气垫平台破冰阻力的模型试验研究

EXPERIMENTAL STUDY OF THE ICE BREAKING RESISTANCE ON AN AIR CUSHION PLATFORM

通过开展低温拖曳冰水池物理模型试验,测试气垫平台在遭遇平整冰时的破冰过程和破冰阻力.在模型试验中,以一座现役破冰气垫平台为原型,建立了合理的模型试验相似律.依据相似律分别对原型平台的结构框架、气道结构、围裙结构和垫升系统等部分进行了模拟,从而得到一套与原型平台结构型式和垫升机制相似的模型平台.模型平台在试验拖车的拖曳下通过低温冰水池中的模型冰排,分别以垫升高度和航行速度为试验参数,对不同试验工况下气垫平台的破冰过程进行测试.通过对模型试验现象和结果的分析,深入解析了气垫平台的破冰过程,揭示了气垫平台的破冰机理.通过试验发现,非全垫升状态更有利于模型平台的破冰作业.气垫平台破冰的关键机理是在冰排底部形成稳定的气腔,从而促使冰排在结构的下压作用和气腔的上顶压力下发生弯曲破坏.在试验中测试了气垫平台破冰风压随结构姿态的变化,在时频域内对风压的变化情况进行了分析,并讨论了风压随航行速度的变化规律.以此为基础,对气垫平台破冰阻力随垫升高度和航行速度的变化规律进行分析,从而为该类气垫平台的结构设计和操船方法提供必要的基础性数据和参考依据.

The ice breaking processes of an air cushion platform were investigated and the corresponding resistances were also measured through model tests performed in ice tank. An actual ice-breaking air cushion platform that is in-service was modelled during the tests, and a reasonable similarity law was established. By obeying the similarity law, each part of the actual platform was simulated, including the structural frame, air ducting, air cell and the cushion system and thus,structural shape and cushion mechanism of model platform was kept in similar with the prototype platform. During the tests, the model platform was towed by the main carriage passing through the model ice sheet with different hover-heights and navigation speeds. The ice breaking process was investigated under each test condition. By analyzing on the test phenomena and measured results, the ice breaking process was deeply discussed and, the ice breaking mechanism was revealed for the air cushion platform. It could be found that the non-full-cushioning condition is more beneficial to the ice breaking operations for the model platform through model tests. The key ice breaking mechanism of an air cushion platform was that a stable air space is formed under the ice sheet. Thereby the ice sheet was pressed down by the model platform and risen upward by the air space, and then the bending failure of the ice sheet occurred. The ice breaking wind pressure of an air cushion platform varying with the structural attitudes was tested during the model tests. Afterwards, the ice breaking wind pressure was analyzed in time and frequency domain respectively, and the regularities of ice breaking wind pressure varying with the navigation speed were discussed. The regularities of ice breaking resistance varying with the hover-height and navigation speed were finally established as the necessary basic data for guiding the structural design and operating control of such type of platform in practice.