Design-oriented thermoelastic analysis, sensitivities, and approximations for shape optimization of aerospace vehicles

Aerospace structures operate under extreme thermal environments. Hot external aerothermal environment at high Mach number flight leads to high structural temperatures. At the same time, cold internal cryogenic-fuel-tanks and thermal management concepts like Thermal Protection System (TPS) and active cooling result in a high temperature gradient through the structure. Multidisciplinary Design Optimization (MDO) of such structures requires a design-oriented approach to this problem. The broad goal of this research effort is to advance the existing state of the art towards MDO of large scale aerospace structures. The components required for this work are the sensitivity analysis formulation encompassing the scope of the physical phenomena being addressed, a set of efficient approximations to cut-down the required CPU cost, and a general purpose design-oriented numerical analysis tool capable of handling problems of this scope. In this work finite element discretization has been used to solve the conduction partial differential equations and the Poljak method has been used to discretize the integral equations for internal cavity radiation. A methodology has been established to couple the conduction finite element analysis to the internal radiation analysis. This formulation is then extended for sensitivity analysis of heat transfer and coupled thermal-structural problems. The most CPU intensive operations in the overall analysis have been identified, and approximation methods have been proposed to reduce the associated CPU cost. Results establish the effectiveness of these approximation methods, which lead to very high savings in CPU cost without any deterioration in the results. The results presented in this dissertation include two cases: a hexahedral cavity with internal and external radiation with conducting walls, and a wing box which is geometrically similar to the orbiter wing.