An implicit coupling framework for numerical simulations between hypersonic nonequilibrium flows and charring material thermal response in the presence of ablation

Schematic of the gas-surface interaction with the SMB and SEB.

An implicit coupling framework for numerical simulations between hypersonic nonequilibrium flows and charring material thermal response in the presence of ablation

Jingchao Zhang,  Jinsheng Cai, Shucheng Pan,∗ School of Aeronautics, Northwestern Polytechnical University, Xi’an 710072, China and National Key Laboratory of Aircraft Configuration Design, Xi’an 710072, China

Chunsheng Nie, Science and Technology on Space Physics Laboratory, China Academy of Launch Vehicle Technology, Beijing 100076, China

 

https://doi.org/10.48550/arXiv.2410.16601

 arXiv:2410.16601v1 

 

Announce Type: new 

 

Abstract: An implicit coupling framework between hypersonic nonequilibrium flows and material thermal response is proposed for the numerical simulation of ablative thermal protection materials during its flight trajectory. Charring ablative materials, when subjected to aerodynamic heating from hypersonic flows, undergo complex processes such as ablation and pyrolysis, involving heterogeneous and homogeneous chemical reactions. 

 

These multi-physical phenomena are simulated by a multicomponent material thermal response (MTR) solver that takes into account the complexity of component of pyrolysis gases. The species concentrations are calculated to improve the accuracy of transport and thermophysical parameters of pyrolysis gases. The MTR solver implements implicit time integration on finite difference discretization form to achieve higher efficiency. The numerical solutions of hypersonic flows and material thermal response are coupled through a gas-surface interaction interface based on surface mass and energy balance on the ablating surface. 

 

The coupled simulation employs the dual time-step technique, which introduces pseudo time step to improve temporal accuracy. The explicit coupling mechanism updates the interfacial quantities at physical time steps, which achieves higher computational efficiency, but introduces time discretization errors and numerical oscillations of interfacial quantities. 

 

In contrast, the implicit coupling mechanism updates the interfacial quantities at pseudo time steps, which reduces the temporal discretization error and suppresses numerical oscillations, but is less efficient. In addition, a simplified ablation boundary based on steady-state ablation assumption or radiation-equilibrium assumption is proposed to approximate solid heat conduction without coupling the MTR solution, providing quasi-steady flow solutions in the presence of ablation.

:arXiv physics.flu-dyn :Oct 22, 2024

Summary

Highlights

An implicit coupling framework for numerical simulations between hypersonic nonequilibrium flows and charring material thermal re sponse in the presence of ablation

• A multicomponent material thermal response solver for numerical simulation methods of charring ablators is developed.
• An ablation boundary is proposed to solve quasi-steady flows in the presence of surface ablation.
• Numerical solutions of hypersonic flows and material thermal response are implicitly coupled by exchanging interfacial quantities at pseudo time step to achieve higher accuracy.
• Implicit coupling mechanism suppresses numerical oscillations of inter-facial quantities and achieves higher time discretization accuracy.

Background of the study:
The paper focuses on developing a numerical framework for simulating the interaction between hypersonic nonequilibrium flows and the thermal response of charring ablative materials during spacecraft reentry.

Research objectives and hypotheses:
The main objectives of the study are:
1. To develop robust numerical methods for modeling the thermal response of ablative materials, considering ablation and pyrolysis.
2. To propose a detailed gas-surface interaction interface for modeling the mass and heat transfer on the ablating surface.
3. To improve the accuracy and efficiency of the coupled simulation between hypersonic flows and ablative material response.

Methodology:
1. The authors develop a multicomponent material thermal response (MTR) solver that considers the complex composition of pyrolysis gases to improve the accuracy of transport and thermophysical parameters.
2. The MTR solver employs implicit time integration to achieve higher computational efficiency.
3. A gas-surface interaction (GSI) interface is proposed to couple the MTR solver with the chemically reacting flow (CRF) solver, accounting for the detailed mass and energy balance on the ablating surface.
4. Simplified ablation boundary conditions based on steady-state ablation and radiation-equilibrium assumptions are developed to approximate the solid heat conduction without the need for the full MTR solution.

Results and findings:
1. The implicit time integration of the MTR solver is more efficient than the explicit method, reducing the computational time by 92% while maintaining accuracy.
2. The implicit coupling mechanism between the CRF and MTR solvers reduces the time discretization errors and suppresses numerical oscillations of the interfacial quantities, compared to the explicit coupling method.
3. The simplified ablation boundary conditions using the steady-state ablation assumption can accurately predict the ablation rate and surface temperature, matching the experimental data.