Application of integrated fluid-thermal-structural analysis methods
Hypersonic vehicles operate in a hostile aerothermal environment which has a significant impact on their aerothermostructural performance. Significant coupling occurs between the aerodynamic flow field, structural heat transfer, and structural response creating a multidisciplinary interaction. Interfacing state-of-the-art disciplinary analysis methods is not efficient, hence interdisciplinary analysis methods integrated into a single aerothermostructural analyzer are needed. The NASA Langley Research Center is developing such methods in an analyzer called LIFTS (Langley Integrated Fluid-Thermal-Structural) analyzer. The evolution and status of LIFTS is reviewed and illustrated through applications.
Effect of Control Surface-Fuselage Inertial Coupling on Hypersonic Vehicle Flight Dynamics
A simulation framework is developed for assessing the eect of control surface inertial loads on hypersonic vehicle response. The framework is based on a partitioned, timemarching approach in which the fuselage and control surface equations of motion are integrated independently and forces/motion at the interface are exchanged between the two systems at pre-determined time intervals. This approach is advantageous in that it does not require direct coupling of the fuselage and control surface models, and therefore allows for the models to be of dissimilar form. Equations of motion for both the fuselage and control surface are presented and a formulation for coupling the two systems is outlined which includes iterations within each aeroelastic time step. The methodology is applied to a representative hypersonic vehicle elevator control surface model which includes aerothermoelastic eects and is attached to a single degree of freedom oscillator representing the fuselage. Results show that control surface inertial eects lead to a departure of the instantaneous control surface lift force by up to a factor of eight with respect to the static value. Investigation of the system response under a commanded change in control surface deection angle shows that control surface inertia results in departure of the instantaneous control surface pitching moment by up to a factor of 500 with respect to the static value.
Recent advances in thermostructural finite element analysis
A comparison study is described which has indicated that the finite element and lumped parameter methods are comparable for steady-state conduction/convection analyses. The finite element model was advantageous because of the ease of model verification with computer graphics. Some problems encountered in constructing compatible thermal and structural models have indicated the need for further methodology developments to automate the transition between thermal and structural analyses. The need for more efficient finite element nonlinear transient algorithms has been cited. With further development in the thermal analysis area, the finite element method offers high potential for an integrated thermal/structural analysis capability.