Speed Wind Tunnel Research Articles

De-Icing Fluid Flow-Off from a Flat Plate in an Accelerating Airstream

De-icing fluid flow-off from a flat plate subjected to an accelerating airflow was studied both experimentally and using computational fluid dynamics (CFD) simulations. The experimental tests were carried out in Aalto University’s Low Speed Wind Tunnel using two different flat plate models, with chords of 0.6 and 1.8 m. The OpenFOAM software library was used in the CFD simulation for the 0.6 m flat plate model. Both measurements and CFD simulations supported the assumption that the solitary waves dominating the flow-off process were kinematic, mass transporting, in nature. For the first 50% of the fluid thickness decrease, the wave speeds and the mean fluid flow speed are almost linearly dependent on the wind tunnel speed on both flat plate models. The fluid thickness at the end of simulation predicted well the measured value.

Wind Tunnel Testing for Vibration Analysis of High Rise Building Due to Wind load

Wind load can induce vibration on high rise building which can cause discomfort to occupants and fatigue in structural members and connections caused by fluctuating wind loads. Vibration on high rise building due to wind load can cause by vortex shedding around the building. Wind tunnel testing is a way to asses vibration on high rise building because of wind load. With doing wind tunnel testing we can analyze vibration cause by vortex shedding which call vortex induced vibration. In this research vortex induced vibration occur at wind speed 8.4 m/s in wind tunnel which excited high rise building dynamic model with 4.1 Hz first natural frequency. The other phenomenon which can be analyze in this research is lock-in phenomenon, lock-in phenomenon is start at 7.8 m/s wind tunnel speed which induce model natural frequency structure at 4.1 Hz, when the wind speed is up to 8.4 m/s the frequency still at 4.1 Hz but the vibration amplitude is rising, and when the wind speed is up to 8.9 m/s the vibration amplitude is decline at the same frequency at 4.1 Hz, when the speed is more than 8.9 m/s the frequency is more than 4.1 Hz and the amplitude decline until the next model natural frequency excited by vortex shedding frequency.

Measurement of the fracture energy in mode I of atmospheric ice accreted on different materials using a blister test

Atmospheric ice is formed when supercooled water droplets strike an object such as a tree, aircraft or wind turbine. Its microstructure and properties vary widely according to the flow and thermal conditions prevailing. The present work was conducted in the Cranfield Icing Wind Tunnel for a european project called STORM (efficient ice protection Systems and simulation Techniques Of ice Release on propulsive systeMs). It aimed at collecting data on the fracture energy of atmospheric ice on four different materials - AL2024-T3, Ti-6Al-4V, Platinum and Alexit-411 - using a blister test. This particular test, firstly introduced by Andrews and Lockington (1983), have been adapted by Cranfield University to be able to test the ice adhesion in situ while ice is still accreting on the surface making it closer to real situation. The second part of the paper will focus on the influence of different parameters like the materials ice is accreted on, the total ambient temperature, the tunnel wind speed and the cloud liquid water content which have been investigated over a few icing conditions.

Line wind speed distribution model of rectangular tunnel cross-section

Accurate monitoring of the tunnel wind speed plays a key role in achieving intelligent mine ventilation. Based on the difficulty faced in precise reflection of the average tunnel wind speed by point wind speed monitoring, this paper puts forward a method for accurate monitoring the tunnel wind speed by large-span ultrasonic linear wind speed sensor based on the method of the time difference. Besides, as to the core problem of representing the average section wind speed by section-linear wind speed, the distribution rules of section wind speed in rectangular tunnel with various support forms is studied through combing theoretical analysis and experimental verification. The results could be well applied to rapid determination of ventilation parameters in other coal mines, which is better for the ventilation management of mines.

Examination of experimental errors in Scanlan derivatives of a closed-box bridge deck

The objective of the investigation is the analysis of wind-tunnel experimental errors, associated with the measurement of aeroelastic coefficients of bridge decks (Scanlan flutter derivatives). A two-degree-of-freedom experimental apparatus is used for the measurement of flutter derivatives. A section model of a closed-box bridge deck is considered in this investigation. Identification is based on free-vibration aeroelastic tests and the Iterative Least Squares method. Experimental error investigation is carried out by repeating the measurements and acquisitions thirty times for each wind tunnel speed and configuration of the model. This operational procedure is proposed for analyzing the experimental variability of flutter derivatives. Several statistical quantities are examined; these quantities include the standard deviation and the empirical probability density function of the flutter derivatives at each wind speed. Moreover, the critical flutter speed of the setup is evaluated according to standard flutter theory by accounting for experimental variability. Since the probability distribution of flutter derivatives and critical flutter speed does not seem to obey a standard theoretical model, polynomial chaos expansion is proposed and used to represent the experimental variability.

A Study on the Wind-Induced Flutter Energy Harvester (WIFEH) Integration into Buildings

In this modern age, low-energy devices are pervasive especially when considering their applications in the built-environment. This study investigates the potential building integration and energy harnessing capabilities of the Wind-Induced Flutter Energy Harvester (WIFEH) – a microgenerator intended to provide energy for low-powered applications. The work presents the experimental investigation of the WIFEH inside a wind tunnel and a case study using Computational Fluid Dynamics (CFD) modelling of a building integrated with a WIFEH system. The experiments examined the WIFEH under various wind tunnel wind speeds varying between 2.3 up to 10 m/s in order to gauge the induced voltage generation capability of the device. The WIFEH was able to generate an RMS voltage of 3 V, peak-to-peak voltage of 8.72 V and short-circuit current of 1 mA when subjected to airflow of 2.3 m/s. With an increase of wind velocity to 5 m/s and subsequent membrane retensioning, the RMS and peak-to-peak voltages and short-circuit current also increase to 4.88 V, 18.2 V, and 3.75 mA, respectively. The simulation used a gable-roof type building model with a 27˚ pitch obtained from the literature. For the CFD modelling integrating the WIFEH into a building, the apex of the roof of the building yielded the highest power output for the device due to flow speed-up maximisation in this region. This location produced the largest power output under the 45˚ angle of approach, generating an estimated 62.4 mW of power under accelerated wind in device position of up to 6.2 m/s. The method and results presented in this work could be useful for the further investigation of the integration of the WIFEH in the urban environment.

Active flow control of bi-stable asymmetric vortices on a slender body by alternating synthetic jets

A synthetic jet actuator with double nozzles is developed to control the leeward vortices behind the slender body at a high angle of attack. Periodic alternating disturbance at the nose tip of the slender body is continuously provided by the alternating synthetic jets. A series of experiments is conducted in a low speed and low turbulence wind tunnel. The results show that the alternating synthetic jets at the nose tip can achieve a suitable control effect in which the lateral force is eliminated. For a very high angle of attack, the leeward vortices behind the slender body are in the inherently bi-stable state; in this state, the symmetric distribution formation by the leeward vortices is nearly impossible. However, the alternating disturbance of the nose tip can break the bi-stable state and transform it into other two states, which are the unsteady switched state of the leeward vortices and the quasi-steady symmetric state. Varying the control frequency significantly affects the state of the leeward vortex. In the range of the lower control frequency, the leeward vortices switch back and forth and follow the cycle of the alternating disturbance at the nose tip. In the range of the higher control frequency, the leeward vortices are in a stable symmetric distribution state. As the alternating disturbance frequency increases from lower to higher, the switched amplitude of the leeward vortices decreases and the unsteady switched state of the leeward vortices gradually changes to the quasi-steady symmetric state. This amplitude reduction occurs because the position of the leeward vortices is very sensitive to the alternating disturbance of the nose tip and is related to the inertia effect of the fluid.

Effect of turbulence intensity on PM emission of heavy duty diesel trucks - Wind tunnel studies

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 increases with increase in distance away from tailpipe. Also indicating the cooling and dilution of the exhaust begins at close vicinity to the tailpipe. The rate of cooling and dilution are greatest in early stages of the dilution process for the areas with high turbulence intensity (TI), where strong mixing phenomena occurs, leading to the formation of a predominant nucleation mode. On the other hand, the core of the plume observes a slower cooling and dilution rate. This difference is reflected in the PM formation and evolution of these two distinct regions, as shown by the particle size distributions and number concentrations. Continuous mixing will tend to mellow those differences, but its “final” result is related to the dilution history.

Study of Reynolds number effect on turbulent boundary layer near the separation

The paper deals with the experimental analysis of strong decelerated turbulent boundary layer developed on a flat plate. The special design of the test section equipped with perforated, movable upper wall allow to generate on the bottom wall turbulent boundary layer, which is at the verge of separation. The objective of the work is to examine the effect of Reynolds number on non-equilibrium boundary layer. A momentum thickness Reynolds number at the inlet to a test section was in the range from 6300 to 10150 what was achieved by varying wind tunnel speed. The emphasis is on the analysis of the streamwise Reynolds stress and mean velocity profiles and on related scaling issues problem. It was found that for the same external conditions defined by the pressure gradient coefficient Cp the effect of Reynolds number close the wall is seen even for such a narrow range of Reynolds number. In particular, the shape factor revealed more flow resistance on separation with increase in Reynolds number. The difference where observed mainly at the beginning of incipient detachment, where there is a drop of turbulence activity near the wall while it reaches a maximum value in the outer region.

Numerical simulation of the interaction between tandem wind turbines

Two model wind turbines operating in tandem are simulated using Tenasi, a node-centered, finite volume unstructured flow solver. The turbine blades are designed using the NREL S826 airfoils. The entire test section of the wind tunnel is simulated since the blockage (based on swept area of the rotor and tower area) was 12%. The simulations included the tunnel walls, wind turbine blades, hubs, nacelles and towers. Detailed experimental data is available for a variety of flow conditions (varying tip-speed-ratios). The results presented here are for tip-speed-ratios of 2.5, 4, and 7 for the rear turbine while the front turbine was always operated at the design tip speed ratio of 6. The tunnel wind speed was 10m/s and the wind turbine RPM was varied to achieve the desired tip-speed-ratios. A DES version of the Menter's SST turbulence model is utilized for the turbulence closure. Turbine performance as well as wake data at various locations is compared to experiment (Blind Test 2 study carried out at NTNU, Norway). Very good agreement is observed for the turbine performance. Good agreement was obtained for velocity fluctuations in the wake region with trends captured very well. Mean velocity predictions agree reasonably well.

Model Analysis of Smoke Control in Long Tunnel: Findings from Hsueh-Shan Tunnel Accident in Taiwan

The common properties of risk in long tunnel fires are high temperature, extreme difficulty of evacuation, rescue urgency and obstacle to rescue operation. Therefore, a complete ventilation design is an indispensable safety measure. Hsueh-Shan Tunnel is the longest in Taiwan, the fifth longest in the world. On May 7, 2012, a serious tunnel fire caused two deaths and numerous victims suffered from smoke inhalation injury. Apart from this, there was smoking entering the cross-passages and shafts which were important for evacuation. In this research, the current ventilation system in Hsueh-Shan Tunnel was simulated with FDS (fire dynamics simulator) software, and the statistics of smoke, visibility and temperature profile were analyzed. The results of this research showed that, with the current ventilation system, the time was shorter and the distance was longer for the smoke spreading windward than in other models. Furthermore, the visibility of windward victims was more affected and the temperature above the fire source was higher than those in other systems. When the wind speed in tunnel is within 2.0~4.0 m/s, the condition for turning off the ventilation fan within 250 m upwind from the fire source can be prominently reduced to 50 m upwind from the fire source. This not only could avoid plume disturbance but also could be maintained. If victims' evacuation should be given the highest priority, it is recommended to straightly activate the maximum power of the fan. Language: en

Experimental and numerical study of a generic conventional submarine at 10° yaw

This investigation discusses the flow physics of the fully appended DSTO generic submarine model at both straight ahead conditions and during a 10° side-slip. Reynolds Averaged Navier Stokes (RANS) and Large Eddy Simulation (LES) computations have been performed and are compared with model-scale experiments. The experiments have been carried out in the DSTO Low-Speed Wind Tunnel, with data collected using pressure probes, Particle Image Velocimetry (PIV) and flow visualization using wool-tuft streamers. Computational studies using LES on unstructured meshes of up to 340 million cells provide detailed surface and off-body flow field data, complementing the experimental investigations and providing the opportunity for reciprocal validation of experiments and computations. Surface-flow patterns for the DSTO generic submarine model at 10° yaw and a freestream Reynolds (Re) number, based on wind tunnel speed and hull length, of Re=4.5×106 were obtained. The cross-stream velocity for the DSTO generic submarine model at 10° yaw and Re=2.7×106 was measured using PIV. The in-plane velocity was measured at three streamwise locations corresponding to 65%, 84% and 98% of the submarine model length. LES computations were performed using an incompressible LES flow solver developed using OpenFOAM and unstructured tetrahedral grids generated utilizing a patch-based approach to facilitate high near-wall resolutions and arbitrary refinement for appendage wakes.

Assessment of across-wind responses for aerodynamic optimization of tall buildings

A general approach of aerodynamic optimization of tall buildings is presented in this paper, focusing on how to best compromise wind issues with other design aspects in the most efficient manner. The given approach is reinforced by establishing an empirical method that can quickly assess the across-wind loads and accelerations as a function of building frequencies, building dimensions, aspect ratios, depth-to-width ratios, and site exposures. Effects of corner modifications, including chamfered corner and recessed corner, can also be assessed in early design stages. Further, to assess the effectiveness of optimization by tapering, stepping or twisting building elevations, the authors introduce a method that takes use of sectional aerodynamic data derived from a simple wind tunnel pressure testing to estimate reductions on overall wind loads and accelerations for various optimization options, including tapering, stepping, twisting and/or their combinations. The advantage of the method is to considerably reduce the amount of wind tunnel testing efforts and speed up the process in finding the optimized building configurations.

Building a Practical Anechoic Chamber for Aero-Acoustic Measurements

The design, manufacture and installation of a practical and cost-effective anechoic chamber for aero-acoustic measurements are presented in this paper. The work was undertaken with a view to measure the aerodynamically generated noise of wind turbines under laboratory conditions. The chamber was designed to be used in conjunction with a wind tunnel. Tests were carried out to compare the reduction of noise levels from external sources with and without the chamber. The results obtained suggest a clear reduction of noise levels with different wind speeds, and as expected, resulted with higher reductions at higher wind tunnel speeds.

Measurement of particle rotation in a saltation layer

ABSTRACTTwo computational methods to measure particle rotations from shadow images of sand particles saltating in a wind tunnel are presented. One method calculates the maximum of the cross‐correlations through multiple angular rotations of an imaged particle. The second method polar transforms both images and then calculates the correlation coefficient for multiple pixel displacements in the θ axis, corresponding to particle rotations. The results from both methods were analysed as a function of height above sand bed (3.7–33.4 mm) and particle size (0.32–0.93 mm equivalent mean diameter). Our results indicate little evidence that particle rotation speeds depend on either their size or height above the sand bed. Though similar results were obtained from both methods, there existed different advantages and disadvantages between the methods. Erroneous results likely arose from particles that were inadequately described by a 2‐D rotation axis, or from poorly imaged particles. At a wind tunnel speed of about 12 m/s, most particles rotated at around 300–400 rev/s. Negative rotations were also found, and their proportion was approximately 15% within the total range of −450 to 850 rev/s. The ratio of displacement kinetic energy to rotation energy was compared across the various groups and had values between 15 and 40. The quotient showed little dependence on height, though decreased with increasing particle size. Wider applicability of the measurement methodology to study snow particle rotation is also discussed. Copyright © 2014 John Wiley & Sons, Ltd.

Badminton Performance Test of Wind Tunnel

The badminton wind tunnel experiment quality classification was influenced by a lot of factors, such as the size of the wind tunnel wind speed Settings, the selection of the wind hole diameter size, Experiment parameter Settings of the test system software used standard and experimental error and so on. Therefore, a factorys wind tunnel experimental facility would be used by this paper, in order to make the quality of badminton, wind tunnel wind speed and wind hole diameter are researched further. Through the experiment testing, and combined with badminton wind tunnel experiment of theory knowledge, get the impact of these factors on the quality of badminton classification rule. Theoretical analysis is the same as the result of experiment, which this conclusion is indicated by the experiment that what we do. So as to choose the right wind tunnel device and system software of the test parameters Settings provide certain reference. Also the Badminton the judgment of the quality grade classification standard was provided the important reference frame by it.

Extremum Seeking Adaptive Separation Control on a Wing with Plasma Synthetic Jet Actuator

Plasma synthetic jet actuator (PSJA) is a flow control device which has structure that insulator is tucked with electrode pair. It generates electrohydrodynamic (EHD) effect and induces a flow. The experiment was held to investigate the effect of flow control using extremum seeking with PSJA placed on the surface of NACA0012 wing installed in the wind tunnel. Frequency of the input signal to PSJA is modulated to maximize the effect of PSJA in flow control. The wake velocity fluctuation is one of indexes on separation control effect. The wake velocity is minimized over the input frequency by employing extremum seeking. The seeking algorithm calculates the correlation of the modulation frequency and wake velocity fluctuation. The modulation signal frequency where the correlation changes from negative to positive minimizes the wake velocity fluctuation. To detect a local minimum of the wake velocity fluctuation by extremum seeking, it is necessary to change the modulation signal frequency with time. Sine and square waves change the modulation signal frequency to PSJA. The wind tunnel speed was changed as an external factor. The experimental results show that the modulation signal frequency can track the optimum value when the wind tunnel speed is changed. This paper shows that adaptive flow control to optimize the modulation signal frequency with PSJA using extremum seeking enables to suppress turbulence on the flow field of wings.

Identification of Flight Vehicle Models Using Fuzzified Eigensystem Realization Algorithm

This paper presents a new approach with a fuzzified eigensystem realization algorithm for identification of flight vehicle models in low-speed wind tunnel (LSWT) and high-speed wind tunnel (HSWT). A variety of variables in model types and testing environment (such as angle-of-attack, sideslip angle, tunnel wind speed) and profile, elevator, and power system (motor and propeller) of mini unmanned aerial vehicle (mini-UAV) model are considered in a power-on mini-UAV testing system in LSWT and an Advisory Group for Aerospace Research and Development (AGARD) standard calibration model in HSWT. The method based on the fuzzy logic inference structure is simple and effective. The results obtained are compared to those obtained by the conventional wind tunnel testing method. To verify the effectiveness of the proposed methodology, simulations are conducted using real-world experimental results that demonstrate that the working performance of the proposed method correlates well as expected.

The new and improved NIST Dragon's LAIR (Lofting and Ignition Research) facility

SUMMARYSeveral studies suggest that the firebrands are a major cause of structural ignition of Wildland–Urban Interface fires in USA and Australia. For 40 years, past firebrand studies have focused on how far firebrands fly and do not assess the vulnerabilities of structures to ignition from firebrand showers. The development of the National Institute of Standards and Technology (NIST) Dragon has allowed the quantification of structure ignition vulnerabilities of full‐scale building assemblies. Full‐scale tests are necessary to highlight vulnerabilities of structures to ignition under firebrand attack, whereas bench‐scale test methods afford the capability to test new firebrand‐resistant technologies and may serve as the basis for new standard testing methodologies. To this end, the present investigation was undertaken to construct a new and improved Dragon's Lofting and Ignition Research facility. This entailed removing the NIST Baby Dragon from the wind tunnel facility and inserting the new and improved NIST continuous feed Baby Dragon. The unique feature of the continuous feed Baby Dragon, over the current NIST Baby Dragon, is the capability to produce a constant firebrand shower in order to expose building materials to continual firebrand bombardment. The efficacy of the new experimental facility to determine ignition regime maps of building materials exposed to wind‐driven firebrand showers is presented. Specifically, ignition regime maps are presented as a function of continuous firebrand generation rate, wind tunnel speed, and cedar moisture content. Copyright © 2011 John Wiley & Sons, Ltd.

The flow around a model helicopter main rotor in ground effect

Wind tunnel measurements of the wake below and ahead of a model helicopter main rotor in simulated forward flight in ground effect are presented. The wind tunnel used was equipped with a rolling road, and the ground speed was matched to the wind tunnel speed for a representative simulation in the wind tunnel of forward flight over the ground. Particle image velocimetry was used to investigate the structure of the wake, and it was observed that the moving ground had a remarkable effect on the flow; the wake is closer to the rotor and its size is reduced compared with the stationary ground case. The detailed distribution of vorticity within the wake is affected by the moving ground, and the mechanism for this is discussed in the paper.