Role of Environmental Wind Shear and Helicity in Simulated Tornadoes

环境风切变和螺旋度在模拟龙卷风中的作用

• 批准号: 8714626
• 负责人: Eugene Wilkins
• 金额: $ 11.7万
• 依托单位: University of Oklahoma Norman Campus
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1987
• 资助国家: 美国
• 起止时间: 1987-11-15 至 1990-04-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=8714626&HistoricalAwards=false
• 关键词: Role; Environmental; Wind; Shear; Helicity

A combined use of a rotating screen at the bottom and an exhaust fan at the top of a cylindrical chamber can produce tornado-like vortices through the conservation of angular momentum. However, the existence of vertical wind shear in a thunderstorm environment can induce horizontal vorticity which in turn induces vertical vorticity when tilted by convective updrafts. By replacing the rotating screen with three tiers of plexiglass guide vanes, thereby simulating the storm-relative, vertically veering winds, the vortex chamber at the University of Oklahoma is now capable of simulating vortices by vorticity tilting instead of vorticity stretching. This project will allow extensive measurements to be made in the vortex chamber and thereby examine the role of environmental wind shear and helicity (the dot product of the vorticity vector and velocity vector) in the simulated tornadoes.

在底部的旋转筛和在底部的旋转筛的组合使用， 在圆柱形腔室顶部的排气风扇可以产生 通过角动量守恒 势头. 然而，垂直风切变的存在， 雷暴环境可以诱发水平涡度， 反过来，当对流倾斜时， 上升气流 通过将旋转屏幕替换为三层 有机玻璃导叶，从而模拟风暴相对， 垂直转向的风，大学的涡流室 俄克拉荷马州的一个实验室现在能够通过涡量来模拟涡 倾斜而不是涡量拉伸。 该项目将 允许在涡流室中进行广泛的测量 从而研究环境风切变的作用， 螺旋度（涡度矢量和速度的点积 矢量）在模拟龙卷风。