3D Thermal Analysis of the Protrusions Inside the Base Cavities of a Capsule

Abstract

German Aerospace Center performed wind tunnel test in the hypersonic flow regime on a capsule geometry to characterize the base heating including small cavities with simplified protrusion elements in the H2K facility. For this wind tunnel campaign two models have been build, one with cavities including simplified protrusions and one with cavities without protrusions, used as a reference. PEEK material was used to allow for IR thermography on main parts of the base. Two different wind tunnel conditions at Mach 5.3 were chosen, one duplicating flight Reynolds number and one with increased Reynolds number. To investigate the flow field in the vicinity of the model and the base region, pressure measurements and Schileren photography have been performed.

The main measurement technique used was infrared thermography to determine the surface heat flux rates during the tests. Due to the small model dimensions within the protrusion area, the usual approach to determine the heat flux with a one dimensional assumption is not valid. Therefore more accurate three dimensional analyses should be carried out.

Current thesis work is performed on a three dimensional thermal analysis with ANSYS based on the available infrared temperature data. Available data has been transformed to ANSYS by defining this as input thermal loads. In this process a projection method should be applied to transform 2D IR thermal data to 3D geometry. Validation results of mesh characteristics were obtained with available one dimensional heat equation analytical solution. Mesh parameter variation and preprocessing methods have been investigated as preparation for the transient thermal analysis. Total and directional heat flux has been evaluated with the developed procedure, compared to one dimensional evaluation results, and discussed with respect to influencing parameters and validity.