Recent developments in the dynamics of wind‐erosion

Abstract

Those particles of the Earth's land‐surface that are in contact with the atmosphere are at the mercy of two powerful natural forces, resulting from water‐ and air‐flow. The story a single soil‐grain could tell of its travels would surpass that of Marco Polo. It is unfortunate that one cannot “get the story” and thus answer many questions that are in the minds of those who wish to explain and control its behavior. The transport of granular material by fluids has been a subject of intense interest, especially in connection with flowing water. A great number of investigations have been made, both in the laboratory and in streams, on the effects of water‐erosion and the underlying mechanisms of the movement of debris. As a result, at least for some phases of the process, explanations and empirical rules have been developed.

Sedimentation Engineering

“…Assuming that the value of E for moderately strong winds lies between 10 4 and 10 5 cm 2 /s, the results given in Table 2.22 were obtained (Malina, 1941). Sand, silt, and clay have diameter ranges of 1.0 mm-0.05 mm, 0.05 mm-0.002 mm, and less than 0.001 mm, respectively.…”

“…The greatest fundamental difference between air and water transportation, however, is associated with the difference in the density of the fluid media. Malina (1941) has listed some of the variables in wind erosion, as shown in Table 2 …”

“…The size of the particle carried thus depends on shape and density but, in general, is smaller than 0.1 mm in diameter (Free, 1911). Von Kármán, as reported by Malina (1941), made an estimate of the length of time and distance traveled by soil particles when lifted from the surface. By using Stokes' law and the assumption that the rms of the height, h, that a particle reaches in arbitrary time, t, because of turbulence is given by the exchange-coefficient, E, the following expressions are obtained:…”

Equilibration of saltation

“…In the neutral atmospheric surface layer the turbulent velocity fluctuations exhibit frequencies of 1 to 10 cycles per minute (Kaimal et al, 1972;Wyngaard, 1992). These gusts have long been suspected to influence sand transport at least through aerodynamic dislodgement sweeps (Malina, 1941;Kalinske, 1943;Williams et al, 1994). The characteristic eddy velocity`felt' near the ground can be as much as 83 per cent of the outer flow velocity U I (Cantwell, 1981).…”

Accident Generated Particulate Materials and Their Characteristics -- A Review of Background Information

“…(Mishima 1975) and are discussea in Section 2.3. (Akiba 1975;Andres 1972;Chepil 1950Chepil , 1959Chepil , 1965Ford 1957;Kawamura 1975;Malina 1941;and Slinn 1976). Agglomerate rather than individual particle resuspension would be more likely in estimating accident releases.…”