Simplified analysis for estimation of the behavior of a submerged floating tunnel in waves and experimental verification

To achieve rational design in waves for a submerged floating tunnel which has emerged as a new offshore transportation infrastructure, it's necessary to understand its hydrodynamic behavior. For simple but accurate estimation of hydrodynamic forces, a theoretical method is proposed and the tests with physical models in a wave flume were carried out for verification. Morison's equation was used to estimate wave loads composed of inertia force and drag force. Forces calculated by applying the linear wave theory to Morison's equation coincided well with those measured by the tests. The test results showed that mooring systems played a significant role in the movement of the submerged floating tunnel in waves. A pendulum model could be used to describe the motion of the submerged floating tunnel with a single vertical mooring. Based on the verified relations, a simple slack condition which causes the submerged floating tunnel to be unstable was also proposed. The simplified approach proposed by this study proved to be useful in designing the submerged floating tunnel in the initial stage.     

Semi-submersible wind turbine hull shape design for a favorable system response behavior

Floating offshore wind turbines are a novel technology, which has reached, with the first wind farm in operation, an advanced state of development. The question of how floating wind systems can be optimized to operate smoothly in harsh wind and wave conditions is the subject of the present work. An integrated optimization was conducted, where the hull shape of a semi-submersible, as well as the wind turbine controller were varied with the goal of finding a cost-efficient design, which does not respond to wind and wave excitations, resulting in small structural fatigue and extreme loads.The optimum design was found to have a remarkably low tower-base fatigue load response and small rotor fore-aft amplitudes. Further investigations showed that the reason for the good dynamic behavior is a particularly favorable response to first-order wave loads: The floating wind turbine rotates in pitch-direction about a point close to the rotor hub and the rotor fore-aft motion is almost unaffected by the wave excitation. As a result, the power production and the blade loads are not influenced by the waves. A comparable effect was so far known for Tension Leg Platforms but not for semi-submersible wind turbines. The methodology builds on a low-order simulation model, coupled to a parametric panel code model, a detailed viscous drag model and an individually tuned blade pitch controller. The results are confirmed by the higher-fidelity model FAST. A new indicator to express the optimal behavior through a single design criterion has been developed.     

集装箱船整船有限元结构分析

文章以一艘１７００箱集装箱船为例,阐述了整船有限元结构分析方法。先建立全船有限元模型和质量模型,再用三维流体动力计算程序进行波浪随机载荷的长期预报,并在此基础上导出设计波参数组,最后,在全船有限元模型上 计算得出船体结构在各个设计波上的应力分布和变形结果,所得到的船体结构有限元分析结果对同类型集装箱船的设计和强度分析有一定的参考价值,对其它类型的船舶结构强度分析也有一定的借鉴意义。     

浅谈近岸、浅海海域波浪对船舶的危害——A轮沉没引发的思考

近岸,浅海海域的波浪与深海海域的波浪性质相异,航海驾驶人员必须特别重视,以防其造成船舶的浪损或更严重的海事发生。     

舰船波浪弯矩响应的频率特性

非直壁式舰船在高浪级和高航速下的弯矩响应中,除了含有低频遭遇频率成分外,还存在着一定数量的遭遇频率的倍频成分及船体各谐调的垂向总振动频率成份,它们都会对舰船波浪弯矩的非线性响应产生相应的影响。如果舰船的第一谐调垂向总振动频率正好是遭遇频率的整数倍,这时弯矩的非线性响应将达到极值。本文从模型试验及理论计算两方面分析了舰船波浪弯矩的频率特性,对船体载荷响应理论的发展及设计载荷的确定具有指导意义。     

Wave spectrum estimation conditioned on machine learning-based output using the wave buoy analogy

In this work, a hybrid approach for wave spectrum estimation is proposed. Fundamentally, the approach is based on the wave buoy analogy, processing ship response measurements, via a framework combining machine learning and a physics-based method dependent on available transfer functions. Specifically, a non-parametric (Bayesian) estimate is obtained of the directional wave spectrum conditioned on integral wave parameters established by a convolutional neural network. The developed method is assessed in a case study considering about two years of data obtained from an in-service container ship. The method produces good results, significantly improved when compared to the initial estimate made without constraints.     

气动式造波机中的横向波

本文讨论了用于产生二维波动的气动式造波机中,一种横向表面重力波的发生及其非线性特性。当输入频率接近于横向波的基频两倍时,利用奇摄动方法,可以得到横向波的振幅发展方程。振幅的理论预测与实验观察是定性相符的。     

水泥混凝土的振动搅拌技术

水泥混凝土的振动搅拌效益显著.这里以独联体、美国、日本等国已有的几种振动搅拌装置为例,就其工作原理、结构、性能指标等方面作了重点介绍,以促使这项技术尽快在我国得以应用.     

闭环电喷系统中的氧传感器波形分析(1)

在电喷摩托车发动机进入闭环控制工况时,ECM将根据氧传感器的电压信号来修正喷油脉宽,使混合气浓度保持在理论空燃比附近。借助发动机数据分析系统对各工况下的氧传感器波形进行分析判断,有助于快速检测出电喷系统中是否存在影响尾气排放的空燃比反馈故障。同时对于完成故障维修的车辆,通过氧传感器波形分析可以验证出维修是否有效,故障是否彻底排除。使车辆在日常使用中的尾气排放也能达到一个良好的状态。     

Filling up gaps in wave data with genetic programming

A given time series of significant wave heights invariably contains smaller or larger gaps or missing values due to a variety of reasons ranging from instrument failures to loss of recorders following human interference. In-filling of missing information is widely reported and well documented for variables like rainfall and river flow, but not for the wave height observations made by rider buoys. This paper attempts to tackle this problem through one of the latest soft computing tools, namely, genetic programming (GP). The missing information in hourly significant wave height observations at one of the data buoy stations maintained by the US National Data Buoy Center is filled up by developing GP models through spatial correlations. The gap lengths of different orders are artificially created and filled up by appropriate GP programs. The results are also compared with those derived using artificial neural networks (ANN). In general, it is found that the in-filling done by GP rivals that by ANN and many times becomes more satisfactory, especially when the gap lengths are smaller. Although the accuracy involved reduces as the amount of gap increases, the missing values for a long duration of a month or so can be filled up with a maximum average error up to 0.21 m in the high seas.