Dynamic Analysis Of Buried Fluid-conveying Pipeline And Rotating Shaft

Buried fluid-conveying pipelines and rotating shafts,as common slender structures,are widely used in oil and gas transportation and rotating machinery,and play an important role in maintaining modern life and the energy industry.It is worth noting that there are still many problems in the research on the dynamic characteristics of buried fluid-conveying pipelines and rotating shafts that need to be analyzed and resolved urgently.The lack of understanding of the dynamic characteristics of buried fluid-conveying pipelines and rotating shafts brings certain difficulties to the design of rotating shaft components in oil and gas pipelines and rotating machinery.Therefore,the in-depth study of the dynamic characteristics of buried fluidconveying pipelines and rotating shafts has important theoretical significance and application value.In this paper,the dynamic characteristics of buried fluid-conveying pipelines and rotating shafts are studied separately through numerical calculations.The main research contents and results are as follows:The mathematical model of buried fluid-conveying pipeline is established based on the Love shell theory.The fluid is considered as ideal fluid,and the velocity potential are used to describe the fluid pressure acting on the pipeline.Using the theory of potential flow,the formula for the pressure of the fluid in the pipe against the pipe wall is derived.Ignoring the coupling of soil and buried pipeline,the soil is simplified to Winkler foundation.The Hamilton principle is used to obtain the governing equations of buried fluid-conveying pipelines.The modal superposition method and Newmark integration method are used to analyze the dynamic response of buried pipelines under blast loading.The results show that in the soil with large acoustic impedance,the response of the pipeline is greater.The Winkler foundation will increase the stiffness of the pipeline.The increase of the scaled distance leads to the decrease in the displacement amplitudes of the pipelines.The increase of the fluid velocity results in the rise of the displacement amplitudes of the pipelines.The maximum displacement increases first and then decreases with the increase of length-to-radius ratio of the pipelines.With the increase of thickness-to-radius ratio,the maximum displacement of the pipelines tends to decrease.In order to analysis the influence of soil on the vibration characteristics of buried pipelines,the soil medium around the buried pipeline is regarded as an elastic medium,and the frequency equation of the buried pipeline is derived using the Love shell theory to obtain the natural frequency of the buried pipeline.The results show that the results show that after considering soil coupling,the natural frequency of the pipeline is higher than that of the pipeline without considering soil coupling.The natural frequency of the pipeline decreases with the increase of length-to-radius ratio of the pipelines.The soil density changes from 1000 kg/m3 increases to 4000 kg/m3,the natural frequency of the steel pipe does not change,and the natural frequency of the PVC pipe gradually increases.Using the momentum equation and the continuity equation,the force of the fluid in the cavity on the rotating shaft is derived.Based on the Euler-Bernoulli beam theory and the Hamilton principle,the equation of motion of the graphene platelets reinforced composite rotating shaft is derived,and the stability of the rotating shaft is analyzed.The results show that:thickness-to-radius ratio of the rotating shaft increases,the instability zone of the structure shifts to the high speed zone;the cavity ratio of the rotating shaft increases,and the instability zone first increases and then decreases.When the cavity ratio of the rotating shaft is 0 and 1,the rotating shaft will not be unstable.As the mass fraction of graphene increases,the structural instability zone shifts to the high-speed zone;the graphene length-to-thickness ratio increases,and the structural instability zone shifts to the high-speed zone.The Capone oil film force model is used to obtain the Reynolds equation of the oil film pressure distribution,and the expression of the oil film force of the sliding bearing on the rotating shaft is derived.The Timoshenko beam theory and Hamilton principle are used to derive the motion equation of the rotating shaft affected by the oil film force.The Runge-Kutta method is used to analyze the nonlinear vibration response of the rotating shaft.The results show that the journal gap of the sliding bearing increases,and the speed at which the first bearing position of the rotating shaft enters a chaotic state becomes smaller.The oil film viscosity coefficient of the sliding bearing increases,and the speed at which the first bearing position of the rotating shaft enters a chaotic state becomes larger and larger.