Based on the Euler-Bernoulli beam theory and Kelvin-Voigt model,a nonlinear model for the transverse vibration of a pipe under the combined action of base motion and pulsating internal flow is established.The governin...Based on the Euler-Bernoulli beam theory and Kelvin-Voigt model,a nonlinear model for the transverse vibration of a pipe under the combined action of base motion and pulsating internal flow is established.The governing partial differential equation is transformed into a nonlinear system of fourth-order ordinary differential equations by using the generalized integral transform technique(GITT).The effects of the combined excitation of base motion and pulsating internal flow on the nonlinear dynamic behavior of the pipe are investigated using a bifurcation diagram,phase trajectory diagram,power spectrum diagram,time-domain diagram,and Poincare map.The results show that the base excitation amplitude and frequency significantly affect the dynamic behavior of the pipe system.Some new resonance phenomena can be observed,such as the period-1 motion under the base excitation or the pulsating internal flow alone becomes the multi-periodic motion,quasi-periodic motion or even chaotic motion due to the combined excitation action.展开更多
At seasonal and intraseasonal time scales, polar motions are mainly excited by angular momentum fluctuations due to mass redistributions and relative motions in the atmosphere, oceans, and continental water, snow, and...At seasonal and intraseasonal time scales, polar motions are mainly excited by angular momentum fluctuations due to mass redistributions and relative motions in the atmosphere, oceans, and continental water, snow, and ice, which are usually provided by various global atmospheric, oceanic, and hydrological models(some with meteorological observations assimilated; e.g., NCEP, ECCO, ECMWF, OMCT and LSDM etc.). Unfortunately, these model outputs are far from perfect and have notable discrepancies with respect to polar motion observations, due to non-uniform distributions of meteorological observatories,as well as theoretical approximations and non-global mass conservation in these models. In this study,the LDC(Least Difference Combination) method is adopted to obtain some improved atmospheric,oceanic, and hydrological/crospheric angular momentum(AAM, OAM and HAM/CAM, respectively)functions and excitation functions(termed as the LDCgsm solutions). Various GRACE(Gravity Recovery and Climate Experiment) and SLR(Satellite Laser Ranging) geopotential data are adopted to correct the non-global mass conservation problem, while polar motion data are used as general constraints. The LDCgsm solutions can reveal not only periodic fluctuations but also secular trends in AAM, OAM and HAM/CAM, and are in better agreement with polar motion observations, reducing the unexplained excitation to the level of about 5.5 mas(standard derivation value; about 1/5-1/4 of those corresponding to the original model outputs).展开更多
基金financially supported by the National Natural Science Foundation of China(Grant Nos.52171288,51890914)the Key Research and Development Program of Shandong Province(Major Innovation Project)(Grant No.2022CXGC020405)+1 种基金the National Ministry of Industry and Information Technology Innovation Special Project-Engineering Demonstration Application of Subsea Oil and Gas Production SystemSubject 4:Research on Subsea Christmas Tree and Wellhead Offshore Testing Technology(Grant No.MC-201901-S01-04)CNPq,CAPES and FAPERJ of Brazil。
文摘Based on the Euler-Bernoulli beam theory and Kelvin-Voigt model,a nonlinear model for the transverse vibration of a pipe under the combined action of base motion and pulsating internal flow is established.The governing partial differential equation is transformed into a nonlinear system of fourth-order ordinary differential equations by using the generalized integral transform technique(GITT).The effects of the combined excitation of base motion and pulsating internal flow on the nonlinear dynamic behavior of the pipe are investigated using a bifurcation diagram,phase trajectory diagram,power spectrum diagram,time-domain diagram,and Poincare map.The results show that the base excitation amplitude and frequency significantly affect the dynamic behavior of the pipe system.Some new resonance phenomena can be observed,such as the period-1 motion under the base excitation or the pulsating internal flow alone becomes the multi-periodic motion,quasi-periodic motion or even chaotic motion due to the combined excitation action.
基金supported in parts by the National 973 Project of China(No.2013CB733301 and 2013CB733305)the National Natural Science Foundation of China(No.41474022,41210006 and 41374022)+2 种基金the R&D Special Fund for Public Welfare Industry(Surveying and Mapping,No.201512001)the Fundamental Research Funds for the Central Universities of China(No.2042016kf0146)the China Postdoctoral Science Foundation(No.2014T70737)
文摘At seasonal and intraseasonal time scales, polar motions are mainly excited by angular momentum fluctuations due to mass redistributions and relative motions in the atmosphere, oceans, and continental water, snow, and ice, which are usually provided by various global atmospheric, oceanic, and hydrological models(some with meteorological observations assimilated; e.g., NCEP, ECCO, ECMWF, OMCT and LSDM etc.). Unfortunately, these model outputs are far from perfect and have notable discrepancies with respect to polar motion observations, due to non-uniform distributions of meteorological observatories,as well as theoretical approximations and non-global mass conservation in these models. In this study,the LDC(Least Difference Combination) method is adopted to obtain some improved atmospheric,oceanic, and hydrological/crospheric angular momentum(AAM, OAM and HAM/CAM, respectively)functions and excitation functions(termed as the LDCgsm solutions). Various GRACE(Gravity Recovery and Climate Experiment) and SLR(Satellite Laser Ranging) geopotential data are adopted to correct the non-global mass conservation problem, while polar motion data are used as general constraints. The LDCgsm solutions can reveal not only periodic fluctuations but also secular trends in AAM, OAM and HAM/CAM, and are in better agreement with polar motion observations, reducing the unexplained excitation to the level of about 5.5 mas(standard derivation value; about 1/5-1/4 of those corresponding to the original model outputs).