Saltational processes

Saltare - To leap. Hence saltation. The noun jump or saltation will be for a single step in the process, and terms such as saltation process , chain extension by saltation , saltation equilibrium , etc. will be used. The infinitive to saltate and the gerund saltat-ing chains will also be used occasionally... 

The author expresses a personal opinion that the slipping mechanism, first conceived by Houwink44, taken up by Dannenberg19 and given a mathematical treatment as a saltation process by Rigbi77, is the only theory actually dealing with the problem. 

The detachment of soil particles from bare ground, and their forward movement, increase toward the leeward side of an eroding area. On the windward side, where erosion begins and where the soil is not bombarded by bouncing particles, wind produces almost no movement of particles. This shows that the saltation process is the major one governing wind erosion without it, most soil particles would remain in place. 

The SDA dispersiveness in the air surface layer is determined by natural dispersiveness of soil as a source of aerosol, and by effectiveness of the sand-jet effect of saltating particles. The formation of the real size distribution of SDA in this atmospheric layer is determined by the processes of sedimentation, impingement, condensation and adsorption of gases and vapors, capture and sedimentation on obstacles and surfaces [6]. Real size distributions of soil-erosion aerosols (SEA) can be described by the power law ... 

These detachments and reattachments, which will be called saltations, occur sporadically, but P and S represent statistically mean points. The value of E is not at present known, nor is it known whether E and Ea are related. E is the energy required to activate the process of saltation, or in brief, the activation energy of saltation. 

As [see Eq. (5 a)] this is half the saltation rate over the potential barrier at zero stress, it follows that the latter is of the order of 1014 per sec. This is rather greater than the value of k T/h (6 x 1012 per sec at 27 °C) which is obtained from Eyring s expression. However, considering the crude way in which the comparisons were made, the indications are that the proposed mechanism bears a close relationship to the real processes controlling stress-softening and, therefore, reinforcement. 

Soil and dust particle mobilization by winds entails physical parameters such as saltation, surface creep, and suspension (Nicholson, 1988a Sehmel, 1980). Saltation, relevant to particles in the size range of 1(X)—500 pm, can move 50—75% of surface particles. Larger particles, 500—1000 pm in size, move by surface creep, up to 25% of all particles. Suspension, the process by which particles enter the ambient air, applies to a size <100 pm and involves up to 40% of soil by weight. 

H.S. Muralidhara, W.J. Rebello, R.P. Kiishnan and C.Y. Wen, Saltation velocity correlations for the design of long-distance horizontal pneumatic coal transport systems, Int. Powder Bulk Solids Handling Processing, Huladelphia, 1979. 

Independently of the equation selected to describe the inner-feed particle size distribution, all such equations can only be regarded as rough approximations to the true size distributions. Fortuitously, perhaps, in most practical situations wherein saltation or mass loading effects occur, the effect tends to dominate the overall collection process and so only a small portion of incoming solids ever report to the inner vortex. As a consequence, the overall collection efficiency is not highly sensitive to the choice of distribution function for the inner feed. If, however, one is only interested in the loss fraction, a difference in the total overall efficiency of 0.9992 and 0.9998, for example, can be significant since, in this case, the amount lost differs by a factor of 4. 

Cahill, T.A., Gill, T.E., Reid, J.S., Gearhart, E.A., and Gillette, D.A. 1996. Saltating particles, playa crusts and dust aerosols at Owens (dry) Lake, California. Earth Surface Processes and Landforms 21(7) 621-640. 

Houser, C.A. and Nickling, W.G. 2001b. The factors influencing the abrasion efficiency of saltating grains on a clay-crusted playa. Earth Surface Processes and Landforms... 

Rasmussen, K.R. and Sprensen, M. 1999. Aeolian mass transport near the saltation threshold. Earth Surface Processes and Lancforms 24(5) 413 22. 

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