A wind tunnel study of the seasonal shelter efficiency of deciduous windbreaks

Abstract

The shelter efficiency of windbreaks constructed with deciduous plants changes with their phenological stage. We used Elaeagnus angustifolia L. (Russian olive) as an example and investigated the airflow field and shelter efficiency of deciduous windbreaks with summer facies (with leaves) and winter facies (without leaves) by means of scaled wind tunnel simulation experiments. Our study revealed that different canopy seasonal porosities exert different wind speed reductions inside the windbreaks, which also determine the upwind and downwind wind speed variation. The variation in wind speed was greater in summer than in winter. For the windbreak with summer facies, a large wind acceleration region above and before the windbreak and a strong wind deceleration region inside and after the windbreak were observed. The wind deceleration region around the windbreak with winter facies was larger than that in summer, but the intensity of the wind speed reduction was relatively low. The results of our study further show that although E. angustifolia windbreaks are highly porous in winter, the shelter efficiency was not less than 80% of that in summer. Like any wind tunnel study on windbreaks, producing an artificial plant model that is highly similar to the real field plant is difficult. Nevertheless, our results clearly revealed the wind reduction patterns of deciduous windbreaks due to seasonal porosity caused by leaf shedding, which may provide valuable data for assessing the shelter efficiency of deciduous windbreaks.