Aeolian dust erosion on different types of hills in a rocky desert: wind tunnel simulations and field measurements

1997 ◽  
Vol 37 (2) ◽  
pp. 209-229 ◽  
Author(s):  
Dirk Goossens ◽  
Zvi Y. Offer
Keyword(s):  
Wind Tunnel ◽  
Field Measurements ◽  
Aeolian Dust ◽  
Rocky Desert ◽  
Different Types

Surface Pressure Distribution on a Blade of a 10 m Diameter HAWT (Field Measurements versus Wind Tunnel Measurements)

2005 ◽  
Vol 127 (2) ◽  
pp. 185-191 ◽  
Author(s):  
T. Maeda ◽  
E. Ismaili ◽  
H. Kawabuchi ◽  
Y. Kamada
Keyword(s):  
Wind Tunnel ◽  
Surface Pressure ◽  
Field Measurements ◽  
Reynolds Numbers ◽  
Blade Surface ◽  
Pressure Data ◽  
Surface Pressure Distribution ◽  
Pressure Distributions ◽  
Wind Tunnel Data ◽  
Local Angle

This paper exploits blade surface pressure data acquired by testing a three-bladed upwind turbine operating in the field. Data were collected for a rotor blade at spanwise 0.7R with the rotor disc at zero yaw. Then, for the same blade, surface pressure data were acquired by testing in a wind tunnel. Analyses compared aerodynamic forces and surface pressure distributions under field conditions against analogous baseline data acquired from the wind tunnel data. The results show that aerodynamic performance of the section 70%, for local angle of attack below static stall, is similar for free stream and wind tunnel conditions and resemblances those commonly observed on two-dimensional aerofoils near stall. For post-stall flow, it is presumed that the exhibited differences are attributes of the differences on the Reynolds numbers at which the experiments were conducted.

Macroplastic Debris Transfer in Rivers: A Travel Distance Approach 

2021 ◽  
Author(s):  
Robert Newbould ◽  
Mark Powell ◽  
Mick Whelan
Keyword(s):  
Average Distance ◽  
Field Measurements ◽  
River System ◽  
Tracer Experiment ◽  
Travel Distance ◽  
Distance Distributions ◽  
Different Types ◽  
Meander Bends ◽  
Distance Approach ◽  
Travel Distances

<p>Plastic accumulation in the marine environment is a major concern given the harmful effects and longevity of plastics at sea. Although rivers significantly contribute to flux of plastic to marine systems, plastic transport in rivers remains poorly understood and estimates of riverine plastic flux derived from field measurements and modelling efforts are highly uncertain. In this study, a new probabilistic model of plastic transport in rivers is presented which describes the main processes controlling displacement to predict the statistical distribution of travel distances for individual items of buoyant macroplastic debris. Macroplastic transport is controlled by retention in temporary stores (or traps) created by vegetation, bank roughness elements and other obstacles. The behaviour of these traps is represented in the model via a series of Bernoulli trials conducted in a Monte Carlo simulation framework. The probability of retention or release from traps is described using physical characteristics such as the type of vegetation, channel width or channel sinuosity index. The model was calibrated using a tracer experiment with six replicates, conducted in a small 1.1 km river reach. For each replicate, 90 closed air-filled plastic bottles were injected at the upstream end of the reach and the location of each bottle was recorded several times over a 24-hour period. Bottles were chosen as ‘model’ macroplastic litter items given their high usage and littering volume. Travel distances were low (the average distance travelled over 24 hours was 231 m and no bottles travelled more than 1.1 km, the length of the study reach) and variable (the coefficient of variation for the replicates ranged between 0.54 and 1.41). The travel distance distributions were controlled by the location and characteristics of discrete traps. The numerical model described the observed travel distance distributions reasonably well (particularly the trapping effect of overhanging trees and flow separation at meander bends), which suggests that modelling plastic transport for longer reaches and even whole catchments using a stochastic travel distance approach is feasible. The approach has the potential to improve estimates of total river plastic flux to the oceans, although significant knowledge gaps remain (e.g. the rate and location of plastic supply to river systems, the transport behaviours of different types of plastic debris in rivers and the effectiveness of different traps in different types of river system).</p>

scholarly journals Characterization and first results from LACIS-T: a moist-air wind tunnel to study aerosol–cloud–turbulence interactions

2020 ◽  
Vol 13 (4) ◽  
pp. 2015-2033 ◽  
Author(s):  
Dennis Niedermeier ◽  
Jens Voigtländer ◽  
Silvio Schmalfuß ◽  
Daniel Busch ◽  
Jörg Schumacher ◽  
...  
Keyword(s):  
Wind Tunnel ◽  
Spatial Scales ◽  
Experimental Studies ◽  
Field Measurements ◽  
Hygroscopic Growth ◽  
Moist Air ◽  
Aerosol Cloud ◽  
Cloud Microphysical Processes ◽  
First Results ◽  
Microphysical Processes

Abstract. The interactions between turbulence and cloud microphysical processes have been investigated primarily through numerical simulation and field measurements over the last 10 years. However, only in the laboratory we can be confident in our knowledge of initial and boundary conditions and are able to measure under statistically stationary and repeatable conditions. In the scope of this paper, we present a unique turbulent moist-air wind tunnel, called the Turbulent Leipzig Aerosol Cloud Interaction Simulator (LACIS-T) which has been developed at TROPOS in order to study cloud physical processes in general and interactions between turbulence and cloud microphysical processes in particular. The investigations take place under well-defined and reproducible turbulent and thermodynamic conditions covering the temperature range of warm, mixed-phase and cold clouds (25∘C>T>-40∘C). The continuous-flow design of the facility allows for the investigation of processes occurring on small temporal (up to a few seconds) and spatial scales (micrometer to meter scale) and with a Lagrangian perspective. The here-presented experimental studies using LACIS-T are accompanied and complemented by computational fluid dynamics (CFD) simulations which help us to design experiments as well as to interpret experimental results. In this paper, we will present the fundamental operating principle of LACIS-T, the numerical model, and results concerning the thermodynamic and flow conditions prevailing inside the wind tunnel, combining both characterization measurements and numerical simulations. Finally, the first results are depicted from deliquescence and hygroscopic growth as well as droplet activation and growth experiments. We observe clear indications of the effect of turbulence on the investigated microphysical processes.

scholarly journals Snow saltation threshold measurements in a drifting-snow wind tunnel

2006 ◽  
Vol 52 (179) ◽  
pp. 585-596 ◽  
Author(s):  
Andrew Clifton ◽  
Jean-Daniel Rüedi ◽  
Michael Lehning
Keyword(s):  
Particle Size ◽  
Wind Tunnel ◽  
Friction Velocity ◽  
Field Measurements ◽  
Drifting Snow ◽  
Velocity Relationship ◽  
Roughness Lengths ◽  
Surface Particle ◽  
Macroscopic Objects ◽  
Natural Snow

AbstractWind tunnel measurements of snowdrift in a turbulent, logarithmic velocity boundary layer have been made in Davos, Switzerland, using natural snow. Regression analysis gives the drift threshold friction velocity (u*t), assuming an exponential drift profile and a simple drift to friction velocity relationship. Measurements over 15 snow covers show that u*t is influenced more by snow density and particle size than by ambient temperature and humidity, and varies from 0.27 to 0.69 ms–1. Schmidt’s threshold algorithm and a modified version used in SNOWPACK (a snow-cover model) agree well with observations if small bond sizes are assumed. Using particle hydraulic diameters, obtained from image processing, Bagnold’s threshold parameter is 0.18. Roughness lengths (z0) vary between snow covers but are constant until the start of drift. Threshold roughness lengths are proportional to . The influence of macroscopic objects on the roughness length is shown by the lower values measured over the smooth and flat snow surface of the wind tunnel (0.04 ≤ z0 ≤ 0.13 mm), compared to field measurements. Mean drifting-snow grain sizes for mainly new and partly decomposed snow are 100–175 μm, and independent of surface particle size.

Wind Tunnel And Field Measurements Of Turbulent Flow In Forests. Part I: Uniformly Thinned Stands

2000 ◽  
Vol 95 (3) ◽  
pp. 457-495 ◽  
Author(s):  
Michael D. Novak ◽  
Jon S. Warland ◽  
Alberto L Orchansky ◽  
Rick Ketler ◽  
Steven Green
Keyword(s):  
Wind Tunnel ◽  
Turbulent Flow ◽  
Field Measurements

A Wind-Tunnel Study of Thermally Stratified Boundary Layers

2002 ◽  
Author(s):  
Marcio Cataldi ◽  
Juliana B. R. Loureiro ◽  
Atila P. Silva Freire
Keyword(s):  
Boundary Layer ◽  
Wind Tunnel ◽  
Boundary Layers ◽  
Turbulent Transport ◽  
Thermal Characteristics ◽  
Main Flow ◽  
Stable Boundary Layers ◽  
Different Types ◽  
Pass Through ◽  
Wind Tunnel Study

The objective of this work is to develop, in a wind tunnel environment, boundary layers with different states of development that simulate the structure present in the atmospheric boundary layer. The work analyses the dymamic and thermal characteristics of different types of thick, artificially-generated, turbulent boundary layers. The thermal boundary layer is obtained by two methods: wall surface heating, made through electrical resistance, can furnish an increase in wall temperature of up to 100 °C above the ambient temparatures and can be applied over a 5000 mm long surface with a controlled variation of 2 °C. The main flow heating is obtained by forcing the flow pass through an array of copper wires whose elements can be heated individually. The main flow can be heated up to 100 °C. The whole system can then be used to produce unstable, neutral and stable boundary layers. The parameters of the thermal boundary layers are qualified according to the following parameters: growth, structure, equilibrium, turbulent transport of heat and energy spectrum. The paper describes in detail the experimental arrangements, including the geometry of the wind tunnel and the instrumentation.

Drift Comparisons of Low-Expansion Foams and Conventional Sprays

Weed Science ◽  
1973 ◽  
Vol 21 (5) ◽  
pp. 405-409 ◽  
Author(s):  
L. F. Bouse ◽  
R. E. Leerskov
Keyword(s):  
Wind Speed ◽  
Wind Tunnel ◽  
Environmental Conditions ◽  
Horizontal Wind ◽  
Low Speed ◽  
Spray Solution ◽  
Different Types ◽  
Expansion Foam

Experiments were conducted to compare the drift of low-expansion foam and conventional sprays in a low-speed horizontal wind tunnel under controlled environmental conditions. Dimensions of the tunnel were 1.30 m high, 0.61 m wide, and 7.32 m long. Wind speed was maintained at 1.52 m/sec. Drift was compared for spray solutions, with and without foam adjuvants, using several different types and sizes of air-inducting nozzles and three sizes of conventional fan nozzles. Large drops produced by the air-inducting nozzles, with and without foam adjuvant, resulted in significantly less drift beyond 1.83 and 6.10 m than sprays from the conventional fan nozzles. The addition of foam adjuvant to the spray solution resulted in increased drift beyond 1.83 m for sprays from the air-induction nozzles in several comparisons but did not result in a significant increase in the drift beyond 6.10 m.

Longitudinal and Angular Drill-String Vibrations With Damping

1968 ◽  
Vol 90 (4) ◽  
pp. 671-679 ◽  
Author(s):  
D. W. Dareing ◽  
B. J. Livesay
Keyword(s):  
Viscous Friction ◽  
Field Measurements ◽  
Computer Programs ◽  
Drill String ◽  
Recording Instrument ◽  
String Vibration ◽  
String Vibrations ◽  
Different Types ◽  
Drilling Operations ◽  
Computer Calculations

This paper discusses longitudinal and angular drill-string vibrations and supporting field measurements taken with a special downhole recording instrument. Computer programs based on the theory are used to calculate longitudinal and angular vibrations (caused by periodic bit motions) along the drill string; field measurements made during actual drilling operations are used to check computer calculations. The main difference between this and other theory on the same problem is the inclusion of friction, which acts along the length of a drill string and impedes longitudinal and angular vibrations. For the sake of simplicity, the effect of different types of friction, such as fluid, rubbing, and material, which act along the string, is approximated by the effect produced by viscous friction. This approximation is generally accepted and appears to give adequate results for the drill-string vibration problem.

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