Calibration and Uncertainty Quantification of VISTA Ablator Material Database Using Bayesian Inference

Rostkowski, Przemyslaw; Venturi, Simone; Panesi, Marco; Omidy, Ali D.; Weng, Haoyue; Martin, Alexandre

doi:10.2514/1.t5396

Cited by 11 publications

(3 citation statements)

References 43 publications

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“…The radiation is predominantly due to atomic N(I) and O(I) lines − with the main spectral feature being the intense 174.29 nm line of atomic nitrogen. Ablating heat shields undergo pyrolysis, resulting in the formation of a gas layer which carries away some of the incident radiation via convection and some by absorption through electronic excitation of the gases, thereby mitigating the radiative heat flux on the spacecraft surface . Accounting for this absorption can cause a reduction in the predicted radiative heat flux impinging on the spacecraft, leading to more efficient designs for heat shields and predictive modeling of hypersonic re-entry flights.…”

Section: Introductionmentioning

confidence: 99%

Carbon Clusters: Thermochemistry and Electronic Structure at High Temperatures

2021

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This paper studies the thermochemistry and electronic structure of small carbon clusters and hydrocarbons, which are major constituents of pyrolysis gases released into the boundary layer of ablating heat shields. Our focus lies on clusters of up to four carbon atoms. Among other molecules, thermochemistry data for molecules such as C3H and C4H have been determined using the Weizmann-1 (W1) method. These molecules have very limited thermochemistry data recorded in the literature, thereby necessitating new and accurate computations of required properties such as electronic energies of low-lying states, heats of formation, harmonic frequencies, and rotational constants. A study of electronically excited states of these molecules computed using the equations of motion coupled cluster singles doubles method revealed C4 and C4H to be potential sources of radiation absorption in the boundary layer. The excited electronic states of interest are studied further to obtain their optimum geometries, rotational constants, and vibrational frequencies. Moreover, we also study the effect of low-lying excited electronic states on the partition function to assess their effect on the thermodynamics of these pyrolysis gases in the high-temperature regime. Neglecting the excited electronic states records a maximum difference of 12% in the computed specific heat capacity values, C p values. Finally, comparisons of the equilibrium mole fractions obtained using the thermodynamics computed in this paper with the existing state-of-the-art tables used for hypersonic applications (e.g., JANAF and Gurvich Tables) show an order of magnitude difference in the mixture compositions. It is shown that the rhombic isomer of C4 (1Ag), which is energetically close to the ground state (3Σg –) and usually neglected in composition calculations, contributes to a 28% increase in the equilibrium mole fraction of the C4 molecule.

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Section: Introductionmentioning

confidence: 99%

Carbon Clusters: Thermochemistry and Electronic Structure at High Temperatures

2021

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“…The use of a Bayesian framework, − allows one to gain physical insight on the PES by studying the propagation of uncertainty from microscale (PES) to the macroscale quantities of interest (gas mixture QoIs). The availability of such information content has two main advantages.…”

Section: Introductionmentioning

confidence: 99%

Bayesian Machine Learning Approach to the Quantification of Uncertainties on Ab Initio Potential Energy Surfaces

2020

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This work introduces a novel methodology for the quantification of uncertainties associated with potential energy surfaces (PESs) computed from first-principles quantum mechanical calculations. The methodology relies on Bayesian inference and machine learning techniques to construct a stochastic PES and to express the inadequacies associated with the ab initio data points and their fit. By combining high fidelity calculations and reduced-order modeling, the resulting stochastic surface is efficiently forward propagated via quasi-classical trajectory and master equation calculations. In this way, the PES contribution to the uncertainty on predefined quantities of interest (QoIs) is explicitly determined. This study is done at both microscopic (e.g., rovibrational-specific rate coefficients) and macroscopic (e.g., thermal and chemical relaxation properties) levels. A correlation analysis is finally applied to identify the PES regions that require further refinement, based on their effects on the QoI reliability. The methodology is applied to the study of singlet (11A′) and quintet (25A′) PESs describing the interaction between O2 molecules and O atoms in their ground electronic state. The investigation of the singlet surface reveals a negligible uncertainty on the kinetic properties and relaxation times, which are found to be in excellent agreement with the ones previously published in the literature. On the other hand, the methodology demonstrated significant uncertainty on the quintet surface, due to inaccuracies in the description of the exchange barrier and the repulsive wall. When forward propagated, this uncertainty is responsible for the variability of 1 order of magnitude in the vibrational relaxation time and of factor four in the exchange reaction rate coefficient, both at 2500 K.

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“…The results show that the ablation depth of the material is closely related to the Thiele number. Rostkowski et al 18 analyzed the thermal decomposition mechanism of the coating resin after undergoing high temperature, but ignored the influence of different resin and fiber components on the heat transfer of the material. The above research clearly obscures the characteristics of the fabric itself when using numerical methods to predict the heat transfer performance of the material, which is unreasonable.…”

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confidence: 99%

Effects of structural parameters on the thermal insulation properties of coated carbon fiber fabrics

Zhang

Zheng

Mao

et al. 2019

Textile Research Journal

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In order to predict the thermal insulation performance of coated carbon fiber fabric, a numerical heat transfer model under high temperature was established. The simulation results were validated by quartz lamp ablation experiment. The experimental values were in agreement with the numerical values, and the average relative error between them was 9.47%. Furthermore, the impact of structural parameters on the thermal insulation of coated carbon fiber fabrics, by using the numerical heat transfer model, was investigated. The results show that thermal insulation for the samples is in the order of plain < 2/1 twill < 3/3 twill < 5/3 stain, when using constant structure density and yarn fineness. Thermal insulation performance of the samples dramatically increases as yarn fineness goes from 3 to 12 K. Furthermore, when the structure density increases to more than 70 ends/10 cm, the thermal insulation property shows an increasing trend.

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Calibration and Uncertainty Quantification of VISTA Ablator Material Database Using Bayesian Inference

Cited by 11 publications

References 43 publications

Carbon Clusters: Thermochemistry and Electronic Structure at High Temperatures

Carbon Clusters: Thermochemistry and Electronic Structure at High Temperatures

Bayesian Machine Learning Approach to the Quantification of Uncertainties on Ab Initio Potential Energy Surfaces

Effects of structural parameters on the thermal insulation properties of coated carbon fiber fabrics

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