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EFFECTS OF A FOREST CLEARING: AN EXPERIMENTAL AND NUMERICAL ASSESSMENT

Tetsuya Nakamura
Department of Mechanical Engineering, Keio University, Yokohama, Japan

Koji Fukagata
Department of Mechanical Engineering, Keio University, Hiyoshi 3-14-1, Kohoku-ku, Yokohama 223-8522,Japan

Antonio Segalini
Linne Flow Centre, KTH Mechanics, Stockholm, Sweden

P. Henrik Alfredsson
Liné Flow Centre, KTH Mechanics, Osquars Backe 18, SE-100 44 Stockholm, Sweden

Abstract

The flow above a forest model with and without the presence of a clearing is investigated experimentally in a wind tunnel facility by means of Particle Image Velocimetry. The results have been analyzed in terms of basic velocity statistics and vertical integral length scale and a comparison of the two geometries is presented. In order to improve the current flow understanding and to complement the experimental results, Large Eddy Simulations of the same flows under similar operating conditions are planned. The experimental results indicate that the clearing is associated to a velocity defect in the mean velocity profile associated with a significant vertical momentum flux. The turbulence is redistributed amongst the various velocity components so that the streamwise velocity variance is reduced while the vertical velocity variance is enhanced. From the clearing windward edge the turbulence mixing contributes to the decrease of the vertical correlation length that increases again after the clearing trailing edge.