Velocities of Windblown Particles in Saltation: Preliminary Laboratory and Field Measurements

Abstract

Publisher Summary This chapter describes the laboratory and field measurements of the velocities of windblown particles in saltation. The methods for determining particle velocities and the preliminary results are presented in the chapter. Tests were run in all three wind tunnels under optimal conditions for aeolian activity in the planetary environment of concern. The particle sizes selected for analysis included those most easily moved by the wind, as well as common dune sand sizes on Earth. Tests were run to determine the particle speed, which is defined as a function of height above the surface. There is a general increase in particle speed with height. This increase in particle speed can be attributed to—(1) the increase in wind speed with height through the boundary layer, and (2) the increase in the trajectory–particle path length with height, affording a longer time for acceleration by the wind. It is found that particle speeds increase with height above the surface, validating the results obtained with the particle velocimeter, although the range in the heights analyzed by film is limited. It is observed that particle velocities on Earth increase throughout the saltation trajectory, reaching a maximum just before impact with the surface.