Turbulence Intensity as Influenced by Surface Roughness and Mean Velocity in a Wind-Tunnel Boundary Layer

Abstract

1.04 1.04 1.03 2 . 8 7 0 .41 0 .18 F t u r b u l e n c e is a factor in movement of solids in the atmospheric boundary layer. When forces generated by wind overcome forces of gravity, cohesion, and particle moment about points of contact, soil particles are set in motion (17)*. A wind strong enough to move soil particles is always turbulent (3) , i.e., its flow has irregular fluctuations of velocity, which are superimposed on the mean flow. The importance of fluctuations in velocity and pressure in determining critical (threshold) values that initiate particle movement has been known many years. Kalinske (9) noted that studies concerned only with mean conditions seemed to lack fundamental soundness. Zingg and Chepil (23) advised thorough investigation of turbulence intensity of wind movement in the field. The level or intensity of turbulence can be described by the q u a n t i t y [ l / 3 ( t / 2 + ^2 + ^ / 2 ) ] % _ 9 o r ? jf the