A Fourier analysis method for discontinuous time series for pressure

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.