Physico–chemical modelling in hypersonic flow simulation

Experimental results obtained in the ONERA F4 hot-shot wind tunnel have been analyzed to address two important problems for this type of wind tunnel, ie, the determination of reservoir conditions and the thermochemical nature of the nozzle flow Numerical tools (one-dimensional and two-dimensional inviscid or viscous, unsteady or space marching codes) are used to reproduce the results of the high-enthalpy experiments To illustrate this approach, several runs are investigated with different arc-chamber material options, for which diode laser infrared absorption spectrometry (DLAS) has provided freestream velocity, translational temperature, and nitric oxide concentration measurements The reservoir enthalpy can be determined using spherical and sharp-cone probe heat-transfer-rate measurements with adequate correlations Recent direct measurements of freestream velocity with electron beam fluorescence time-of-flight technique are used to cross check DLAS and heat-transfer-rate probe results Concerning the thermochemical nature of F4 nozzle flows, an unexpected conclusion is obtained, as the nozzle wall pressure and translational temperature are observed to be close to equilibrium values at high-enthalpy operating conditions

Flow Characterization in the ONERA F4 High-Enthalpy Wind Tunnel

Numerical and experimental study on thermal shock damage of CVD ZnS infrared window material

The aim of this paper is to present an accurate evaluation of the phenomena appearing for high pressure air plasmas supposed to be in local thermodynamic equilibrium (LTE) In the past, we already calculated the net emission coefficient for air mixtures at atmospheric pressure and for temperatures up to 30kK (molecular contribution being restricted to 10kK) Unfortunately, the existence of high pressures does not allow us to use this database due to the non-ideality of the plasma (Viriel and Debye corrections, energy cut-off ), and due to the significant shifts of molecular reactions towards upper temperatures Consequently, this paper proposes an improvement of our previous works with a consideration of high pressure corrections in the composition algorithm in order to take into account the pressure effects, and with a new calculation of all the contributions of the plasma radiation (atomic lines and continuum, molecular continuum, and molecular bands) using an updated database A particular attention is paid to calculate the contribution of all the major molecular band systems to the radiation: O2 (Schumann–Runge), N2 (VUV, 1st and 2nd positive), NO (IR, β, γ, δ, ) and N2+ (1st negative and Meinel) The discrete atomic lines and molecular bands radiation including the overlapping are calculated by a line-by-line method up to 30kK and 100 bar This updated database is validated in the case of optically thin plasmas and pressure of 1bar by the comparison of our integrated emission strength with the published results Finally, this work shows the necessity to extend the molecular radiation database up to 15kK at high pressure (bands and continuum) since their corresponding contributions could not be neglected at high temperature

https://iopscience.iop.org/article/10.1088/1742-6596/406/1/012010/pdf

P. Sagnier

Papers

On the validation of high enthalpy wind tunnel simulations