海岛局部风场特性的风洞试验和数值模拟研究

Wind tunnel test and numerical simulation of partial wind field characteristics of islands

针对海岛局部风效应突出的问题,采用边界层风洞试验与数值模拟相结合的方法,对3种坡度的理想化海岛地形的风剖面进行了数值拟合,定义了差异系数来描述风剖面变化,利用数值模拟研究了差异系数和最大加速比在迎风侧的分布,重点探讨了海岛坡度和高度对最大加速比和差异系数的影响;基于风洞数据,对迎风侧和背风侧顺风向、横风向和竖向湍流强度和阵风因子分布进行了研究。结果表明:数值模拟与风洞试验结果较接近,风剖面指数在迎风侧较小;靠近坡顶的加速效应尤为明显,其最大加速比为0.4~1.0;坡腰处的差异系数较小,随着岛脊线角度的增加,差异系数为0的位置有向坡脚靠近的趋势;坡度增大到25°、0°岛脊线上最大加速比和差异系数均较大;迎风侧的三向湍流强度分布较规律,而背风侧的三向湍流强度分布较杂乱,尤其是在距海岛表面100 m高度范围内;阵风因子和湍流强度的变化趋势具有较高的一致性。

In view of the prominent partial wind effect on islands, the wind profiles of idealized islands topography with three slopes are fitted by means of boundary layer wind tunnel test and numerical simulation. The difference factor is defined to describe the variation of wind profile, the distribution of maximum acceleration ratio and difference factor on the windward side of islands is studied by numerical simulation, and the effects of island slope and height on maximum acceleration ratio and difference factor are discussed comprehensively. Moreover, based on the wind tunnel data, the along-wind, cross-wind and vertical turbulence intensity and gust factor of the windward and leeward sides are studied. The results show that the numerical simulation is basically consistent with the wind tunnel test results and the wind profile exponent(α) is smaller on the windward side of islands. It also shows acceleration effect near the top of the island is particularly obvious and its maximum acceleration ratio is between 0.4 and1.0. Moreover, the difference factor at the hillside is lower, and with the increase of the angle of the island ridge,the position where the difference factor is 0 tends to approach the slope toe. As the island slope increases to 25°, the maximum acceleration ratio and difference factor on the 0° island ridge are large. The distribution of three-dimensional turbulence intensity on the windward side is relatively regular, while that on the leeward side is disordered especially in the range of 100 m away from the island’s surface. It is worth noting that the trends of gust factor and turbulence intensity are highly consistent.