Field measurements of the flux and speed of wind-blown sand

Universal Journal of Agricultural Research, 2022

This study was to analyze the efficiency (E) of traps in holding suspended soil particles that cause dust, environmental and agricultural problems by wind erosion in NWCZ, Egypt. These vertical and passive sediment traps with different design in rotary and fixed reservoir box and different methods of measured soil loss. Rotary Distance (RD), Fixed Distance (FD), Rotary Point (RP) and Fixed Point (FP) traps were compared with traditional trap Big Spring Number Eight (BSNE). The variation between traps' efficiency as a function of height was significantly (P≤0.05) and was as follow: RD, FD, RP, and FP more increase than BSNE. The performance of the trap types as an efficiency of suspension particles (assumed to possess E=1 for suspended particle sizes) was as follow RD> FD> RP> FP> BSNE; 99%, 98%, 88%, 85%, 65% respectively. The efficiency of traps in suspension particles size (<45, 45-63 and >100 µm) were significant (P ≤ 0.05) and the best efficient were RD and FD. Therefore, RD and FD traps have direct methods for measuring soil loss by wind erosion and have the most acceptable, accurate, fastest and easiest in soil particle analyzed and therefore the most effective way to discriminate suspension particles.

Journal of Geophysical Research, 2004

1] We carried out a wind tunnel experiment on aeolian transport of sand. Fluorescencedyed grains of sand were embedded in the sand bed in a wind tunnel, and their dispersion was recorded by a video camera. Dispersion of colored sand both downwind and in the crosswind direction are examined. The concentration of colored sand decreases as an exponential function of the downwind distance y, Ae Àky , whereas the cross-sectional distribution is approximated by a Gaussian distribution with the standard deviation proportional to ffiffi ffi y p . The characteristic length scale is 1000 times greater in the downwind than in the crosswind direction. A simple stochastic model is proposed to explain these findings. We also found that our experimental results conform to the assumptions of the Werner model, which reproduces aeolian dune dynamics well. We derived conditions on the parameters of the Werner model from the experimental results and suggest the applicability of the Werner model to real problems such as sandy coasts, deserts, and regions whose surface is contaminated.

Journal of Geophysical Research, 1994

A system of experimental and mathematical models was developed from data on grain particle transport, collected from a series of experiments in a large-scale wind tunnel, and from mathematical principles. The experimental model was derived from a FORTRAN program using the observed data. As a first attempt, it took into account the role played by the following factors in grain particle transport: the grain-size distribution, the mean diameter of the particle size class, the mean diameter of the effective surface particles, the surface mobility, friction velocity, and threshold velocity. The comparison between the observed and the predicted results indicated that the experimental model was able to predict the transport rate of grain particles in different size classes over time with good reliability. The mathematical models used in conjunction with the experimental model could be employed to calculate the variation of the mean grain size, the grain-size distribution, the approximate fluid threshold velocity, and the accumulated erosion of the particle surface over time. The experimental model should be applied with caution to natural conditions because of the assumption of a dry, loose, and large-roughness-free surface and aerodynamically dominant fluid. The mathematical models, except for fluid threshold velocity, were accurate, given a precise transport rate of grain particles in different size classes over time.

Geomorphology, 2011

The measurement of eolian sediment transport still remains one of the biggest challenges in eolian research. This paper presents the experimental results on the trap efficiency of a newly designed cyclone-type trap (BEST) and Wilson and Cook trap (WAC) under various wind speeds in the Eremology Wind Tunnel Facility at Gent University, Belgium. The performance of the two traps were tested for four different sediment sizes (b 100, 100-200, 200-300 and 300-500 μm) and under four free-flow wind speeds (12, 13, 14, and 15 m s − 1 ). The test results showed that the efficiency of the BEST was higher than that of the WAC, and the efficiencies of BEST and WAC varied between 75 and 100% and 12 and 52%, respectively. In addition, the coefficient of variation (CV) indicated that the variability in the efficiency of the BEST was lower with wind speed and particle size. These higher and more consistent efficiencies of the BEST were chiefly attributed to its cyclone design, which provided: i) separation of particles from air (particle settling) by means of the accelerated gravitational force achieved by a rapid air rotation, ii) the reduced stagnation pressure at the catcher inlet by gradually increasing the outlet velocity, and iii) the reduced turbulence within its body by a regular circulating path.

Sedimentology, 1995

This paper reviews some aspects of wind tunnel experiments on sand-transporting winds. It follows previous papers that have discussed the influence of the outer region of the boundary layer on wind velocity measurements. This influence was quantified with the use Coles' Wake function. In this paper this correction is applied to six previously described wind velocity profiles. An attempt is made to calculate the profile parameter I7 from these measurements. The values found were not consistent with the expected l7, which was determined by Coles for clean air flow. This value (n=0.55) was assumed to be valid in previous analyses for sand-transporting winds. Evidence for a mutual dependency of friction velocity and profile parameter is presented and the difficulty in determining u , is pointed out. It is suggested that the constant stress region of the boundary layer should be kept large enough for measurements when Coles' Wake function is not to be used in the data analysis.

Aeolian Research, 2020

A cyclone type continuous-weigh sand trap (CCST) has been constructed. The performance of the CCST was investigated for farmland environment during two storms in the Kangbao County of the agro-pastoral ecotone of northern China. The results revealed that the CCST captures the real-time variations in aeolian sediment flux caused by fluctuations in wind speed measured at 1 min resolution. Significant power relationships between the horizontal sediment flux and wind speed was observed for the inlet heights of 5, 15 and 40 cm, respectively. The sediment flux collected by the Big Spring Number Eight (BSNE) closely linearly correlated with that by the CCST. From all testing performed to date, the CCST appears to be a useful device to examine the relationship between horizontal sediment flux and wind speed for field use. Further improvements on a wind-driven rotating and lower-cost CCST are needed.

Geomorphology, 2011

Wind tunnel experiments were performed in order to investigate the effect of mixing on the aeolian transport of sands with different grain sizes. Two types of sand with different grain size distributions and an equal-mass binary mixture of these sands were used. Comparing the gradients of their measured mass flux profiles and some published profiles for mixed sand transport with those for nearly uniform sand transport, it was found that for both of these types of sand bed, the negative gradient of the mass flux profile on a log-linear plot varies with the mass averaged grain size of the sand bed according to the same power law. Hence it can be deduced that, during the aeolian transport of mixed sand beds, the mean vertical ejection speeds of different sized grains are nearly identical to that for the transport of monospecific-sized sand with the same mass averaged grain size. Theoretical analysis was undertaken to explore the characteristics of ejections of different sized grains during the aeolian transport of sand with mixed-size grains. It is proposed that the mean ejection angles and the mean ejection speeds for sand grains of different sizes are nearly identical and are equivalent to that for monospecific-sized sand with the same mass averaged grain size. It was also evident that the ratio between the transport rate of each grain size group expressed as the fraction in the whole transport rate and its mass fraction in the mixed-size sand is a combined consequence of both the wind effect on the mean saltation distance of different sized grains and the effect of the mass fraction of each grain size group in the original mixture on its ejection potential responding to an impact of a saltating sand grain.

Journal of Hydraulic Engineering, 2016

Geomorphology, 2003

Vertical profiles of the horizontal mass flux of blown sand are investigated experimentally using a passive vertical array in a wind tunnel. Considering lower sampling efficiency of the sand trap in the near-bed region, this investigation is complemented by the measurements of the longitudinal profiles of mass flux made using a horizontal sand trap. The experiments were conducted with two test sands and five different stream velocities.In the upper part of the vertical profile, the measured data exhibit an exponential decay distribution with a positive deviation occurring in the near-bed region. The measured longitudinal profiles are similar to the measured vertical profiles. Linking both profiles and the modes of sand transport, it is possible that saltating sand grains give rise to the well-known exponential decay distribution of mass flux, and that creeping and reptating grains force a deviation from it. A simple equation applicable for both the vertical and the longitudinal sand mass flux variations is introduced and the parameters are estimated from experimental data.

Coastal Engineering 1980, 1980

Field investigations on sand-transport by wind were carried out at German North-Sea coast. A special trap was constructed, which allows to measure bed load and suspended load seperated. In addition wind speed was measured up to 10 m over the bottom. The results of the field investigations were used to calibrate a transport-equation for sandtransport by wind.