Abstract
Traditional windbreak trees called Igune, located in Osaki Koudo in northern Miyagi Prefecture, Japan, consist of taller trees and shorter shrubs. These Igune are planted on the west and north sides of residences to protect against prevailing winds in the winter season. In this study, large-eddy simulation (LES) of airflow around two-dimensional Igune rows were performed. Proper orthogonal decomposition (POD) was subsequently applied to the simulated flow fields to understand the mechanisms of the flow behind the Igune. Two Igune situations were considered: one with both tall trees and shrubs, and another with only shrubs following the removal of tall trees. The LES results revealed that when only shrubs were present, a highly turbulent wind environment with reverse flow developed behind them. Conversely, when both shrubs and trees were present, the turbulent fluctuations of the reverse flow behind the trees were relaxed. The spatial and temporal functions of the first two dominant POD modes were similar. However, in the case where only shrubs were present, the third and higher POD modes contributed to the reverse flow, whereas these modes were absent when both shrubs and trees were present.
