A laboratory experiment on momentum and heat transfer in the stratified surface layer

Abstract

Abstract Stratification effects on transport processes in the atmospheric surface layer or in the wall region are investigated by a laboratory experiment. A fully developed stratified condition was attained in turbulent flow between horizontal parallel plates kept at different temperatures. The experiment was performed both for stable and unstable conditions and provided conclusive data on stratification effects. A local gradient model is proposed, based on the concept that stratification effects may be evaluated at the same non‐dimensional distance from the wall z + (= zu* w /v w u*, v w being friction velocity and kinematic viscosity, respectively, at the wall), the effects depending only on ε (ε z/L; L being the Monin‐Obukhov length). A comparison of the shear functions with previous field and laboratory experiments shows excellent agreement. By use of this concept, the measured intensities of velocity and temperature fluctuations near the wall are also well correlated with ε.