中文摘要：

随着全球气候条件的变化和城市化进程的不断加快，由暴雨引起的城市洪水频繁发生。停在路面上的汽车在洪水中容易被冲走，并有可能对周边行人和基础设施等造成严重损害。因此有必要对洪水中汽车的稳定性进行理论分析与模型试验研究。本文首先分析了洪水中部分淹没状态下汽车的受力情况，采用基于泥沙起动理论推导出洪水中汽车的起动流速公式；然后选用两款模型小车（大小两种比尺），在遵循相似理论的条件下，在水槽中进行了一系列的汽车起动试验；采用大比尺模型小车的试验结果率定公式中的两个关键参数，并用公式计算出原型车辆在不同水深下的起动流速。最后采用小比尺模型小车的试验结果，根据比尺关系计算出原型汽车的起动流速，与公式计算值符合较好。研究结果表明：来流水深越大，部分淹没下汽车的起动流速越小；在相同来流水深条件下，当水流流向正对于侧面时比正对于头部时汽车更容易起动。

英文摘要：

With the changes of global climate and continuous urban expansion, the occurrence probability of flash floods in urban areas has increased in recent years. Vehicles parking on the roads are susceptible to be- come instable during flood events. Once a vehicle is under instability, it might cause injuries to passengers and pedestrians or damage to buildings and infrastructure. Therefore, it is necessary to conduct a study of the- oretical analysis and flume experiments on the stability of flooded vehicles. In the study, all forces acting on a partially submerged vehicle are analyzed, and a formula of incipient velocity for flooded vehicles is derived based on the theory of incipient motion of sediment. A series of flume experiments for the incipient motion of vehicles were therefore conducted using two types of scaled model vehicles, with two scales for each type. The experimental data obtained for the larger-scale model vehicles are used to determine two parameters in the de- rived formula and the corresponding incipient velocities under various incoming water depths are computed u- sing the formula for the prototype of these two vehicles. Finally, the prediction accuracy of this formula is vali- dated using the experimental data obtained for the smaller-scale model vehicles. The results indicate that： （i） for a certain vehicle, the greater incoming water depth, the smaller incipient velocity for a partially submerged vehicle; and （ii） for a certain incoming water depth, vehicles parking vertical to the flow direction are easier to slip than those parking parallel to the flow direction.