旋转风螺旋度及其在暴雨演变过程中的作用

利用中尺度有限区域模式ＭＭ４对１９９１年７月５～６日的江淮梅雨锋暴雨过程进行了数值模拟，在模拟结果可靠的基础上，用模式输出的细网格动力协调资料，根据螺旋度（Ｈｅｌｉｃｉｔｙ）理论分析了这次过程中的暴雨演变以及对流层低层的中尺度低涡及地面气旋发生发展的原因。结果表明，正的旋转风螺旋度大值中心及其演变较好地对应和反映了暴雨中心及造成暴雨的中尺度涡旋的发生位置及演变，较大的螺旋度值是暴雨及低层中尺度低涡和地面气旋系统发生发展的机制之一；螺旋度的强度变化对暴雨发生有一定的指示意义。

旋转风螺旋度在广西春季一次冰雹大风天气分析中的应用

利用旋转风螺旋度对 2 0 0 1年 4月发生在桂中地区的冰雹大风天气进行分析 ,结果表明 :低层旋转风螺旋度对冰雹大风等强对流天气有一定的指示意义 ,冰雹大风天气易产生于低层正旋转风螺旋度大值中心与中低层对流性不稳定能量储存区所包围的区域 ,其上空 5 0 0 h Pa以下旋转风螺旋度为正 ,40 0 h

The Mechanism of Flow Field around a Rotating Cylinder with Fins for High Performance Magnus Wind Turbine

Spiral Magnus is a unique wind turbine system that rotates with cylinders which have spiral-shaped fins coiled around them （instead of using the more common propeller-type blades）. In the present study, three models （cylinder with no fins, cylinder with straight fins and cylinder with spiral fins） were installed, and fluid force measurements were performed by a strain gauge force balance. A PIV （particle image velocimetry） system was used to better understand the flow fields around the cylinder. Considering the results of the experiment, it was confirmed that, the aerodynamic performance of the rotating cylinder can be improved by the fin. However, the straight fin makes the flow close to the cylinder surface ineffective. The rotary cylinder with the spiral fins was able to generate the greatest lift among three models, because the spiral fin effectively influences the vicinity of the cylinder surface.