Full-scale Wind Tunnel Research Articles

Analysis of Rear Window Buffeting Characteristics Using a Production Sedan

In this paper rear left side window buffeting characteristics of a production sedan under different yaw angles and different window opening sizes are investigated through full-scale aeroacoustic wind tunnel tests. By yaw angle -10 degree, as driver position on the lee side, the resonance peak SPL is much less than that by yaw angle 0 or +10 degree and the corresponding frequency is also some lower than that by yaw angle 0 or +10 degree. As window opening size turns small, the resonance peak SPL decreases. By side window with 25% opening size, the peak SPL is much less than that by side window with 50% or 100% opening size. In addition, the corresponding frequency is also some lower than that by side window with 50% or 100% opening size. Different test positions at the front row or back row show very similar buffeting characteristics.

An Experimental Investigation of Sunroof Buffeting Characteristics of a Sedan

After a short introduction about vehicle wind buffeting noise generation mechanisms, sunroof buffeting characteristics of a production sedan under different wind speeds and operating modes are investigated through full-scale aeroacoustic wind tunnel tests. As sunroof fully open, the severest buffeting effect occurs at wind speed 50kph, with the peak SPL 122dB and the corresponding resonance frequency 18Hz for the test point at the front row. From ca. 60kph it seems that the buffeting effect disappeared. As sunroof tilt, the severest buffeting effect occurs at wind speed equal or less than 30kph, the resonance frequency equal or less than 15Hz. From ca. 40kph the buffeting effect almost disappeared. Whether sunroof fully open or tilt, the resonance frequency increases all along as wind speed goes up till the buffeting effect disappeared (less than 20Hz). Different test positions at the front row or back row show very similar buffeting characteristics.

Performance evaluation of Canton Tower under winds based on full-scale data

Canton Tower is a 610m tall tower, located at the edge of the most active typhoon prone area in the world. Therefore, the wind effects are critical to the satisfactory performance of the tower. Although the finite element analysis and wind tunnel tests have been conducted in response to this concern, the full-scale monitoring provides a unique opportunity to study the actual performance of the structure under winds. A sophisticated long-term Structural Health Monitoring system consisting of about 700 sensors has been implemented by The Hong Kong Polytechnic University. This paper presents wind characteristics (wind speed, direction, and turbulence intensity) and structural responses (strain, acceleration, and displacement responses) during several typhoon events. A comparison between the full-scale data and wind tunnel predictions is conducted. Prior to modal identification, stationarity check is conducted and then different techniques are employed to identify the modal properties with errors. In addition, the amplitude-dependence in modal properties is investigated. Finally, the tower serviceability during different typhoon events is evaluated and the performance is found to be satisfactory from human comfort consideration.

Influence of Crosswind to Automobile Interior Aerodynamic Noise

After a brief introduction about aerodynamic noise generation and transmission mechanisms, the influence of crosswind to vehicle interior aerodynamic noise for a production automobile sedan was investigated through full-scale aeroacoustic wind tunnel tests. Through analysis of sound pressure level of vehicle interior driver ear position and pressure fluctuation level on vehicle side window glass under different yaw angles, the following results are obtained: The frequency characteristics of vehicle interior aerodynamic noise vary as yaw angle changes under one certain wind speed. Whether on the leeside or by windward, sound pressure level increases as yaw angle goes up. Under the same yaw angle, interior noise level on the leeside is higher than that by windward. Test results between pressure fluctuation level on side window glass and vehicle interior aerodynamic noise of driver ear position show good correlation

Measurement of high solidity vertical axis wind turbine aerodynamic loads under high vibration response conditions

A series of full-scale experimental wind tunnel tests were performed to determine the aerodynamic loading behaviour on the airfoils of a high solidity, H-type, vertical axis wind turbine. During the course of this investigation, high amplitude vibration of the turbine was observed over a wide range of test conditions. The primary vibration excitation mechanism was resonance of the dominant whirling mode of the turbine with the operating blade pass frequency. In addition, for a significant number of test cases, resonance of the airfoil support struts at higher frequencies was also observed. This large vibration response resulted in conditions that made it difficult or impossible to measure the underlying aerodynamic loading. As a result, in order to gain a greater understanding of the aerodynamic loading, a vibration isolation methodology was developed to remove the effect of vibration from the measured aerodynamic forces on the blades. This included tests with two different support shaft end conditions over a range of flow velocities from 8 to 11m/s, and the use of band-stop filtering to remove residual small amplitude vibrations. In this way, an accurate and complete measurement of the aerodynamic loading on the turbine blades could be obtained to better understand the effects of dynamic stall and validate the results of numerical model predictions.

Methods to control low frequency pulsation in open-jet wind tunnel

Low frequency pulsation affects both aerodynamic and acoustic measurements in an open jet wind tunnel. Avoiding it and establishing a good experiment environment are primary concerns for the wind tunnels. The characteristics of the low frequency pulsation and a combination control method of changing angles of the collector flaps and opening a hole in the test section chamber above nozzle were researched in a 1:15 model wind tunnel. On the basis of the method, two new control methods that are based on a Helmholtz resonator and addition pipes connected with airline of wind tunnel were put forward and validation tests were done. The results show that although the method can reduce the magnitude of the pulsation, the control effect is not the acme of perfection. The new methods effectively reduce the pulsation in different wind speeds and frequency ranges, and they can make the pulsation to keep a stable level in whole wind speeds, which is beneficial to the application of a full scale wind tunnel.

Experimental investigation of structure vulnerabilities to firebrand showers

Attempting to experimentally quantify the vulnerabilities of structures to ignition from firebrand showers has remained elusive. The coupling of two facilities has begun to unravel this difficult problem. The NIST Firebrand Generator (NIST Dragon) is an experimental device that can generate a firebrand shower in a safe and repeatable fashion. Since wind plays a critical role in the spread of WUI fires in the USA and urban fires in Japan, NIST has established collaboration with the Building Research Institute (BRI) in Japan. BRI maintains one of the only full scale wind tunnel facilities in the world designed specifically for fire experimentation; the Fire Research Wind Tunnel Facility (FRWTF). The present investigation is aimed at extensively quantifying firebrand penetration through building vents using full scale tests. A structure was placed inside the FRWTF and firebrand showers were directed at the structure using the NIST Dragon. The structure was fitted with a generic building vent, consisting of only a frame fitted with a metal mesh. Six different mesh sizes openings were used for testing. Behind the mesh, four different materials were placed to ascertain whether the firebrands that were able to penetrate the building mesh assembly could ignite these materials. Reduced scale test methods afford the capability to test new vent technologies and may serve as the basis for new standard testing methodologies. As a result, a new experimental facility developed at NIST is presented and is known as the NIST Dragon's LAIR (Lofting and Ignition Research). The NIST Dragon's LAIR has been developed to simulate a wind driven firebrand attack at reduced scale. The facility consists of a reduced scale Firebrand Generator (Baby Dragon) coupled to a bench scale wind tunnel. Finally, a series of full scale experiments were conducted to visualize the flow of firebrands around obstacles placed downstream of the NIST Dragon. Firebrands were observed to accumulate in front of these obstacles at a stagnation plane, as was observed when the structure was used for firebrand penetration through building vent experiments, due to flow recirculation. The accumulation of firebrands at a stagnation plane presents a severe threat to ignitable materials placed near structures.

Sail pressures from full-scale, wind-tunnel and numerical investigations

The main results of a two-year project aimed at comparing full-scale tests, wind tunnel tests, and numerical analysis predictions are presented. Pressure measurements were obtained from both full-scale tests and wind tunnel tests, in upwind and downwind conditions. The upwind wind tunnel test condition was modelled using a Vortex Lattice code, while the downwind wind tunnel test was modelled using a Navier–Stokes code. The pressures obtained from the three different methods are compared on three horizontal sections of the headsail, mainsail and asymmetric spinnaker. In general the pressure from the three experiments showed good agreement. In particular, very good agreement was obtained between the numerical computations and the wind tunnel test results. Conversely, the results from the downwind full-scale pressure measurements showed less similarity due to a slightly tightened trim being used for the spinnaker in the on-water tests. Full-scale tests allow the action of unsteadiness due to the wind, wave and yacht movements to affect the results. This unstable environment caused the asymmetric spinnaker to move around, and a tightened trim was required to prevent the spinnaker from collapsing.

An Experimental Investigation of Automobile Interior Wind Noise Using a Production Vehicle

Based on the analysis of automobile aerodynamic noise generation mechanisms and the components of interior wind noise, the spectra characteristics and spatial distribution rule of sound level of interior wind noise were investigated at first, then the frequency characteristics and noise level under different wind speeds, different yaw angles in SAWTC full-scale aeroacoustic wind tunnel were studied. The results show that: the interior noise level was nearly symmetric on vehicle left and right side, noise level of outboard ear was normally higher than that of inboard ear. The frequency characteristics under different wind speeds were almost the same, the linear OASPL of interior noise increased at about 4.4th power and A-weighted OASPL at about 5.5th power of wind speed. In addition, the acoustic power increased as yaw angle rose up, and noise level by leeward side was normally higher than that by windward under the same yaw angle.

Numerical Simulation of Wind Pressure Distribution on Structure Roofs with Suspension Solar Panels

This paper presents the results of full-scale numerical wind tunnel tests of wind pressure on structure roofs with suspension solar panels. Solar roof project is popularized in this century. Solar panels are suspended above the structure roof. So the wind load effect on the structure roof is varied. The wind tunnel experiments are often expensive. A 3D model is introduced and solved using ADINA. The wind pressure distribution coefficients are calculated.

Aerodynamic loads on buses due to crosswind gusts: extended analysis

The objective of this work is to use inverse simulations on measured vehicle data in order to estimate the aerodynamic loads on a bus when exposed to crosswind situations. Tyre forces, driver input, wind velocity and vehicle response were measured on a typical coach when subjected to natural crosswind gusts. Based on these measurements and a detailed MBS vehicle model, the aerodynamic loads were estimated through inverse simulations. In order to estimate the lift force, roll and pitch moments in addition to the lateral force and yaw moment, the simulation model was extended by also incorporating the estimation of the vertical road disturbances. The proposed method enables the estimation of aerodynamic loads due to crosswind gusts without using a full scale wind tunnel adapted for crosswind excitation.

Effect of wind direction on greenhouse ventilation rate, airflow patterns and temperature distributions

The effect of wind direction, relative to a multi-span naturally ventilated greenhouse, on the airflow patterns and air temperature distribution inside the house and at the openings is investigated in the present study, in a greenhouse with vertical roof openings. Experiments in a full-scale greenhouse, CFD (Computational Fluid Dynamics) full-scale simulations and wind tunnel tests on a small-scale model were carried out. The results showed a significant effect of the wind direction on the flow patterns both inside the house and at the roof openings. Furthermore, wind direction significantly affected the ventilation rate and the air and crop temperature distributions. A reasonable qualitative agreement was achieved between the experiments, numerical simulations and wind tunnel tests with respect to flow patterns through the openings. Quantitatively, the numerically predicted ventilation rates are in reasonable agreement with estimates of ventilation rates obtained by a model given in the literature. However, numerically predicted air velocities at the greenhouse openings differ from the measured values and possible reasons for the differences are highlighted and discussed.

Computational Prediction of Nose-Down Control for F/A-18E at High Alpha

Computational fluid dynamics was used to predict the longitudinal stability and control characteristics of the preproduction F/A-18E Super Hornet configuration with neutral and full nose-down control at high angle of attack, subsonic conditions. Such data contribute to an analysis of the ability of the pilot to recover from extreme angles of attack and are usually obtained and extrapolated from wind-tunnel tests. The current computational study was intended to be an exploratory study of the usefulness of computational fluid dynamics to aid the designer and analysts in predictions of flight behavior. The calculations were made for Mach 0.082 at a Reynolds number of 1.15 x 10 6 based on mean aerodynamic chord at angles of attack between 0 and 60 deg. The F/A-18E was modeled with 34-deg leading-edge flaps, 4-deg trailing-edge flaps, 0-deg aileron deflection, a rudder deflection of 30 deg, a spoiler deflection of 60 deg, and horizontal-tail deflections of 0 and 20 deg. The flow conditions and configuration corresponded to those used in tests of a 15%-scale F/A-18E wind-tunnel model tested at the 30- by 60-ft full-scale wind tunnel at the NASA Langley Research Center in Hampton, Virginia. The flow solver used during this project was USM3D, which was developed by the NASA Langley Research Center. The forces and moments predicted by USM3D compared well to the wind-tunnel data for angles of attack between 0 and 40 deg. For angles of attack from 40 to 60 deg, however, the results from USM3D differed from the wind-tunnel data. These differences are attributed to the unsteady nature of the flow and turbulence effects not adequately captured by the computations.

Improvements of the Beamforming Technique in Pininfarina Full Scale Wind Tunnel by using a 3D Scanning System

Improvements of the Beamforming Technique in Pininfarina Full Scale Wind Tunnel by using a 3D Scanning System

Single-sided natural ventilation driven by wind pressure and temperature difference

Even though opening a window for ventilation of a room seems very simple, the flow that occurs in this situation is rather complicated. The amount of air going through the window opening will depend on the wind speed near the building, the temperatures inside and outside the room, the wind direction, the turbulence characteristics in the wind and the pressure variations caused by e.g. wind gusts. Finally, it also depends on the size, type and location of the opening. Many of these parameters are unsteady which makes the calculation of air-change rates even more complicated. In this work, full-scale wind tunnel experiments have been made with the aim of making a new expression for calculation of the airflow rate in single-sided natural ventilation. During the wind tunnel experiments it was found that the dominating driving force differs between wind speed and temperature difference depending on the ratio between the forces and the wind direction. This change is also found in the velocity profiles measured in the opening, which might change from wind dominated to temperature dominated under the same wind direction but with increasing temperature difference.

WS2-2 スズキ低騒音実車風洞の紹介(1)(自動車に関連する実験計測・数値計算に関するワークショップ,ワークショップ)

WS2-2 スズキ低騒音実車風洞の紹介(1)(自動車に関連する実験計測・数値計算に関するワークショップ,ワークショップ)

Neural Network Modeling of UH-60A Pilot Vibration

Full-scale flight-test pilot floor vibration is modeled using neural networks and full-scale wind tunnel test data for low speed level flight conditions. Neural network connections between the wind tunnel test data and the tlxee flight test pilot vibration components (vertical, lateral, and longitudinal) are studied. Two full-scale UH-60A Black Hawk databases are used. The first database is the NASMArmy UH-60A Airloads Program flight test database. The second database is the UH-60A rotor-only wind tunnel database that was acquired in the NASA Ames SO- by 120- Foot Wind Tunnel with the Large Rotor Test Apparatus (LRTA). Using neural networks, the flight-test pilot vibration is modeled using the wind tunnel rotating system hub accelerations, and separately, using the hub loads. The results show that the wind tunnel rotating system hub accelerations and the operating parameters can represent the flight test pilot vibration. The six components of the wind tunnel N/rev balance-system hub loads and the operating parameters can also represent the flight test pilot vibration. The present neural network connections can significandy increase the value of wind tunnel testing.

Numerical modeling of the flow conditions in a closed-circuit low-speed wind tunnel

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 full-scale Jules Verne climatic wind tunnel in which experimental data have been obtained. Due to the specific features of this closed-circuit wind tunnel, the conventional CFD modeling approach, in which only the flow in the wind tunnel test section is modeled, is inadequate. To obtain accurate results the entire wind tunnel has to be modeled. In the numerical closed-circuit wind tunnel, the conventional flow inlet and outlet are replaced by a single “fan boundary condition”. Special attention is given to the theoretical background and the practical implementation of this type of boundary condition in the CFD model. The numerical model is validated for the case of an empty wind tunnel and for the case in which a block-type building is placed in the test section. It will be shown that this methodology can generally reproduce the wind tunnel measurements of mean velocities with an error equal to or less than 10% despite the occurrence of multiple flow separations upstream of the test section. This provides perspectives for the future use of this methodology as a tool for wind tunnel design and testing and for CFD validation purposes.

Active Flow Control on the Stingray Uninhabited Air Vehicle: Transient Behaviour

The application of leading-edge separation control on an uninhabited air vehicle (UAV) with 50-deg leading-edge sweep is investigated experimentally in a full-scale close-return wind tunnel using arrays of synthetic jet actuators. Active flow control is used to enhance vehicle control at moderate and high angles of attack for takeoff and landing activities or gust load alleviation. The surface-mounted synthetic jet actuators are operated in various waveforms where the carrier frequency is at least an order of magnitude higher than the characteristic shedding frequency of the UAV. Actuation yields a suction peak near the leading edge, however, while excitation with a sinusoidal waveform results in a sharp suction peak near the leading edge; pulse modulation yields a larger and wider suction peak. The flow transients associated with controlled reattachment and separation of the flow over the UAV are investigated using amplitude modulation of the actuation waveform by measuring the dynamic surface pressure at different locations on the upper surface of the UAV’s wing. Phase-locked measurements show that the transients, associated with the onset of reattachment and separation, at high angles of attack are accompanied by the shedding of large-scale vortical structures and oscillations of the surface pressure. However, no oscillations are observed when the baseline flow is attached.

Rotor Performance of a UH-60 Rotor System in the NASA Ames 80- by 120-Foot Wind Tunnel

Abstract : A full-scale four-bladed UH-60 rotor system was tested in the NASA Ames 80- by 120-Foot Wind Tunnel. A quality data set at low forward speed, 0 to 80 knots, has been obtained to support future rotor developments and analysis improvements. To evaluate the NASA Ames 80- by 120- Foot Wind Tunnel as a hover testing facility, rotor performance data were compared with predictions, UH-60 aircraft flight test data, and UH-60 model-scale data from other test facilities. Results indicate that valid hover data for this size rotor can be obtained from this facility at low to medium thrust conditions. Comparisons with flight test and model-scale data demonstrate the variability between existing data sets. Predictions show good agreement with full-scale data. To evaluate the analytical modeling in the 0 to 80 knot speed range, forward flight rotor performance data were acquired and compared with predictions. Comparisons were also made with existing model-scale and flight test data. Power calculations show fair to good agreement with full-scale wind tunnel data at advance ratios between 0.10 to 0.19 and poor agreement at advance ratios below 0.10. Comparisons with flight test and model-scale data show good agreement at all advance ratios tested. Propulsive force calculations show good correlation with full-scale wind tunnel data at advance ratios of 0.10 to 0.19.