Movement of Soil Particles in Saltation

Bisal, Frederick; Nielsen, K. F.

doi:10.4141/cjss62-012

Cited by 40 publications

(26 citation statements)

References 1 publication

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“…Threshold friction speeds (u t ) affect both direct suspension, in which the wind force is sufficient to overcome the inertia of small particles (such as those in the PM 2.5 and PM 10 fractions), and saltation suspension (Bisal and Nielsen, 1962;Gillies and Lancaster, 2013), in which larger particles (>10 lm) are levitated, then impact the surface, thereby deagglomerating or liberating additional small particles. The sheltering effect of the larger particles is diminished during saltation.…”

Section: Threshold Friction Speeds For Initial Suspension and Saltatimentioning

confidence: 99%

Wind erosion potential for fugitive dust sources in the Athabasca Oil Sands Region

et al. 2015

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Section: Threshold Friction Speeds For Initial Suspension and Saltatimentioning

confidence: 99%

Wind erosion potential for fugitive dust sources in the Athabasca Oil Sands Region

et al. 2015

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“…The existing results about impact and lift-off angles differ considerably. Bagnold (1941), Chepil (1945), Bisal and Nielsen (1962) and Owen (1964) …”

Section: Impacting and Lift-off Speedmentioning

confidence: 99%

Impact–entrainment relationship in a saltating cloud

Dong

et al. 2002

Earth Surf Processes Landf

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The problem of impact-entrainment relationship is one of the central issues in understanding saltation, a primary aeolian transport mode. By using particle dynamic analyser measurement technology the movement of saltating particles at the very near-surface level (1 mm above the bed) was detected. The impacting and entrained particles in the same impact-entrainment process were identified and the speeds, angle with respect to the horizontal, and energy of the impacting and entrained sand cloud were analysed. It was revealed that both the speed and angle of impacting and entrained particles vary widely. The probability distribution of the speed of impacting and entrained particles in the saltating cloud is best described by a Weibull distribution function. The mean impact speed is generally greater than the mean lift-off speed except for the 0Ð1-0Ð2 mm sand whose entrainment is significantly influenced by air drag. Both the impact and lift-off angles range from 0°to 180°. The mean lift-off angles range from 39°to 94°while the mean impact angles range from 40°to 78°, much greater than those previously reported. The greater mean lift-off and especially the mean impact angles are attributed to mid-air collisions at the very low height, which are difficult to detect by conventional high-speed photography and are generally ignored in the existing theoretical simulation models. The proportion of backward-impacting particles also evidences the mid-air collisions. The impact energy is generally greater than the entrainment energy except for the 0Ð1-0Ð2 mm sand. There exists a reasonably good correlation of the mean speed, angle and energy between the impacting and entrained cloud in the impact-entrainment process. The results presented in this paper deserve to be considered in modelling saltation.

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“…On no occasion were grains observed to rise vertically from the bed as previously reported by some authors for aerodynamically entrained particles (e.g. Chepil, 1954;Bisal and Nielsen, 1962;Greeley and Iversen, 1985). Further discussion of similar entrainment observations is given in Williams et al (in press, a).…”

Section: Resultsmentioning

confidence: 51%

“…In the past, several authors (e.g. Bisal and Nielsen, 1962;Warren, 1979) have speculated regarding the effects of bed permeability on these processes, but no study has attempted to evaluate these effects directly. If, however, bed permeability does influence entrainment significantly, then spatial and temporal variations in the permeability of natural sediments may be expected to give rise to local modification of entrainment thresholds and grain dislodgement rates.…”

Section: Introductionmentioning

confidence: 99%

Aerodynamic entrainment thresholds and dislodgement rates on impervious and permeable beds

Williams

Butterfield

Clark

1990

Earth Surf Processes Landf

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In the literature it has been suggested that on permeable, granular beds, both the threshold and rate of aerodynamic entrainment may be affected significantly by seepage flows into and out of the bed induced by fluctuating pressures in the overlying turbulent boundary layer. Using a range of grain sizes and flow conditions, the series of laboratory experiments reported here compares directly the aerodynamic entrainment of loose grains overlying fixed permeable sediment beds with that occuring over fixed impervious beds. For a given granular material, no significant differences in entrainment dynamics on the two types of bed were observed and in the range of flow conditions examined both the threshold shear velocity ( f l * T ) and the aerodynamic entrainment coefficient ( k ) were found to be independent of bed permeability.

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Movement of Soil Particles in Saltation

Cited by 40 publications

References 1 publication

Wind erosion potential for fugitive dust sources in the Athabasca Oil Sands Region

Wind erosion potential for fugitive dust sources in the Athabasca Oil Sands Region

Impact–entrainment relationship in a saltating cloud

Aerodynamic entrainment thresholds and dislodgement rates on impervious and permeable beds

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