Expansion tube investigation of shock stand-offdistances in high-enthalpy CO_2flow over blunt bodies

摘要

The shock standoff distance in front of a blunt body is sensitive to the thermo-chemical state of the free stream. Recently, experimental and numerical studieshave reported significantly different bow shock profiles in high-enthalpy carbondioxide flows, a discrepancy that may result from non-equilibrium processes duringflow acceleration in ground-based facilities. In this work, an expansion tube is usedto create a Mach 5.7 carbon dioxide flow, matching the stagnation enthalpy andthe velocity of previous studies. Images of shock layers are obtained for spheri-cal geometries and a scaled model of the Mars Science Lander. Different sphere diameters are used in order to access non-equilibrium and equilibrium stagnation line shock profiles predicted by theory. Mars Science Lander profiles at zero angleof attack are in good agreement with available data from the LENS X expansiontunnel facility, confirming results are facility-independent for the same type of flowacceleration, and indicating the flow velocity is a suitable first-order matching pa-rameter for comparative testing. Heat transfer measurements on the Mars Science ander are also presented for the three different angle of attacks, and the resultsare consistent with previous studies. Initial results from a proposed organo-metallicbased emission spectroscopy technique for bow shock layer interrogation are alsopresented. 18431