Expansion Tube Investigation of Shock Stand-Off Distances in High-Enthalpy CO2 Flow Over Blunt Bodies

Abstract

The shock standoff distance in front of a blunt body is sensitive to the thermochemical state of the free stream. Recently, experimental and numerical studies have reported significantly different bow shock profiles in high-enthalpy carbon dioxide flows, a discrepancy that may result from non-equilibrium processes during flow acceleration in ground-based facilities. In this work, an expansion tube is used to create a Mach 5.7 carbon dioxide flow, matching the stagnation enthalpy and the velocity of previous studies. Images of shock layers are obtained for spherical 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 angle of attack are in good agreement with available data from the LENS X expansion tunnel facility, confirming results are facility-independent for the same type of flow acceleration, and indicating the flow velocity is a suitable first-order matching parameter for comparative testing. Heat transfer measurements on the Mars Science Lander are also presented for the three different angle of attacks, and the results are consistent with previous studies. Initial results from a proposed organo-metallic based emission spectroscopy technique for bow shock layer interrogation are also presented.

Comparative Surface Heat Transfer Measurements in Hypervelocity Flow

“…The equation developed by Filippis provides the best prediction of the heat flux, with a 23% deviation in Air 4, a 26% deviation in Air 5, and a 35% deviation in Air 6. Though catalysis effects have been shown in the past to augment heat flux measurements in similar facilities, previous work in the HET has shown that catalytic effects are not expected to be an issue at these conditions [32].…”

Numerical simulation of a hypersonic flow past a blunt body

“…Furthermore, the simulation of hypersonic flows is also a rather complex and difficult issue. Many researchers focused on the computational fluid dynamics, which is an efficient way to solve hypersonic problem (Farbar et al, 2013;Yih and Tahir, 2013;Sharma et al, 2010;James, 2006, 2008). Four-stage third-order implicit-explicit Runge-Kutta method, which represents a powerful tool for the time discretization of partial differential equations, can be applied to solve one-dimensional nonlinear equation (Ayati et al, 2016).…”

Mars entry afterbody radiative heating: an experimental study of nonequilibrium CO2 expanding flow

“…The HET condition was used by Sharma et al [111] [108] to study the shock standoff and surface heat transfer of various diameter sphere models and a scaled MSL model at various angles of attack.…”