龙卷风风场下水面船舶倾覆的力学机理研究
Aerodynamic Forces on a Ship in Tornado and Their Impact on Ship Capsizing

为研究龙卷风风场对船舶稳定性的影响,利用龙卷风风场模型分析了船舶风荷载特性及其随方位的变化规律。龙卷风风场模型在柱坐标系下形成并假定流场定常,龙卷风的漏斗外形轴对称,且从外围到中心的气压降主要由切向风速产生的离心力来平衡;以“东方之星”船舶简化模型为例,计算了船舶的最小倾覆力矩,并从船舶航向以及船舶位于龙卷风风场的不同径向位置分析了船舶倾覆的力学条件。研究结果表明:船舶航向垂直于龙卷风的径向时,船两侧负压差大于最小倾覆力矩,从而导致船舶倾覆;船舶航向平行于龙卷风的径向时,船舶受高速风的冲击而发生倾覆,倾覆方向与龙卷风的切向一致;船舶航向与龙卷风风场径向成任意夹角时,倾覆取决于船舶相对于龙卷风中心的位置、龙卷风切向风速以及船舶航速。该结果可为船舶设计及龙卷风预警研究提供参考。
To investigate the impacts of tornado wind field on ship stability, the characteristics of wind loads on the ship and ship capsizing law are analyzed. A tornado wind field model is constructed on cylindrical coordinates, the flow field of the tornado is supposed as steady and the tornado funnel as axisymmetric in its shape. The air pressure drop from the tornado periphery to its center is assumed to be mainly balanced by the centrifugal force derived from tangential velocity of tornado. Taking simplified Eastern Star ship model as an example, the minimum overturning moment of the suffering ship is evaluated, and the tornado’s aerodynamic impact on ship capsizing is analyzed considering the vessel sailing directions and different radial positions of the field where the vessel is located. According to the results, when sailing direction is perpendicular to the radial direction of the tornado, the ship capsizes as the pressure difference between both ship sides gets greater than its minimum overturning moment; when sailing along the radial direction, mainly due to dynamic impacts of high？？speed incoming wind, the ship capsizes in the tangential direction of the tornado; when the ship sails in any direction, whether the ship capsizes depends on the ship’s radial distance from the tornado center, the tangential wind speed of the tornado and the ship velocity. This results may provide a reference for ship design and tornado？？warning research