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Nonlinear Vibrations and Stability Analysis of Rotating Cylindrical Shells Conveying Annular Fluid Medium

Abdollahi Dehkordi, Rahim | 2021

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 54231 (45)
  4. University: Sharif University of Technology
  5. Department: Aerospace Engineering
  6. Advisor(s): Dehghan Firouzabadi, Rohollah; Rahmanian, Mohammad
  7. Abstract:
  8. In this study, stability as well as linear and nonlinear vibrations of coaxial rotating cylindrical shells conveying annular incompressible fluid medium are investigated. To this aim the inner isotropic and elastic rotating cylindrical shell along with the rigid and stationary outer cylinder are considered. Equations of motion for the inner cylinder are determined according to the Hamilton’s principle and using the Sanders-Koiter theory assumptions. In order to generalize the boundary condition implementation, some translational and rotational springs are attached to the boundaries at the mid-plane. The final system of equations are solved by means of the extended Galerkin method – being an energy based approach – which starts by utilizing a set of approximate trial functions. In the first place, free vibration analysis of the structure is presented at different boundary conditions and various configurations. On the other hand, the governing fluid equations are determined by linearizing the Naiver-Stokes equations and by using the impermeability conditions at the structure-fluid interface. As a result, dynamic pressure and forces acting on the cylindrical shells are obtained, which consequently lead to the coupled system of equations. Using the Runge-Kutta direct integration technique, the solution to the nonlinear coupled system of equations is determined. To have a reliable nonlinear solution, both driven and companion mode shapes are included in the solution procedure. The solution convergence and validity of the results are found to be totally reasonable. Stability of rotating beams conveying flow in external annular fluid is considered as the first step in the current study. Then in the next step, both linear and nonlinear dynamic analysis and stability of rotating cylindrical shells in external annular fluid are carried out. Using the developed algorithm, effects of various parameters such as rotation speed, external to internal cylinders’ radii ratio, fluid to structure mass ratio and different boundary conditions are investigated in linear and nonlinear test cases
  9. Keywords:
  10. Fluid-Structure Interaction ; Nonlinear Stability ; Nonlinear Vibration ; Rotating Cylindrical Shell ; Annular Fluid Medium ; Coaxial Cylindrical Shell

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