Coupled Analysis Comparison of Thermal Flow and Thermal Stress

Using the temperature distribution of solid parts calculated by a flow-solid coupled CFD analysis, thermal-stress analyses are conducted. Four approaches are investigated. 1) The mesh and the temperature distribution of FLOTRAN are used in a thermal-stress analysis directly. While this is the simplest and most direct approach, designing a suitable mesh for FLOTRAN is generally difficult for complex models such as an engine exhaust manifold. 2) SCRYU/Tetra, a FVM based CFD software, is used instead of FLOTRAN to solve the temperature and flow field. SCRYU/Tetra uses a mesh consisting of tetrahedron, hexahedron, prism and pyramid, or a hybrid mesh. Because the hybrid mesh is compatible between ANSYS element type 95 and SCRYU/Tetra, not only the temperature distribution of solid part but also the mesh can be re-used for thermal-stress analysis in ANSYS. 3) Flow and temperature field is solved using SCRYU/Tetra and the resulting film coefficient between solid and fluid and the ambient flow temperature are interpolated to corresponding surface of a mesh generated for thermal-stress analysis. The temperature distribution within the solid part is re-calculated and then thermal-stress analysis is done using ANSYS. 4) Flow and temperature field is solved using SCRYU/Tetra and resulting temperature field is interpolated to the nodes of the mesh for thermal-stress analysis. Thermal stress analysis is done using ANSYS. Above 4 methods are compared in this paper with a simple cross pipe model. Approach 4) is found to be most reasonable in terms of computational flexibility and efficiency. Finally as an application, a complex engine exhaust manifold is analyzed to show the accuracy, flexibility and efficiency of the combined use of SCRYU/Tetra and ANSYS.

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