Laboratory Wind Tunnel Research Articles

Wind Tunnel‐Based Comparison of PM10 Emission Rates for Volcanic Ash and Glaciogenic Aerosol Sources Within Iceland

AbstractIceland contributes 30–40 million tons of mineral dust to the atmosphere each year. Emission events are linked to exceedingly high concentrations of PM10, poor air quality, and respiratory disease, particularly in Reykjavík. Volcaniclastic aerosols have unique microphysical properties, and usually are porous and highly angular, with large surface areas bearing ultrafine, nanoscale dustcoats. The large internal void space contributes to low particle density, believed to affect emission and deposition rates in the atmospheric boundary layer, as well as the range of transport. However, the aerodynamic and sedimentological factors that govern dust entrainment in these high‐latitude settings are not well constrained empirically, providing little guidance for the parameterization of aerosol dispersion models. A series of laboratory wind tunnel simulations were carried out under full climate control to evaluate these effects for Icelandic samples collected from five active dust sources, inclusive of volcanic ash and glaciofluvial sediments. PM10 emission rates measured in this study are similar in magnitude to those obtained in a small number of field studies within selected high‐latitude regions, and for volcanic ash using a PI‐SWERL. The scaling with friction velocity is well described by the 1988 dust emission model of Gillette and Passi, while the parameterization appears to be strongly dependent on the median particle size. Sediments from the coarsest Icelandic dust sources were found to be most emissive, owing to the importance of particle impact, while the proportionate amount of PM10 within the test bed was not found to correlate with the emission rate.

Critical standing crop residue amounts for wind erosion control in the inland Pacific Northwest, USA

Crop residue is an important factor influencing wind erosion of cultivated soils. Establishing soil surface protection afforded by standing crop residue is critical for land managers seeking to reduce or prevent soil loss by wind erosion and the impacts of blowing dust from agricultural lands. The objectives of this study were to evaluate the effect of standing residue on soil wind erosion in the inland Pacific Northwest (iPNW), USA, and test the performance of the plant factor algorithm of the Agricultural Policy/Environmental eXtender (APEX) and Revised Wind Erosion Equation (RWEQ) models in influencing soil loss. The effect of standing winter wheat (Triticum aestivum L.), spring canola (Brassica napus L.), and chickpea (Cicer arietinum) residue on wind erosion, remaining from major commodity crops in the region, was tested in a laboratory wind tunnel using four levels of residue density. The impact of standing residue in controlling wind erosion was compared and analyzed in terms of residue density and their respective frontal area index. Our results show that residue at a density characteristic of the production environment (110 standing residue elements m−1 for winter wheat, 20 standing elements m−1 for canola, and 16 standing elements m−1 for chickpea) provided significant protection to the soil surface from wind erosion. Soil loss at this level of residue density was reduced by 73.3, 53.4, and 60.9% for respectively winter wheat, spring canola, and chickpea (frontal area indexes are 0.172, 0.104, and 0.026 respectively) compared with a surface without residue. The soil surface was found to be at significant risk from wind erosion when residue densities of the three crop types were <50% of the typical production amounts. Although not consistently significant, soil loss decreased as wind direction shifted from parallel to perpendicular with the standing residue row. The APEX model adequately simulated winter wheat and spring canola residue protection but had low accuracy in representing chickpea residue effects relative to the wind tunnel experiments. In contrast, the RWEQ model appeared inadequate in simulating soil loss for the winter wheat and canola treatments but adequately represented chickpea residue effects. Differences in model accuracy for different crop types must be considered by producers and managers to determine whether model information used to select practices to control wind erosion are likely to result in under- or over-protection of soil resources.

PENGARUH MATERIAL BILAH DAN KECEPATAN ANGIN TERHADAP PERFORMANSI TURBIN ANGIN HORISONTAL SKALA MIKRO

&lt;p&gt;&lt;em&gt;The availability of fossil fuels in Indonesia has recently been running low due to exaggerated use of the fuel. To fulfill the electrical energy needs of the community which more environmentally friendly used, wind turbines can be used. In this study, researchers use a micro-scale horizontal axis wind turbine from wood and composite materials on the blades, where it try to determine the effect of each performance. This study uses an experimental method which is carried out at the Wind Tunnel Laboratory of the Mechanical Engineering Education, Sebelas Maret University. The variables are blades with a variety of composite and wood material. Performance of electrical power is investigated in this research. Data shows that the wind speed 5m/s - 6m/s composite without load produces the highest rotate, which is 544.64 rpm. While, wood material take lower at 494.2 rpm. The wind turbine is driven at 5 m/s – 6 m/s by using 12V of load. It produces 367.68 rpm and 6.771 watts for composites, and 303.6 rpm and 5.047 watts for wood. So it can be concluded blade materials could effect to the turbine performance.&lt;/em&gt;&lt;/p&gt;

Large-Eddy Simulations of Turbulent Flows around Buildings Using the Atmospheric Boundary Layer Environment–Lattice Boltzmann Model (ABLE-LBM)

ABSTRACTA three-dimensional, prognostic Atmospheric Boundary Layer Environment–Lattice Boltzmann Model (ABLE-LBM) using the multiple-relaxation-time lattice Boltzmann method was developed for large-eddy simulation of urban boundary layer atmospheric flows. In this article we describe the details of the ABLE-LBM for urban flow, its implementation of complex boundaries, and the subgrid turbulence parameterizations. As a first validation of this newly developed model, the simulation results were evaluated with two wind-tunnel datasets that were collected using particle image velocimetry and Irwin probes, respectively. The ABLE-LBM simulations use the same building layout and Reynolds numbers used in the laboratory wind tunnels. The ABLE-LBM simulations compare favorably to both laboratory studies in terms of the mean wind fields. The turbulent fluxes simulated by the model in the observational planes also agreed reasonably well with the laboratory results. The model produced urban canyon flows and vortices on the lee side and over the building tops that are similar to those of the laboratory studies in strength and location. This validation study using laboratory data indicates that our new ABLE-LBM is a viable approach for modeling atmospheric turbulent flows in urban environments. A numerical implementation using a graphics processing unit shows that real-time simulations are achieved for these two validation cases.

Review of aerodynamics of high-speed train-bridge system in crosswinds

Serviceability and running safety of the high-speed train on/through a bridge are of major concern in China. Due to the uncertainty chain of the train dynamic analysis in crosswinds originating mainly from the aerodynamic assessment, this paper primarily reviews five meaningful progresses on the aerodynamics of the train-bridge system done by Wind Tunnel Laboratory of Central South University in the past several years. Firstly, the flow around the train and the uncertainty origin of the aerodynamic assessment are described from the fluid mechanism point of view. After a brief introduction of the current aerodynamic assessment methods with their strengths and weaknesses, a new-developed TRAIN-INFRASTRUCTURE rig with the maximum launch speed of 35 m/s is introduced. Then, several benchmark studies are presented, including the statistic results of the characterized geometry parameters of the currently utilized bridge-decks, the aerodynamics of the train, and the aerodynamics of the flat box/truss bridge-decks. Upon compared with the foregoing mentioned benchmarks, this paper highlights the aerodynamic interference of the train-bridge system associated with its physical natures. Finally, a porosity- and orientation-adjustable novel wind barrier with its effects on the aerodynamics of the train-bridge system is discussed.

PM2.5 and PM10 emissions by abrasion of agricultural soils

Abrasion of soil clods by wind erosion is one process contributing to fine particulate emissions, which degrades air quality. Little is known about the abrasion process that generates and emits particulate matter with aerodynamic diameter of less than 2.5 μm (PM2.5) or those less than 10 μm (PM10). Both PM2.5 and PM10 are regulated by the US-Environmental Protection Agency as health hazards. We used a laboratory wind tunnel to study the abrasion induced emissions of 15 aggregated soils from across the U.S. We subjected aggregated soils in trays as well as sets of aggregates placed on the wind tunnel floor to abrader sand (0.29 to 0.42 mm diameter) blown at 13 m s−1. PM2.5 and PM10 emissions were found to vary by soil type. Sandy soils had the poorest aggregation as well as lowest primary fine particulate contents and were found to have the greatest abrasion coefficients (AC) and highest emission of PM2.5 and PM10 under abrasion. By contrast, soils higher in clay had lower AC and emissions under abrasion. In addition, five of the soils tested had long-term histories of both conventional tillage (CT) and no-till (NT) management for paired comparisons of emission based on CT and NT managements. CT management tended to show higher AC values and greater abrasion emissions compared to NT management for the same soil, although only three of five management pairs were significant. Dry aggregate stability parameters were found to have an exponential relationship to AC with break force being a better AC predictor (R2 = 0.936) than dry stability (R2 = 0.894). We also developed equations that predict PM2.5 emissions as a fraction of PM10 emissions for aggregated soils (R2 = 0.932) and individual aggregates alone (R2 = 0.854). This research contributes to the understanding and prediction of PM2.5 and PM10 emission through the abrasion process.

The Aerodynamic Characteristics of Road Vehicles Overtaking on Bridge Deck under Crosswinds

The aerodynamic characteristics of road vehicles in windy environments are the prerequisites for the evaluation and prediction of the driving safety and stability. To investigate the aerodynamic characteristics of the overtaking vehicles on the bridge deck under the effects of crosswinds, models of a cable‐stayed bridge with a typical flat box girder and road vehicles involving articulated lorry and commercial van with a scale of 1 : 40 were tested in the wind tunnel laboratory. A series of tests figured out the variation of the aerodynamic forces of road vehicles during the overtaking process after considering the aerodynamic interference between lorry and lorry, van and van, and lorry and van. Additionally, the influence of the lateral overtaking distance between the overtaking vehicles was regarded as well. The result reveals the upstream vehicle has a significant influence on the aerodynamic coefficients of the downstream vehicle, which have experienced dramatic fluctuations during the overtaking process, and the various shapes of the aerodynamic coefficients are highly dependent on it.

Wind tunnel experimental variability of aerodynamic loads for wind turbine blades

The lift and drag coefficients of airfoils, used in wind turbine blades, are measured by wind tunnel tests. Large uncertainties are possible due to experimental errors and wind tunnel laboratory variability. Uncertainties in the aerodynamic loads have an important effect on the structural reliability of wind turbine blades. In this paper, the aleatory behaviors of the aerodynamic loads for a three-dimensional wind turbine blade are investigated by wind tunnel tests. Different angles of attack and Reynolds numbers are considered to quantify the uncertainties in the lift coefficients.

Modeling pictures of the flow past rough and smooth surfaces in the program comsol multiphysics

The aim of this work was to obtain simulated flow patterns of rough surfaces by aerodynamic flow at different speeds for comparison with the results obtained by anemometry from images of particles in a laboratory wind tunnel. The results obtained by the program Comsol Multiphysics, which is used to simulate complex high-turbulent flows characteristic of gas flows in aircraft engines and gas turbine plants.

An empirical test of the impact of drying events and physical disturbance on wind erosion of zooplankton egg banks in temporary ponds

Most temporary pond zooplankton species produce drought-resistant eggs that accumulate in the sediment and form an egg bank. When a pond dries and the egg bank is exposed, wind erodes eggs and wind action has been suggested as an important determinant of population demographics. While field observations suggest that egg bank erosion may be highest shortly after pond drying and physical disturbance of the sediment crust, this remains to be tested empirically. We performed a laboratory wind tunnel experiment to assess the effects of wind speed and sediment characteristics on egg pickup rates over time in a controlled environment. We used sediment samples in which an egg bank of the fairy shrimp Branchipodopsis wolfi was embedded and compared the number of eggs that blew away from dry, drying and disturbed egg banks as a function of time. Few eggs were picked up when the egg bank was dry prior to exposure, even at winds of 70 km h−1. Most eggs were eroded when the egg bank was exposed to wind before it dried out, after the last water evaporated. Likewise, physical disturbance resulted in strong erosion fluxes. Overall, our results suggest that the state of the egg bank may be more important for egg bank erosion rates than the prevailing wind speed or the wind exposure time. Also, our findings are worrying in the context of climate change since they imply that predicted increases in drying events and reduced inundation lengths may compromise egg bank persistence in temporary ponds.

Wind erosion researches in Hungary – past, present and future possibilities

Wind erosion is one of the most important land degradation processes in Hungary in the areas with low yearly precipitation values. The total land area suffering from wind erosion is approximately 10,000 km2, 10 per cent of the country area. Observations and discussions on wind erosion and its negative impacts in Hungary started in the last century. Since the 1950s, scientists investigated wind erosion processes and its role in the evolution of alluvial fans in an integrative way, including laboratory measurements and field observations with respect to the stabilization and utilization of soils in agricultural areas. Since the late 2000s, there is an increasing demand worldwide to characterize the role of climate change and human activities in triggering land degradation processes. Studies have been conducted to investigate the mechanics, causes and control techniques related to wind erosion applying laboratory and field wind tunnel simulation tests and field observations. Some encouraging achievements have been made. In this paper we summarize the main research results of wind erosion research, and put forward some perspectives and suggestions on the problems of wind erosion research and control practices in Hungary.

Force of Nature: The Boundary Layer Wind Tunnel Laboratory

The Boundary Layer Wind Tunnel in Ontario, Canada, pioneered the field of wind engineering and improved a generation of thin and light bridges and towers.

CFD Simulation of Chemical Gas Dispersion Under Atmospheric Boundary Conditions

Pollutant control is one of the key concerns in the design of buildings, for the sake of occupational health, safety and environment sustainability. In particular, risk analyses related to emergency leakage of chemicals from storage tanks or chemical processes have aroused increasing attentions in recent days, as well as the effectiveness of mitigation measures in order to eliminate, reduce and control the risks. In this paper, a CFD methodology with nonreactive chemical gases treated as passive scalars has been developed to simulate the gas dispersion across urban environments, subject to atmospheric boundary layer wind conditions. Special treatments to maintain the consistency in atmospheric boundary layer flow profiles, turbulence modeling and boundary conditions have also been accounted for. The proposed CFD methodology for gas dispersion has been implemented in the open source CFD code — OpenFOAM. It has been validated by modeling the gas dispersions for two urban-related test cases: the CODASC street canyon test case measured in a laboratory wind tunnel and the Mock Urban Setting Test (MUST) field experiment conducted in the desert area of Utah State. Effects of turbulent Schmidt number (Sct have been primarily addressed in this study. Statistical analyses about the discrepancies between predicted and experimental data have been carried out and statistical performance measures are used to quantify the accuracy of the proposed methodology. Simulations results from passive scalar transport equation demonstrate good agreement with experimental data, though tracer gases heavier than the atmospheric air were used in both the measurements. Furthermore, sensitivity tests also indicate that the accuracy of the simulation results is sensitive to the value of turbulent Schmidt number.

Assessing Landscape Dust Emission Potential Using Combined Ground‐Based Measurements and Remote Sensing Data

AbstractModeled estimates of eolian dust emission can vary by an order of magnitude due to the spatiotemporal heterogeneity of emissions. To better constrain location and magnitude of emissions, a surface erodibility factor is typically employed in models. Several landscape‐scale schemes representing surface dust emission potential for use in models have recently been proposed, but validation of such schemes has only been attempted indirectly with medium‐resolution remote sensing of mineral aerosol loadings and high‐resolution land surface mapping. In this study, we used dust emission source points identified in Namibia with Landsat imagery together with field‐based dust emission measurements using a Portable In‐situ Wind Erosion Laboratory wind tunnel to assess the performance of schemes aiming to represent erodibility in global dust cycle modeling. From analyses of the surface and samples taken at the time of wind tunnel testing, a Boosted Regression Tree analysis identified the significant factors controlling erodibility based on Portable In‐situ Wind Erosion Laboratory dust flux measurements and various surface characteristics, such as soil moisture, particle size, crusting degree, and mineralogy. Despite recent attention to improving the characterization of surface dust emission potential, our assessment indicates a high level of variability in the measured fluxes within similar geomorphologic classes. This variability poses challenges to dust modeling attempts based on geomorphology and/or spectral‐defined classes. Our approach using high‐resolution identification of dust sources to guide ground‐based testing of emissivity offers a valuable means to help constrain and validate dust emission schemes. Detailed determination of the relative strength of factors controlling emission can provide further improvement to regional and global dust cycle modeling.

Characteristics and performances of a small-scale model of the closed-circuit multiple controlled fan wind tunnel.

The development of a method to simulate desired approach turbulence characteristics and improve the typhoon resistance ability for complex building and transmission tower-line system in a multiple controlled fan wind tunnel is described. A case study is investigated using a closed-circuit single controlled fan wind tunnel model of the Full-Scale Test Facility at the State Grid Fujian Electric Power Research Institute for State Grid Wind Tunnel Laboratory. A small-scale model of the closed-circuit single controlled fan wind tunnel is designed and established to simulate the turbulence characteristics and develop the target turbulent flow generating methods efficiently. The results reveal that the value of the maximum average wind speed can reach 18.2 m/s and the maximum circular frequency is 7 Hz. Here, the mean wind speed of the sinusoidal wave flow is 15.1 m/s at the peak of amplitude of 3.8 m/s. The generated sinusoidal wave flow has a high correlation coefficient at 94.3% with the target.

Energy consumption and increased EV range evaluation through heat pump scenarios and low GWP refrigerants in the new test procedure WLTP

The aim of this work is to evaluate the cabin heating energy consumption and driving range for a battery electric vehicle. The vehicle was tested in climatic wind tunnel laboratory under Worldwide Harmonized Light-duty vehicle Test Cycle. A heating load model was established and used to predict the heating requirements of the vehicle in different climate conditions. Three different heat pump systems and five refrigerants are also investigated. Results show an error within 5% for the established heating load model. Compared with PTC heating, the heat pump systems lead to much lower energy consumption between 41% and 72% for different scenarios. Besides, 20% and 30% recirculation air can reduce the overall consumed energy by an average of 28.5% and 36.6%, respectively. Finally, the driving range of all the heat pump systems are much higher than that of PTC, which is between 14.2% and 31%.

Probabilistic serviceability-performance assessment of tall mass-timber buildings subjected to stochastic wind loads: Part I - structural design and wind tunnel testing

Tall mass-timber buildings utilize engineered wood panels to form their main gravity and lateral load resisting systems, which makes them lighter and very flexible. As a result, frequent exposure to excessive wind-induced vibrations can cause occupant discomfort and unserviceability due to horizontal floor acceleration and excessive deflection. Therefore, the objective of this and the companion paper is to assess the serviceability performance of tall mass-timber buildings probabilistically. For this purpose, the Alan G. Davenport Wind Loading Chain is adapted as a probabilistic Performance-Based Wind Engineering framework. The framework is applied to quantify the serviceability performance of a 102-m tall mass-timber building. In this paper, a complete tall-mass timber building structural design process is outlined. Wind loads are obtained from aerodynamic wind tunnel tests conducted at the Boundary Layer Wind Tunnel Laboratory at Western University. The design process involves preliminary strength design using the provisions of building codes, design revisions using wind load from wind tunnel tests, and serviceability checks. The structural design of the case study tall mass-timber building considers the axial compression, in-plane-shear, and in-plane and out-of-plane bending moment demands, along with their interactions due to gravity and wind loads. Dynamic analysis is carried out to assess the drift performance of the case study mass-timber building. The results show that the building satisfies the drift requirements prescribed by the building codes with a small safety margin. For the designed tall mass-timber building, an in-depth probabilistic serviceability-performance assessment and vulnerability estimations are presented in the companion paper.

Effects of Wind, Temperature, and Barometric Pressure on Asian Citrus Psyllid (Hemiptera: Liviidae) flight behavior.

The Asian citrus psyllid, Diaphorina citri Kuwayama (Hemiptera: Liviidae), is the vector of the bacterium responsible for huanglongbing, a deadly plant disease affecting citrus worldwide. We investigated the effects of wind direction and speed on flight duration and direction of D. citri, as well as the effects of temperature and barometric pressure on sustained flight duration of D. citri. Experiments were performed with laboratory flight mills and wind tunnels. Flight activity of D. citri increased with increasing temperature. Of the few insects that flew at 18°C, most performed short duration flights (<60 s). When exposed to temperatures between 21 and 28°C, D. citri performed long duration flights (>60 s). In addition, the distance covered increased with temperature. Interestingly, males were more sensitive to cold temperature and flew significantly shorter distances than females at 21 and 25°C. Barometric pressure recorded before and during the flight mill experiment suggested that decreasing pressure reduced distance flown by D. citri. Flight direction was strongly influenced by wind. In wind tunnel experiments where psyllids were challenged to reach citrus leaf flush positioned either downwind or upwind, most D. citri moved downwind when exposed to continuous airflow. In a subsequent experiment, we challenged psyllids to pulsed wind blowing at higher speeds. In this case, most psyllids progressed upwind, suggesting upwind movement by psyllids during pauses within pulsed airflow. Collectively, the results indicate that D. citri are able to modify their flight behavior in response to abiotic factors.

Experimental and numerical study of natural ventilation in four-sided wind tower traps

In the past, wind towers were applied as the main architectural part of building construction in the desert areas of Iran. These almost high structures were used as cooling load suppliers at residential buildings. In the present study, the effect of symmetric four-sided wind tower in flow induction to the bottom space has been analysed by using a wind tunnel and numerical simulations. In the numerical simulation, the flow is assumed to be three-dimensional, unsteady, compressible and turbulent. The experimental studies have been performed by placing a model of these structures at a laboratory wind tunnel. At this state, crossing airflow through every channel is measured for analysing the induction performance of wind tower at different angles of wind blowing. Moreover, the turbulence effect is analysed by adding horizontal and vertical blades and crowns at the top and bottom of the internal gate of traps for attaining better performance. Two different geometries are used for simulations. The results showed that inserting the blade and crown at the bottom and topaffect on the flow rate have effect on the flow rate. For instance, inserting horizontal blades and crown at the top of the model leads to 8 and 16% increase in the flow rate, respectively. The results of the numerical simulations have shown acceptable agreement with experimental results.

Numerical and experimental investigation of damage effect on a hemispherical parachute performance

The effect of the canopy fabric damage on parachute performance has been investigated numerically and experimentally in the present paper. For this aim, first, flow structure around the parachute canopy has been studied for both damaged and undamaged parachutes. Then, the drag coefficient as the main characteristic of a parachute performance has been examined and compared experimentally and numerically in four Reynolds numbers. Experimental tests for undamaged and damaged canopies have been carried out in an open-circuit wind tunnel laboratory at the velocities 15, 20, 25, and 30 m/s. In order to measure the drag force, a valid tensile load-cell has been used. Also, the smoke flow visualization has been utilized to find the flow behavior at different regions of the parachute. For the numerical simulation, an incompressible pressure-based CFD code using the finite volume method has been applied to solve the complex turbulent flow field around the inflated parachute canopy. To increase accuracy of the numerical simulation, the permeability boundary condition on the parachute canopy has been implemented and its effects have been considered on the flow field. The numerical results indicate that the permeability assumption on the canopy makes desirable results compatible with the experimental ones. Moreover, comparison of the results between damaged and undamaged canopies demonstrates significant differences in the streamlines, pressure distributions, and drag coefficients. As the reliability is the main criterion for the parachute system, investigation on the damage effects would be useful and it has been considered in the present work.