摘要:
提出了一种用于对不连续压力采样序列的傅立叶分析方法.此方法将周期函数展开成傅立叶级数,但在数值积分时取函数周期内有采样值的区间作为积分域,然后求解线性方程组得到傅立叶级数的系数值.为了检验本方法的有效性,利用此方法对解析函数进行了拟合,当一个周期内的取样时间大于1/2周期时,利用此方法能够得到满意的结果.利用实验方法研究了波浪作用下截断圆柱表面的压力分布.在波浪作用下静水面附近的测点在露出水面时没有压力值.利用所提出的傅立叶分析方法对略低于静水面位置的实测压力进行了分析,拟合结果与实测结果吻合很好,说明此方法在处理物理模型实验中间断采样得到的数据是有效的.利用数值方法对波浪压力进行了计算,并将一阶和二阶波压力的数值结果与实测值进行了比较.
关键词:
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傅立叶分析 /
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波浪 /
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压力 /
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模型实验
Abstract:
A Fourier analysis method is proposed for analyzing the discontinuous time series of pressure.In this method a periodic function is expended as Fourier series,but the integral is performed over the sub-period that is part of the function's whole period.Then,a matrix equation is solved to compute the coefficients in the Fourier series.A periodic analytical function is approximated by the Fourier series according to this method for testits validity.If the sampling time is greater than 1/2 of the functions period,the method can give a satisfying result.Experiments are carried out to study the pressure distribution on the surface of a truncated cylinder under the wave action.At the position near the still water surface level,there is no pressure value when it is above the water surface during the wave action.The Fourier analysis method proposed is applied to analyzing the pressure at the position near the still water surface level,and the fitting results agree well with the experimental data,indicating that this method is valid for dealing with the discontinuous data series obtained in the experiment.The wave pressures are computed numerically and the computed first-order and second-order harmonic wave pressures are compared with the measu ed data.
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