International Journal of

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Wind as an atmospheric element has some annoying aspects, therefore, controlling it and reducing its speed is one of the most important matters, which should be examined in landscape engineering. Natural windbreaks such as rows of trees with different gap distances between them are used to decrease wind velocity. The current study numerically investigates the effect of trees with irregular canopy form on wind speed reduction in urban open spaces and green belts. The computational fluid dynamics (CFD) is used to simulate airflow through the trees as 3D forms. Quercus sp. is chosen as a typical tree with irregular crown shape. The influence of some criteria such as; 1. Number of tree rows, 2. Gaps between trees, 3. Trees arrangement patterns, and 4. Height levels on wind speed reduction are examined at this study.  According to the results, the best reduction is observed for the heights above 5 meters with 0.50 m gap distance between trees. The results also reveal that rectangular two-row arrangement of trees with irregular forms is more effective than the other arrangements in reducing wind velocity.