Effects of a two-dimensional low hill in a thermally neutral and stably stratified turbulent boundary layer

• Published in: Atmospheric environment (1994) Vol. 28; no. 11; pp. 1871 - 1878
• Main Authors: Zegadi, R., Ayrault, M., Mejean, P.
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Oxford Elsevier Ltd 1994; Elsevier Science
• Subjects: Convection, turbulence, diffusion. Boundary layer structure and dynamics; Earth, ocean, space; Exact sciences and technology; External geophysics; Meteorology; Turbulent boundary layer; wakes of hill; atmospheric flow; stable stratification; thermal neutral; Air flow; Hill; Wind tunnel; Thermal wake; Atmospheric boundary layer; Two dimensional model; Experimental study; Thermal stratification
• ISSN: 1352-2310; 1873-2844
• DOI: 10.1016/1352-2310(94)90326-3

This paper presents an experimental study of the effects of a two-dimensional low hill on the mean and turbulent structure of a thermally neutral and a stably stratified boundary layer. The experiments are carried out in an atmospheric diffusion wind tunnel. The thermal stable stratification is obtained by an intense cooling of the floor by means of liquid and gaseous nitrogen. The hill, having a height of about 1 8 the boundary layer thickness and an aspect ratio equal to 1 3 , is placed perpendicular to the air flow. The measurements are made for the two stratification cases in different sections downwind of the hill and compared with the results obtained in flow without the hill. A mean velocity and temperature deficit is noted. Observations indicate that the thermal wake thickens more strongly than the neutral. The hill effects induce large perturbations on the Reynolds stresses, the vertical R.M.S. values and turbulent heat flux. The values in mean and fluctuant perturbations in the wake are found to decay as [X- X c L ] −1 .