Turbulence Near the Ground

Abstract

Turbulent motion in open air must be studied in a way differing from that followed in laboratory experiments. We cannot choose or arrange for the most suitable conditions; we have to make the best of what nature offers; it is nearly impossible to stain air masses sufficiently so that they show streamlines-we have to judge their possible form from complicated effects. The results arrived at will depend upon the means at one's disposal and the way pursued.

Recent developments in the dynamics of wind‐erosion

“…He relates this behavior to the action of the particles as projectiles, which upon striking the surface rebound and continue their movement downstream or initiate the movement of one or more particles upon striking the bed. For uniform s~nd, he found the dynamic-threshold velocity, ur· in em per second, to be given by the relation (4) .. here p' is the effective sand-density and k 1 is the new focus of the velocity-distribution curves obtained from (l) when the flow is carrying particles. For all nearly uniform sands, Bagnold found k' to have roughly the same value, 0.3 em.…”

Wind Structure in Winter Storms

“…One of the most recent and most successful investigations of this kind was conducted by Wilhelm Schmidt. 5 By taking motion pictures of a line of pendulum plates and observing the angles through which they were deflected, he was able to determine the average wind velocities existing at the various plates for intervals of time as small as 1 / 7 of a second, if the wind velocity did not exceed 10 meters per second (22.4 m.p.h.). The length and height of the front over which observations can be made in this way are rather limited.…”