不同结构林带防风效能风洞模拟

Windbreak Effect Model of Forest Belts with Different Structure

防风林带结构是影响防风效能的主要因素。建立不同宽度、不同株行距林带防风效能与林带后距离之间的统计模型,可以为防风林建设提供指导性意见。通过风洞实验,在11 m·s-1风速下,对4种宽度、5种株行距林带的背风面0~10H(H为林带高度)的风速进行测定,采用曲线参数估计法、傅立叶模型、SSF模型(Sum of Sin Functions),构建了不同结构林带防风效能与林带后距离间的统计模型。结果表明:傅立叶模型拟合不同宽度林带的防风效能与林带后距离的关系效果最优,可决系数(R2)均在98%以上;SSF模型拟合不同株行距林带的防风效能与林带后距离的关系效果最优(R2>0.98)。根据构建的统计模型,风速为11 m·s-1左右时,林带宽度8 m(两行一带)的防风林的防风效能存在明显优势;5种株行距的林带中,株行距为8 m×8 m的防风林带本试验条件下防风效果最好。

The structure of windbreak forest belts is the main factor affecting windbreak effect. The main purpose of this paper is to establish statistical models between windbreak effect of forest belts with different widths and spacing and the distance behind the windbreak forest belts so as to provide guidance for the construction of windbreak forests. The wind speeds at 0-10 H(H is tree height) on the leeward side of forest belts with 4 kinds of widths and 5 kinds spacing are measured by wind tunnel test when the wind speed is 11 m·s-1. The statistical model between windbreak effect and distance behind forest belts is constructed by using curve parameter estimation method, Fourier model and SSF model(Sum of Sin Functions) under different forest belt structures. The results shows that Fourier model had the best effect on fitting the relationship between the windbreak effect of different width forest belts and the distance behind the forest belts, and the coefficient of determination(R2) was above 98%. SSF model had the best effect on fitting the relationship between the windbreak effect of different spacing forest belts and the distance behind the forest belts, with the lowest coefficient of determination(R2) being 89%. According to the statistical model, when the wind speed is about 11 m·s-1, the windbreak effect of the windbreak forest structure with a forest belt width of 8 m(two rows and one belt) has prominent advantage;among the five forest belts with different row spacing, the windbreak forest belt with a tree spacing of 8 m×8 m is the best structure for wind protection under the test conditions.