Nonlinear vibrations of a cantilevered pipe conveying pulsating two phase flow
Adeshina Adegoke1, Akin Fashanu2, Olayinka Adewumi1, Ayowole Oyediran1
of Mechanical Engineering, University of Lagos, Lagos, Nigeria
2Department of Systems Engineering, University of Lagos, Lagos, Nigeria
Pulsating two-phase flow;
This work studied the nonlinear transverse vibrations of a cantilevered pipe conveying pulsatile two-phase flow. Internal flow induced parametric resonance is expected because of the time varying velocity of the conveyed fluid. This unsteady behaviour of the conveyed two-phase flow is considered in the governing equation as time dependent individual velocities with the harmonically varying components fluctuating about the constant mean velocities. Method of multiple scales analysis is adopted to study the nonlinear parametric resonance of dynamics of the cantilevered pipe. Contrary to the dynamics of pulsating single-phase flow, the assessment shows that if the frequencies of pulsation of the two phases are close, both can resonate with the pipe’s transverse or axial frequencies together and both can also independently resonate with the pipe’s transverse or axial frequencies distinctively. For the planar dynamics when only transverse frequencies are resonated, in the absence of internal resonance, numerical results show that the system exhibits softening nonlinear behavior. At post critical flow conditions, the system oscillates between subcritical and supercritical pitchfork bifurcation to simulate the nonlinear Mathieu’s equation. However, in the presence of internal resonance, a nonlinear anti-resonance property is developed. Hence, the overall dynamics is quasi-periodic.
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