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UNSTEADY WIND FORCES IN TATSUMAKI

龙卷不稳定的风力

基本信息

批准号：
06452288
负责人：
TANIIKE Yoshihito
金额：
$ 3.97万
依托单位：
Osaka City University (1995)Kyoto University (1994)
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (B)
财政年份：
1994
资助国家：
日本
起止时间：
1994 至 1995
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-06452288/
关键词：
Tatsumaki Unsteady Wind Force Rankine Vortex Added Mass Velocity Potential Morison's Equation Wind Tunnel Experiment 渦構造物被害加速度ランキン

项目摘要

The word 'tatsumaki' is used in Japan to designate meteorological phenomena as tornadoes and waterspounts. In surbeys of tatsumaki damage, great differences are often observed in the magnitude of damage to buildings, housings, towers, pylons, poles and signboards, depending on where these structures were located relative to the path of the tatsumaki. Generally, there is little regularity in the direction these structures are torn down or in which way missiles such as roofing tiles, timbers and gravels are scattered. These are results of rotational windstorms and fluctuational velocities, that are characteristic of tatsumakis. As a tatsumaki passes over, the speed and direction of wind will change constantly, creating rapid transitions in the magnitude and direction of wind loads on structures it encounters, both in time and space. Wind forces on bodies induced by unsteady flows are inevitably different from those by steady flows with constant velocity. Therefore, tatsumaki-induced wind … More loads on structures should be different from those induced by typhoons or monsoons, as both can be approximated as steady flows.In the present study, we assumed the swirling motion of tatsumakis as a Rankine vortex that moves with a constant velocity, and analyzed the unsteady horizontal flow at arbitrary points along the tatsumaki path. By the action of unsteady/accelerating flow, the inertial force is generated on bodies and it can be estimated by the previous experimental data or by the theoretical calculation using the velocity potential of inviscid flow. The inertial force and the drag force which is proportional to the square of fluid velocity were combined and incorporated into the Morison's equation, which was then able to express the total fluid force. The fluctuating fluid forces generated during the passage of a tatsumaki on arbitrary located structures were numerically estimated.The velocity and acceleration at arbitrary points in the tatsumaki varied continuously with time and both reached maximum at the core of the vortex. The acceleration did not depend on the translation velocity of the tatsumaki and was directed towards the center of the vortex.It was found that the total wind force acting on structures became maximum at the leeward core of the tatsumaki vortex. The inertial force due to the acceleration of fluid was about 30% of the drag obtained from the square of fluid velocity. The directions in which the bodies are blown down by a tatsumaki may be reversed on the different sides of the path of the vortex center. This was shown to be consistent with the results of a field survey on actual tatsumaki damage. Less

在日本，“龙卷风”一词被用来指代龙卷风和水柱等气象现象。根据建筑物、房屋、塔楼、塔架、杆子和招牌所处的位置，建筑物、房屋、塔楼、塔架、杆柱和招牌的受损程度往往有很大差异。一般来说，这些建筑被拆除的方向或瓦片、木材和碎石等导弹的散布方式几乎没有规律性。这是旋转风暴和脉动速度的结果，这是托萨马基斯的特征。当TatSumaki经过时，风速和风向将不断变化，导致其遇到的建筑物上的风荷载的大小和方向在时间和空间上都发生了快速变化。非定常流对物体的作用力必然不同于恒定流对物体的作用力。因此，TatSumaki诱导的Wind…由于台风或季风对建筑物的作用应不同于台风或季风对建筑物的作用，因此两者都可以近似为定常流动。在本文中，我们假设TatSumakis的旋转运动是一个以恒定速度移动的朗肯涡旋，并分析了TatSumaki路径上任意点上的非定常水平流动。在非定常/加速流的作用下，物体上产生惯性力，这种惯性力可以通过以往的实验数据或利用无粘流的速度势进行理论计算来估算。将惯性力和与流体速度的平方成正比的阻力组合在Morison方程中，从而能够表示总的流体力。数值计算了龙卷风通过任意位置的结构物时产生的脉动流体力，在龙卷风中任意点的速度和加速度随时间连续变化，并在涡核达到最大值。加速度不依赖于玉崎涡的平移速度，而是指向涡旋的中心，在玉崎涡的背风核心处，作用在建筑物上的总风力最大。流体加速产生的惯性力约为流体速度平方阻力的30%。在涡旋中心路径的不同侧，被立崎吹倒的物体的方向可能是相反的。这与田崎实际受灾情况的实地调查结果相一致。较少