerodynamic entrainment showed strong positive correlation, no significant correlation, and weak negative correlation, for the clay, silty clay loam, and clay loam, respectively, with the erodible soil surface roughness. The dust in aerodynamic entrainment was significant constituting up to 28.3, 41.4, and 146.4% compared to sandblasting for the clay, silty clay loam, and clay loam, respectively. PSD of emitted dust was sensitive to soil type in both sandblasting and aerodynamic entrainment. PSD was sensitive to the friction velocity in aerodynamic entrainment but not in sandblasting. Our results highlight the need to consider the details of sandblasting and direct aerodynamic entrainment processes in parameterizing dust emission in global/regional climate models.
Parajuli, Sagar Prasad
Numerous parameterizations have been developed for predicting wind erosion, yet the physical mechanism of dust emission is not fully understood. Sandblasting is thought to be the primary mechanism, but recent studies suggest that dust emission by direct aerodynamic entrainment can be significant under certain conditions. In this work, using wind tunnel experiments, we investigated some of the lesser understood aspects of dust emission in sandblasting and aerodynamic entrainment for three soil types, namely clay, silty clay loam, and clay loam. First, we explored the role of erodible surface roughness on dust emitted by aerodynamic entrainment. Second, we compared the emitted dust concentration in sandblasting and aerodynamic entrainment under a range of wind friction velocities. Finally, we explored the sensitivity of emitted dust particle size distribution (PSD) to soil type and wind friction velocity in these two processes. The dust concentration in aerodynamic entrainment showed strong positive correlation, no significant correlation, and weak negative correlation, for the clay, silty clay loam, and clay loam, respectively, with the erodible soil surface roughness. The dust in aerodynamic entrainment was significant constituting up to 28.3, 41.4, and 146.4% compared to sandblasting for the clay, silty clay loam, and clay loam, respectively. PSD of emitted dust was sensitive to soil type in both sandblasting and aerodynamic entrainment. PSD was sensitive to the friction velocity in aerodynamic entrainment but not in sandblasting. Our results highlight the need to consider the details of sandblasting and direct aerodynamic entrainment processes in parameterizing dust emission in global/regional climate models.
Downey, Austin; Laflamme, Simon; Ubertini, Filippo
Condition evaluation of wind turbine blades is difficult due to their large size, complex geometry and lack of economic and scalable sensing technologies capable of detecting, localizing, and quantifying faults over a blade’s global area. A solution is to deploy inexpensive large area electronics over strategic areas of the monitored component, analogous to sensing skin. The authors have previously proposed a large area electronic consisting of a soft elastomeric capacitor (SEC). The SEC is highly scalable due to its low cost and ease of fabrication, and can, therefore, be used for monitoring large-scale components. A single SEC is a strain sensor that measures the additive strain over a surface. Recently, its application in a hybrid dense sensor network (HDSN) configuration has been studied, where a network of SECs is augmented with a few off-the-shelf strain gauges to measure boundary conditions and decompose the additive strain to obtain unidirectional surface strain maps. These maps can be analyzed to detect, localize, and quantify faults. In this work, we study the performance of the proposed sensing skin at conducting condition evaluation of a wind turbine blade model in an operational environment. Damage in the form of changing boundary conditions and cuts in the monitored substrate are induced into the blade. An HDSN is deployed onto the interior surface of the substrate, and the blade excited in a wind tunnel. Results demonstrate the capability of the HDSN and associated algorithms to detect, localize, and quantify damage. These results show promise for the future deployment of fully integrated sensing skins deployed inside wind turbine blades for condition evaluation.
Shafer, Jaclyn A.; Wheeler, Mark M.
The 30th Operational Support Squadron Weather Flight (30 OSSWF) provides comprehensive weather services to the space program at Vandenberg Air Force Base (VAFB) in California. One of their responsibilities is to monitor upper-level winds to ensure safe launch operations of the Minuteman III ballistic missile. The 30 OSSWF tasked the Applied Meteorology Unit (AMU) to analyze VAFB sounding data with the goal of determining the probability of violating (PoV) their upper-level thresholds for wind speed and shear constraints specific to this launch vehicle, and to develop a tool that will calculate the PoV of each constraint on the day of launch. In order to calculate the probability of exceeding each constraint, the AMU collected and analyzed historical data from VAFB. The historical sounding data were retrieved from the National Oceanic and Atmospheric Administration Earth System Research Laboratory archive for the years 1994-2011 and then stratified into four sub-seasons: January-March, April-June, July-September, and October-December. The maximum wind speed and 1000-ft shear values for each sounding in each subseason were determined. To accurately calculate the PoV, the AMU determined the theoretical distributions that best fit the maximum wind speed and maximum shear datasets. Ultimately it was discovered that the maximum wind speeds follow a Gaussian distribution while the maximum shear values follow a lognormal distribution. These results were applied when calculating the averages and standard deviations needed for the historical and real-time PoV calculations. In addition to the requirements outlined in the original task plan, the AMU also included forecast sounding data from the Rapid Refresh model. This information provides further insight for the launch weather officers (LWOs) when determining if a wind constraint violation will occur over the next few hours on day of launch. The interactive graphical user interface (GUI) for this project was developed in
This dissertation describes the characteristics and the construction of a compact atomic force/scanning tunneling microscope (AFM/STM). The basics and the method of preparing a tunneling junction between a chemically etched tunneling tip and a micro-manufactured cantilever is outlined by analyzing the forces between tunneling tip and cantilever as well as between force-sensing tip and sample surfaces. To our best knowledge this instrument is the first one using a commercial cantilever with only one piezoelectric tube carrying the whole tunneling sensor. The feedback control system has been optimized after a careful analysis of the electronic loop characteristics. The mode of operation has been determined by analyzing the dynamic characteristics of the scan heads and by investigating the time characteristics of the data acquisition system. The vibration isolation system has been calibrated by analyzing the characteristics of the damping setup and the stiffness of the scan head. The calculated results agree well with the measured ones. Also, a software package for data acquisition and real time display as well as for image processing and three-dimensional visualization has been developed. With this home-made software package, the images can be processed by means of a convolution filter, a Wiener filter and other 2-D FFT filters, and can be displayed in different ways. Atomic resolution images of highly oriented pyrolytic graphite (HOPG) and graphite surfaces have been obtained in AFM and STM mode. New theoretical explanations have been given for the observed anomalous STM and AFM images of graphite by calculating the asymmetric distribution of quantum conductance and tip-surface forces on a graphite surface. This not only resolved the theoretical puzzles of STM and AFM of graphite, but also revealed the relation between atomic force microscopy and scanning tunneling microscopy of graphite. Applications of STM and AFM to micro-electronic devices have been investigated
Pena Garcia, Raymundo [Instituto de Investigaciones Electricas, Cuernavaca (Mexico)
The calibration of a wind tunnel is performed in such a way as to warrant a very low turbulence grade. When there is recently built tunnel, as is the case of the IIE`s tunnel, the turbulence in its testing chambers is large; for this reason it is necessary to integrate in it aerodynamic devices and elements capable of reducing it. At the end of the calibration studies can be performed in models with controlled scale. From these and from the results obtained it will be decided if the designed prototypes are built or modified. [Espanol] La calibracion de un tunel de viento se realiza de tal forma que garantiza un grado de turbulencia muy bajo. Cuando se tiene un tunel recien construido, como es el caso del tunel de viento del IIE, la turbulencia en sus camaras de prueba es grande; por lo que es necesario integrarle dispositivos y elementos aerodinamicos que sean capaces de reducirla. Al terminar la calibracion pueden realizarse estudios en modelos con escala controlada. De estos y de los resultados que se obtengan se decidira si se construyen o se modifican los prototipos disenados.
Danehy, Paul M.; Alderfer, David W.; Inman, Jennifer A.; Berger, Karen T.; Buck, Gregory M.; Schwartz, Richard J.
Reentry models for use in hypersonic wind tunnel tests were fabricated using a stereolithography apparatus. These models were produced in one day or less, which is a significant time savings compared to the manufacture of ceramic or metal models. The models were tested in the NASA Langley Research Center 31-Inch Mach 10 Air Tunnel. Only a few of the models survived repeated tests in the tunnel, and several failure modes of the models were identified. Planar laser-induced fluorescence (PLIF) of nitric oxide (NO) was used to visualize the flowfields in the wakes of these models. Pure NO was either seeded through tubes plumbed into the model or via a tube attached to the strut holding the model, which provided localized addition of NO into the model s wake through a porous metal cylinder attached to the end of the tube. Models included several 2- inch diameter Inflatable Reentry Vehicle Experiment (IRVE) models and 5-inch diameter Crew Exploration Vehicle (CEV) models. Various model configurations and NO seeding methods were used, including a new streamwise visualization method based on PLIF. Virtual Diagnostics Interface (ViDI) technology, developed at NASA Langley Research Center, was used to visualize the data sets in post processing. The use of calibration "dotcards" was investigated to correct for camera perspective and lens distortions in the PLIF images.
Pena Garcia, Raymundo [Instituto de Investigaciones Electricas, Cuernavaca (Mexico)
The calibration of a wind tunnel is performed in such a way as to warrant a very low turbulence grade. When there is recently built tunnel, as is the case of the IIE`s tunnel, the turbulence in its testing chambers is large; for this reason it is necessary to integrate in it aerodynamic devices and elements capable of reducing it. At the end of the calibration studies can be performed in models with controlled scale. From these and from the results obtained it will be decided if the designed prototypes are built or modified. [Espanol] La calibracion de un tunel de viento se realiza de tal forma que garantiza un grado de turbulencia muy bajo. Cuando se tiene un tunel recien construido, como es el caso del tunel de viento del IIE, la turbulencia en sus camaras de prueba es grande; por lo que es necesario integrarle dispositivos y elementos aerodinamicos que sean capaces de reducirla. Al terminar la calibracion pueden realizarse estudios en modelos con escala controlada. De estos y de los resultados que se obtengan se decidira si se construyen o se modifican los prototipos disenados.
Allan, Brian G.; Jones, Greg; Lin, John C.
Numerical simulations are performed using a Reynolds-averaged Navier-Stokes (RANS) flow solver for a circulation control airfoil. 2D and 3D simulation results are compared to a circulation control wind tunnel test conducted at the NASA Langley Basic Aerodynamics Research Tunnel (BART). The RANS simulations are compared to a low blowing case with a jet momentum coefficient, C(sub u), of 0:047 and a higher blowing case of 0.115. Three dimensional simulations of the model and tunnel walls show wall effects on the lift and airfoil surface pressures. These wall effects include a 4% decrease of the midspan sectional lift for the C(sub u) 0.115 blowing condition. Simulations comparing the performance of the Spalart Allmaras (SA) and Shear Stress Transport (SST) turbulence models are also made, showing the SST model compares best to the experimental data. A Rotational/Curvature Correction (RCC) to the turbulence model is also evaluated demonstrating an improvement in the CFD predictions.
Sloan, B.; Ebtehaj, A. M.; Guala, M.
The understanding of heat and water vapor transfer from the land surface to the atmosphere by evapotranspiration (ET) is crucial for predicting the hydrologic water balance and climate forecasts used in water resources decision-making. However, the complex distribution of vegetation, soil and atmospheric conditions makes large-scale prognosis of evaporative fluxes difficult. Current ET models, such as Penman-Monteith and flux-gradient methods, are challenging to apply at the microscale due to ambiguity in determining resistance factors to momentum, heat and vapor transport for realistic landscapes. Recent research has made progress in modifying Monin-Obukhov similarity theory for dense plant canopies as well as providing clearer description of diffusive controls on evaporation at a smooth soil surface, which both aid in calculating more accurate resistance parameters. However, in nature, surfaces typically tend to be aerodynamically rough and vegetation is a mixture of sparse and dense canopies in non-uniform configurations. The goal of our work is to parameterize the resistances to evaporation based on spatial distributions of sparse plant canopies using novel wind tunnel experimentation at the St. Anthony Falls Laboratory (SAFL). The state-of-the-art SAFL wind tunnel was updated with a retractable soil box test section (shown in Figure 1), complete with a high-resolution scale and soil moisture/temperature sensors for recording evaporative fluxes and drying fronts. The existing capabilities of the tunnel were used to create incoming non-neutral stability conditions and measure 2-D velocity fields as well as momentum and heat flux profiles through PIV and hotwire anemometry, respectively. Model trees (h = 5 cm) were placed in structured and random configurations based on a probabilistic spacing that was derived from aerial imagery. The novel wind tunnel dataset provides the surface energy budget, turbulence statistics and spatial soil moisture data under varying
Theodore, Colin R.; Russell, Carl R.; Willink, Gina C.; Pete, Ashley E.; Adibi, Sierra A.; Ewert, Adam; Theuns, Lieselotte; Beierle, Connor
An approximately 6-percent scale model of the NASA Second-Generation Large Civil Tiltrotor (LCTR2) Aircraft was tested in the U.S. Army 7- by 10-Foot Wind Tunnel at NASA Ames Research Center January 4 to April 19, 2012, and September 18 to November 1, 2013. The full model was tested, along with modified versions in order to determine the effects of the wing tip extensions and nacelles; the wing was also tested separately in the various configurations. In both cases, the wing and nacelles used were adopted from the U.S. Army High Efficiency Tilt Rotor (HETR) aircraft, in order to limit the cost of the experiment. The full airframe was tested in high-speed cruise and low-speed hover flight conditions, while the wing was tested only in cruise conditions, with Reynolds numbers ranging from 0 to 1.4 million. In all cases, the external scale system of the wind tunnel was used to collect data. Both models were mounted to the scale using two support struts attached underneath the wing; the full airframe model also used a third strut attached at the tail. The collected data provides insight into the performance of the preliminary design of the LCTR2 and will be used for computational fluid dynamics (CFD) validation and the development of flight dynamics simulation models.
Kim, Pilbum; Panesi, Marco; Freund, Jonathan
We study a model arc-heater using direct numerical simulations, in a configuration motivated by its used to generated inflow of a high-speed wind tunnel for hypersonics research. The flow is assumed to be in local thermal equilibrium (LTE) and is modeled with with 11 species (N2, O2, NO, N, O, N2+,O2+,NO+, N+, O+, e-). The flow equations are solved in conjunction with an electrostatic field solver and the gas electric conductivity in LTE. The flow rate and the mean arc power are set to be 50.42 g/s and 84.7 kW with 214.0 V of the mean arc voltage , respectively. We study the flow details, the heading and thrust mechanisms, and make general comparisons with a corresponding, though geometrically more complex, experimental configuration. We particularly interested in the radical species it produces and will potentially be present in the wind-tunnel test section. This material is based in part upon work supported by the Department of Energy, National Nuclear Security Administration, under Award Number DE-NA0002374.
Full Text Available For atmospheric reentries at high enthalpies ablative heat shield materials are used, such as those for probes entering the atmosphere of Saturn’s moon Titan, such as Cassini-Huygens in December, 2004. The characterization of such materials in a nitrogen/methane atmosphere is of interest. A European ablative material, AQ60, has been investigated in plasma wind tunnel tests at the IRS plasma wind tunnel PWK1 using the magnetoplasma dynamic generator RD5 as plasma source in a nitrogen/methane atmosphere. The dimensions of the samples are 45 mm in length with a diameter of 39 mm. The actual ablator has a thickness of 40 mm. The ablator is mounted on an aluminium substructure. The experiments were conducted at two different heat flux regimes, 1.4 MW/m2 and 0.3 MW/m2. In this paper, results of emission spectroscopy at these plasma conditions in terms of plasma species’ temperatures will be presented, including the investigation of the free-stream species, N2 and N2+, and the major erosion product C2, at a wavelength range around 500 nm–600 nm.
Marshall, J.; Bratton, C.; Kosmo, J.; Trevino, R.
Experiments in the Mars Wind Tunnel at NASA Ames Research Center show that under Mars conditions, spacesuit materials are highly susceptible to dust contamination when exposed to windblown soil. This effect was suspected from knowledge of the interaction of electrostatically adhesive dust with solid surfaces in general. However, it is important to evaluate the respective roles of materials, meteorological and radiation effects, and the character of the soil. The tunnel permits evaluation of dust contamination and sand abrasion of space suits by simulating both pressure and wind conditions on Mars. The long-term function of space suits on Mars will be primarily threatened by dust contamination. Lunar EVA activities caused heavy contamination of space suits, but the problem was never seriously manifest because of the brief utilization of the suits, and the suits were never reused. Electrostatically adhering dust grains have various detrimental effects: (1) penetration and subsequent wear of suit fabrics, (2) viewing obscuration through visors and scratching/pitting of visor surfaces, (3) penetration, wear, and subsequent seizing-up of mechanical suit joints, (4) changes in albedo and therefore of radiation properties of external heat-exchanger systems, (5) changes in electrical conductivity of suit surfaces which may affect tribocharging of suits and create spurious discharge effects detrimental to suit electronics/radio systems. Additional information is contained in the original.
Full Text Available Faulty control surface actuator in a small Unmanned Aerial Vehicles (sUAV could be overcome with a few techniques. Redundant actuators, analytical redundancy or combination of both are normally used as fault accommodation techniques. In this paper, the accommodation technique of faulty elevator actuator is presented. This technique uses a standby control surface as temporary control reallocation. Wind tunnel measurement facility is set up for the experimental validation and it is compared with FoilSim software. Flat plate airfoil which was used as horizontal stabilizer, is simulated using numerical model and it is validated using the wind tunnel test. Then, a flat airfoil is designed to be used as stabilator for the recovery of faulty elevator actuator. Results show the different deflection angle is needed when transferring from one control surface to another. From the analysis, the proposed method could be implemented without affecting the pitch stability during control surface transition. The alternate control surface accommodation technique proves to be promising for higher reliability sUAV in the case of a faulty on-board actuator.
Whitmore, Stephen A.; Sprague, Stephanie; Naughton, Jonathan W.; Curry, Robert E. (Technical Monitor)
This paper presents results of wind-tunnel tests that demonstrate a novel drag reduction technique for blunt-based vehicles. For these tests, the forebody roughness of a blunt-based model was modified using micomachined surface overlays. As forebody roughness increases, boundary layer at the model aft thickens and reduces the shearing effect of external flow on the separated flow behind the base region, resulting in reduced base drag. For vehicle configurations with large base drag, existing data predict that a small increment in forebody friction drag will result in a relatively large decrease in base drag. If the added increment in forebody skin drag is optimized with respect to base drag, reducing the total drag of the configuration is possible. The wind-tunnel tests results conclusively demonstrate the existence of a forebody dragbase drag optimal point. The data demonstrate that the base drag coefficient corresponding to the drag minimum lies between 0.225 and 0.275, referenced to the base area. Most importantly, the data show a drag reduction of approximately 15% when the drag optimum is reached. When this drag reduction is scaled to the X-33 base area, drag savings approaching 45,000 N (10,000 lbf) can be realized.
Britcher, C.; Goodyer, M. J.; Scurlock, R. G.; Wu, Y. Y.
The engineering practicality of a persistent high-field superconducting solenoid cryostat as a magnetic suspension and balance system (MSBS) for wind-tunnel testing of aircraft and missile models is examined. The test apparatus is a simple solenoid of filamentary NbTi superconductor with a cupronickel matrix. The apparatus, with a length-to-diameter ratio of 6 to 1 and a radius of 32 mm, used a 0.25 mm wire with a critical current of 27 A in an external field of 6 T. The total heat inleak of 150 mW was achieved. Helium boiloff rates were tested over a range of operating conditions, including pitch attitudes from 10 deg nose down to 90 deg nose up; the rate was estimated as low, but the aerodynamic acceptability of venting gaseous helium has not been determined. It is shown that the effectiveness of the concept increases with increasing scale, and performance in excess of that of conventional ferromagnets is achievable with reduction in size and costs, and with aptness to transonic wind-tunnel testing. Detailed specifications and schematics are included.
Full Text Available In this paper, we propose a simulative experimental system in wind tunnel conditions for the separation of auxiliary fuel tanks from an aircraft. The experimental system consists of a simulative release mechanism, a scaled model and a pose measuring system. A new release mechanism was designed to ensure stability of the separation. Scaled models of the auxiliary fuel tank were designed and their moment of inertia was adjusted by installing counterweights inside the model. Pose parameters of the scaled model were measured and calculated by a binocular vision system. Additionally, in order to achieve high brightness and high signal-to-noise ratio of the images in the dark enclosed wind tunnel, a new high-speed image acquisition method based on miniature self-emitting units was presented. Accuracy of the pose measurement system and repeatability of the separation mechanism were verified in the laboratory. Results show that the position precision of the pose measurement system can reach 0.1 mm, the precision of the pitch and yaw angles is less than 0.1° and that of the roll angle can be up to 0.3°. Besides, repeatability errors of models’ velocity and angular velocity controlled by the release mechanism remain small, satisfying the measurement requirements. Finally, experiments for the separation of auxiliary fuel tanks were conducted in the laboratory.
Kuhlman, J. M.
The aerodynamic design of a wind-tunnel model of a wing representative of that of a subsonic jet transport aircraft, fitted with winglets, was performed using two recently developed optimal wing-design computer programs. Both potential flow codes use a vortex lattice representation of the near-field of the aerodynamic surfaces for determination of the required mean camber surfaces for minimum induced drag, and both codes use far-field induced drag minimization procedures to obtain the required spanloads. One code uses a discrete vortex wake model for this far-field drag computation, while the second uses a 2-D advanced panel wake model. Wing camber shapes for the two codes are very similar, but the resulting winglet camber shapes differ widely. Design techniques and considerations for these two wind-tunnel models are detailed, including a description of the necessary modifications of the design geometry to format it for use by a numerically controlled machine for the actual model construction.
Full Text Available The paper reports on hot wire turbulence intensity measurements performed in the entry of a suction-type wind tunnel, used for investigation of flow-induced vibration of airfoils and slender structures. The airfoil is elastically supported with two degrees of freedom (pitch and plunge in the test section of the wind tunnel with lateral optical access for interferometric measurements, and free to oscillate. The turbulence intensity was measured for velocities up to M = 0.3 i with the airfoil blocked, ii with the airfoil self-oscillating. Measurements were performed for a free inlet and further with two different turbulence grids generating increased turbulence intensity levels. For the free inlet and static airfoil, the turbulence intensity lies below 0.4%. The turbulence grids G1 and G2 increase the turbulence level up to 1.8% and 2.6%, respectively. When the airfoil is free to oscillate due to fluid-structure interaction, its motion disturbs the surrounding flow field and increases the measured turbulence intensity levels up to 5%.
Kovar-Panskus, A.; Moulinneuf, L.; Savory, E.; Abdelqari, A.; Sini, J.-F.; Rosant, J.-M.; Robins, A.; Toy, N.
A wind tunnel study has been undertaken to assess the influence of solar-induced wall heating on the airflow pattern within a street canyon under low-speed wind conditions. This flow is normally dominated by large-scale vortical motion, such that the wind moves downwards at the downstream wall. In the present work the aim has been to examine whether the buoyancy forces generated at this wall by solar-induced heating are of sufficient strength to oppose the downward inertial forces and, thereby, change the canyon flow pattern. Such changes will also influence the dispersion of pollutants within the street. In the experiments the windward-facing wall of a canyon has been uniformly heated to simulate the effect of solar radiation.Four different test cases, representing different degrees of buoyancy (defined by a test Froude number, Fr), have been examined using a simple, 2-D, square-section canyon model in a wind tunnel. For reference purposes, the neutral case (no wall heating), has also been studied. The approach flow boundary layer conditions have been well defined, with the wind normal to the main canyon axis, and measurements have been taken of canyon wall and air temperatures and profiles of mean velocities and turbulence intensities.Analysis of the results shows clear differences in the flow patterns. As Fr decreases from the neutral case there are reductions of up to 50% in the magnitudes of the reverseflow velocities near the ground and in the upward motion near the upstream wall. A marked transition occurs at Fr ∼ 1, where the single dominant vortex, existing at higher Fr values, weakens and moves upwards whilst a lower region of relatively stagnant flow appears. This transition had previously been observed in numerical model predictions but at a Fr at least an order of magnitude higher
Bastankhah, M.; Porté-Agel, F.
Comprehensive wind tunnel experiments were carried out to study the interaction of a turbulent boundary layer with a wind turbine operating under different tip-speed ratios and yaw angles. Force and power measurements were performed to characterize the variation of thrust force (both magnitude and direction) and generated power of the wind turbine under different operating conditions. Moreover, flow measurements, collected using high-resolution particle-image velocimetry as well as hot-wire anemometry, were employed to systematically study the flow in the upwind, near-wake, and far-wake regions. These measurements provide new insights into the effect of turbine operating conditions on flow characteristics in these regions. For the upwind region, the results show a strong lateral asymmetry under yawed conditions. For the near-wake region, the evolution of tip and root vortices was studied with the use of both instantaneous and phase-averaged vorticity fields. The results suggest that the vortex breakdown position cannot be determined based on phase-averaged statistics, particularly for tip vortices under turbulent inflow conditions. Moreover, the measurements in the near-wake region indicate a complex velocity distribution with a speed-up region in the wake center, especially for higher tip-speed ratios. In order to elucidate the meandering tendency of far wakes, particular focus was placed on studying the characteristics of large turbulent structures in the boundary layer and their interaction with wind turbines. Although these structures are elongated in the streamwise direction, their cross sections are found to have a size comparable to the rotor area, so that they can be affected by the presence of the turbine. In addition, the study of spatial coherence in turbine wakes reveals that any statistics based on streamwise velocity fluctuations cannot provide reliable information about the size of large turbulent structures in turbine wakes due to the effect of wake
Nony, Laurent; Bocquet, Franck; Para, Franck; Loppacher, Christian
A combined experimental and theoretical approach to the coupling between frequency-shift (Δ f ) , damping, and tunneling current (It) in combined noncontact atomic force microscopy/scanning tunneling microscopy using quartz tuning forks (QTF)-based probes is reported. When brought into oscillating tunneling conditions, the tip located at the QTF prong's end radiates an electromagnetic field which couples to the QTF prong motion via its piezoelectric tensor and loads its electrodes by induction. Our approach explains how those It-related effects ultimately modify the Δ f and the damping measurements. This paradigm to the origin of the coupling between It and the nc-AFM regular signals relies on both the intrinsic piezoelectric nature of the quartz constituting the QTF and its electrodes design.
Kushner, Laura K.; Drain, Bethany A.; Schairer, Edward T.; Heineck, James T.; Bell, James H.
Both AoA and MDM measurements can be made using an optical system that relies on photogrammetry. Optical measurements are being requested by customers in wind tunnels with increasing frequency due to their non-intrusive nature and recent hardware and software advances that allow measurements to become near real time. The NASA Ames Research Center Unitary Plan Wind Tunnel is currently developing a system based on photogrammetry to measure model deformation and model angle of attack. This paper describes the new system, its development, its use on recent tests and plans to further develop the system.
Bohn, J. G.; Jones, J. E.
The development and use of a digital computer simulation of the proposed wind tunnel facility is described. The feasibility of automatic control of wind tunnel airspeed and other parameters was examined. Specifications and implementation recommendations for a computer based automatic control and monitoring system are presented.
Najafi, Nadia; Paulsen, Uwe Schmidt
This paper is about development and use of a research based stereo vision system for vibration and operational modal analysis on a parked, 1-kW, 3-bladed vertical axis wind turbine (VAWT), tested in a wind tunnel at high wind. Vibrations were explored experimentally by tracking small deflections of the markers on the structure with two cameras, and also numerically, to study structural vibrations in an overall objective to investigate challenges and to prove the capability of using stereo vision. Two high speed cameras provided displacement measurements at no wind speed interference. The displacement time series were obtained using a robust image processing algorithm and analyzed with data-driven stochastic subspace identification (DD-SSI) method. In addition of exploring structural behaviour, the VAWT testing gave us the possibility to study aerodynamic effects at Reynolds number of approximately 2 × 10"5. VAWT dynamics were simulated using HAWC2. The stereo vision results and HAWC2 simulations agree within 4% except for mode 3 and 4. The high aerodynamic damping of one of the blades, in flatwise motion, would explain the gap between those two modes from simulation and stereo vision. A set of conventional sensors, such as accelerometers and strain gauges, are also measuring rotor vibration during the experiment. The spectral analysis of the output signals of the conventional sensors agrees the stereo vision results within 4% except for mode 4 which is due to the inaccuracy of spectral analysis in picking very closely spaced modes. Finally, the uncertainty of the 3D displacement measurement was evaluated by applying a generalized method based on the law of error propagation, for a linear camera model of the stereo vision system. - Highlights: • The stereo vision technique is used to track deflections on a VAWT in the wind tunnel. • OMA is applied on displacement time series to study the dynamic behaviour of the VAWT. • Stereo vision results enabled us to
Erickson, Gary E.
A wind tunnel experiment was conducted in the NASA Langley 8-Foot Transonic Pressure Tunnel to determine the effects of passive porosity on vortex flow interactions about a slender wing configuration at subsonic and transonic speeds. Flow-through porosity was applied in several arrangements to a leading-edge extension, or LEX, mounted to a 65-degree cropped delta wing as a longitudinal instability mitigation technique. Test data were obtained with LEX on and off in the presence of a centerline vertical tail and twin, wing-mounted vertical fins to quantify the sensitivity of the aerodynamics to tail placement and orientation. A close-coupled canard was tested as an alternative to the LEX as a passive flow control device. Wing upper surface static pressure distributions and six-component forces and moments were obtained at Mach numbers of 0.50, 0.85, and 1.20, unit Reynolds number of 2.5 million, angles of attack up to approximately 30 degrees, and angles of sideslip to +/-8 degrees. The off-surface flow field was visualized in cross planes on selected configurations using a laser vapor screen flow visualization technique. Tunnel-to-tunnel data comparisons and a Reynolds number sensitivity assessment were also performed. 15.
Li, Qing'an; Maeda, Takao; Kamada, Yasunari; Murata, Junsuke; Furukawa, Kazuma; Yamamoto, Masayuki
Small wind turbine performance and safety standard for straight-bladed Vertical Axis Wind Turbine (VAWT) have not been developed in the world because of the lack of fundament experimental data. This paper focuses on the evaluation of aerodynamic forces depending on several numbers of blades in wind tunnel experiment. In the present study, the test airfoil of blade is symmetry airfoil of NACA 0021 and the number of blades is from two to five. Pressure acting on the surface of rotor blade is measured during rotation by multiport pressure devices and transmitted to a stationary system through wireless LAN. And then, the aerodynamic forces (tangential force, normal force et al.) are discussed as a function of azimuth angle, achieving a quantitative analysis of the effect of numbers of blades. Finally, the loads are compared with the experimental data of six-component balance. As a result, it is clarified that the power coefficient decreases with the increase of numbers of blades. Furthermore, the power which is absorbed from wind by wind turbine mainly depends on upstream region of azimuth angle of θ = 0°∼180°. In this way, these results are very important for developing the simple design equations and applications for straight-bladed VAWT. - Highlights: • Aerodynamic forces are measured by not only torque meter but also six-component balance. • The pressure distribution on the surface of rotor blade is directly measured by multiport pressure devices. • The power coefficient decreases with the increase of numbers of blades. • The fluctuation amplitudes from six-component balance show larger value than the results of pressure distribution.
Beckwith, I. E.; Spokowski, A. J.; Harvey, W. D.; Stainback, P. C.
The basic theory and sound attenuation mechanisms, the design procedures, and preliminary experimental results are presented for a small axisymmetric sound shield for supersonic wind tunnels. The shield consists of an array of small diameter rods aligned nearly parallel to the entrance flow with small gaps between the rods for boundary layer suction. Results show that at the lowest test Reynolds number (based on rod diameter) of 52,000 the noise shield reduced the test section noise by about 60 percent ( or 8 db attenuation) but no attenuation was measured for the higher range of test reynolds numbers from 73,000 to 190,000. These results are below expectations based on data reported elsewhere on a flat sound shield model. The smaller attenuation from the present tests is attributed to insufficient suction at the gaps to prevent feedback of vacuum manifold noise into the shielded test flow and to insufficient suction to prevent transition of the rod boundary layers to turbulent flow at the higher Reynolds numbers. Schlieren photographs of the flow are shown.
Fisher, David F.; Lanser, Wendy R.
Pressure distributions were obtained at nearly identical fuselage stations and wing chord butt lines in flight on the F-18 HARV at NASA Dryden Flight Research Center and in the NASA Ames Research Center's 80 by 120 ft wind tunnel on a full-scale F/A-18 aircraft. The static pressures were measured at the identical five stations on the forebody, three stations on the left and right leading-edge extensions, and three spanwise stations on the wing. Comparisons of the flight and wind-tunnel pressure distributions were made at alpha = 30 deg, 45 deg, and 60 deg/59 deg. In general, very good agreement was found. Minor differences were noted at the forebody at alpha = 45 deg and 60 deg in the magnitude of the vortex footprints and a Mach number effect was noted at the leading-edge extension at alpha = 30 deg. The inboard leading edge flap data from the wind tunnel at alpha = 59 deg showed a suction peak that did not appear in the flight data. This was the result of a vortex from the corner of the leading edge flap whose path was altered by the lack of an engine simulation in the wind tunnel.
The feasibility of employing thin-film heat-flux gages was studied as a method of defining boundary layer characteristics at supersonic speeds in a high speed blowdown wind tunnel. Flow visualization techniques (using oil) were employed. Tabulated data (computer printouts), a test facility description, and photographs of test equipment are given.
McTaggart and Sav- age  describe model tests conducted on a generic frigate model to determine wind forces influencing ship capsize. Van Manen and van ...Fn will be 0.06. Based on data presented by van Manen and van Oossanen , the fric- tional resistance coefficient will be approximately 0.002 and...Conference on Stability of Ships and Ocean Vehicles (Melbourne, Florida, 1994). 2. J.D. van Manen and P. van Oossanen, Principles of Naval Architecture, Volume
Schepers, J.G.; Boorsma, K. [Energy research Center of the Netherlands ECN, Petten (Netherlands); Cho, T. [Korea Aerospace Research Institute KARI, Daejeon (Korea, Republic of); Gomez-Iradi, S. [National Renewable Energy Center of Spain CENER, Sarriguren (Spain); Schaffarczyk, P. [A. Jeromin University of Applied Sciences, CEWind EG, Kiel (Germany); Shen, W.Z. [The Technical University of Denmark, Kongens Lyngby (Denmark); Lutz, T. [K. Meister University of Stuttgart, Stuttgart (Germany); Stoevesandt, B. [ForWind, Zentrum fuer Windenergieforschung, Oldenburg (Germany); Schreck, S. [National Renewable Energy Laboratory NREL, Golden, CO (United States); Micallef, D.; Pereira, R.; Sant, T. [Delft University of Technology TUD, Delft (Netherlands); Madsen, H.A.; Soerensen, N. [Risoe-DTU, Roskilde (Denmark)
This report describes the work performed within the first phase of IEA Task 29 Mexnext. In this IEA Task 29 a total of 20 organisations from 11 different countries collaborated in analysing the measurements which have been performed in the EU project 'Mexico'. Within this Mexico project 9 European institutes carried out a wind tunnel experiment in the Large Low Speed Facility (LLF) of the German Dutch Wind Facilities DNW on a rotor with a diameter of 4.5 m. Pressure distributions were measured at five locations along the blade along with detailed flow field measurements around the rotor plane using stereo PIV. As a result of the international collaboration within this task a very thorough analysis of the data could be carried out and a large number of codes were validated not only in terms of loads but also in terms of underlying flow field. The detailed pressure measurements along the blade in combination with the detailed flow field measurements gave a unique opportunity to better understand the response of a wind turbine to the incoming flow field. Deficiencies in modelling have been established and directions for model improvement can be given.
Soderman, Paul T.
Background noise levels are measured in the NASA Ames Research Center 40- by 80-Foot Wind Tunnel following installation of a sound-absorbent lining on the test-section walls. Results show that the fan-drive noise dominated the empty test-section background noise at airspeeds below 120 knots. Above 120 knots, the test-section broadband background noise was dominated by wind-induced dipole noise (except at lower harmonics of fan blade-passage tones) most likely generated at the microphone or microphone support strut. Third-octave band and narrow-band spectra are presented for several fan operating conditions and test-section airspeeds. The background noise levels can be reduced by making improvements to the microphone wind screen or support strut. Empirical equations are presented relating variations of fan noise with fan speed or blade-pitch angle. An empirical expression for typical fan noise spectra is also presented. Fan motor electric power consumption is related to the noise generation. Preliminary measurements of sound absorption by the test-section lining indicate that the 152 mm thick lining will adequately absorb test-section model noise at frequencies above 300 Hz.
Smith, Nathanial T.; Heineck, James T.; Schairer, Edward T.
Background oriented Schlieren images have historically been generated by calculating the observed pixel displacement between a wind-on and wind-o image pair using normalized cross-correlation. This work uses optical flow to solve the displacement fields which generate the Schlieren images. A well established method used in the computer vision community, optical flow is the apparent motion in an image sequence due to brightness changes. The regularization method of Horn and Schunck is used to create Schlieren images using two data sets: a supersonic jet plume shock interaction from the NASA Ames Unitary Plan Wind Tunnel, and a transonic flight test of a T-38 aircraft using a naturally occurring background, performed in conjunction with NASA Ames and Armstrong Research Centers. Results are presented and contrasted with those using normalized cross-correlation. The optical flow Schlieren images are found to provided significantly more detail. We apply the method to historical data sets to demonstrate the broad applicability and limitations of the technique.
Rhew, Ray D.; Parker, Peter A.
Measurement systems are typically calibrated based on standard practices established by a metrology standards laboratory, for example the National Institute for Standards and Technology (NIST), or dictated by an organization's metrology manual. Therefore, the calibration is designed and executed according to an established procedure. However, for many aerodynamic research measurement systems a universally accepted standard, traceable approach does not exist. Therefore, a strategy for how to develop a calibration protocol is left to the developer or user to define based on experience and recommended practice in their respective industry. Wind tunnel balances are one such measurement system. Many different calibration systems, load schedules and procedures have been developed for balances with little consensus on a recommended approach. Especially lacking is guidance the number of calibration data points needed. Regrettably, the number of data points tends to be correlated with the perceived quality of the calibration. Often, the number of data points is associated with ones ability to generate the data rather than by a defined need in support of measurement objectives. Hence the title of the paper was conceived to challenge recent observations in the wind tunnel balance community that shows an ever increasing desire for more data points per calibration absent of guidance to determine when there are enough. This paper presents fundamental concepts and theory to aid in the development of calibration procedures for wind tunnel balances and provides a framework that is generally applicable to the characterization and calibration of other measurement systems. Questions that need to be answered are for example: What constitutes an adequate calibration? How much data are needed in the calibration? How good is the calibration? This paper will assist a practitioner in answering these questions by presenting an underlying theory on how to evaluate a calibration based on
This contribution provides the development of a stochastic lift and drag model for an airfoil FX 79-W-151A under unsteady wind inflow based on wind tunnel measurements. Here we present the integration of the stochastic model into a well-known standard BEM (Blade Element Momentum) model to obtain the corresponding aerodynamic forces on a rotating blade element. The stochastic model is integrated as an alternative to static tabulated data used by classical BEM. The results show that in comparison to classical BEM, the BEM with stochastic approach additionally reflects the local force dynamics and therefore provides more information on aerodynamic forces that can be used by wind turbine simulation codes. (author)
Muhammad Ramzan Luhur
Full Text Available This contribution provides the development of a stochastic lift and drag model for an airfoil FX 79-W-151A under unsteady wind inflow based on wind tunnel measurements. Here we present the integration of the stochastic model into a well-known standard BEM (Blade Element Momentum model to obtain the corresponding aerodynamic forces on a rotating blade element. The stochastic model is integrated as an alternative to static tabulated data used by classical BEM. The results show that in comparison to classical BEM, the BEM with stochastic approach additionally reflects the local force dynamics and therefore provides more information on aerodynamic forces that can be used by wind turbine simulation codes
Theodore, Colin R.; Tischler, Mark B.
An automatic rotor trim control system was developed and successfully used during a wind tunnel test of a full-scale UH-60 rotor system with Individual Blade Control (IBC) actuators. The trim control system allowed rotor trim to be set more quickly, precisely and repeatably than in previous wind tunnel tests. This control system also allowed the rotor trim state to be maintained during transients and drift in wind tunnel flow, and through changes in IBC actuation. The ability to maintain a consistent rotor trim state was key to quickly and accurately evaluating the effect of IBC on rotor performance, vibration, noise and loads. This paper presents details of the design and implementation of the trim control system including the rotor system hardware, trim control requirements, and trim control hardware and software implementation. Results are presented showing the effect of IBC on rotor trim and dynamic response, a validation of the rotor dynamic simulation used to calculate the initial control gains and tuning of the control system, and the overall performance of the trim control system during the wind tunnel test.
Full Text Available The first Additive Manufacturing (AM) non-load-bearing, client furnished part was used in the CSIR’s wind tunnels in 2007. The advent of metal-grown materials, and the acquisition of machines to grow them in South Africa, has made it feasible...
Wu, Y. Y.
The design of a horizontal liquid helium cryostat for refrigerating a flying superconducting magnet in a wind tunnel is presented. The basic principles of magnetic suspension theory are described and theoretical calculations of the superconducting magnet are provided. The experimental results of the boil-off of liquid nitrogen and liquid helium in the cryostat are reported.
Jenni-Eiermann, Susanne; Jenni, Lukas; Kvist, Anders; Lindström, Åke; Piersma, Theunis; Visser, G. Henk
This study examines fuel use and metabolism in a group of long-distance migrating birds, red knots Calidris canutus (Scolopacidae), flying under controlled conditions in a wind tunnel for up to 10 h. Data are compared with values for resting birds fasting for the same time. Plasma levels of free
Fuglsang, P.; Bak, Christian; Gaunaa, Mac
This report contains 2D measurements of the Risø-B1-18 and Risø-B1-24 airfoils. The aerodynamic properties were derived from pressure measurements on the airfoil surface and in the wake. The measurements were conducted in the VELUX open jet wind tunnel,which has a background turbulence intensity...
Jwo, Ching-Song; Chien, Zi-Jie; Chen, Yen-Lin; Chien, Chao-Chun
The requirements of providing electric energy through the wind-forced generator to the heat pump for water cooling and hot water heating grow significantly by now. This study proposes a new technique to directly adopt the wind force to drive heat pump systems, which can effectively reduce the energy conversion losses during the processes of wind force energy converting to electric energy and electric energy converting to kinetic energy. The operation of heat pump system transfers between chil...
The deposition of submicron particles on collector plates parallel to the flow was studied experimentally in a wind-tunnel. The validity of a theoretical model based on brownian diffusion was investigated and its Inadequacies tested. The aerosol sample consisted of uranine particles (mean geometrical radius: about 0. 1 μm). The average flow speeds varied from 1 to 10 m/s and the length of the collector plates between 1 and 10 cm. Results showed that capture was mainly due to diffusion and was in good agreement with the theoretical model; however a noticeable deposit of particles on the front part of the collector edge was observed. Sedimentation was insignificant in almost all the cases. (author) [fr
This paper is intended as a tutorial introduction to certain aspects of response surface modeling, for the experimentalist who has started to explore these methods as a means of improving productivity and quality in wind tunnel testing and other aerospace applications. A brief review of the productivity advantages of response surface modeling in aerospace research is followed by a description of the advantages of a common coding scheme that scales and centers independent variables. The benefits of model term reduction are reviewed. A constraint on model term reduction with coded factors is described in some detail, which requires such models to be well-formulated, or hierarchical. Examples illustrate the consequences of ignoring this constraint. The implication for automated regression model reduction procedures is discussed, and some opinions formed from the author s experience are offered on coding, model reduction, and hierarchy.
Klein, Vladislav; Murphy, Patrick C.
A concept of system identification applied to high performance aircraft is introduced followed by a discussion on the identification methodology. Special emphasis is given to model postulation using time invariant and time dependent aerodynamic parameters, model structure determination and parameter estimation using ordinary least squares an mixed estimation methods, At the same time problems of data collinearity detection and its assessment are discussed. These parts of methodology are demonstrated in examples using flight data of the X-29A and X-31A aircraft. In the third example wind tunnel oscillatory data of the F-16XL model are used. A strong dependence of these data on frequency led to the development of models with unsteady aerodynamic terms in the form of indicial functions. The paper is completed by concluding remarks.
Stephens, Julia; Hubbard, Erin; Walter, Joel; McElroy, Tyler
This paper presents methods and results of a detailed measurement uncertainty analysis that was performed for the 8- by 6-foot Supersonic Wind Tunnel located at the NASA Glenn Research Center. The statistical methods and engineering judgments used to estimate elemental uncertainties are described. The Monte Carlo method of propagating uncertainty was selected to determine the uncertainty of calculated variables of interest. A detailed description of the Monte Carlo method as applied for this analysis is provided. Detailed uncertainty results for the uncertainty in average free stream Mach number as well as other variables of interest are provided. All results are presented as random (variation in observed values about a true value), systematic (potential offset between observed and true value), and total (random and systematic combined) uncertainty. The largest sources contributing to uncertainty are determined and potential improvement opportunities for the facility are investigated.
A NACA0015 airfoil section was instrumented with an array of highfrequency microphones mounted on its surface and measured in the wind tunnel at LM Glasfiber at various inflow speeds, angles of attack, and with different turbulent inflow conditions. The aim of this work is to analyze these measurement data, including the turbulent inflow characteristics. The airfoil surface pressure data are considered in the perspective of turbulent inflow noise in order to identify the potential for using these data to validate and possibly improve associated noise models from the literature. In addition, these data are further analyzed in the context of trailing edge noise modeling which is directly related to the surface pressure fluctuations in the vicinity of the trailing edge. (au)
Roeder, James W., Jr.
In early 1996, the ability to run NASA Lewis Research Center's Abe Silverstein 10- by 10- Foot Supersonic Wind Tunnel (10x10) at subsonic test section speeds was reestablished. Taking advantage of this new speed range, a subsonic research test program was scheduled for the 10x10 in the fall of 1996. However, many subsonic aircraft test models require an exhaust source to simulate main engine flow, engine bleed flows, and other phenomena. This was also true of the proposed test model, but at the time the 10x10 did not have a model exhaust capability. So, through an in-house effort over a period of only 5 months, a new model exhaust system was designed, installed, checked out, and made ready in time to support the scheduled test program.
Thompson, R.S. [Environmental Protection Agency, Research Triangle Park, NC (United States)
Surface coal mining operations (blasting, shoveling, loading, trucking, etc.) are sources of airborne particles. The 1990 Clean Air Act Amendments direct the EPA to analyze the accuracy of the Industrial Source Complex model and the AP-42 emission factors, and to make revisions as may be necessary to eliminate any significant over-prediction of air concentration of fugitive particles from surface coal mines. A wind-tunnel study was performed at the US EPA`s Fluid Modeling Facility to investigate dispersion from surface coal mines in support of the dispersion modeling activities. Described here is the portion of the study directed at determining the residence time that material released near the floor of a mine will stay within the mine.
Cassell, Alan M.
The testing of 3- and 6-meter diameter Hypersonic Inflatable Aerodynamic Decelerator (HIAD) test articles was completed in the National Full-Scale Aerodynamics Complex 40 ft x 80 ft Wind Tunnel test section. Both models were stacked tori, constructed as 60 degree half-angle sphere cones. The 3-meter HIAD was tested in two configurations. The first 3-meter configuration utilized an instrumented flexible aerodynamic skin covering the inflatable aeroshell surface, while the second configuration employed a flight-like flexible thermal protection system. The 6-meter HIAD was tested in two structural configurations (with and without an aft-mounted stiffening torus near the shoulder), both utilizing an instrumented aerodynamic skin.
Full Text Available The paper is concerned with numerical modelling of transition in a separated boundary layer. The model of laminar/turbulent transition is based on the combination of empirical terms determining position of the transition and averaged Navier – Stokes equations closed by the k – ω SST turbulence model. The model of transition is applied in computation of 2D flow past NACA63A421 airfoil. Computation is performed using the commercial code ANSYS Fluent 6.3.26, in which the transition method is implemented as a User-Defined-Function. Computed distributions of Cp along the airfoil are verified by comparison with experimental data, which were obtained by measurements in a closed circuit wind tunnel at the constant Reynolds number and several angles of attack. Comparisons prove applicability of the implemented transitional model.
Bilka, M; Anthoine, J; Schram, C
An anechoic wind tunnel dedicated to fan self-noise studies has been designed and constructed at the von Karman Institute The multi-chamber, mass flow driven design allows for all fan performance characteristics, aerodynamic quantities (e.g., wake turbulence measurements), and acoustic properties to be assessed in the same facility with the same conditions. The acoustic chamber performance is assessed using the optimum reference method and found to be within the ISO 3745 standards down to 150 Hz for pure tone and broadband source mechanisms. The additional influence of installation effects of an aerodynamic inlet was found to create a scattered sound field only near the source location, while still providing good anechoic results at more distant sound pressure measurement positions. It was found to have inflow properties, span-wise uniformity, and low turbulence intensity, consistent with those desired for fan self-noise studies. © 2011 Acoustical Society of America
Lund, Ivar; Jensen, Peter Kryger; Miller, Paul
wide surface area with a length of 200 mm. The test was conducted in the wind tunnel at Silsoe Spray Applications Unit in the UK. The measurements consisted of two test series; airborne drift was collected on polyethylene lines more than 375 mm away from the centerline of the nozzle and ground deposits...... and arranged to deliver a pulse of spray using the WeedSeeker valve. The tests were conducted to determine accumulated spray deposit at different crosswind and forward speeds. In general, the deposits, especially those measured downwind close to the target zone showed significant increase as the crosswind......Sensor-based precision weed control system at a high resolution requires a high spray application accuracy to keep the spray in a small target zone. The objective of this research was to investigate the target accuracy and spray drift from individual controlled sprayer nozzles targeting a 250 mm...
Rajkumar, T.; Aragon, Cecilia; Bardina, Jorge; Britten, Roy
A fast, reliable way of predicting aerodynamic coefficients is produced using a neural network optimized by a genetic algorithm. Basic aerodynamic coefficients (e.g. lift, drag, pitching moment) are modelled as functions of angle of attack and Mach number. The neural network is first trained on a relatively rich set of data from wind tunnel tests of numerical simulations to learn an overall model. Most of the aerodynamic parameters can be well-fitted using polynomial functions. A new set of data, which can be relatively sparse, is then supplied to the network to produce a new model consistent with the previous model and the new data. Because the new model interpolates realistically between the sparse test data points, it is suitable for use in piloted simulations. The genetic algorithm is used to choose a neural network architecture to give best results, avoiding over-and under-fitting of the test data.
Bailey, R. O.; Maraz, M. R.; Hiley, P. E.
A wind-tunnel model of a supersonic VSTOL fighter aircraft configuration has been developed for use in the evaluation of airframe-propulsion system aerodynamic interactions. The model may be employed with conventional test techniques, where configuration aerodynamics are measured in a flow-through mode and incremental nozzle-airframe interactions are measured in a jet-effects mode, and with the Compact Multimission Aircraft Propulsion Simulator which is capable of the simultaneous simulation of inlet and exhaust nozzle flow fields so as to allow the evaluation of the extent of inlet and nozzle flow field coupling. The basic configuration of the twin-engine model has a geometrically close-coupled canard and wing, and a moderately short nacelle with nonaxisymmetric vectorable exhaust nozzles near the wing trailing edge, and may be converted to a canardless configuration with an extremely short nacelle. Testing is planned to begin in the summer of 1982.
Amer, Tahani R.; Goad, William K.
Wing-Viewer is a computer program for acquisition and reduction of image data acquired by any of five different scientificgrade commercial electronic cameras used at Langley Research center to observe wind-tunnel models coated with pressure or temperature-sensitive paints (PSP/TSP). Wing-Viewer provides full automation of camera operation and acquisition of image data, and has limited data-preprocessing capability for quick viewing of the results of PSP/TSP test images. Wing- Viewer satisfies a requirement for a standard interface between all the cameras and a single personal computer: Written by use of Microsoft Visual C++ and the Microsoft Foundation Class Library as a framework, Wing-Viewer has the ability to communicate with the C/C++ software libraries that run on the controller circuit cards of all five cameras.
Weick, Fred E; Sanders, Robert
Wind-tunnel tests have been made to find the lift, drag, and center-of-pressure characteristics of a Hall high-lift wing model. The Hall wing is essentially a split-flap airfoil with an internal air passage. Air enters the passage through an opening in the lower surface somewhat back of and parallel to the leading edge, and flows out through an opening made by deflecting the rear portion of the under surface downward as a flap. For ordinary flight conditions the front opening and the rear flap can be closed, providing in effect a conventional airfoil (the Clark Y in this case). The tests were made with various flap settings and with the entrance to the passage both open and closed. The highest lift coefficient found, C(sub L) = 2.08, was obtained with the passage closed.
Scungio, M.; Arpino, F.; Focanti, V.; Profili, M.; Rotondi, M.
Highlights: • Wind tunnel investigations of Darrieus-style VAWT with auxiliary blades have been made. • Results have been compared with those from standard Darrieus VAWT. • Static and dynamic power and torque coefficients were measured and evaluated. • The auxiliary airfoils have demonstrated to give more torque at the lower wind speeds. • The proposed VAWT configuration is able to work in a wide range of wind speeds. - Abstract: Renewable sources of energy, needed because of the increasing price of fossil derivatives, global warming and energy market instabilities, have led to an increasing interest in wind energy. Among the different typologies, small scale Vertical Axis Wind Turbines (VAWT) present the greatest potential for off grid power generation at low wind speeds. In the present work, wind tunnel investigations about the performance of an innovative configuration of straight-blades Darrieus-style vertical axis micro wind turbine, specifically developed for small scale energy conversion at low wind speeds, has been made on scaled models. The micro turbine under investigation consists of three pairs of airfoils. Each pair consists of a main and auxiliary airfoil with different chord lengths. A standard Darrieus configuration, consisting of three single airfoils, was also tested for comparison. The experiments were conducted in a closed circuit open chamber wind tunnel facility available at the Laboratory of Industrial Measurements (LaMI) of the University of Cassino and Lazio Meridionale (UNICLAM). Measured data were reported in terms of dimensionless power and torque coefficients for dynamic performance analysis and static torque coefficient for static performance analysis. The adoption of auxiliary airfoils has demonstrated to give more dynamic torque at the lower wind speeds with respect to a standard Darrieus rotor, resulting in better performance for all the wind speeds considered. In terms of dynamic power coefficient, the standard Darrieus
Evangelista, Raquel; Mcghee, Robert J.; Walker, Betty S.
This paper presents results obtained from two airfoil analysis methods compared with previously published wind tunnel test data at chord Reynolds numbers below 500,000. The analysis methods are from the Eppler-Somers airfoil design/analysis code and from ISES, the Drela-Giles Airfoil design/analysis code. The experimental data are from recent tests of the Eppler 387 airfoil in the NASA Langley Low Turbulence Pressure Tunnel. For R not less than 200,000, lift and pitching moment predictions from both theories compare well with experiment. Drag predictions from both theories also agree with experiment, although to different degrees. However, most of the drag predictions from the Eppler-Somers code are accompanied with separation bubble warnings which indicate that the drag predictions are too low. With the Drela-Giles code, there is a large discrepancy between the computed and experimental pressure distributions in cases with laminar separation bubbles, although the drag polar predictions are similar in trend to experiment.
Full Text Available Design of a Pump Jet Propulsor (PJP was undertaken for an underwater body with axisymmetric configuration using axial flow compressor design techniques supported by Computational Fluid Dynamics (CFD analysis for performance prediction. Experimental evaluation of the PJP was carried out through experiments in a Wind Tunnel Facility (WTF using momentum defect principle for propulsive performance prior to proceeding with extensive experimental evaluation in towing tank and cavitation tunnel. Experiments were particularly conducted with respect to Self Propulsion Point (SPP, residual torque and thrust characteristics over a range of vehicle advance ratio in order to ascertain whether sufficient thrust is developed at the design condition with least possible imbalance torque left out due to residual swirl in the slip stream. Pumpjet and body models were developed for the propulsion tests using Aluminum alloy forged material. Tests were conducted from 0 m/s to 30 m/s at four rotational speeds of the PJP. SPP was determined confirming the thrust development capability of PJP. Estimation of residual torque was carried out at SPP corresponding to speeds of 15, 20 and 25 m/s to examine the effectiveness of the stator. Estimation of thrust and residual torque was also carried out at wind speeds 0 and 6 m/s for PJP RPMs corresponding to self propulsion tests to study the propulsion characteristics during the launch of the vehicle in water where advance ratios are close to Zero. These results are essential to assess the thrust performance at very low advance ratios to accelerate the body and to control the body during initial stages. This technique has turned out to be very useful and economical method for quick assessment of overall performance of the propulsor and generation of exhaustive fluid dynamic data to validate CFD techniques employed.
Korte, John J.
A new procedure which unifies the best of current classical design practices, computational fluid dynamics (CFD), and optimization procedures is demonstrated for designing the aerodynamic lines of hypersonic wind-tunnel nozzles. The new procedure can be used to design hypersonic wind tunnel nozzles with thick boundary layers where the classical design procedure has been shown to break down. An efficient CFD code, which solves the parabolized Navier-Stokes (PNS) equations using an explicit upwind algorithm, is coupled to a least-squares (LS) optimization procedure. A LS problem is formulated to minimize the difference between the computed flow field and the objective function, consisting of the centerline Mach number distribution and the exit Mach number and flow angle profiles. The aerodynamic lines of the nozzle are defined using a cubic spline, the slopes of which are optimized with the design procedure. The advantages of the new procedure are that it allows full use of powerful CFD codes in the design process, solves an optimization problem to determine the new contour, can be used to design new nozzles or improve sections of existing nozzles, and automatically compensates the nozzle contour for viscous effects as part of the unified design procedure. The new procedure is demonstrated by designing two Mach 15, a Mach 12, and a Mach 18 helium nozzles. The flexibility of the procedure is demonstrated by designing the two Mach 15 nozzles using different constraints, the first nozzle for a fixed length and exit diameter and the second nozzle for a fixed length and throat diameter. The computed flow field for the Mach 15 least squares parabolized Navier-Stokes (LS/PNS) designed nozzle is compared with the classically designed nozzle and demonstrates a significant improvement in the flow expansion process and uniform core region.
Ho, Yat-Kiu; Liu, Chun-Ho
Dynamics in the roughness (RSLs) and inertial (ISLs) sublayers in the turbulent boundary layers (TBLs) over idealised urban surfaces are investigated analytically and experimentally. In this paper, we derive an analytical solution to the mean velocity profile, which is a continuous function applicable to both RSL and ISL, over rough surfaces in isothermal conditions. Afterwards, a modified mixing-length model for RSL/ISL transport is developed that elucidates how surface roughness affects the turbulence motions. A series of wind tunnel experiments are conducted to measure the vertical profiles of mean and fluctuating velocities, together with momentum flux over various configurations of surface-mounted ribs in cross flows using hot-wire anemometry (HWA). The analytical solution agrees well with the wind tunnel result that improves the estimate to mean velocity profile over urban surfaces and TBL dynamics as well. The thicknesses of RSL and ISL are calculated by monitoring the convergence/divergence between the temporally averaged and spatio-temporally averaged profiles of momentum flux. It is found that the height of RSL/ISL interface is a function of surface roughness. Examining the direct, physical influence of roughness elements on near-surface RSL flows reveals that the TBL flows over rough surfaces exhibit turbulence motions of two different length scales which are functions of the RSL and ISL structure. Conclusively, given a TBL, the rougher the surface, the higher is the RSL intruding upward that would thinner the ISL up to 50 %. Therefore, the conventional ISL log-law approximation to TBL flows over urban surfaces should be applied with caution.
Gregorio, Fabrizio De
The aim of the present chapter is to consider the use of PIV technique in an industrial icing wind tunnel (IWT) and the potentiality/advantages of applying the PIV technique to this specific field. The purpose of icing wind tunnels is to simulate the aircraft flight condition through cloud formations. In this operational condition ice accretions appear on the aircraft exposed surfaces due to the impact of the water droplets present in the clouds and the subsequent solidification. The investigation of aircraft aerodynamic performances and flight safety in icing condition is a fundamental aspect in the phase of design, development and certification of new aircrafts. The description of this unusual ground testing facility is reported. The assessment of PIV in CIRA-IWT has been investigated. Several technological problems have been afforded and solved by developing the components of the measurement system, such as the laser system and the recording apparatus, both fully remotely controlled, equipped with several traversing mechanism and protected by the adverse environment conditions (temperature and pressure). The adopted solutions are described. Furthermore, a complete test campaign on a full-scale aircraft wing tip, equipped with moving slat and deicing system has been carried out by PIV. Two regions have been investigated. The wing leading-edge (LE) area has been studied with and without ice accretion and for different cloud characteristics. The second activitiy was aimed at the investigation of the wing-wake behavior. The measurements were aimed to characterize the wake for the model in cruise condition without ice formation and during the ice formation.
M. P. van der Laan
Full Text Available The interaction between the Coriolis force and a wind farm wake is investigated by Reynolds-averaged Navier–Stokes simulations, using two different wind farm representations: a high roughness and 5 × 5 actuator disks. Surprisingly, the calculated wind farm wake deflection is the opposite in the two simulations. A momentum balance in the cross flow direction shows that the interaction between the Coriolis force and the 5 × 5 actuator disks is complex due to turbulent mixing of veered momentum from above into the wind farm, which is not observed for the interaction between the Coriolis force and a roughness change. When the wind farm simulations are performed with a horizontally constant Coriolis force in order to isolate the effect of the wind veer, the wind farm wake deflection of the 5 × 5 actuator disks simulation remains unchanged. This proves that the present wind veer deflects the wind farm wake and not the local changes in the Coriolis force in the wake deficit region. An additional simulation of a single actuator disk, operating in a shallow atmospheric boundary layer, confirms that the Coriolis force indirectly turns a wind turbine wake clockwise, as observed from above, due to the presence of a strong wind veer.
Prasad, A. S. Guru; Sharath, U.; Nagarjun, V.; Hegde, G. M.; Asokan, S.
Measurement of temperature and pressure exerted on the leeward surface of a blunt cone specimen has been demonstrated in the present work in a hypersonic wind tunnel using fiber Bragg grating (FBG) sensors. The experiments were conducted on a 30° apex-angle blunt cone with 51 mm base diameter at wind flow speeds of Mach 6.5 and 8.35 in a 300 mm hypersonic wind tunnel of Indian Institute of Science, Bangalore. A special pressure insensitive temperature sensor probe along with the conventional bare FBG sensors was used for explicit temperature and aerodynamic pressure measurement respectively on the leeward surface of the specimen. computational fluid dynamics (CFD) simulation of the flow field around the blunt cone specimen has also been carried out to obtain the temperature and pressure at conditions analogous to experiments. The results obtained from FBG sensors and the CFD simulations are found to be in good agreement with each other.
Guru Prasad, A S; Sharath, U; Asokan, S; Nagarjun, V; Hegde, G M
Measurement of temperature and pressure exerted on the leeward surface of a blunt cone specimen has been demonstrated in the present work in a hypersonic wind tunnel using fiber Bragg grating (FBG) sensors. The experiments were conducted on a 30° apex-angle blunt cone with 51 mm base diameter at wind flow speeds of Mach 6.5 and 8.35 in a 300 mm hypersonic wind tunnel of Indian Institute of Science, Bangalore. A special pressure insensitive temperature sensor probe along with the conventional bare FBG sensors was used for explicit temperature and aerodynamic pressure measurement respectively on the leeward surface of the specimen. computational fluid dynamics (CFD) simulation of the flow field around the blunt cone specimen has also been carried out to obtain the temperature and pressure at conditions analogous to experiments. The results obtained from FBG sensors and the CFD simulations are found to be in good agreement with each other. (paper)
Erickson, Gary E.
The vortex dominated aerodynamic characteristics of a generic 65 degree cropped delta wing model were studied in a wind tunnel at subsonic through supersonic speeds. The lee-side flow fields over the wing-alone configuration and the wing with leading edge extension (LEX) added were observed at M (infinity) equals 0.40 to 1.60 using a laser vapor screen technique. These results were correlated with surface streamline patterns, upper surface static pressure distributions, and six-component forces and moments. The wing-alone exhibited vortex breakdown and asymmetry of the breakdown location at the subsonic and transonic speeds. An earlier onset of vortex breakdown over the wing occurred at transonic speeds due to the interaction of the leading edge vortex with the normal shock wave. The development of a shock wave between the vortex and wing surface caused an early separation of the secondary boundary layer. With the LEX installed, wing vortex breakdown asymmetry did not occur up to the maximum angle of attack in the present test of 24 degrees. The favorable interaction of the LEX vortex with the wing flow field reduced the effects of shock waves on the wing primary and secondary vortical flows. The direct interaction of the wing and LEX vortex cores diminished with increasing Mach number. The maximum attainable vortex-induced pressure signatures were constrained by the vacuum pressure limit at the transonic and supersonic speeds.
Full Text Available The hydrodynamic circulation in estuaries is primarily driven by tides, river inflows and surface winds. While tidal and river data can be quite easily obtained for input to hydrodynamic models, sourcing accurate surface wind data is problematic. Inaccurate wind data can lead to inaccuracies in the surface currents computed by three-dimensional hydrodynamic models. In this research, a high-resolution wind model was coupled with a three-dimensional hydrodynamic model of Galway Bay, a semi-enclosed estuary on the west coast of Ireland, to investigate the effect of wind forcing on model accuracy. Two wind-forcing conditions were investigated: (1 using wind data measured onshore on the NUI Galway campus (NUIG and (2 using offshore wind data provided by a high resolution wind model (HR. A scenario with no wind forcing (NW was also assessed. The onshore wind data varied with time but the speed and direction were applied across the full model domain. The modeled offshore wind fields varied with both time and space. The effect of wind forcing on modeled hydrodynamics was assessed via comparison of modeled surface currents with surface current measurements obtained from a High-Frequency (HF radar Coastal Ocean Dynamics Applications Radar (CODAR observation system. Results indicated that winds were most significant in simulating the north-south surface velocity component. The model using high resolution temporally- and spatially-varying wind data achieved better agreement with the CODAR surface currents than the model using the onshore wind measurements and the model without any wind forcing.
Full Text Available Scour is the result of degradation and aggradation by wind or moving fluid in the front and back of a pole standing in sand, respectively, and is often observed at the bottom of bridge piers in rivers. In this study, we propose a method of estimating the scour depth around a cylindrical structure standing in sand. The relationships among the depth of the scour, the aspect ratio of the structure (= height/diameter, the fluid velocity, and the sand properties (particle size and density were determined experimentally using a wind tunnel. The experiments were carried out under clear-water scour conditions. In the experiments, the aspect ratio of the cylindrical structure, the fluid velocity, and the sand particle size were varied systematically. The diameters of the structure were 20, 40, and 60 mm, and the aspect ratio was varied from 0.25 to 3.0. Sand particles of four sizes (200, 275, 475, and 600 μm were used in the experiment, and the velocity was varied from 4 to 11 m/s. The depth and radius of the scour were measured. As a result, we have developed an equation for estimating the scour depth that uses the aspect ratio, fluid velocity, and sand particle size as parameters.
Stein, Victor P.; Kaltenbach, Hans-Jakob
Wind-tunnel measurements on the near-wake evolution of a three bladed horizontal axis wind turbine model (HAWT) in the scale 1:O(350) operating in uniform flow conditions and within a turbulent boundary layer at different tip speed ratios are presented. Operational conditions are chosen to exclude Reynolds number effects regarding the turbulent boundary layer as well as the rotor performance. Triple-wire anemometry is used to measure all three velocity components in the mid-vertical and mid-horizontal plane, covering the range from the near- to the far-wake region. In order to analyse wake properties systematically, power and thrust coefficients of the turbine were measured additionally. It is confirmed that realistic modelling of the wake evolution is not possible in a low-turbulence uniform approach flow. Profiles of mean velocity and turbulence intensity exhibit large deviations between the low-turbulence uniform flow and the turbulent boundary layer, especially in the far-wake region. For nearly constant thrust coefficients differences in the evolution of the near-wake can be identified for tip speed ratios in the range from 6.5 to 10.5. It is shown that with increasing downstream distances mean velocity profiles become indistinguishable whereas for turbulence statistics a subtle dependency on the tip speed ratio is still noticeable in the far-wake region.
by the wind speed. Darrieus turbines are ordinarily inexpensive and are used for electricity generation and irrigation. One advantage to a...AN EVALUATION OF WIND TURBINE TECHNOLOGY...02 AN EVALUATION OF WIND TURBINE TECHNOLOGY AT PETERSON AIR FORCE BASE THESIS Presented to the Faculty Department of
Sydnor, Goerge H.
The National Aeronautics and Space Administration's (NASA) Aeronautics Test Program (ATP) is implementing five significant ground-based test facility projects across the nation with funding provided by the American Recovery and Reinvestment Act (ARRA). The projects were selected as the best candidates within the constraints of the ARRA and the strategic plan of ATP. They are a combination of much-needed large scale maintenance, reliability, and system upgrades plus creating new test beds for upcoming research programs. The projects are: 1.) Re-activation of a large compressor to provide a second source for compressed air and vacuum to the Unitary Plan Wind Tunnel at the Ames Research Center (ARC) 2.) Addition of high-altitude ice crystal generation at the Glenn Research Center Propulsion Systems Laboratory Test Cell 3, 3.) New refrigeration system and tunnel heat exchanger for the Icing Research Tunnel at the Glenn Research Center, 4.) Technical viability improvements for the National Transonic Facility at the Langley Research Center, and 5.) Modifications to conduct Environmentally Responsible Aviation and Rotorcraft research at the 14 x 22 Subsonic Tunnel at Langley Research Center. The selection rationale, problem statement, and technical solution summary for each project is given here. The benefits and challenges of the ARRA funded projects are discussed. Indirectly, this opportunity provides the advantages of developing experience in NASA's workforce in large projects and maintaining corporate knowledge in that very unique capability. It is envisioned that improved facilities will attract a larger user base and capabilities that are needed for current and future research efforts will offer revenue growth and future operations stability. Several of the chosen projects will maximize wind tunnel reliability and maintainability by using newer, proven technologies in place of older and obsolete equipment and processes. The projects will meet NASA's goal of
Kim, Dae-Kwan; Han, Jae-Hung; Kwon, Ki-Jung
In the present study, a biomimetic flexible flapping wing was developed on a real ornithopter scale by using macro-fiber composite (MFC) actuators. With the actuators, the maximum camber of the wing can be linearly changed from −2.6% to +4.4% of the maximum chord length. Aerodynamic tests were carried out in a low-speed wind tunnel to investigate the aerodynamic characteristics, particularly the camber effect, the chordwise flexibility effect and the unsteady effect. Although the chordwise wing flexibility reduces the effective angle of attack, the maximum lift coefficient can be increased by the MFC actuators up to 24.4% in a static condition. Note also that the mean values of the perpendicular force coefficient rise to a value of considerably more than 3 in an unsteady aerodynamic flow region. Additionally, particle image velocimetry (PIV) tests were performed in static and dynamic test conditions to validate the flexibility and unsteady effects. The static PIV results confirm that the effective angle of attack is reduced by the coupling of the chordwise flexibility and the aerodynamic force, resulting in a delay in the stall phenomena. In contrast to the quasi-steady flow condition of a relatively high advance ratio, the unsteady aerodynamic effect due to a leading edge vortex can be found along the wing span in a low advance ratio region. The overall results show that the chordwise wing flexibility can produce a positive effect on flapping aerodynamic characteristics in quasi-steady and unsteady flow regions; thus, wing flexibility should be considered in the design of efficient flapping wings
Réthoré, Pierre-Elouan; Sørensen, Niels N.
at the position of the wind turbine rotor to estimate correctly the power production and the rotor loading. The method proposed in this paper solves this issue by spreading the force on the direct neighbouring cells and applying an equivalent pressure jump at the cell faces. This can potentially open......This paper describes an algorithm for allocating discrete forces in computational fluid dynamics (CFD). Discrete forces are useful in wind energy CFD. They are used as an approximation of the wind turbine blades’ action on the wind (actuator disc/line), to model forests and to model turbulent...
Zhang, Ye; Van Zuijlen, Alexander; Van Bussel, Gerard
In this paper, three dimensional flow over non-rotating MEXICO blades is simulated by CFD methods. The numerical results are compared with the latest MEXICO wind turbine blades measurements obtained in the low speed low turbulence (LTT) wind tunnel of Delft University of Technology. This study aims to validate CFD codes by using these experimental data measured in well controlled conditions. In order to avoid use of wind tunnel corrections, both the blades and the wind tunnel test section are modelled in the simulations. The ability of Menter's k – ω shear stress transport (SST) turbulence model is investigated at both attached flow and massively separated flow cases. Steady state Reynolds averaged Navier Stokes (RANS) equations are solved in these computations. The pressure distribution at three measured sections are compared under the conditions of different inflow velocities and a range of angles of attack. The comparison shows that at attached flow condition, good agreement can be obtained for all three airfoil sections. Even with massively separated flow, still fairly good pressure distribution comparison can be found for the DU and NACA airfoil sections, although the RISØ section shows poor comparison. At the near stall case, considerable deviations exists on the forward half part of the upper surface for all three sections
Michael L. Whiteman
Full Text Available This paper explores the use of a cyber-physical systems (CPS “loop-in-the-model” approach to optimally design the envelope and structural system of low-rise buildings subject to wind loads. Both the components and cladding (C&C and the main wind force resisting system (MWFRS are considered through multi-objective optimization. The CPS approach combines the physical accuracy of wind tunnel testing and efficiency of numerical optimization algorithms to obtain an optimal design. The approach is autonomous: experiments are executed in a boundary layer wind tunnel (BLWT, sensor feedback is monitored and analyzed by a computer, and optimization algorithms dictate physical changes to the structural model in the BLWT through actuators. To explore a CPS approach to multi-objective optimization, a low-rise building with a parapet wall of variable height is considered. In the BLWT, servo-motors are used to adjust the parapet to a particular height. Parapet walls alter the location of the roof corner vortices, reducing suction loads on the windward facing roof corners and edges, a C&C design load. At the same time, parapet walls increase the surface area of the building, leading to an increase in demand on the MWFRS. A combination of non-stochastic and stochastic optimization algorithms were implemented to minimize the magnitude of suction and positive pressures on the roof of a low-rise building model, followed by stochastic multi-objective optimization to simultaneously minimize the magnitude of suction pressures and base shear. Experiments were conducted at the University of Florida Experimental Facility (UFEF of the National Science Foundation’s (NSF Natural Hazard Engineering Research Infrastructure (NHERI program.
Hoad, D. R.; Martin, R. M.
Many open jet wind tunnels experience pulsations of the flow which are typically characterized by periodic low frequency velocity and pressure variations. One method of reducing these fluctuations is to install vanes around the perimeter of the jet exit to protrude into the flow. Although these vanes were shown to be effective in reducing the fluctuation content, they can also increase the test section background noise level. The results of an experimental acoustic program in the Langley 4- by 7-Meter Tunnel is presented which evaluates the effect on tunnel background noise of such modifications to the jet exit nozzle. Noise levels for the baseline tunnel configuration are compared with those for three jet exit nozzle modifications, including an enhanced noise reduction configuration that minimizes the effect of the vanes on the background noise. Although the noise levels for this modified vane configuration were comparable to baseline tunnel background noise levels in this facility, installation of these modified vanes in an acoustic tunnel may be of concern because the noise levels for the vanes could be well above background noise levels in a quiet facility.
McCluer, Megan S.; Johnson, Jeffrey L.; Rutkowski, Michael (Technical Monitor)
Most helicopter data trends cannot be extrapolated to tiltrotors because blade geometry and aerodynamic behavior, as well as rotor and fuselage interactions, are significantly different for tiltrotors. A tiltrotor model has been developed to investigate the aeromechanics of tiltrotors, to develop a comprehensive database for validating tiltrotor analyses, and to provide a research platform for supporting future tiltrotor designs. The Full-Span Tiltrotor Aeroacoustic Model (FS TRAM) is a dual-rotor, powered aircraft model with extensive instrumentation for measurement of structural and aerodynamic loads. This paper will present the Full-Span TRAM test capabilities and the first set of data obtained during a 40- by 80-Foot Wind Tunnel test conducted in late 2000 at NASA Ames Research Center. The Full-Span TRAM is a quarter-scale representation of the V-22 Osprey aircraft, and a heavily instrumented NASA and U.S. Army wind tunnel test stand. Rotor structural loads are monitored and recorded for safety-of-flight and for information on blade loads and dynamics. Left and right rotor balance and fuselage balance loads are monitored for safety-of-flight and for measurement of vehicle and rotor aerodynamic performance. Static pressure taps on the left wing are used to determine rotor/wing interactional effects and rotor blade dynamic pressures measure blade airloads. All of these measurement capabilities make the FS TRAM test stand a unique and valuable asset for validation of computational codes and to aid in future tiltrotor designs. The Full-Span TRAM was tested in the NASA Ames Research Center 40- by 80-Foot Wind Tunnel from October through December 2000. Rotor and vehicle performance measurements were acquired in addition to wing pressures, rotor acoustics, and Laser Light Sheet (LLS) flow visualization data. Hover, forward flight, and airframe (rotors off) aerodynamic runs were performed. Helicopter-mode data were acquired during angle of attack and thrust sweeps for
Vakhshouri, Amin; Hashimoto, Katsushi; Hirayama, Yoshiro
We have developed a method of atomic force microscopy (AFM)-assisted scanning tunneling spectroscopy (STS) under ambient conditions. An AFM function is used for rapid access to a selected position prior to performing STS. The AFM feedback is further used to suppress vertical thermal drift of the tip-sample distance during spectroscopy, enabling flexible and stable spectroscopy measurements at room temperature. © The Author 2014. Published by Oxford University Press on behalf of The Japanese Society of Microscopy. All rights reserved. For permissions, please e-mail: firstname.lastname@example.org.
Observation and Manipulation of Polymers by Scanning Tunneling and Atomic Force Microscooy 12. PERSONAL AUTHOR(S) M.M. Dovek, T.R. Albrecht, S.W.J. Kuan, C.A...COUNT FIELD GOP SU8 -GROUP 19. ABSTRACT (Continue on reverse if ncosay and kIti1I by block numbor) ~AM\\~ v~~\\~A Dhe properties of monolayer films of...organic materi s are importantl i--V~ ety of technologies. We have employed the STM and AFM t study’ LanD~ ..-odgett films of a varie ’ty of polymers
Braafladt, Alexander; Lucero, John M.; Hirt, Stefanie M.
During operation of the NASA Glenn Research Center 15- by 15-Centimeter Supersonic Wind Tunnel (SWT), a significant, undesirable corner flow separation is created by the three-dimensional interaction of the wall and floor boundary layers in the tunnel corners following an oblique-shock/ boundary-layer interaction. A method to minimize this effect was conceived by connecting the wall and floor boundary layers with a radius of curvature in the corners. The results and observations of a trade study to determine the effectiveness of candidate materials for creating the radius of curvature in the SWT are presented. The experiments in the study focus on the formation of corner fillets of four different radii of curvature, 6.35 mm (0.25 in.), 9.525 mm (0.375 in.), 12.7 mm (0.5 in.), and 15.875 mm (0.625 in.), based on the observed boundary layer thickness of 11.43 mm (0.45 in.). Tests were performed on ten candidate materials to determine shrinkage, surface roughness, cure time, ease of application and removal, adhesion, eccentricity, formability, and repeatability. Of the ten materials, the four materials which exhibited characteristics most promising for effective use were the heavy body and regular type dental impression materials, the basic sculpting epoxy, and the polyurethane sealant. Of these, the particular material which was most effective, the heavy body dental impression material, was tested in the SWT in Mach 2 flow, and was observed to satisfy all requirements for use in creating the corner fillets in the upcoming experiments on shock-wave/boundary-layer interaction.
Ho, Yat-Kiu; Liu, Chun-Ho
Extensive human activities (e.g. increased traffic emissions) emit a wide range of pollutants resulting in poor urban area air quality. Unlike open, flat and homogenous rural terrain, urban surface is complicated by the presence of buildings, obstacles and narrow streets. The irregular urban surfaces thus form a random roughness that further modifies the near-surface flows and pollutant dispersion. In this study, a physical modelling approach is employed to commence a series of wind tunnel experiments to study the urban-area air pollution problems. The flow characteristics over different hypothetical urban roughness surfaces were studied in a wind tunnel in isothermal conditions. Preliminary experiments were conducted based on six types of idealized two-dimensional (2D) street canyon models with various building-height-to-street-width (aspect) ratios (ARs) 1, 1/2, 1/4, 1/8, 1/10 and 1/12. The main instrumentation is an in-house 90o X-hotwire anemometry. In each set of configuration, a sampling street canyon was selected near the end of the streamwise domain. Its roof level, i.e. the transverse between the mid points of the upstream and downstream buildings, was divided into eight segments. The measurements were then recorded on the mid-plane of the spannwise domain along the vertical profile (from building roof level to the ceiling of wind tunnel) of the eight segments. All the data acquisition processes were handled by the NI data acquisition modules, NI 9239 and CompactDAQ-9188 hardware. Velocity calculation was carried out in the post-processing stage on a digital computer. The two-component flow velocities and velocity fluctuations were calculated at each sampling points, therefore, for each model, a streamwise average of eight vertical profiles of mean velocity and velocity fluctuations was presented. A plot of air-exchange rate (ACH) against ARs was also presented in order to examine the ventilation performance of different tested models. Preliminary results
Karavosov, R. K.; Prozorov, A. G.
We have investigated the spectra of pressure pulsations in the near field of the open working section of the wind tunnel with a vortex flow behind the tunnel blower formed like the flow behind the hydroturbine of a hydraulic power plant. We have made a comparison between the measurement data for pressure pulsations and the air stream velocity in tunnels of the above type and in tunnels in which a large-scale vortex structure behind the blower is not formed. It has been established that the large-scale vortex formation in the incompressible medium behind the blade system in the wind tunnel is a source of narrow-band acoustic radiation capable of exciting resonance self-oscillations in the tunnel channel.
Yamazaki, Shiro; Maeda, Keisuke; Sugimoto, Yoshiaki; Abe, Masayuki; Zobač, Vladimír; Pou, Pablo; Rodrigo, Lucia; Mutombo, Pingo; Pérez, Ruben; Jelínek, Pavel; Morita, Seizo
We assemble bistable silicon quantum dots consisting of four buckled atoms (Si4-QD) using atom manipulation. We demonstrate two competing atom switching mechanisms, downward switching induced by tunneling current of scanning tunneling microscopy (STM) and opposite upward switching induced by atomic force of atomic force microscopy (AFM). Simultaneous application of competing current and force allows us to tune switching direction continuously. Assembly of the few-atom Si-QDs and controlling their states using versatile combined AFM/STM will contribute to further miniaturization of nanodevices.
Smith, Brian E.; Naumowicz, Tim
The aerodynamic characteristics of the 40- by 80-Foot Wind Tunnel at Ames Research Center were measured by using a 1/50th-scale facility. The model was configured to closely simulate the features of the full-scale facility when it became operational in 1986. The items measured include the aerodynamic effects due to changes in the total-pressure-loss characteristics of the intake and exhaust openings of the air-exchange system, total-pressure distributions in the flow field at locations around the wind tunnel circuit, the locations of the maximum total-pressure contours, and the aerodynamic changes caused by the installation of the acoustic barrier in the southwest corner of the wind tunnel. The model tests reveal the changes in the aerodynamic performance of the 1986 version of the 40- by 80-Foot Wind Tunnel compared with the performance of the 1982 configuration.
Dong, Zhibao; Wang, Hongtao; Zhang, Xiaohang; Ayrault, Michael
Attempt is made to define the particle concentration in an aeolian saltating cloud and its variation with height using artificial spherical quartz sand in a wind tunnel. The height profiles of the relative particle concentration in aeolian saltating cloud at three wind velocities were detected by the state of the art PIV (Particle Image Velocimetry) MSD (Mie Scattering Diffusion) technique, and converted to actual concentration based on sand transport rate and the variation with height of velocity of the saltating cloud. The particle concentration was found to decay exponentially with height and to increase with wind velocity. It decayed more rapidly when the wind velocity decreased. The volume/volume concentration in the near-surface layer was at the order of 10-4. The results obtained by PIV MSD technique were in good agreement with those derived from the sand flux and velocity profiles, the former being about 15% greater than the later.
After the first attempted ground-tow tests of the M2-F1 in March 1963, the vehicle was taken to the Ames Research Center, Mountain View, CA, for wind-tunnel testing. During these tests, Milt Thompson and others were in the M2-F1 to position the control surfaces for each test. The wingless, lifting body aircraft design was initially conceived as a means of landing an aircraft horizontally after atmospheric reentry. The absence of wings would make the extreme heat of re-entry less damaging to the vehicle. In 1962, Dryden management approved a program to build a lightweight, unpowered lifting body as a prototype to flight test the wingless concept. It would look like a 'flying bathtub,' and was designated the M2-F1, the 'M' referring to 'manned' and 'F' referring to 'flight' version. It featured a plywood shell placed over a tubular steel frame crafted at Dryden. Construction was completed in 1963. The first flight tests of the M2-F1 were over Rogers Dry Lake at the end of a tow rope attached to a hopped-up Pontiac convertible driven at speeds up to about 120 mph. This vehicle needed to be able to tow the M2-F1 on the Rogers Dry Lakebed adjacent to NASA's Flight Research Center (FRC) at a minimum speed of 100 miles per hour. To do that, it had to handle the 400-pound pull of the M2-F1. Walter 'Whitey' Whiteside, who was a retired Air Force maintenance officer working in the FRC's Flight Operations Division, was a dirt-bike rider and hot-rodder. Together with Boyden 'Bud' Bearce in the Procurement and Supply Branch of the FRC, Whitey acquired a Pontiac Catalina convertible with the largest engine available. He took the car to Bill Straup's renowned hot-rod shop near Long Beach for modification. With a special gearbox and racing slicks, the Pontiac could tow the 1,000-pound M2-F1 110 miles per hour in 30 seconds. It proved adequate for the roughly 400 car tows that got the M2-F1 airborne to prove it could fly safely and to train pilots before they were towed behind a C
Elliott, R. D.; Werner, N. M.; Baker, W. M.
The Aerodynamic Data Analysis and Integration System (ADAIS), developed as a highly interactive computer graphics program capable of manipulating large quantities of data such that addressable elements of a data base can be called up for graphic display, compared, curve fit, stored, retrieved, differenced, etc., was described. The general nature of the system is evidenced by the fact that limited usage has already occurred with data bases consisting of thermodynamic, basic loads, and flight dynamics data. Productivity using ADAIS of five times that for conventional manual methods of wind tunnel data analysis is routinely achieved. In wind tunnel data analysis, data from one or more runs of a particular test may be called up and displayed along with data from one or more runs of a different test. Curves may be faired through the data points by any of four methods, including cubic spline and least squares polynomial fit up to seventh order.
Nguyen, Nhan; Ardema, Mark
This paper describes a modeling method and a new optimal control approach to investigate a Mach number control problem for the NASA Ames 11-Foot Transonic Wind Tunnel. The flow in the wind tunnel is modeled by the 1-D unsteady Euler equations whose boundary conditions prescribe a controlling action by a compressor. The boundary control inputs to the compressor are in turn controlled by a drive motor system and an inlet guide vane system whose dynamics are modeled by ordinary differential equations. The resulting Euler equations are thus coupled to the ordinary differential equations via the boundary conditions. Optimality conditions are established by an adjoint method and are used to develop a model predictive linear-quadratic optimal control for regulating the Mach number due to a test model disturbance during a continuous pitch
Jiang, Naibo; Webster, Matthew; Lempert, Walter R; Miller, Joseph D; Meyer, Terrence R; Ivey, Christopher B; Danehy, Paul M
Nitric oxide planar laser-induced fluorescence (NO PLIF) imaging at repetition rates as high as 1 MHz is demonstrated in the NASA Langley 31 in. Mach 10 hypersonic wind tunnel. Approximately 200 time-correlated image sequences of between 10 and 20 individual frames were obtained over eight days of wind tunnel testing spanning two entries in March and September of 2009. The image sequences presented were obtained from the boundary layer of a 20° flat plate model, in which transition was induced using a variety of different shaped protuberances, including a cylinder and a triangle. The high-speed image sequences captured a variety of laminar and transitional flow phenomena, ranging from mostly laminar flow, typically at a lower Reynolds number and/or in the near wall region of the model, to highly transitional flow in which the temporal evolution and progression of characteristic streak instabilities and/or corkscrew-shaped vortices could be clearly identified.
Bradshaw, James F.; Sandefur, Paul G., Jr.; Young, Clarence P., Jr.
A comprehensive study of braze alloy selection process and strength characterization with application to wind tunnel models is presented. The applications for this study include the installation of stainless steel pressure tubing in model airfoil sections make of 18 Ni 200 grade maraging steel and the joining of wing structural components by brazing. Acceptable braze alloys for these applications are identified along with process, thermal braze cycle data, and thermal management procedures. Shear specimens are used to evaluate comparative shear strength properties for the various alloys at both room and cryogenic (-300 F) temperatures and include the effects of electroless nickel plating. Nickel plating was found to significantly enhance both the wetability and strength properties for the various braze alloys studied. The data are provided for use in selecting braze alloys for use with 18 Ni grade 200 steel in the design of wind tunnel models to be tested in an ambient or cryogenic environment.
Full Text Available For more than fifty years, atmospheric dispersion predictions based on the joint use of a Gaussian plume model and wind tunnel experiments have been applied in both Japan and the U.K. for the evaluation of public radiation exposure in nuclear safety analysis. The effective source height used in the Gaussian model is determined from ground-level concentration data obtained by a wind tunnel experiment using a scaled terrain and site model. In the present paper, the concentrations calculated by this method are compared with data observed over complex terrain in the field, under a number of meteorological conditions. Good agreement was confirmed in near-neutral and unstable stabilities. However, it was found to be necessary to reduce the effective source height by 50% in order to achieve a conservative estimation of the field observations in a stable atmosphere.
Zavadsky, Andrey; Shemer, Lev
This manuscript describes an experimental procedure that allows obtaining diverse quantitative information on temporal and spatial evolution of water waves excited by time-dependent and steady wind forcing. Capacitance-type wave gauge and Laser Slope Gauge (LSG) are used to measure instantaneous water surface elevation and two components of the instantaneous surface slope at a number of locations along the test section of a wind-wave facility. The computer-controlled blower provides airflow over the water in the tank whose rate can vary in time. In the present experiments, the wind speed in the test section initially increases quickly from rest to the set value. It is then kept constant for the prescribed duration; finally, the airflow is shut down. At the beginning of each experimental run, the water surface is calm and there is no wind. Operation of the blower is initiated simultaneously with the acquisition of data provided by all sensors by a computer; data acquisition continues until the waves in the tank fully decay. Multiple independent runs performed under identical forcing conditions allow determining statistically reliable ensemble-averaged characteristic parameters that quantitatively describe wind-waves' variation in time for the initial development stage as a function of fetch. The procedure also allows characterizing the spatial evolution of the wave field under steady wind forcing, as well as decay of waves in time, once the wind is shut down, as a function of fetch.
Nichols, M. E.
The results are documented of jet plume effects wind tunnel test of the 0.020-scale 88-OTS launch configuration space shuttle vehicle model in the 11 x 11 foot leg of the NASA/Ames Research Center Unitary Plan Wind Tunnel. This test involved cold gas main propulsion system (MPS) and solid rocket motor (SRB) plume simulations at Mach numbers from 0.6 to 1.4. Integrated vehicle surface pressure distributions, elevon and rudder hinge moments, and wing and vertical tail root bending and torsional moments due to MPS and SRB plume interactions were determined. Nozzle power conditions were controlled per pretest nozzle calibrations. Model angle of attack was varied from -4 deg to +4 deg; model angle of sideslip was varied from -4 deg to +4 deg. Reynolds number was varied for certain test conditions and configurations, with the nominal freestream total pressure being 14.69 psia. Plotted force and pressure data are presented.
Suwa, Shigeaki; Kusukawa, Ken-ichi.
The wind tunnel interference problem in magnetohydrodynamics, in which an inviscid compressible fluid with small electrical conductivity flows steadily past a slender axi-symmetric pointed body of revolution placed in a cylindrical perfectly insulated wind tunnel, in the presence of a crossed magnetic field, is considered. Using the analytical method which was studied by one of the present authors, the streamlines and the space charge in a cross section are calculated. (auth.)
Frammelsberger, Werner; Benstetter, Guenther; Stamp, Richard; Kiely, Janice; Schweinboeck, Thomas
As charge tunnelling through thin and ultra-thin silicon dioxide layers is regarded as the driving force for MOS device degradation the determination and characterisation of electrically week spots is of paramount importance for device reliability and failure analysis. Conductive atomic force microscopy (C-AFM) is able to address this issue with a spatial resolution smaller than the expected breakdown spot. For the determination of the electrically active oxide thickness in practice an easy to use model with sufficient accuracy and which is largely independent of the oxide thickness is required. In this work a simplified method is presented that meets these demands. The electrically active oxide thickness is determined by matching of C-AFM voltage-current curves and a tunnelling current model, which is based on an analytical tunnelling current approximation. The model holds for both the Fowler-Nordheim tunnelling and the direct tunnelling regime with one single tunnelling parameter set. The results show good agreement with macroscopic measurements for gate voltages larger than approximately 0.5-1 V, and with microscopic C-AFM measurements. For this reason arbitrary oxides in the DT and the FNT regime may be analysed with high lateral resolution by C-AFM, without the need of a preselection of the tunnelling regime to be addressed
Toshimitsu, Kazuhiko; Narihara, Takahiko; Kikugawa, Hironori; Akiyoshi, Arata; Kawazu, Yuuya
The effects of turbulent intensity and vortex scale of simulated natural wind on performance of a horizontal axis wind turbine (HAWT) are mainly investigated in this paper. In particular, the unsteadiness and turbulence of wind in Japan are stronger than ones in Europe and North America in general. Hence, Japanese engineers should take account of the velocity unsteadiness of natural wind at installed open-air location to design a higher performance wind turbine. Using the originally designed five wind turbines on the basis of NACA and MEL blades, the dependencies of the wind frequency and vortex scale of the simulated natural wind are presented. As the results, the power coefficient of the newly designed MEL3-type rotor in the simulated natural wind is 130% larger than one in steady wind.
Goodyer, M. J.
Cryogenic wind tunnel users must have available surface flow visualization techniques to satisfy a variety of needs. While the ideal from an aerodynamic stand would be non-intrusive, until an economical technique is developed there will be occasions when the user will be prepared to resort to an intrusive method. One such method is proposed, followed by preliminary evaluation experiments carried out in environments representative of the cryogenic nitrogen tunnel. The technique uses substances which are gases at normal temperature and pressure but liquid or solid at cryogenic temperatures. These are deposited on the model in localized regions, the patterns of the deposits and their subsequent melting or evaporation revealing details of the surface flow. The gases were chosen because of the likelihood that they will not permanently contaminate the model or tunnel. Twenty-four gases were identified as possibly suitable and four of these were tested from which it was concluded that surface flow direction can be shown by the method. Other flow details might also be detectable. The cryogenic wind tunnel used was insulated on the outside and did not show signs of contamination.
We study the 2-D, time-dependent hydrodynamics of radiation-driven winds from luminous accretion disks threaded by a strong, large-scale, ordered magnetic field. The radiation force is due to spectral lines and is calculated using a generalized multidimensional formulation of the Sobolev approximation. The effects of the magnetic field are approximated by adding a force that emulates a magnetocentrifugal force. Our approach allows us to calculate disk winds when the magnetic field controls th...
Avecilla, Fernando; Panebianco, Juan E.; Mendez, Mariano J.; Buschiazzo, Daniel E.
The PM10 emission efficiency of soils has been determined through different methods. Although these methods imply important physical differences, their outputs have never been compared. In the present study the PM10 emission efficiency was determined for soils through a wide range of textures, using three typical methodologies: a rotary-chamber dust generator (EDG), a laboratory wind tunnel on a prepared soil bed, and field measurements on an experimental plot. Statistically significant linear correlation was found (p < 0.05) between the PM10 emission efficiency obtained from the EDG and wind tunnel experiments. A significant linear correlation (p < 0.05) was also found between the PM10 emission efficiency determined both with the wind tunnel and the EDG, and a soil texture index (%sand + %silt)/(%clay + %organic matter) that reflects the effect of texture on the cohesion of the aggregates. Soils with higher sand content showed proportionally less emission efficiency than fine-textured, aggregated soils. This indicated that both methodologies were able to detect similar trends regarding the correlation between the soil texture and the PM10 emission. The trends attributed to soil texture were also verified for two contrasting soils under field conditions. However, differing conditions during the laboratory-scale and the field-scale experiments produced significant differences in the magnitude of the emission efficiency values. The causes of these differences are discussed within the paper. Despite these differences, the results suggest that standardized laboratory and wind tunnel procedures are promissory methods, which could be calibrated in the future to obtain results comparable to field values, essentially through adjusting the simulation time. However, more studies are needed to extrapolate correctly these values to field-scale conditions.
Jenni-Eiermann, Susanne; Jenni, Lukas; Kvist, Anders; Lindström, Åke; Piersma, Theunis; Visser, G. Henk
This study examines fuel use and metabolism in a group of long-distance migrating birds, red knots Calidris canutus (Scolopacidae), flying under controlled conditions in a wind tunnel for up to 10 h. Data are compared with values for resting birds fasting for the same time. Plasma levels of free fatty acids, glycerol and uric acid were elevated during flight, irrespective of flight duration (1–10 h). Triglyceride levels, the estimated concentration of very-low-density lipoproteins (VLDLs) and...
Brazier , J.P.; Schramm , J.M.; Paris , S.; Gawehn , T.
International audience; HyFIE project aimed at improving the measurement techniques in hypersonic wind-tunnels and comparing the experimental data provided by four major European facilities: DLR HEG and H2K, ONERA F4 and VKI Longshot. A common geometry of EXPERT body was chosen and four different models were used. A large amount of experimental data was collected and compared with the results of numerical simulations. Collapsing all the measured values showed a good agreement between the diff...
Kikko, Satoshi; Tanifuji, Katsuya; Sakanoue, Kei; Nanba, Kouichiro
In this paper, we aimed to model the aerodynamic force that acts on a train running at high speed in a tunnel. An analytical model of the aerodynamic force is developed from pressure data measured on car-body sides of a test train running at the maximum revenue operation speed. The simulation of an 8-car train running while being subjected to the modeled aerodynamic force gives the following results. The simulated car-body vibration corresponds to the actual vibration both qualitatively and quantitatively for the cars at the rear of the train. The separation of the airflow at the tail-end of the train increases the yawing vibration of the tail-end car while it has little effect on the car-body vibration of the adjoining car. Also, the effect of the moving velocity of the aerodynamic force on the car-body vibration is clarified that the simulation under the assumption of a stationary aerodynamic force can markedly increase the car-body vibration.
Tan, Jin; Hu, Weihao; Wang, Xiaoru
The main focus of forced low frequency oscillations is to analyze the disturbance source and the origin of forced oscillations. In this paper, the origin of low-frequency periodical oscillations induced by wind turbines’ mechanical power is investigated and the mechanism is studied of fluctuating...... power transfer through permanent magnet generator wind turbine system. Considering the tower shadow and the wind shear effect, the mechanical and generator coupling model is developed by PSCAD. Simulation is done to analyze the impacts on output power of operation points and mechanical fluctuation...... components. It is shown that when the oscillation frequency of tower shadow coincides with the system natural frequency, it may cause forced oscillations, whereas, the wind shear and natural wind speed fluctuation are not likely to induce forced oscillations....
Ji, Wenjing; Zhao, Bin
Vegetation, especially trees, is effective in reducing the concentration of particulate matter. Trees can efficiently capture particles, improve urban air quality, and may further decrease the introduction of outdoor particles to indoor air. The objective of this study is to investigate the effects of trees on particle distribution and removal around buildings using wind tunnel experiments. The wind tunnel is 18m long, 12m wide, and 3.5m high. Trees were modeled using real cypress branches to mimic trees planted around buildings. At the inlet of the wind tunnel, a "line source" of particles was released, simulating air laden with particulate matter. Experiments with the cypress tree and tree-free models were conducted to compare particle concentrations around the buildings. The results indicate that cypress trees clearly reduce PM 2.5 concentrations compared with the tree-free model. The cypress trees enhanced the PM 2.5 removal rate by about 20%. The effects of trees on PM 2.5 removal and distribution vary at different heights. At the base of the trees, their effect on reducing PM 2.5 concentrations is the most significant. At a great height above the treetops, the effect is almost negligible. Copyright © 2017 Elsevier B.V. All rights reserved.
Erickson, Gary E.
A procedure to analyze a split-plot experimental design featuring two input factors, two levels of randomization, and two error structures in a low-speed wind tunnel investigation of a small-scale model of a fighter airplane configuration is described in this report. Standard commercially-available statistical software was used to analyze the test results obtained in a randomization-restricted environment often encountered in wind tunnel testing. The input factors were differential horizontal stabilizer incidence and the angle of attack. The response variables were the aerodynamic coefficients of lift, drag, and pitching moment. Using split-plot terminology, the whole plot, or difficult-to-change, factor was the differential horizontal stabilizer incidence, and the subplot, or easy-to-change, factor was the angle of attack. The whole plot and subplot factors were both tested at three levels. Degrees of freedom for the whole plot error were provided by replication in the form of three blocks, or replicates, which were intended to simulate three consecutive days of wind tunnel facility operation. The analysis was conducted in three stages, which yielded the estimated mean squares, multiple regression function coefficients, and corresponding tests of significance for all individual terms at the whole plot and subplot levels for the three aerodynamic response variables. The estimated regression functions included main effects and two-factor interaction for the lift coefficient, main effects, two-factor interaction, and quadratic effects for the drag coefficient, and only main effects for the pitching moment coefficient.
In the last two decades urban climatology has developed to a pragmatically oriented field of research. Synthetic-functional maps of the climate and derived maps for town planning have widely been accepted by municipal or communal management. However, there is a disadvantage of the generalized urban-climatic maps because they only show the actual climatic state for stable sunny weather conditions. When future planning is done with due regard to forecasts on possible changes of the climatic or air-hygienic conditions, it is necessary to carry out model calculations and/or wind tunnel experiments. Because of the complexity of urban building structures, it is still difficult to acquire necessary information by numeric models. In most cases wind tunnel measurements will have to be carried out. After having illustrated the methods of wind tunnel experiments, the following paper shows results from measurements carried out for a street canyon with dense traffic in Duesseldorf's northern quarter Moersenbroich. This investigation intended to show how the field of immissions - mainly caused by traffic - changes after the construction of a six-storey office building on a remaining free space. It proved that the planned building wouldn't really lead to a deterioration of the field of the immissive situation. On the contrary, in most cases we could measure a reduced amount of pollution compared to the former building structure with a free spot. Only in few cases, the new building led to increased values in proportion to the given threshold values. (orig.) [de
Nikbay, Melike; Heeg, Jennifer
This paper originates from the joint efforts of an aeroelastic study team in the Applied Vehicle Technology Panel from NATO Science and Technology Organization, with the Task Group number AVT-191, titled "Application of Sensitivity Analysis and Uncertainty Quantification to Military Vehicle Design." We present aeroelastic uncertainty quantification studies using the SemiSpan Supersonic Transport wind tunnel model at the NASA Langley Research Center. The aeroelastic study team decided treat both structural and aerodynamic input parameters as uncertain and represent them as samples drawn from statistical distributions, propagating them through aeroelastic analysis frameworks. Uncertainty quantification processes require many function evaluations to asses the impact of variations in numerous parameters on the vehicle characteristics, rapidly increasing the computational time requirement relative to that required to assess a system deterministically. The increased computational time is particularly prohibitive if high-fidelity analyses are employed. As a remedy, the Istanbul Technical University team employed an Euler solver in an aeroelastic analysis framework, and implemented reduced order modeling with Polynomial Chaos Expansion and Proper Orthogonal Decomposition to perform the uncertainty propagation. The NASA team chose to reduce the prohibitive computational time by employing linear solution processes. The NASA team also focused on determining input sample distributions.
Kohlman, D. L.; Elias, L.; Orlik-Ruckemann, K.
A study of the feasibility of investigating the effects of ablation in a helium hypersonic wind tunnel was performed. Exploratory experiments were carried out at Mach 16.4 and at 600 psi stagnation pressure using (a) metal models at room temperature, (b) models with copper inserts, cooled to -140 deg C, and (c) models with carbon dioxide inserts. All models were flat plates at zero incidence, with a sharp leading edge in front of the insert. Surface temperature, surface recession rates and pitot pressure profiles were determined at several longitudinal stations. Suitable model fabrication and experimental techniques have been developed. A simple theoretical method of predicting recession rates and surface temperatures has been proposed. It has been demonstrated that the ablation of carbon dioxide into an unheated Mach 16.4 helium flow at 600 psi stagnation pressure is significant enough to result in measurable flat plate recession rates and measurable changes in pitot pressure profiles. In addition, it has been shown that it is possible to distinguish between the effects on pitot pressure of reduction in surface temperature and of mass addition through sublimation of carbon dioxide. It was also found that the first order theoretical analysis predicts proper trends and correct approximate magnitude of sublimation rates.
Fromme, J. A.; Golberg, M. A.
Lift interference effects are discussed based on Bland's (1968) integral equation. A mathematical existence theory is utilized for which convergence of the numerical method has been proved for general (square-integrable) downwashes. Airloads are computed using orthogonal airfoil polynomial pairs in conjunction with a collocation method which is numerically equivalent to Galerkin's method and complex least squares. Convergence exhibits exponentially decreasing error with the number n of collocation points for smooth downwashes, whereas errors are proportional to 1/n for discontinuous downwashes. The latter can be reduced to 1/n to the m+1 power with mth-order Richardson extrapolation (by using m = 2, hundredfold error reductions were obtained with only a 13% increase of computer time). Numerical results are presented showing acoustic resonance, as well as the effect of Mach number, ventilation, height-to-chord ratio, and mode shape on wind-tunnel interference. Excellent agreement with experiment is obtained in steady flow, and good agreement is obtained for unsteady flow.
Truong, Samson Siu
For a multi-hole test probe undergoing wind tunnel tests, the resulting data needs to be analyzed for any significant trends. These trends include relating the pressure distributions, the geometric orientation, and the local velocity vector to one another. However, experimental runs always involve some sort of error. As a result, a calibration procedure is required to compensate for this error. For this case, it is the misalignment bias angles resulting from the distortion associated with the angularity of the test probe or the local velocity vector. Through a series of calibration steps presented here, the angular biases are determined and removed from the data sets. By removing the misalignment, smoother pressure distributions contribute to more accurate experimental results, which in turn could be then compared to theoretical and actual in-flight results to derive any similarities. Error analyses will also be performed to verify the accuracy of the calibration error reduction. The resulting calibrated data will be implemented into an in-flight RTF script that will output critical flight parameters during future CCIE experimental test runs. All of these tasks are associated with and in contribution to NASA Dryden Flight Research Center s F-15B Research Testbed s Small Business Innovation Research of the Channeled Centerbody Inlet Experiment.
Alfyorov, V.I.; Dmitriev, L.M.; Yegorov, B.V.; Markachev, Yu.E.
The calculation results for nonequilibrium physicochemical processes in the circuit of the hypersonic MHD-gas acceleration wind tunnel are presented. The flow in the primary nozzle is shown to be in thermodynamic equilibrium at To=3400 K, Po=(2∼3)x10 5 Pa, M=2 used in the plenum chamber. Variations in the static pressure due to oxidation reaction of Na, K are pointed out. The channels of energy transfer from the electric field to different degrees of freedom of an accelerated gas with Na, K seeds are considered. The calculation procedure for gas dynamic and kinetic processes in the MHD-channel using measured parameters is suggested. The calculated results are compared with the data obtained in a thermodynamic gas equilibrium assumption. The flow in the secondary nozzle is calculated under the same assumptions and the gas parameters at its exit are evaluated. Particular attention is given to the influence of seeds on flows over bodies. It is shown that the seeds exert a very small influence on the flow behind a normal shock wave. The seeds behind an oblique shock wave accelerate deactivation of vibrations of N 2 , but this effect is insignificant
Siddall, Robert; Ortega Ancel, Alejandro; Kovač, Mirko
Aerial robots capable of locomotion in both air and water would enable novel mission profiles in complex environments, such as water sampling after floods or underwater structural inspections. The design of such a vehicle is challenging because it implies significant propulsive and structural design trade-offs for operation in both fluids. In this paper, we present a unique Aquatic Micro Air Vehicle (AquaMAV), which uses a reconfigurable wing to dive into the water from flight, inspired by the plunge diving strategy of water diving birds in the family Sulidae . The vehicle's performance is investigated in wind and water tunnel experiments, from which we develop a planar trajectory model. This model is used to predict the dive behaviour of the AquaMAV, and investigate the efficacy of passive dives initiated by wing folding as a means of water entry. The paper also includes first field tests of the AquaMAV prototype where the folding wings are used to initiate a plunge dive.
Gray, Tim; Brown, Michael; Flanagan, Ken; Werth, Alexandra; Lukin, V.
A helical, relaxed plasma state has been observed in a long cylindrical volume. The cylinder has dimensions L = 1 m and R = 0.08 m. The cylinder is long enough so that the predicted minimum energy state is a close approximation to the infinite cylinder solution. The plasma is injected at v >=50 km/s by a coaxial magnetized plasma gun located at one end of the cylindrical volume. Typical plasma parameters are Ti= 25 eV, ne>=10^15 cm-3, and B = 0.25 T. The relaxed state is rapidly attained in 1--2 axial Alfv'en times after initiation of the plasma. Magnetic data is favorably compared with an analytical model. Magnetic data exhibits broadband fluctuations of the measured axial modes during the formation period. The broadband activity rapidly decays as the energy condenses into the lowest energy mode, which is in agreement to the minimum energy eigenstate of ∇xB = λB. While the global structure roughly corresponds to the minimum energy eigenstate for the wind tunnel geometry, the plasma is high beta (β= 0.5) and does not have a flat λ profile. Merging of two plasmoids in this configuration results in noticeably more dynamic activity compared to a single plasmoid. These episodes of activity exhibit s
Schuh, Michael J.; Melton, John E.; Stremel, Paul M.
It is challenging to review and assimilate large data sets created by Computational Fluid Dynamics (CFD) simulations and wind tunnel tests. Over the past 10 years, NASA Ames Research Center has developed and refined a software tool dubbed the MiniWall to increase productivity in reviewing and understanding large CFD-generated data sets. Under the recent NASA ERA project, the application of the tool expanded to enable rapid comparison of experimental and computational data. The MiniWall software is browser based so that it runs on any computer or device that can display a web page. It can also be used remotely and securely by using web server software such as the Apache HTTP server. The MiniWall software has recently been rewritten and enhanced to make it even easier for analysts to review large data sets and extract knowledge and understanding from these data sets. This paper describes the MiniWall software and demonstrates how the different features are used to review and assimilate large data sets.
Walpot, L.; Di Clemente, M.; Vos, J.; Etchells, J.; Trifoni, E.; Thoemel, J.; Gavira, J.
In the frame of the “In-Flight Test Measurement Techniques for Aerothermodynamics” activity of the EXPERT Program, the EXPERT Instrumented Open Flap Assembly experiment has the objective to verify the design/sensor integration and validate the CFD tools. Ground based measurements were made in Europe’s largest high enthalpy plasma facility, Scirocco in Italy. Two EXPERT flaps of the flight article, instrumented with 14 thermocouples, 5 pressure ports, a pyrometer and an IR camera mounted in the cavity instrumented flap will collect in-flight data. During the Scirocco experiment, an EXPERT flap model identical to the flight article was mounted at 45 deg on a holder including cavity and was subjected to a hot plasma flow at an enthalpy up to 11MJ/kg at a stagnation pressure of 7 bar. The test model sports the same pressure sensors as the flight article. Hypersonic state-of-the-art codes were then be used to perform code-to-code and wind tunnel-to-code comparisons, including thermal response of the flap as collected during the tests by the sensors and camera.
Beresh, Steven; Kearney, Sean; Wagner, Justin; Guildenbecher, Daniel; Henfling, John; Spillers, Russell; Pruett, Brian; Jiang, Naibo; Slipchenko, Mikhail; Mance, Jason; Roy, Sukesh
Time-resolved particle image velocimetry (TR-PIV) has been achieved in a high-speed wind tunnel, providing velocity field movies of compressible turbulence events. The requirements of high-speed flows demand greater energy at faster pulse rates than possible with the TR-PIV systems developed for low-speed flows. This has been realized using a pulse-burst laser to obtain movies at up to 50 kHz, with higher speeds possible at the cost of spatial resolution. The constraints imposed by use of a pulse-burst laser are limited burst duration of 10.2 ms and a low duty cycle for data acquisition. Pulse-burst PIV has been demonstrated in a supersonic jet exhausting into a transonic crossflow and in transonic flow over a rectangular cavity. The velocity field sequences reveal the passage of turbulent structures and can be used to find velocity power spectra at every point in the field, providing spatial distributions of acoustic modes. The present work represents the first use of TR-PIV in a high-speed ground-test facility. (paper)
Dunn, Steven C.; Schlank, John J.
In 2004, NASA awarded the Research, Operations, Maintenance, and Engineering (ROME) contract at NASA Langley Research Center to a team led by Jacobs Technology, Inc. A key component of the contract was the transitioning of the five large wind tunnel facilities from NASA managed and NASA or NASA/contractor workforces to fully contractor operated. The contractor would manage daily operations while NASA would continue to develop long-term strategies, make decisions regarding commitment of funds and commitment of facilities, and provide oversight of the contractor's performance. A major challenge would be the transition of knowledge of facility operations and maintenance from the incumbent civil servant workforce to the contractor workforce. While the contract has since been modified multiple times, resulting in a blended NASA/ROME workforce across the facilities, the processes developed and implemented to capture and document facility knowledge from the incumbent subject matter experts, build training and certification programs, and grow individual skills across subject areas and across facilities, are worthy of documentation. This is the purpose of this paper.
Král, Radomil; Pospíšil, Stanislav; Náprstek, Jiří
In this paper, a wind tunnel analysis of two degrees-of-freedom system represented by sectional girders is carried out. Besides an evaluation of the aeroelastic coefficients, the analysis is focused on the influence of the natural frequency ratio on the initiation of unstable vibration, which can be of practical interest. On the phenomenological level, the paper also discusses experimentally ascertained response regimes, with an emphasis on their stability character. The attention is paid to the memory effect in the response described by the hysteresis loop together with the separation curves determining the stability boundaries. The influence of initial disturbance on the stability is examined. Two types of cross-sections were investigated: (i) rectangular one with the aspect ratio 1:5, and (ii) bridge-like cross-section with comparable principal dimensions. For both types of cross-sections, the limits of the stability are significantly affected by an intentionally introduced initial disturbance. This holds especially with regard to the rectangular profile where the separation curves create very narrow sub-domains between a stable and an unstable response, while the bridge-like cross-section demonstrates much stable behaviour.
Woodward, Richard P.; Dittmar, James H.; Hall, David G.; Kee-Bowling, Bonnie
The acoustic capability of the NASA Lewis 9 by 15 Foot Low Speed Wind Tunnel has been significantly improved by reducing the background noise levels measured by in-flow microphones. This was accomplished by incorporating streamlined microphone holders having a profile developed by researchers at the NASA Ames Research Center. These new holders were fabricated for fixed mounting on the tunnel wall and for an axially traversing microphone probe which was mounted to the tunnel floor. Measured in-flow noise levels in the tunnel test section were reduced by about 10 dB with the new microphone holders compared with those measured with the older, less refined microphone holders. Wake interference patterns between fixed wall microphones were measured and resulted in preferred placement patterns for these microphones to minimize these effects. Acoustic data from a model turbofan operating in the tunnel test section showed that results for the fixed and translating microphones were equivalent for common azimuthal angles, suggesting that the translating microphone probe, with its significantly greater angular resolution, is preferred for sideline noise measurements. Fixed microphones can provide a local check on the traversing microphone data quality, and record acoustic performance at other azimuthal angles.
Zasso, A.; Argentini, T.; Bayati, I.; Belloli, M.; Rocchi, D.
The super long fjord crossings in E39 Norwegian project pose new challenges to long span bridge design and construction technology. Proposed solutions should consider the adoption of bridge deck with super long spans or floating solutions for at least one of the towers, due to the relevant fjord depth. At the same time, the exposed fjord environment, possibly facing the open ocean, calls for higher aerodynamic stability performances. In relation to this scenario, the present paper addresses two topics: 1) the aerodynamic advantages of multi-box deck sections in terms of aeroelastic stability, and 2) an experimental setup in a wind tunnel able to simulate the aeroelastic bridge response including the wave forcing on the floating.
Debsarma, Suma; Senapati, Sudipta; Das, K. P.
The present work is motivated by the work of Leblanc ["Amplification of nonlinear surface waves by wind," Phys. Fluids 19, 101705 (2007)] which showed that Stokes waves grow super exponentially under fair wind as a result of modulational instability. Here, we have studied the effect of wind in a situation of crossing sea states characterized by two obliquely propagating wave systems in deep water. It is found that the wind-forced uniform wave solution in crossing seas grows explosively with a super-exponential growth rate even under a steady horizontal wind flow. This is an important piece of information in the context of the formation of freak waves.
Parker, David Huw
Although small scale magnetic suspension and balance systems (MSBSs) for wind tunnel use have been in existence for many years, they have not found general application in the production testing of flight vehicles. One reason for this is thought to lie in the relatively limited range of attitudes over which a wind tunnel model may be suspended. Modifications to a small MSBS to permit the suspension and control of axisymmetric models over angles of attack from less than zero to over ninety degrees are reported. Previous work has shown that existing arrangement of ten electromagnets was unable to generate one of the force components needed for control at extreme attitudes. Examination of possible solutions resulted in a simple alteration to rectify this deficiency. To generate the feedback signals to control the suspended model, an optical position sensing system using collimated laser beams and photodiode arrays was installed and tested. An analytical basis was developed for distributing the demands for force and moment needed for model stabilization amonge the electromagnets over the full attitude range. This was implemented by an MSBS control program able to continually adjust the distribution for the instantaneous incidence in accordance with prescheduled data. Results presented demonstrate rotations of models from zero to ninety degrees at rates up to ninety degrees per second, with pitching rates rising to several hundred degrees per second in response to step-change demands. A study of a design for a large MSBS suggests that such a system could be given the capability to control a model in six degrees of freedom over an unlimited angle of attack range.
Jaques, Peter A; Hsiao, Ta-Chih; Gao, Pengfei
A recirculation aerosol wind tunnel was designed to maintain a uniform airflow and stable aerosol size distribution for evaluating aerosol sampler performance and determining particle penetration through protective clothing materials. The oval-shaped wind tunnel was designed to be small enough to fit onto a lab bench, have optimized dimensions for uniformity in wind speed and particle size distributions, sufficient mixing for even distribution of particles, and minimum particle losses. Performance evaluation demonstrates a relatively high level of spatial uniformity, with a coefficient of variation of 1.5-6.2% for wind velocities between 0.4 and 2.8 m s(-1) and, in this range, 0.8-8.5% for particles between 50 and 450 nm. Aerosol concentration stabilized within the first 5-20 min with, approximately, a count median diameter of 135 nm and geometric standard deviation of 2.20. Negligible agglomerate growth and particle loss are suggested. The recirculation design appears to result in unique features as needed for our research.
Endalew, A. Melese; Hertog, M.; Delele, M.A.; Baetens, K.; Persoons, T.; Baelmans, M.; Ramon, H.; Nicolai, B.M.; Verboven, P.
The efficiency of pesticide application to agricultural fields and the resulting environmental contamination highly depend on atmospheric airflow. A computational fluid dynamics (CFD) modelling of airflow within plant canopies using 3D canopy architecture was developed to understand the effect of the canopy to airflow. The model average air velocity was validated using experimental results in a wind tunnel with two artificial model trees of 24 cm height. Mean air velocities and their root mean square (RMS) values were measured on a vertical plane upstream and downstream sides of the trees in the tunnel using 2D hotwire anemometer after imposing a uniform air velocity of 10 m s -1 at the inlet. 3D virtual canopy geometries of the artificial trees were modelled and introduced into a computational fluid domain whereby airflow through the trees was simulated using Reynolds-Averaged Navier-Stokes (RANS) equations and k-ε turbulence model. There was good agreement of the average longitudinal velocity, U between the measurements and the simulation results with relative errors less than 2% for upstream and 8% for downstream sides of the trees. The accuracy of the model prediction for turbulence kinetic energy k and turbulence intensity I was acceptable within the tree height when using a roughness length (y 0 = 0.02 mm) for the surface roughness of the tree branches and by applying a source model in a porous sub-domain created around the trees. The approach was applied for full scale orchard trees in the atmospheric boundary layer (ABL) and was compared with previous approaches and works. The simulation in the ABL was made using two groups of full scale orchard trees; short (h = 3 m) with wider branching and long (h = 4 m) with narrow branching. This comparison showed good qualitative agreements on the vertical profiles of U with small local differences as expected due to the spatial disparities in tree architecture. This work was able to show airflow within and above the
Adelfang, S. I.
A statistical analysis of the temporal variability of wind vectors at 1 km altitude intervals from 0 to 27 km altitude taken from a 10-year data sample of twice-daily rawinsode wind measurements over Vandenberg Air Force Base, California is presented.
van der Laan, Paul; Sørensen, Niels N.
simulations. A momentum balance in the cross flow direction shows that the interaction between the Coriolis force and the 5 × 5 actuator disks is complex due to turbulent mixing of veered momentum from above into the wind farm, which is not observed for the interaction between the Coriolis force...... wake and not the local changes in the Coriolis force in the wake deficit region. An additional simulation of a single actuator disk, operating in a shallow atmospheric boundary layer, confirms that the Coriolis force indirectly turns a wind turbine wake clockwise, as observed from above, due...
Rebstock, Rainer; Lee, Edwin E., Jr.
An initial wind tunnel test was made to validate a new wall adaptation method for 3-D models in test sections with two adaptive walls. First part of the adaptation strategy is an on-line assessment of wall interference at the model position. The wall induced blockage was very small at all test conditions. Lift interference occurred at higher angles of attack with the walls set aerodynamically straight. The adaptation of the top and bottom tunnel walls is aimed at achieving a correctable flow condition. The blockage was virtually zero throughout the wing planform after the wall adjustment. The lift curve measured with the walls adapted agreed very well with interference free data for Mach 0.7, regardless of the vertical position of the wing in the test section. The 2-D wall adaptation can significantly improve the correctability of 3-D model data. Nevertheless, residual spanwise variations of wall interference are inevitable.
Meyn, Larry A.; Zell, Peter T.; Hagan, John L.; Schoch, David
Modifications to the high-lift system of a full-scale F/A-I8A were tested in the 80- by 120-Foot Wind Tunnel of the National Full-Scale Aerodynamics Complex at the NASA Ames Research Center in Moffett Field, California. The objective was to measure the effect of simple modifications on the aerodynamic performance of the high-lift system. The modifications included the placement of a straight fairing in the shroud cove above the trailing-edge flap and the addition of seals to prevent air leakage through the hinge lines of the leading-edge flap, the trailing-edge shroud, and the wing fold. The test was carried out on an actual F/A-18A with it's flaps deployed in the landing approach configuration. The angle of attack ranged from 0 to 16 degrees and the wind speed was 100 knots. At an angle of attack of 8 degrees, the trimmed lift coefficient was improved by 0.09 with all wing seals in place. This corresponds to a reduction in the approach speed for the F/A-I8A of about 5 knots. The seal along the wing fold hinge, a feature present on many naval aircraft, provided one third of the total increment in trimmed lift. A comparison of the full-scale wind-tunnel results with those obtained from flight test is also presented.
Zhang, Caixia; Wang, Xunming; Dong, Zhibao; Hua, Ting
Wind tunnel studies, which remain limited, are an important tool to understand the aeolian processes of dried-up riverbeds. The particle size, chemical composition, and the mineral contents of sediments arising from the dried river beds are poorly understood. Dried-up riverbeds cover a wide area in the Hexi Corridor, China, and comprise a complex synthesis of different land surfaces, including aeolian deposits, pavement surfaces, and Takyr crust. The results of the present wind tunnel experiment suggest that aeolian transport from the dried-up riverbeds of the Hexi Corridor ranges from 0 to 177.04 g/m 2 /min and that dry riverbeds could be one of the main sources of dust emissions in this region. As soon as the wind velocity reaches 16 m/s and assuming that there are abundant source materials available, aeolian transport intensity increases rapidly. The dried-up riverbed sediment and the associated aeolian transported material were composed mainly of fine and medium sands. However, the transported samples were coarser than the bed samples, because of the sorting effect of the aeolian processes on the sediment. The aeolian processes also led to regional elemental migration and mineral composition variations.
Nguyen, Nhan; Ting, Eric; Lebofsky, Sonia
This paper presents data analysis of a flexible wing wind tunnel model with a variable camber continuous trailing edge flap (VCCTEF) design for drag minimization tested at the University of Washington Aeronautical Laboratory (UWAL). The wind tunnel test was designed to explore the relative merit of the VCCTEF concept for improved cruise efficiency through the use of low-cost aeroelastic model test techniques. The flexible wing model is a 10%-scale model of a typical transport wing and is constructed of woven fabric composites and foam core. The wing structural stiffness in bending is tailored to be half of the stiffness of a Boeing 757-era transport wing while the torsional stiffness is about the same. This stiffness reduction results in a wing tip deflection of about 10% of the wing semi-span. The VCCTEF is a multi-segment flap design having three chordwise camber segments and five spanwise flap sections for a total of 15 individual flap elements. The three chordwise camber segments can be positioned appropriately to create a desired trailing edge camber. Elastomeric material is used to cover the gaps in between the spanwise flap sections, thereby creating a continuous trailing edge. Wind tunnel data analysis conducted previously shows that the VCCTEF can achieve a drag reduction of up to 6.31% and an improvement in the lift-to-drag ratio (L=D) of up to 4.85%. A method for estimating the bending and torsional stiffnesses of the flexible wingUWAL wind tunnel model from static load test data is presented. The resulting estimation indicates that the stiffness of the flexible wing is significantly stiffer in torsion than in bending by as much as 9 to 1. The lift prediction for the flexible wing is computed by a coupled aerodynamic-structural model. The coupled model is developed by coupling a conceptual aerodynamic tool Vorlax with a finite-element model of the flexible wing via an automated geometry deformation tool. Based on the comparison of the lift curve slope
Sayın, Erdem; Eronat, Canan
The dominant circulation pattern of İzmir Bay on the Aegean Sea coast of Turkey is studied taking into consideration the influence of wind and thermohaline forces. İzmir Bay is discussed by subdividing the bay into outer, middle and inner areas. Wind is the most important driving force in the İzmir coastal area. There are also thermohaline forces due to the existence of water types of different physical properties in the bay. In contrast to the two-layer stratification during summer, a homogeneous water column exists in winter. The free surface version of the Princeton model (Killworth's 3-D general circulation model) is applied, with the input data obtained through the measurements made by the research vessel K. Piri Reis. As a result of the simulations with artificial wind, the strong consistent wind generates circulation patterns independent of the seasonal stratification in the bay. Wind-driven circulation causes cyclonic or anticyclonic movements in the middle bay where the distinct İzmir Bay Water (IBW) forms. Cyclonic movement takes place under the influence of southerly and westerly winds. On the other hand, northerly and easterly winds cause an anticyclonic movement in the middle bay. The outer and inner bay also have the wind-driven recirculation patterns expected.
Theodore, Colin R.
A full-scale wind tunnel test to evaluate the effects of Individual Blade Control (IBC) on the performance, vibration, noise and loads of a UH-60A rotor was recently completed in the National Full-Scale Aerodynamics Complex (NFAC) 40- by 80-Foot Wind Tunnel . A key component of this wind tunnel test was an automatic rotor trim control system that allowed the rotor trim state to be set more precisely, quickly and repeatably than was possible with the rotor operator setting the trim condition manually. The trim control system was also able to maintain the desired trim condition through changes in IBC actuation both in open- and closed-loop IBC modes, and through long-period transients in wind tunnel flow. This ability of the trim control system to automatically set and maintain a steady rotor trim enabled the effects of different IBC inputs to be compared at common trim conditions and to perform these tests quickly without requiring the rotor operator to re-trim the rotor. The trim control system described in this paper was developed specifically for use during the IBC wind tunnel test
Moes, Timothy R.; Whitmore, Stephen A.; Jordan, Frank L., Jr.
A nonintrusive airdata-sensing system was calibrated in flight and wind-tunnel experiments to an angle of attack of 70 deg and to angles of sideslip of +/- 15 deg. Flight-calibration data have also been obtained to Mach 1.2. The sensor, known as the flush airdata sensor, was installed on the nosecap of an F-18 aircraft for flight tests and on a full-scale F-18 forebody for wind-tunnel tests. Flight tests occurred at the NASA Dryden Flight Research Facility, Edwards, California, using the F-18 High Alpha Research Vehicle. Wind-tunnel tests were conducted in the 30- by 60-ft wind tunnel at the NASA LaRC, Hampton, Virginia. The sensor consisted of 23 flush-mounted pressure ports arranged in concentric circles and located within 1.75 in. of the tip of the nosecap. An overdetermined mathematical model was used to relate the pressure measurements to the local airdata quantities. The mathematical model was based on potential flow over a sphere and was empirically adjusted based on flight and wind-tunnel data. For quasi-steady maneuvering, the mathematical model worked well throughout the subsonic, transonic, and low supersonic flight regimes. The model also worked well throughout the angle-of-attack and sideslip regions studied.
Solano, Miguel; Garcia, Edgardo; Leonardi, Stafano; Canals, Miguel; Capella, Jorge
The response of the ocean circulation to various wind forcing products has been studied using the Regional Ocean Modeling System. The computational domain includes the main islands of Puerto Rico, Saint John and Saint Thomas, located on the continental shelf dividing the Caribbean Sea and the Atlantic Ocean. Data for wind forcing is provided by an anemometer located in a moored buoy, the Coupled Ocean-Atmosphere Mesoscale Prediction System (COAMPS) model and the National Digital Forecast Database (NDFD). Hindcast simulations have been validated using hydrographic data at different locations in the area of study. Three cases are compared to quantify the impact of high resolution wind forcing on the ocean circulation and the vertical structure of salinity, temperature and velocity. In the first case a constant wind velocity field is used to force the model as measured by an anemometer on top of a buoy. In the second case, a forcing field provided by the Navy's COAMPS model is used and in the third case, winds are taken from NDFD in collaboration with the National Centers for Environmental Prediction. Validated results of ocean currents against data from Acoustic Doppler Current Profilers at different locations show better agreement using high resolution wind data as expected. Thanks to CariCOOS and NOAA.
CAO Huiqiu; ZHOU Liangming; LI Shuiqing; WANG Zhifeng
This paper presents a study on drag coefficients under typhoon wind forcing based on observations and numerical experiments.The friction velocity and wind speed are measured at a marine observation platform in the South China Sea.Three typhoons:SOULIK (2013),TRAMI (2013) and FITOW (2013) are observed at a buoy station in the northeast sea area of Pingtan Island.A new parameterization is formulated for the wind drag coefficient as a function of wind speed.It is found that the drag coefficient (Ca) increases linearly with the slope of 0.083× 10-3 for wind speed less than 24 m s-1.To investigate the drag coefficient under higher wind conditions,three numerical experiments are implemented for these three typhoons using SWAN wave model.The wind input data are objective reanalysis datasets,which are assimilated with many sources and provided every six hours with the resolution of 0.125° ×0.125°.The numerical simulation results show a good agreement with wave observation data under typhoon wind forcing.The results indicate that the drag coefficient levels off with the linear slope of 0.012× 10-3 for higher wind speeds (less than 34 m s-1) and the new parameterization improvese the simulation accuracy compared with the Wu (1982) default used in SWAN.
In connection with the question on the applicability of test results obtained from cryogenic wind tunnels to the large-scale model the similarity parameter is referred to. A simple method is given for calculating the similarity parameter. From the numerical values obtained it can be deduced that nitrogen behaves practically like an ideal gas when it is close to the saturation point and in a pressure range up to 4 bar. The influence of this parameter on the pressure distribution of a supercritical profile confirms this finding.
tests were conducted on two geometrica lly similar models of each of two aerofoil sections -—t he NA CA 00/ 2 and the BGK- 1 sections -and covered a...and slotted-wall tes t sections are corrected for wind tunnel wall interference efJ~cts by the application of classical linearized theory. For the...solid wall results , these corrections appear to produce data which are very close to being free of the effects of interference. In the case of
Hughes, Christopher E.
A comprehensive aeroacoustic research program called the Source Diagnostic Test was recently concluded in NASA Glenn Research Center's 9- by 15-Foot Low Speed Wind Tunnel. The testing involved representatives from Glenn, NASA Langley Research Center, GE Aircraft Engines, and the Boeing Company. The technical objectives of this research were to identify the different source mechanisms of noise in a modern, high-bypass turbofan aircraft engine through scale-model testing and to make detailed acoustic and aerodynamic measurements to more fully understand the physics of how turbofan noise is generated.
Full Text Available Schlieren flow visualization methods are an important part of high speed wind tunnel testing, being a fast and reliable method of graphically presenting complex dynamic phenomena that occur in high subsonic, transonic and supersonic regimes. Images can be processed and effects of configuration changes can be understood faster. Quantitative variations of the Schlieren method enable CFD simulations to use real data, resulting in greater precision and thus help improve efficiency of the re-design phase for the aerodynamic object. A modification of the classic Schlieren system is proposed, that would enable extraction of such data with minimal costs
Wolken-Moehlmann, Gerrit [ForWind - Center for Wind Energy Research, University of Oldenburg (Germany); Knebel, Pascal [ForWind - Center for Wind Energy Research, University of Oldenburg (Germany); Barth, Stephan [ECN Wind Energy, Energy research Centre of the (Netherlands); Peinke, Joachim [ForWind - Center for Wind Energy Research, University of Oldenburg (Germany)
We report on an experimental setup for measurements of dynamic stall for airfoils via the pressure distribution over wind tunnel walls. This measuring technique, hitherto used for lift measurements under static conditions, is also an adequate method for dynamic conditions until stall occurs. A step motor is used, allowing for sinusoidal as well as non-sinusoidal and stochastic pitching to simulate fast fluctuating flow conditions. Measurements with sinusoidal pitching and constant angular velocities were done and show dynamic stall characteristics. Under dynamic stall conditions, maximum lift coefficients were up to 80% higher than the maximum for static lift.
van der Laan, Paul; Hansen, Kurt Schaldemose; Sørensen, Niels N.
A Reynolds-averaged Navier-Stokes code is used to simulate the interaction of two neighboring wind farms. The influence of the Coriolis force is investigated by modeling the atmospheric surface/boundary layer with three different methodologies. The results show that the Coriolis force is negligible...
Colovini, L.; Martinelli, G.; Morini, A.
The determination of values and distribution of the forces acting on the components of a superconducting generator is important when designing the machine, particularly in the choice of materials. The paper analyses the electromagnetic forces acting on the field and armature windings; for this purpose, with reference to the preliminary design of a two-pole 300 MVA superconducting generator, a two-dimensional analytical method set up by the authors is utilized to calculate the forces on the windings under steady state operation and results are compared with those obtained by means of a numerical method
Gabor, Oliviu Sugar
, the spanwise number of actuation stations as well as the displacement limits were established. The performance improvements obtained and the limitations of the morphing wing concept were studied. To verify the optimization results, high-fidelity Computational Fluid Dynamics simulations were also performed, giving very accurate indications of the obtained gains. For the morphing model based on an aircraft wing tip, the skin shapes were optimized in order to control laminar flow on the upper surface. An automated structured mesh generation procedure was developed and implemented. To accurately capture the shape of the skin, a precision scanning procedure was done and its results were included in the numerical model. High-fidelity simulations were performed to determine the upper surface transition region and the numerical results were validated using experimental wind tunnel data.
Ishibashi, Fuminori; Takemasa, Ryo; Matsushita, Makoto; Nishizawa, Takashi; Noda, Shinichi
Brushless permanent magnet motors have been widely used in home applications and industrial fields. These days, high efficiency and low noise motors are demanded from the view point of environment. Electromagnetic noise and iron loss of the motor are produced by the harmonic fluxes and electromagnetic forces. However, order and space pattern of these have not been discussed in detail. In this paper, fluxes, electromagnetic forces and magneto-motive forces of brushless permanent magnet motors with concentric winding were analyzed analytically, experimentally and numerically. Time harmonic fluxes and time electromagnetic forces in the air gap were measured by search coils on the inner surface of the stator teeth and analyzed by FEM. Space pattern of time harmonic fluxes and time electromagnetic forces were worked out with experiments and FEM. Magneto motive forces due to concentric winding were analyzed with equations and checked by FEM.
Brocklehurst, Aidan; Boon, Alex; Barlow, Janet; Hayden, Paul; Robins, Alan
The source area of an instrument is an estimate of the area of ground over which the measurement is generated. Quantification of the source area of a measurement site provides crucial context for analysis and interpretation of the data. A range of computational models exists to calculate the source area of an instrument, but these are usually based on assumptions which do not hold for instruments positioned very close to the surface, particularly those surrounded by heterogeneous terrain i.e. urban areas. Although positioning instrumentation at higher elevation (i.e. on masts) is ideal in urban areas, this can be costly in terms of installation and maintenance costs and logistically difficult to position instruments in the ideal geographical location. Therefore, in many studies, experimentalists turn to rooftops to position instrumentation. Experimental validations of source area models for these situations are very limited. In this study, a controlled tracer gas experiment was conducted in a wind tunnel based on a 1:200 scale model of a measurement site used in previous experimental work in central London. The detector was set at the location of the rooftop site as the tracer was released at a range of locations within the surrounding streets and rooftops. Concentration measurements are presented for a range of wind angles, with the spread of concentration measurements indicative of the source area distribution. Clear evidence of wind channeling by streets is seen with the shape of the source area strongly influenced by buildings upwind of the measurement point. The results of the wind tunnel study are compared to scalar concentration source areas generated by modelling approaches based on meteorological data from the central London experimental site and used in the interpretation of continuous carbon dioxide (CO2) concentration data. Initial conclusions will be drawn as to how to apply scalar concentration source area models to rooftop measurement sites and
Espinoza, Karlos; Valera, Diego L; Torres, José A; López, Alejandro; Molina-Aiz, Francisco D
Wind tunnels are a key experimental tool for the analysis of airflow parameters in many fields of application. Despite their great potential impact on agricultural research, few contributions have dealt with the development of automatic control systems for wind tunnels in the field of greenhouse technology. The objective of this paper is to present an automatic control system that provides precision and speed of measurement, as well as efficient data processing in low-speed wind tunnel experiments for greenhouse engineering applications. The system is based on an algorithm that identifies the system model and calculates the optimum PI controller. The validation of the system was performed on a cellulose evaporative cooling pad and on insect-proof screens to assess its response to perturbations. The control system provided an accuracy of integrated software unit that manages the tests in terms of airflow speed and pressure drop set points.
Christhilf, David M.
It has long been recognized that frequency and phasing of structural modes in the presence of airflow play a fundamental role in the occurrence of flutter. Animation of simulation results for the long, slender Semi-Span Super-Sonic Transport (S4T) wind-tunnel model demonstrates that, for the case of mass-ballasted nacelles, the flutter mode can be described as a traveling wave propagating downstream. Such a characterization provides certain insights, such as (1) describing the means by which energy is transferred from the airflow to the structure, (2) identifying airspeed as an upper limit for speed of wave propagation, (3) providing an interpretation for a companion mode that coalesces in frequency with the flutter mode but becomes very well damped, (4) providing an explanation for bursts of response to uniform turbulence, and (5) providing an explanation for loss of low frequency (lead) phase margin with increases in dynamic pressure (at constant Mach number) for feedback systems that use sensors located upstream from active control surfaces. Results from simulation animation, simplified modeling, and wind-tunnel testing are presented for comparison. The simulation animation was generated using double time-integration in Simulink of vertical accelerometer signals distributed over wing and fuselage, along with time histories for actuated control surfaces. Crossing points for a zero-elevation reference plane were tracked along a network of lines connecting the accelerometer locations. Accelerometer signals were used in preference to modal displacement state variables in anticipation that the technique could be used to animate motion of the actual wind-tunnel model using data acquired during testing. Double integration of wind-tunnel accelerometer signals introduced severe drift even with removal of both position and rate biases such that the technique does not currently work. Using wind-tunnel data to drive a Kalman filter based upon fitting coefficients to
S. T. Navalkar
Full Text Available Wind turbine load alleviation has traditionally been addressed in the literature using either full-span pitch control, which has limited bandwidth, or trailing-edge flap control, which typically shows low control authority due to actuation constraints. This paper combines both methods and demonstrates the feasibility and advantages of such a combined control strategy on a scaled prototype in a series of wind tunnel tests. The pitchable blades of the test turbine are instrumented with free-floating flaps close to the tip, designed such that they aerodynamically magnify the low stroke of high-bandwidth actuators. The additional degree of freedom leads to aeroelastic coupling with the blade flexible modes. The inertia of the flaps was tuned such that instability occurs just beyond the operational envelope of the wind turbine; the system can however be stabilised using collocated closed-loop control. A feedforward controller is shown to be capable of significant reduction of the deterministic loads of the turbine. Iterative feedforward tuning, in combination with a stabilising feedback controller, is used to optimise the controller online in an automated manner, to maximise load reduction. Since the system is non-linear, the controller gains vary with wind speed; this paper also shows that iterative feedforward tuning is capable of generating the optimal gain schedule online.
Mohamed Sadok GUEZGUEZ
Full Text Available In this project, a wing tip of a real aircraft was designed and manufactured. This wing tip was composed of a wing and an aileron. The wing was equipped with a composite skin on its upper surface. This skin changed its shape (morphed by use of 4 electrical in-house developed actuators and 32 pressure sensors. These pressure sensors measure the pressures, and further the loads on the wing upper surface. Thus, the upper surface of the wing was morphed using these actuators with the aim to improve the aerodynamic performances of the wing-tip. Two types of ailerons were designed and manufactured: one aileron is rigid (non-morphed and one morphing aileron. This morphing aileron can change its shape also for the aerodynamic performances improvement. The morphing wing-tip internal structure is designed and manufactured, and is presented firstly in the paper. Then, the modern communication and control hardware are presented for the entire morphing wing tip equipped with actuators and sensors having the aim to morph the wing. The calibration procedure of the wing tip is further presented, followed by the open loop controller results obtained during wind tunnel tests. Various methodologies of open loop control are presented in this paper, and results obtained were obtained and validated experimentally through wind tunnel tests.
Full Text Available It is known that the honeybee, Apis mellifera, uses olfactory stimulus as important information for orienting to food sources. Several studies on olfactory-induced orientation flight have been conducted in wind tunnels and in the field. From these studies, optical sensing is used as the main information with the addition of olfactory signals and the navigational course followed by these sensory information. However, it is not clear how olfactory information is reflected in the navigation of flight. In this study, we analyzed the detailed properties of flight when oriented to an odor source in a wind tunnel. We recorded flying bees with a video camera to analyze the flight area, speed, angular velocity and trajectory. After bees were trained to be attracted to a feeder, the flight trajectories with or without the olfactory stimulus located upwind of the feeder were compared. The results showed that honeybees flew back and forth in the proximity of the odor source, and the search range corresponded approximately to the odor spread area. It was also shown that the angular velocity was different inside and outside the odor spread area, and trajectories tended to be bent or curved just outside the area.
Korte, John J.; Kumar, Ajay; Singh, D. J.; White, J. A.
A design program is developed which incorporates a modern approach to the design of supersonic/hypersonic wind-tunnel nozzles. The approach is obtained by the coupling of computational fluid dynamics (CFD) with design optimization. The program can be used to design a 2D or axisymmetric, supersonic or hypersonic, wind-tunnel nozzles that can be modeled with a calorically perfect gas. The nozzle design is obtained by solving a nonlinear least-squares optimization problem (LSOP). The LSOP is solved using an iterative procedure which requires intermediate flowfield solutions. The nozzle flowfield is simulated by solving the Navier-Stokes equations for the subsonic and transonic flow regions and the parabolized Navier-Stokes equations for the supersonic flow regions. The advantages of this method are that the design is based on the solution of the viscous equations eliminating the need to make separate corrections to a design contour, and the flexibility of applying the procedure to different types of nozzle design problems.
Bak, C.; Fuglsang, P.; Johansen, J.
This report contains 2D measurements of the NACA 63-415 and a NACA 63-415 airfoil with modified leading edge called NACA 63-415-Risø-D. The aerodynamic properties were derived from pressure measurements on the airfoil surface and in the wake. The VELUXopen jet wind tunnel was used having a backgr......This report contains 2D measurements of the NACA 63-415 and a NACA 63-415 airfoil with modified leading edge called NACA 63-415-Risø-D. The aerodynamic properties were derived from pressure measurements on the airfoil surface and in the wake. The VELUXopen jet wind tunnel was used having...... a background turbulence intensity of 1%, an inlet flow velocity of 40 m/s which resulted in a Reynolds number of 1.6×106. The airfoil sections had a chord of 0.600 m and 0.606 m for NACA 63-415 and NACA 63-415-Risø-D,respectively. The span was 1.9 m and end plates were used to minimise 3D flow effects...
Full Text Available We report results gained with a three-dimensional, semi-implicit, semi-spectral model of the shallow water equations on the rotating Earth that allowed one to compute the wind-induced motion in lakes. The barotropic response to unidirectional, uniform winds, Heaviside in time, is determined in a rectangular basin with constant depth, and in Lake Constance, for different values and vertical distributions of the vertical eddy viscosities. It is computationally demonstrated that both the transitory oscillating, as well as the steady state current distribution, depends strongly upon the absolute value and vertical shape of the vertical eddy viscosity. In particular, the excitation and attenuation in time of the inertial waves, the structure of the Ekman spiral, the thickness of the Ekman layer, and the exact distribution and magnitude of the upwelling and downwelling zones are all significantly affected by the eddy viscosities. Observations indicate that the eddy viscosities must be sufficiently small so that the oscillatory behaviour can be adequately modelled. Comparison of the measured current-time series at depth in one position of Lake Constance with those computed on the basis of the measured wind demonstrates fair agreement, including the rotation-induced inertial oscillation.Key words. Oceanography: general (limnology – Oceanography: physical (Coriolis effects; general circulation
Full Text Available We report results gained with a three-dimensional, semi-implicit, semi-spectral model of the shallow water equations on the rotating Earth that allowed one to compute the wind-induced motion in lakes. The barotropic response to unidirectional, uniform winds, Heaviside in time, is determined in a rectangular basin with constant depth, and in Lake Constance, for different values and vertical distributions of the vertical eddy viscosities. It is computationally demonstrated that both the transitory oscillating, as well as the steady state current distribution, depends strongly upon the absolute value and vertical shape of the vertical eddy viscosity. In particular, the excitation and attenuation in time of the inertial waves, the structure of the Ekman spiral, the thickness of the Ekman layer, and the exact distribution and magnitude of the upwelling and downwelling zones are all significantly affected by the eddy viscosities. Observations indicate that the eddy viscosities must be sufficiently small so that the oscillatory behaviour can be adequately modelled. Comparison of the measured current-time series at depth in one position of Lake Constance with those computed on the basis of the measured wind demonstrates fair agreement, including the rotation-induced inertial oscillation.
Key words. Oceanography: general (limnology – Oceanography: physical (Coriolis effects; general circulation
Treon, S. L.
A survey of the U.S. aerospace industry in late 1977 suggests that there will be an increasing use of computer-aided prediction-design technology (CPD Tech) in the aircraft development process but that, overall, only a modest reduction in wind-tunnel test requirements from the current level is expected in the period through 1995. Opinions were received from key spokesmen in 23 of the 26 solicited major companies or corporate divisions involved in the design and manufacture of nonrotary wing aircraft. Development programs for nine types of aircraft related to test phases and wind-tunnel size and speed range were considered.
The basic principle of odor sampling from surface sources is based primarily on the amount of air obtained from a specific area of the ground, which acts as a source of malodorous compounds. Wind tunnels and flux chambers are often the only available, direct method of evaluating the odor fluxes from small area sources. There are currently no widely accepted chamber-based methods; thus, there is still a need for standardization of these methods to ensure accuracy and comparability. Previous research has established that there is a significant difference between the odor concentration values obtained using the Lindvall chamber and those obtained by a dynamic flow chamber. Thus, the present study compares sampling methods using a streaming chamber modeled on the Lindvall cover (using different wind speeds), a static chamber, and a direct sampling method without any screens. The volumes of chambers in the current work were similar, ~0.08 m 3 . This study was conducted at the mechanical-biological treatment plant in Poland. Samples were taken from a pile covered by the membrane. Measured odor concentration values were between 2 and 150 ou E /m 3 . Results of the study demonstrated that both chambers can be used interchangeably in the following conditions: odor concentration is below 60 ou E /m 3 , wind speed inside the Lindvall chamber is below 0.2 m/sec, and a flow value is below 0.011 m 3 /sec. Increasing the wind speed above the aforementioned value results in significant differences in the results obtained between those methods. In all experiments, the results of the concentration of odor in the samples using the static chamber were consistently higher than those from the samples measured in the Lindvall chamber. Lastly, the results of experiments were employed to determine a model function of the relationship between wind speed and odor concentration values. Several researchers wrote that there are no widely accepted chamber-based methods. Also, there is still a
Hudecz, Adriána; Koss, Holger; Hansen, Martin Otto Laver
In this paper, both experimental and numerical simulations of the effects of ice accretion on a NACA 64-618 airfoil section with 7° angle of attack are presented. The wind tunnel tests were conducted in a closed-circuit climatic wind tunnel at Force Technology in Denmark. The changes of aerodynamic...... forces were monitored as ice was building up on the airfoil for glaze, rime and mixed ice. In the first part of the numerical analysis, the resulted ice profiles of the wind tunnel tests were compared to profiles estimated by using the 2D ice accretion code TURBICE. In the second part, Ansys Fluent...... of the rime iced ice profile follows the streamlines quite well, disturbing the flow the least. The TURBICE analysis agrees fairly with the profiles produced during the wind tunnel testing....
Hoffman, T. R.
Researchers at the NASA Glenn Research Center at Lewis Field successfully tested a variable cowl lip inlet at simulated takeoff conditions in Glenn s 10- by 10-Foot Supersonic Wind Tunnel (10x10 SWT) as part of the High-Speed Research Program. The test was a follow-on to the Two-Dimensional Bifurcated (2DB) Inlet/Engine test. At the takeoff condition for a High-Speed Civil Transport aircraft, the inlet must provide adequate airflow to the engine with an acceptable distortion level and high-pressure recovery. The test was conducted to study the effectiveness of installing two rotating lips on the 2DB Inlet cowls to increase mass flow rate and eliminate or reduce boundary layer flow separation near the lips. Hardware was mounted vertically in the test section so that it extended through the tunnel ceiling and that the 2DB Inlet was exposed to the atmosphere above the test section. The tunnel was configured in the aerodynamic mode, and exhausters were used to pump down the tunnel to vacuum levels and to provide a maximum flow rate of approximately 58 lb/sec. The test determined the (1) maximum flow in the 2DB Inlet for each variable cowl lip, (2) distortion level and pressure recovery for each lip configuration, (3) boundary layer conditions near variable lips inside the 2DB Inlet, (4) effects of a wing structure adjacent to the 2DB Inlet, and (5) effects of different 2DB Inlet exit configurations. It also employed flow visualization to generate enough qualitative data on variable lips to optimize the variable lip concept. This test was a collaborative effort between the Boeing Company and Glenn. Extensive inhouse support at Glenn contributed significantly to the progress and accomplishment of this test.
Hansma, P K; Elings, V B; Marti, O; Bracker, C E
The scanning tunneling microscope (STM) and the atomic force microscope (AFM) are scanning probe microscopes capable of resolving surface detail down to the atomic level. The potential of these microscopes for revealing subtle details of structure is illustrated by atomic resolution images including graphite, an organic conductor, an insulating layered compound, and individual adsorbed oxygen atoms on a semiconductor. Application of the STM for imaging biological materials directly has been hampered by the poor electron conductivity of most biological samples. The use of thin conductive metal coatings and replicas has made it possible to image some biological samples, as indicated by recently obtained images of a recA-DNA complex, a phospholipid bilayer, and an enzyme crystal. The potential of the AFM, which does not require a conductive sample, is shown with molecular resolution images of a nonconducting organic monolayer and an amino acid crystal that reveals individual methyl groups on the ends of the amino acids. Applications of these new microscopes to technology are demonstrated with images of an optical disk stamper, a diffraction grating, a thin-film magnetic recording head, and a diamond cutting tool. The STM has even been used to improve the quality of diffraction gratings and magnetic recording heads.