Laboratory Wind Tunnel Research Articles

PM10 emission efficiency for agricultural soils: Comparing a wind tunnel, a dust generator, and the open-air plot

Abstract 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

Optomotor steering and flight control requires a specific sub-section of the compound eye in the hawkmoth, Manduca sexta.

While tracking odor plumes, male hawkmoths use optic flow cues to stabilize their flight movements with respect to their environment. We studied the responses of freely flying moths tracking odor plumes in a laboratory wind tunnel and tethered moths in an optomotor flight simulator to determine the locations on the compound eye on which critical optic flow cues are detected. In these behavioral experiments, we occluded specific regions of the compound eye and systematically examined the moths' behavior for specific deficits in optic flow processing. Freely flying moths with the dorsal half of the compound eye painted were unable to maintain stable flight and track the wind-borne odor plume. However, the plume tracking performance of moths with the ventral half of their compound eyes painted was the same as unpainted controls. In a matched set of experiments, we presented tethered moths with moving vertically oriented sinusoidal gratings and found that individuals with their eyes unpainted, ventrally painted and medially painted all responded by attempting optomotor-driven turns in the same proportion. In contrast, individuals with their compound eyes dorsally painted, laterally painted and completely painted showed no optomotor turning response. We decreased the contrast of the visual stimulus and found that this relationship was consistent down to a contrast level of 2.5%. We conclude that visual input from the dorso-lateral region of the moth's visual world is critical for successful maintenance of flight stability and that this species' visual environment must meet or exceed a contrast ratio of 2.5% to support visual flight control.

Inter-Facility Correlations of Transonic Test Results of the AGARD-C Standard Wind-Tunnel Model

Aerodynamic characteristics of an AGARD-C model in the transonic Mach number range in the 1.5 m T-38 trisonic wind tunnel of the Military Technical Institute (VTI) in Belgrade were compared with those from other wind tunnel laboratories. Inter-facility correlations were based on test results of physically the same model in the NRC and INCREST trisonic wind tunnels and in the T-38 wind tunnel during its early period. Analysis of test results confirmed an excellent measurement chain in the T-38 wind tunnel, except small differences in the pitching moment coefficient data obtained in inverted runs procedurally performed for test section symmetry check. The AGARD-C model is being known for the high sensitivity of the pitching moment to local conditions and it has been concluded that the effects may have been caused by the asymmetry of the model support mechanism

Herbivores alter plant-wind interactions by acting as a point mass on leaves and by removing leaf tissue.

In nature, plants regularly interact with herbivores and with wind. Herbivores can wound and alter the structure of plants, whereas wind can exert aerodynamic forces that cause the plants to flutter or sway. While herbivory has many negative consequences for plants, fluttering in wind can be beneficial for plants by facilitating gas exchange and loss of excess heat. Little is known about how herbivores affect plant motion in wind. We tested how the mass of an herbivore resting on a broad leaf of the tulip tree Liriodendron tulipifera, and the damage caused by herbivores, affected the motion of the leaf in wind. For this, we placed mimics of herbivores on the leaves, varying each herbivore's mass or position, and used high‐speed video to measure how the herbivore mimics affected leaf movement and reconfiguration at two wind speeds inside a laboratory wind tunnel. In a similar setup, we tested how naturally occurring herbivore damage on the leaves affected leaf movement and reconfiguration. We found that the mass of an herbivore resting on a leaf can change that leaf's orientation relative to the wind and interfere with the ability of the leaf to reconfigure into a smaller, more streamlined shape. A large herbivore load slowed the leaf's fluttering frequency, while naturally occurring damage from herbivores increased the leaf's fluttering frequency. We conclude that herbivores can alter the physical interactions between wind and plants by two methods: (1) acting as a point mass on the plant while it is feeding and (2) removing tissue from the plant. Altering a plant's interaction with wind can have physical and physiological consequences for the plant. Thus, future studies of plants in nature should consider the effect of herbivory on plant–wind interactions, and vice versa.

The response of a guyed transmission line system to boundary layer wind

The current study investigates the aeroelastic characteristics and structural response of a multiple-span guyed lattice transmission line system, through a simultaneous testing of four aeroelastic guyed lattice towers and conductors. The transmission line system simulated in the current study is a generic guyed transmission tower used by different hydro companies in North America and in different parts of the world. The aeroelastic model is designed for a geometry scale of 1:50 and tested in the Boundary Layer Wind Tunnel Laboratory at the University of Western Ontario, Canada. The model is tested using an open exposure wind profile. The aeroelastic test is performed for three different wind directions and for two configurations, with and without the transmission lines (conductors and ground-wires). Such aeroelastic model of guyed transmission line system with multiple-spans is not reported in literature. This represent a new contribution to the existing literature of the aeroelastic behaviour of transmission lines under wind actions. The study investigates the aeroelastic model response to boundary layer wind loading under different wind speeds and configurations. For the 37 wind speeds, two configurations, and three angles of attack used in the current aeroelastic test, no instabilities are observed for the tested transmission towers or lines. The measured natural frequencies of the aeroelastic model match those obtained by numerical modelling and those provided in the literature, and are affected by the value of the pretension force applied to the supporting guys. The results indicate that the multiple-span guyed transmission line system aeroelastic model responded in a quasi-static manner to boundary layer wind loads. Resonant dynamic response is less significant and becomes less distinguished by increasing the wind speeds. The results are used to understand the response of guyed transmission line systems to boundary layer wind loads.

External Pressure Coefficients on the Atypical High-Rise Building – Computing Simulation and Measurements in Wind Tunnel

This paper deals with determination of the external pressure coefficients on the new planned high-rise building with atypical cross-section. The building will be built in the center of Bratislava (Slovakia). The real area surrounding of the designed building was also considered. The main aim of this research was to find out the accuracy of the results obtained by computing simulation. Two types of surfaces of the model were taken into account – smooth and rough ones. The real structure had the surface roughened by using a façade with windows and columns between them. As the reference values of external pressure coefficients were considered the results obtained from the experimental measurements carried out in the wind tunnel laboratory. Short description of the designed structure and its surroundings, wind tunnel laboratory, experimental measurements, scale model of the structure, and computing simulation with considered input parameters are mentioned here. The Computational Fluid Dynamics (CFD) simulation was performed using 3D Reynolds-averaged Navier-Stokes CFD with the SST k-ω turbulence model. At the end of the paper, obtained results are discussed and some recommendations for planning engineers are presented.

Effect of windproof barrier on aerodynamic performance of vehicle-bridge system

The wind barrier is usually installed on the high-speed railway bridge in wind zone for the running safety of the high-speed train, which will change obviously the flow field characteristic around the bridge. So it is very essential to study the aerodynamic properties considering the wind barrier on vehicle-bridge system in order to calculate the dynamic response of bridges and vehicles, the running safety of train under cross winds. Thus the wind tunnel test is adopted to obtain the three-component coefficients of the bridge and the vehicle with wind barriers which have different heights, and opening ratios. And the data of aerodynamic coefficients including the side force coefficient, lift force coefficient, moment coefficient for the vehicle, the drag force coefficient, lift force coefficient, moment coefficient for the bridge are from three different wind tunnel laboratories. The results show that the side force coefficient of vehicle is parabolic curve to opening ratio of wind barriers, as well as the lift coefficient and moment coefficient. And the drag force coefficient of bridge is also parabolic curve to opening ratio of wind barriers, as well as the lift coefficient and moment coefficient. But the aerodynamic coefficients of the vehicle and bridge have no significant change law to the height of wind barriers. In summary, the side force coefficient and moment coefficient of the vehicle decrease with the increasing height of wind barriers, while the drag force coefficient and moment coefficient of the bridge increase with the increasing height of wind barriers.

Investigation of Strouhal number of ice-accreted bridge cables at moderate flow turbulence

This paper is concerned with the investigation of the Strouhal number ( St ) for a stationary iced cable model of cable-supported bridges using wind tunnel tests with respect to three principal angles of wind attack. The investigations were carried out in the Climatic Wind Tunnel Laboratory of the Czech Academy of Sciences in Telc. The St values were determined at the flow turbulence intensity of the order of 12%, within the range of the Reynolds number from 2.4·10 4 to 12.9·10 4 , based on the dominant vortex shedding frequencies measured in the wake of the model. The obtained experimental St values of the iced cable of a cable-supported bridge will allow to determine the critical wind velocity as well as will be helpful for prediction of the cable response due to the vortex excitation phenomenon at moderate flow turbulence condition.

Dry deposition velocities of submicron aerosols on water surfaces: Laboratory experimental data and modelling approach

This article presents new experimental values of deposition velocities of submicron and hygroscopic aerosols of uranine with the objective to analyze dry deposition mechanisms of submicron aerosols on water surfaces in function of wind, water current and differences between air and water temperatures. A special attention is paid to phoretic effects which have been poorly considered by previous experimental studies. Experiments were performed in a laboratory wind tunnel for different conditions precisely characterized in function of aerosol size distribution, air turbulence, water current, water surface deformations, air and water temperatures and relative humidity. The experimental results do not allow detecting any effects of water current nor water surface deformation. The deposition velocity dimensionless with the friction velocity varies according to a V curve as a function of the air-water temperature difference. The minimum of this curve (≈ 2.0×10−5) is reached when the air-water temperature difference is equal to −7.5°C. To analyse these experimental results, appropriate models of hygroscopicity growth, diffusiophoresis and thermophoresis are implemented in the Slinn resistance model (Slinn & Slinn, 1980). Comparisons between experimental and modelling results confirm that the dry deposition velocity of submicron aerosol over water surface is mainly influenced by the turbulent diffusion and show that the influence of hygroscopicity growth is negligible. Furthermore, it is shown that adding the diffusiophoresis and thermophoresis velocities in the deposition layer transfer coefficient greatly improves the agreement between the experimental deposition velocity and the model. Particularly, these results reveal the important role of the thermophoresis when the air-water temperature difference becomes lower than -3°C.

Measuring Spray Droplet Size from Agricultural Nozzles Using Laser Diffraction

When making an application of any crop protection material such as an herbicide or pesticide, the applicator uses a variety of skills and information to make an application so that the material reaches the target site (i.e., plant). Information critical in this process is the droplet size that a particular spray nozzle, spray pressure, and spray solution combination generates, as droplet size greatly influences product efficacy and how the spray moves through the environment. Researchers and product manufacturers commonly use laser diffraction equipment to measure the spray droplet size in laboratory wind tunnels. The work presented here describes methods used in making spray droplet size measurements with laser diffraction equipment for both ground and aerial application scenarios that can be used to ensure inter- and intra-laboratory precision while minimizing sampling bias associated with laser diffraction systems. Maintaining critical measurement distances and concurrent airflow throughout the testing process is key to this precision. Real time data quality analysis is also critical to preventing excess variation in the data or extraneous inclusion of erroneous data. Some limitations of this method include atypical spray nozzles, spray solutions or application conditions that result in spray streams that do not fully atomize within the measurement distances discussed. Successful adaption of this method can provide a highly efficient method for evaluation of the performance of agrochemical spray application nozzles under a variety of operational settings. Also discussed are potential experimental design considerations that can be included to enhance functionality of the data collected.

Measuring Spray Droplet Size from Agricultural Nozzles Using Laser Diffraction.

When making an application of any crop protection material such as an herbicide or pesticide, the applicator uses a variety of skills and information to make an application so that the material reaches the target site (i.e., plant). Information critical in this process is the droplet size that a particular spray nozzle, spray pressure, and spray solution combination generates, as droplet size greatly influences product efficacy and how the spray moves through the environment. Researchers and product manufacturers commonly use laser diffraction equipment to measure the spray droplet size in laboratory wind tunnels. The work presented here describes methods used in making spray droplet size measurements with laser diffraction equipment for both ground and aerial application scenarios that can be used to ensure inter- and intra-laboratory precision while minimizing sampling bias associated with laser diffraction systems. Maintaining critical measurement distances and concurrent airflow throughout the testing process is key to this precision. Real time data quality analysis is also critical to preventing excess variation in the data or extraneous inclusion of erroneous data. Some limitations of this method include atypical spray nozzles, spray solutions or application conditions that result in spray streams that do not fully atomize within the measurement distances discussed. Successful adaption of this method can provide a highly efficient method for evaluation of the performance of agrochemical spray application nozzles under a variety of operational settings. Also discussed are potential experimental design considerations that can be included to enhance functionality of the data collected.

3D unsteady flow analysis around a rotor blade of horizontal axis wind turbine-Rutland 503

The unsteady aerodynamics computational fluid dynamics simulations of the flow-field around a three-bladed Rutland 503 horizontal axis wind turbine rotor have been conducted in this paper to provide information needed to predict the three-dimensional aerodynamics behavior. In the CFD analysis, the variation of wind velocity between 9.3m/s and 15m/s is investigated. The Detached Eddy Simulation method is used with the turbulence model SST. A multiblock structured mesh is used for the discretization of the study domain. The solutions are obtained by using the Solver Fluent 6.3 which uses the method of finites volumes. The results of simulations obtained are compared with the experimental data [1] obtained in Wind Tunnel Laboratory LMA Arts and Metiers Paris-Tech in order to validate these results. Results of the numerical simulation in three dimensions of the unsteady field of flow around the blade are presented.

Ten questions concerning modeling of near-field pollutant dispersion in the built environment

Outdoor air pollution is a major current environmental problem. The precise prediction of pollutant concentration distributions in the built environment is necessary for building design and urban environmental assessment. Near-field pollutant dispersion, involving the interaction of a plume and the flow field perturbed by building obstacles, is an element of outdoor air pollution that is particularly complex to predict. Modeling methodologies have been discussed in a wide range of research fields for many years. The modeling approaches are categorized into field measurements, laboratory (wind and water tunnel) experiments, (semi-) empirical models, and computational fluid dynamics (CFD) models. Each of these approaches has advantages and disadvantages. It is therefore important to use due consideration for the underlying theory and limitations when applying these modeling approaches. This paper considers some of the most common questions confronting researchers and practitioners in the modeling of near-field pollutant dispersion in the built environment.

Seeing is believing: the nocturnal malarial mosquito Anopheles coluzzii responds to visual host-cues when odour indicates a host is nearby.

BackgroundThe immediate aim of our study was to analyse the behaviour of the malarial mosquito Anopheles coluzzii (An. gambiae species complex) near a human host with the ultimate aim of contributing to our fundamental understanding of mosquito host-seeking behaviour and the overall aim of identifying behaviours that could be exploited to enhance sampling and control strategies.ResultsBased on 3D video recordings of individual host-seeking females in a laboratory wind-tunnel, we found that despite being a nocturnal species, An. coluzzii is highly responsive to a visually conspicuous object, but only in the presence of host-odour. Female mosquitoes approached and abruptly veered away from a dark object, which suggests attraction to visual cues plays a role in bringing mosquitoes to the source of host odour. It is worth noting that the majority of our recorded flight tracks consisted of highly stereotyped ‘dipping’ sequences near the ground, which have been mentioned in the literature, but never before quantified.ConclusionsOur quantitative analysis of female mosquito flight patterns within ~1.5 m of a host has revealed highly relevant information about responsiveness to visual objects and flight height that could revolutionise the efficacy of sampling traps; the capturing device of a trap should be visually conspicuous and positioned near the ground where the density of host-seeking mosquitoes would be greatest. These characteristics are not universally present in current traps for malarial mosquitoes. The characterisation of a new type of flight pattern that is prevalent in mosquitoes suggests that there is still much that is not fully understood about mosquito flight behaviour.Electronic supplementary materialThe online version of this article (doi:10.1186/s13071-016-1609-z) contains supplementary material, which is available to authorized users.

A measure of scale-dependent asymmetry in turbulent boundary layer flows: scaling and Reynolds number similarity

The distribution of temporal scale-dependent streamwise velocity increments is investigated in turbulent boundary layer flows at laboratory and atmospheric Reynolds numbers, using the St. Anthony Falls Laboratory wind tunnel and the Surface Layer Turbulence and Environmental Science Test dataset, respectively. The third-order moments of velocity increments, or asymmetry index $A(a,z)$, is computed for varying wall distance $z$ and time scale separation $a$, where it was observed to leave a robust, distinct signature in the form of a hump, independent of Reynolds number and located across the inertial range. The hump is observed in wall region limited to $z^{+}<5\times 10^{3}$, with a tendency to shift towards smaller time scales as the surface is approached ($z^{+}<70$). Comparing the two datasets, the hump, and its location, are found to obey inner wall scaling and is regarded as a genuine feature of the canonical turbulent boundary layer. The magnitude cumulant analysis of the scale-dependent velocity increments further reveals that intermittency is also enhanced near the wall, in the same flow region where the asymmetry signature was observed. The combination of asymmetry and intermittency is inferred to point at non-local energy transfer and scale coupling across a range of scales. From a turbulent structure perspective, such non-local energy transfer can be seen as the result of strong scale-interaction processes between outer scale motions in the logarithmic layer impacting and distorting smaller scales at the wall, through abrupt energy transfer across scales bypassing the typical energy cascade of the inertial range.

Strouhal number of bridge cables with ice accretion at low flow turbulence

The paper concerns with the method and results of wind tunnel investigations of the Strouhal number (St) of a stationary iced cable model of cable-supported bridges with respect to different angles of wind attack. The investigations were conducted in the Climatic Wind Tunnel Laboratory of the Czech Academy of Sciences in . The methodology leading to the experimental icing of the inclined cable model was prepared in a climatic section of the laboratory. The shape of the ice on the cable was registered by a photogrammetry method. A section of an iced cable model with a smaller scale was reproduced with a 3D printing procedure for subsequent aerodynamic investigations. The St values were determined within the range of the Reynolds number (Re) between and , based on the dominant vortex shedding frequencies measured in the wake of the model. The model was oriented at three principal angles of wind attack for each of selected Re values. The flow regimes were distinguished for each model configuration. In order to recognize the tunnel blockage effect the St of a circular smooth cylinder was also tested. Good agreement with the reported values in the subcritical Re range of a circular cylinder was obtained. The knowledge of the flow regimes of the airflow around an iced cable and the associated St values could constitute a basis to formulate a mathematical description of the vortex-induced force acting on the iced cable of a cable-supported bridge and could allow predicting the cable response due to the vortex excitation phenomenon.

ENGLISH

Strut arms contribute significantly to the overall drag in VAWT and reduces the overall power output. Four low drag air foil cross section profiles suitable for strut arm construction were simulated and optimized using the XFOIL 1.0 program. The profile with the lowest simulated drag coefficient, UWI-1, was constructed and tested in an open-circuit suction type conventional non-return laboratory wind tunnel. The flow characteristic was examined experimentally using surface pressure measurements. The results showed that an increase in the Reynolds number from 3.32 x 105 to 9.64 x 105 resulted in a decrease in the drag coefficient from 0.01241 to 0.00984. This is a significantly lower drag coefficient when compared to the nominal value of about 0.4 for cylinders in cross flow within the Reynolds number range tested. The results obtained for the experimental drag coefficient values and the simulated XFOIL were within 10.7%.

Application of tuned liquid dampers in controlling the torsional vibration of high rise buildings

Excessive motions in buildings cause occupants to become uncomfortable and nervous. This is particularly detrimental to the tenants and ultimately the owner of the building, with respect to financial considerations. Serviceability issues, such as excessive accelerations and inter-story drifts, are more prevalent today due to advancements in the structural systems, strength of materials, and design practices. These factors allow buildings to be taller, lighter, and more flexible, thereby exacerbating the impact of dynamic responses. There is a growing need for innovative and effective techniques to reduce the serviceability responses of these tall buildings. The current study considers a case study of a real building to show the effectiveness and robustness of the TLD in reducing the coupled lateral-torsional motion of this high-rise building under wind loading. Three unique multi-modal TLD systems are designed specifically to mitigate the torsional response of the building. A procedure is developed to analyze a structure-TLD system using High Frequency Force Balance (HFFB) test data from the Boundary Layer Wind Tunnel Laboratory (BLWTL) at the University of Western Ontario. The effectiveness of the unique TLD systems is investigated. In addition, a parametric study is conducted to determine the robustness of the systems in reducing the serviceability responses. Three practical parameters are varied to investigate the robustness of the TLD system: the height of water inside the tanks, the amplitude modification factor, and the structural modal frequencies.

Effective Factors in Fine-Grained Soil Stabilization to Prevent Dust Generation

A laboratory research program was arranged to study the effect of different factors influencing the stability of fine soils against wind action. For this purpose, a laboratory wind tunnel was stabilized and several soil samples were examined by putting the sample trays inside the wind tunnel for different rates of wind velocities. The tray for soil samples was 20×30 cm 2 with the depth of 5 cm, and the fine soil samples were chosen with different sizes of particle and porosity. Because the main aim of this research was to investigate the effect of some polymer additives to the soil, many samples were made of the soils improved by different additives in different percentages. Furthermore, the effect of infiltration of the liquid additives was also examined, which could show different infiltration heights as functions of soil type, additive type and the height of pouring. Some of the results were examined by using software. The lab results in this research were compared with some proposed theoretical ones. It was found that as the average diameter of particles increases, erodibility under the same wind velocity decreases, and the applied polymer emulsions decrease the erodibility up to 90% compared to the initial condition. Impacts of dust emission due to the suspended dispersion of fine particles and creeping movements of coarse particles are mitigated as a result of treatment with these emulsions. Variations in erosion of soils at various wind velocities depend on the value of threshold friction velocity with the result that the soil erosion values in case of coarser soils after the increase in velocity would be higher than those of threshold friction velocity. Finally, a relationship is proposed for estimation of soil erosion in terms of wind velocity. The results are consistent with the transport rate relationships proposed by different scholars.

Large-eddy simulation of wind effects on a super-tall building in urban environment conditions

A combined study of large-eddy simulation (LES), wind tunnel testing and full-scale measurement is conducted for the evaluation of wind effects on a super-tall building in a complex urban area. To validate the numerical simulations, the wind tunnel experiments including synchronous multi-pressure and high-frequency force balance model tests are conducted in a boundary layer wind tunnel laboratory. The numerical predictions are then compared with the experimental results, demonstrating that the LES can provide comparable predictions of the wind effects on the super-tall building. Furthermore, the cross-validation of the predicted displacement responses by the LES against the wind tunnel and full-scale measurements are presented and the agreement among them is reasonably good. The main objective of this study is to explore an effective numerical approach for the accurate estimation of wind effects on tall buildings in urban environment conditions and promote the practical use of the LES in the wind-resistant design of complex structures.