Analysis and Comparison of Different Chemistry Models for the Computation of Reacting Flows on Re-entry and Hypersonic Vehicles

Paper in proceeding, 2019

An aircraft in hypersonic flight regime is enveloped in a plasma layer due to the high temperatures involved. This electronic plasma layer will be responsible for cutting-off communications to and from the aircraft, in a phenomenon known as radio blackout. Several methods have been proposed to mitigate radio blackout, amongst which is the "magnetic window". In the magnetic window method a magnetic field is imposed near the antenna, opening a spectral window, allowing the passage of electromagnetic waves without distortion. Experimental replication of hypersonic flight is extremely costly, generating a keen interest in the development of numerical codes capable of simulating weakly ionized flow around a hypersonic vehicle. This is specially relevant for investigating blackout mitigation methods, since a validated numerical code will allow the preliminary design and optimization of new concepts, in a much faster and cheaper way. A numerical code that is used to simulate a plasma layer around an aircraft needs to accurately predict the electron density and associated plasma properties. Several distinct chemistry models have been proposed. In this paper, four chemistry models will be studied, each accounting for 11 species commonly found in an atmospheric plasma layer: N2; O2; NO; N; O; N2+ ; O2+ ; NO+; N+; O+ and e−. The electron number density calculated with each model is compared with the electron number density calculated in the RAM-C II experimental flight. The models will be compared in terms of simulation runtime as well, in an attempt to assess which requires less processing power.