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.
Enhanced Modal Solutions for Structural Dynamics in Aerothermoelastic Analysis
Hypersonic vehicle design and simulation require models that are of low order. Modeling of hypersonic vehicles is complicated due to complex interactions between aerodynamic heating, heat transfer, structural dynamics, and aerodynamics in the hypersonic regime. This work focuses on the development of ecient modal solutions for structural dynamics of hypersonic vehicle structures under transient thermal loads. The problem is outlined and aerothermoelastic coupling mechanisms are described. A previously developed reducedorder, time-domain aerothermoelastic simulation framework is used as the starting point for this study. This paper focuses on three main modeling areas: 1) The eect of aerodynamic heating on the evolution of free vibration modes shapes and frequencies is examined, 2) A surrogate modeling technique is employed for directly updating the generalized stiness matrix and thermal loads based on the transient temperature distribution and 3) Basis augmentation techniques are employed in order to obtain more accurate solutions for the structural dynamic response. The techniques to be studied are described and applied to a representative hypersonic vehicle elevator structure.
Experimental study of thermal modeling for stratospheric platform airships
R&D work on the Japanese stratospheric platform airship is discussed from the viewpoint of the thermal modeling. The work includes two experiments on the thermal characteristics of the 25m-long airship and the 35m-long PV-equipped airship model. The validity of the current thermal model was confirmed by comparing the calculated results with the measured data. The other important work is the Ground-to-Stratosphere (GTS) flight test. A 47mlong airship-shaped balloon was flown to the stratosphere. The flight simulation program into which the thermal model was integrated, was developed and applied successfully to predict the ascent behavior and the flight trajectory.