scholarly journals Wind velocity profiles with a blowing sand boundary layer: Theoretical simulation and experimental validation

2007 ◽  
Vol 112 (D19) ◽  
Author(s):  
Zhibao Dong ◽  
Qingsong Mu ◽  
Hongtao Wang
Keyword(s):  
Boundary Layer ◽  
Wind Velocity ◽  
Experimental Validation ◽  
Velocity Profiles ◽  
Theoretical Simulation

Lidar Measurement of Wind Velocity Profiles in the Boundary Layer

1980 ◽  
Vol 19 (5) ◽  
pp. 598-605 ◽  
Author(s):  
Jeffery T. Sroga ◽  
Edwin W. Eloranta ◽  
Ted Barber
Keyword(s):  
Boundary Layer ◽  
Wind Velocity ◽  
Velocity Profiles ◽  
Lidar Measurement

Flow characteristics above a forest using light detection and ranging measurement data

2011 ◽  
Vol 226 (4) ◽  
pp. 921-939 ◽  
Author(s):  
B Shannak ◽  
K Träumner ◽  
A Wieser ◽  
U Corsmeier ◽  
Ch Kottmeier
Keyword(s):  
Boundary Layer ◽  
Wind Velocity ◽  
Drag Force ◽  
Roughness Length ◽  
Measurement Data ◽  
Flow Characteristics ◽  
Velocity Profiles ◽  
Light Detection And Ranging ◽  
Physical Parameters ◽  
Light Detection

New wind velocity measurement method using a light detection and ranging instrument was conducted. Based on the presented experimental data, the airflow characteristics above a forest were investigated: wind velocity distribution, friction (shear) wind velocity, roughness length, stream lines, drag force, and depth of the boundary layer. The results demonstrated that windward the forest, the boundary layer is shifted and sloped above the forest. Thereby, the fluid streamlines cannot abruptly change direction, as a consequence flat wind velocity profiles, wavy inflected wind velocity profiles, eddies, and flow recirculation were developed; hence, flow separation at a forest ratio x/ h of 2, flow contraction at x/ h of 12, and flow expansion at x/ h of 22 appeared. The shear wind velocity was about 1/10 of the mean wind velocity and the roughness length 1/15 of the forest height. Within a boundary layer depth of about 130 m, the drag force of the forest was 1300 times greater than that of the grass. Behind the forest, the air flow expands and eddies were developed at x/ h of about 7. Passing through the agriculture area and the forest, the physical parameters (turbulent kinetic energy, friction wind velocity, drag force, and depth of the boundary layer) are increasing at the point of roughness increase. To decrease such parameters and to avoid energy and friction losses and damage to trees due to divergence, convergence, separation, and recirculation of airflow, the sharp edge of the forest should be rounded in the range x/ h up to 2. A curved cutting of the front area of the forest may allow to decrease the slope of the boundary layer and the streamlines before, above, and behind the forest and hence lead to a quasi-steady and stable flow with less turbulence, momentum, heat, and mass transfer between the canopy and the atmosphere.

Observations of Small-Scale Turbulence and Energy Dissipation Rates in the Cloudy Boundary Layer

2006 ◽  
Vol 63 (5) ◽  
pp. 1451-1466 ◽  
Author(s):  
Holger Siebert ◽  
Katrin Lehmann ◽  
Manfred Wendisch
Keyword(s):  
Boundary Layer ◽  
Energy Dissipation ◽  
Wind Velocity ◽  
Turbulence Theory ◽  
Horizontal Wind ◽  
Inertial Subrange ◽  
Intermittent Flow ◽  
Small Scale ◽  
Dissipation Rates ◽  
Wide Range

Abstract Tethered balloon–borne measurements with a resolution in the order of 10 cm in a cloudy boundary layer are presented. Two examples sampled under different conditions concerning the clouds' stage of life are discussed. The hypothesis tested here is that basic ideas of classical turbulence theory in boundary layer clouds are valid even to the decimeter scale. Power spectral densities S( f ) of air temperature, liquid water content, and wind velocity components show an inertial subrange behavior down to ≈20 cm. The mean energy dissipation rates are ∼10−3 m2 s−3 for both datasets. Estimated Taylor Reynolds numbers (Reλ) are ∼104, which indicates the turbulence is fully developed. The ratios between longitudinal and transversal S( f ) converge to a value close to 4/3, which is predicted by classical turbulence theory for local isotropic conditions. Probability density functions (PDFs) of wind velocity increments Δu are derived. The PDFs show significant deviations from a Gaussian distribution with longer tails typical for an intermittent flow. Local energy dissipation rates ɛτ are derived from subsequences with a duration of τ = 1 s. With a mean horizontal wind velocity of 8 m s−1, τ corresponds to a spatial scale of 8 m. The PDFs of ɛτ can be well approximated with a lognormal distribution that agrees with classical theory. Maximum values of ɛτ ≈ 10−1 m2 s−3 are found in the analyzed clouds. The consequences of this wide range of ɛτ values for particle–turbulence interaction are discussed.

On wind velocity profiles over urban area

2003 ◽  
Vol 20 (1/2/3/4/5/6) ◽  
pp. 196
Author(s):  
Klara Bezpalcova ◽  
Zbynek Janour ◽  
Viktor M.M. Prior ◽  
Cecilia Soriano ◽  
Michal Strizik
Keyword(s):  
Urban Area ◽  
Wind Velocity ◽  
Velocity Profiles

scholarly journals Remote Sensing of Wind Velocity by Boundary Layer Radar

1996 ◽  
Vol 1996 (67) ◽  
pp. 39-42 ◽  
Author(s):  
Hidetoshi HAYASHIDA ◽  
Syoichiro FUKAO ◽  
Takahisa KOBAYASHI ◽  
Hiroshi NIRASAWA ◽  
Yoshihiro MATAKI ◽  
...  
Keyword(s):  
Remote Sensing ◽  
Boundary Layer ◽  
Wind Velocity
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