1 1/50 0。6,0。7,0。8,0。9,1。0,1。1,1。2,1。3,1。5,2。0

2 1/40 0。5,0。6,0。7,0。8,0。9,1。0,1。1,1。2,1。3,1。4,

1。5,2。0

3 1/30 0。6,0。7,0。8,0。9,1。0,1。1,1。2,1。3,1。4,1。5,

1。8,2。0

4 1/20 1。0,1。1,1。2,1。3,1。4,1。5,1。6,1。7,1。8,1。9,

2。0,2。2

To observe the asymmetric behaviour of the vertical bending moment (i。e。 sagging and hogging), zero levels were recorded when the model was at rest in still water。 Whilst the model travels at Fn=0。275, the measured dynamic bending moments are presented relative to the static bending moment values in still water, and include the steady state component  due to the forward speed。

Test results and wavelet analysis

The 2-node flexible mode frequency (9。4 Hz) and the structural damping ratio (0。067) of the model floating in still water were measured by an impulsive loading tech- nique (Chen et al 2001)。

The non-dimensional expressions for the amplitude of vertical acceleration ZT , pitch  , heave Z and the verti- cal bending moment M are respectively given as:来;自]优Y尔E论L文W网www.youerw.com +QQ752018766-

indicate a slower vibration behaviour。 For example, the value at Level –1 describes the static component differ- ence between sagging and hogging vertical bending moment, whilst components at Level 6 and Level 7 are dominated by the first harmonic and the second har- monic wave induced responses。 The lower level fre- quency components exhibit steady variation with re- spect to time。 However, for the higher level compo- nents, especially at Levels 8 and 9, an impulsive re- sponse behaviour is observed correlating with the im- pulsive excited interval of the encounter  wave period。 To examine in detail the frequency properties of each level component, Fig 2 illustrates a discrete cosine Fou- rier transform of both the original signal and the derived wavelet component at each frequency level。 For the vessel travelling in severe regular head waves, a typical response in the frequency domain of the mid-ship verti- cal bending moment is derived from the Fourier trans- form of the original data。 It shows the dominant first harmonic component and higher harmonic components of not negligible values, especially responses relating to the second harmonic and 2-node natural frequency har- monic contributions。 It is clear that the summation of components at Level 5 and Level 6 provides the main contribution to the whole response within the frequency region (0。5-1。5 Hz), whilst components at Levels 7, 8 and 9 contribute to the response in the frequency ranges (1。0-3。5Hz), (2。5-7。5Hz) and above 4。5Hz respectively。 Frequency overlap of responses between adjacent levels exists, and therefore synthesis of several level compo- nents may be necessary to derive results for further analysis。摘要简要描述小波分析过程以及运用 Daubechies 小波函数的方法。在波浪中移动的自行推进的 S175 型集装箱简易船模的测量数据由傅里叶变换滤波和小波分析法分析。被标记刚体移动的高频率构件 可以忽略主要特征参数的实质影响。分解随时间变化的弯矩为低频及高频分量，使得冲击出现次数 以及他的振幅可以容易的被找到。这些数据为在波浪中航行的船舶遭遇一般性载荷和仿真短暂冲击 载荷（例如：抨击，甲板上浪）的力学模型的发展提供了重要信息。

毕业论文关键词小波分析；简易模型测试；波浪载荷；非线性

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