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CASE BASED SCALING: RECENT DEVELOPMENTS IN ICE MODEL TESTING TECHNOLOGY

机译:基于案例的缩放:ICE模型测试技术的最新进展

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Model ice testing is the state of the art validation and testing method for ships and structures interacting with ice. Its initial design objective was the prediction of resistance forces of ice breaking ships by using Froude and Cauchy similitude to account to the most significant force ratios. In the ice breaking process the forces due to downward bending are considered most significant and therewith much emphasis was spent on the correct scaling of the bending strength or flexural strength of the model ice. Recent research on the mechanical behavior of model ice shows a significantly higher compliance in downward bending than targeted when following the applied scaling laws. This can lead to scale effects in the resistance force also when testing ice breaking ships. The too compliant ice facilitates an additional ride-up of the ship onto the ice and the vertical motions manifest as additional resistance contribution. The low compliance of model ice also imposes uncertainties on wave-ice interaction tests, which gain increasing significance due to the climatic changes in Polar regions. The modeling of ice break-up due to waves, with the current standard model ice, requires much steeper waves than in full scale as the ice surface needs to experience a much higher de- flection to reach the critical failure stress. A similar issue arises for vertical structures exposed to drifting ice. In full-scale a pile-up of ice around the structure is observed and in the contact area so called high-pressure zones may form. Such effects cannot be modeled with classic model ice as it easily bends downwards and produces a failure pattern and failure process very different from full-scale as well as high-pressure zones do not form which is due to the string property gradient in model ice. The mentioned three scenarios are considered being highly relevant in marine research and for the marine industry and therefore this paper introduces two new model ice types with which those scenarios can be modeled. The 'model ice of virtual equivalent thickness' uses a different modeling approach to reach a scaled stiffness for improved modeling of waves in ice and ships' resistance in thicker ice. The 'wave model ice is modeled by using waves in the formation process and can resemble high-pressure-zones acting on a vertical structure. Both methods are considered as an extension to the existing standard model ice for dedicated scenarios by scaling or putting emphasis on different ice properties by altering the production process. The presented approach also emphasizes case-based-scaling, which means that the scaling or the model ice type needs is defined by the modeled scenario as the standard model ice is obviously not fully capable to reflect all properties of sea ice in scale.
机译:模型冰测试是船舶和结构与冰相互作用的验证和测试方法的状态。其初始设计目标是使用Froude和Cauchy Mieilitude对最重要的力量来预测冰爆发的抵抗力的预测。在冰破碎过程中,由于向下弯曲导致的力被认为是最重要的,并且在其它重点上都花在了模型冰的弯曲强度或弯曲强度的正确缩放上。最近关于模型冰的力学行为的研究表明,随着应用缩放法律时,模拟冰的力学行为显示出比目标下降的符合性明显更高。当测试破冰船时,这也可以导致阻力力的效果。太巧合的冰促进了船舶的额外乘车到冰上,垂直运动表现为额外的抵抗贡献。模型冰的低依从性也对波 - 冰相互作用测试施加了不确定性,这导致极性地区的气候变化导致的显着性。随着冰面需要体验更高的缺陷以达到临界失效应力,冰块引起的冰块冰块造型比全刻度更陡峭的波浪。为暴露于漂流冰的垂直结构而产生类似的问题。在满量程中,观察到结构周围的冰堆,并且在接触面积中,所以可以形成高压区域。这些效果不能用经典模型冰进行建模,因为它可以轻松地向下弯曲,并产生与全尺度的故障模式和故障过程非常不同,并且不形成由于模型冰中的字符串属性梯度,因此不会形成。所提到的三种情景被认为是海洋研究和海洋工业的高度相关,因此本文介绍了两种新的模型冰类型,可以建模这些方案。 “虚拟等效厚度的模型冰”使用了不同的建模方法来达到缩放刚度,以改善冰和船舶在较厚的冰上的抗性中的波浪建模。 “波模型冰是通过在形成过程中使用波的建模的,并且可以类似于作用在垂直结构上的高压区域。通过通过改变生产过程,这两种方法都被视为专用场景的现有场景的延伸,以便在不同的冰属性上进行强调。所提出的方法还强调基于案例的结垢,这意味着缩放或模型冰类型的需要被建模的情况下定义为标准模型冰显然是不完全能够以反映规模海冰的所有属性。

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