Study On The Vibration Response Of Dike Crossing Pipeline Based On Empirical Wavelet Transform And Time-Wavelet Scaling Spectrum

As an important part of the city’s water project to secure water supply,it is especially crucial to ensure the safety and stability of the dike crossing pipeline.Under different operating conditions,the dike crossing pipe may have different degrees of harmful vibration due to the external environment,operation and hydraulic pressure conditions,and the violent vibration of the pipeline may cause loosening,leakage and even rupture of the contact parts of the pipeline,endangering the safety of dike.Therefore,finding an effective vibration analysis method for dike crossing pipe,extracting the time and frequency domain characteristics of the pipe vibration signal,finding out the cause of the pipeline vibration,analyzing the pipeline vibration status,and taking necessary maintenance measures is the top priority to ensure the safe and stable operation of the dike crossing pipeline.Using the 6#dike crossing pipe of the Yang’er water plant in Foshan City,Guangdong Province as the research object,the vibration signal of the pipeline was obtained by switching on and off the unit,starting with the three working conditions of shutdown,start-up and normal operation,with the help of pipeline prototype observation data,Combined with the improved Empirical Wavelet Transform-Singular Value Decomposition(EWT-SVD),wavelet transform,cross wavelet transform,Multi-Channel Weighted Multi-Scale Permutation Entropy(MWMPE)and other methods,the time domain and frequency domain characteristics of pipeline vibration are studied,and the causes,process,spatio-temporal correlation and state of pipeline vibration are explored in order to realize the whole process of vibration of dike crossing pipe.The following elements make up the majority of the research content:(1)Study on the extraction of vibration information of dike crossing pipe.Firstly,a modal parameter identification method is proposed to improve the EWT algorithm,and a joint feature extraction method based on improved EWT-SVD is proposed;Then,a simulation signal is constructed to verify the effectiveness of the improved EWT-SVD method.It is found that this method can effectively remove interference signals and extract signal feature information;Finally,applying this method to the engineering of pipelines crossing dike,it was found that the characteristic frequencies of pipeline vibration signals,29.5Hz,36.5Hz,and59.0Hz,can correspond to the rotational frequency multiplication and leaf frequency of the pipeline unit.The improved EWT-SVD method has good engineering applicability,expands the idea of feature information extraction and provides effective support for structural vibration analysis for pipelines crossing dike.(2)Research on the time domain and frequency domain characteristics of the vibration of the dike crossing pipeline.Comprehensively analyze the vibration signals of various measuring points under shutdown,startup,and normal operating conditions.From a time domain perspective,it is found that the pipeline vibration is the most intense under shutdown conditions.The strongest vibration positions in the X and Y directions are the inlet elbow section,with vibration acceleration peaks of 1751.3mm/s~2 and 2813.5mm/s~2.The strongest vibration positions in the Z direction are the water conveyance straight pipe section,with vibration acceleration peaks of 2019.2mm/s~2;From the perspective of frequency domain,with the frequency-wavelet energy spectrum based on wavelet transform,the main characteristic frequencies of the pipeline vibration process were identified,and it was found that the maximum characteristic frequencies were 29.5Hz,36.5Hz and 59.0Hz under each operating condition,and the corresponding vibration sources are 6#,7#unit rotation frequency doubling and 6#unit leaf frequency.This indicates that the unit rotation frequency doubling and leaf frequency are the main vibration sources leading to pipeline vibration through the dike.(3)Study on the spatial and temporal correlation characteristics of the vibration of the dike crossing pipeline.Using the cross wavelet transform method,we analyzed the spatio-temporal correlation characteristics of the vibration of the dike crossing pipeline,and found that the peak energy of the vibration between each measurement point was concentrated at the frequencies of 29.5 Hz and 59.0 Hz;the relevant vibration sources are rotation frequency multiplication and blade frequency of the 6#pipeline unit,indicating that the 6#pipeline unit is the cause of synchronous vibration of the pipe body;According to the correlation coefficient analysis results,the correlation coefficient between the pipe body measurement points(measurement point 1,measurement point 2,and measurement point 4)is significantly greater than the correlation coefficient between the pipe body measurement points and the anchor block measurement point(measurement point 3),indicating that the anchor block will significantly reduce the transmission effect of pipeline vibration and reduce the correlation of vibration.(4)Research on monitoring and early warning of the operating condition the dike crossing pipeline.A method of operation condition monitoring and early warning of dike crossing pipeline based on MWMPE is proposed.Firstly,by using simulation signal,the method’s efficacy is confirmed,and then the vibration state monitoring is carried out by taking three working conditions of the pipeline as an example.It is found that the entropy curve jumps at the moment of shutdown and start-up condition and the vibration is in an"abnormal"state;In normal operation,the entropy curve is stable and the vibration is in a"normal"state,which shows that MWMPE algorithm has good effectiveness and applicability in monitoring and early warning of dike crossing pipeline.In summary,the study on the vibration response of dike crossing pipeline based on empirical wavelet transform and time-wavelet scaling spectrum broadens the perspective of pipeline vibration signal analysis,and realizes the identification of strong vibration location,main frequency of vibration,cause of vibration,time-domain characteristics of vibration source,vibration correlation and vibration state of dike-penetrating pipeline.This study can reveal the vibration characteristics of the dike crossing pipeline under the effect of fluidic vibration,put forward rationalized suggestions for the dike crossing pipeline vibration reduction and vibration isolation project from the theoretical level,which is of great significance to improve the quality and efficiency of the dike crossing pipeline project.