In most cases, a ship is launched in open water, where the flow may be quite different and would have an impact on the safety of the launched ship. Currently, calculations of the launching are mostly done with hydrostatic method, and the influence of flow, especially transverse flow, is usually ignored. In fact, transverse flow at high speed could make ship not only rotate around the pivot near the bow, but also move transversely. The ship with large lateral movement may collide with the bank. In present study, a 50000 DWT multi-purpose carrier is discussed. A series of model tests is performed in still water and under different transverse flow conditions. Curves of ship’s draft at stern, transverse drift, direction angle and traction versus slippage are obtained with Froude conversion method. The effect of transverse flow on the launching ship is analyzed, which could be helpful to assess the safety of ship launching.%船舶下水多在开放水域进行，所在下水水域的水文环境，水流情况各有不同，对下水船舶的影响也不尽相同。目前船厂在进行船舶下水计算时，多采用静力学计算法，忽略了水流（尤其是横流）对下水船舶的影响。事实上，流速较高的横流，不但可以使船舶绕首支点发生转动，还能使船舶发生横向漂移。过大的横移将使船舶撞向岸壁，发生碰撞事故。论文以一艘50000 DWT 多用途货船为例进行平流和不同横流速度环境下的系列缩尺船模下水试验，采用弗劳德换算法得到船舶艉吃水、横向偏移、方向角和拉力随滑程的变化曲线。通过对比不同工况的下水数据结果，分析横流参数对船舶下水的影响，为类似船舶在横流环境下的下水的安全性评估提供参考。
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