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Analyzing Fluid–Structure Interaction Problems in Compressible Flows

Azampour, Mohammad Hadi | 2016

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 50801 (45)
  4. University: Sharif University of Technology
  5. Department: Aerospace Engineering
  6. Advisor(s): Hejranfar, Kazem
  7. Abstract:
  8. The goal of this thesis is the development and application of the finite volume method (FVM) with a same solution procedure in the fluid and structure domains for the simulation of fluid-structure interaction (FSI) problems in the compressible fluid flow. The unsteady Euler equations written in the arbitrary Lagrangian–Eulerian (ALE) form are considered as the governing equations of the compressible fluid flow and the moderate/large nonlinear deformation of the elastic structure is considered to be governed by the Cauchy equations in the Lagrangian/total Lagrangian forms. Therefore, the nonlinear phenomena in the unsteady compressible fluid flow and the large deformation of the elastic structure can be properly simulated. Both the domains are discretized by applying the cell-vertex (CV) and cell-centered (CC) FVMs with the second-order accuracy in space on arbitrary unstructured quadrilateral/triangular grids and a second-order implicit method in time. The Lagrangian/total Lagrangian forms of the Cauchy equations can handle different types of boundary conditions including the simply-supported ones for which a special formulation is developed. Also, the total Lagrangian formulation can properly model the panel thickness and therefore the stress distribution within the structure can be reasonably obtained. The accuracy and performance of the CV and CC FVMs for both the structural and fluidic parts are examined by the simulation of some standard problems. It is indicated that the results obtained by applying the CV and CC FVMs for the problems considered here are in good agreement with the analytical solutions and these two methods are equivalent in terms of the accuracy and convergence rate on the regular quadrilateral grids. The study shows that the CV FVM is more efficient than the CC FVM in term of the computational cost for the analysis of the structural dynamic problems, and therefore, the CV FVM is applied for the simulation of the large nonlinear deformation of the thin-walled structure. The solution of the Euler equations is performed by applying both the upwind and central schemes and their accuracy and performance are compared with each other by simulating different compressible inviscid flows. For simulating FSI problems, the fluidic and structural parts are coupled in a partitioned manner where at the interface the grids of the two domains are coincident. A modified version of the linear spring analogy is used to perform a robust unstructured mesh movement strategy for the grid deformation of the fluidic part in response to the movement of the structural part. To assess the accuracy and capability of the FSI code developed, two typical problems are simulated. In the first problem, the transonic flow over a rigidly moving airfoil in the flapping and pitching degrees of freedom. The second problem is the 2D panel flutter in which the supersonic flow passing over the elastic thin-walled panel causes the flutter phenomenon. The present results for these problems are compared with the available numerical and experimental results which show good agreement. Simplicity of the implementation and similarity of the discretization procedure of the fluidic and structural parts are the advantages of the present solution method. It is also demonstrated that the solution methodology proposed based on the FVM is capable of accurately simulating fluid–structure interaction (FSI) problems in compressible flows
  9. Keywords:
  10. Finite Volume Method ; Fluid-Structure Interaction ; Compressible Flow ; Eulerian-Lagrangian Form Euler Equations ; Cell-Centered Scheme ; Cel-Vertex Scheme

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