Multi-scale hypersonic ablation prediction via CFD-MD coupling
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Solution Overview
Problem
Current numerical simulation methods for hypersonic aircraft heat resistant systems fail to accurately predict ablation behavior due to limitations in representing heterogeneous reaction mechanisms at the gas-solid interface, leading to inaccuracies in heat distribution and mass transfer.
Innovation Solution
A multi-scale prediction method that couples macro-scale and micro-scale numerical simulations, using ANSYS Fluent for macro CFD calculations and LAMMPS for micro RMD simulations, to model the ablation behavior of hypersonic aircraft heat resistant structures, thereby improving the accuracy of heat prediction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If traditional CFD numerical simulation methods adopt finite chemical reaction rate models based on macro continuity hypothesis, then calculation efficiency is improved, but measurement precision of heat prediction deteriorates due to failure of continuity hypothesis at high Knudsen number
Solution Approach 1:
The patent segments the simulation into two distinct scales: macro-scale CFD simulation for overall flow field and heat distribution, and micro-scale molecular dynamics simulation for detailed gas-solid interface reactions. This segmentation allows each scale to be simulated with appropriate methods, resolving the contradiction between calculation efficiency and precision.
Solution Approach 2:
The micro-scale molecular dynamics simulation is nested within the macro-scale CFD framework. The macro simulation provides boundary conditions and bulk flow properties, while the micro simulation is embedded at the gas-solid interface to provide detailed reaction mechanisms and heat transfer coefficients, creating a nested multi-scale simulation system.
2Measurement precision
If micro-scale molecular dynamics simulation is conducted to study heterogeneous reaction paths at gas-solid interface, then measurement precision of heat prediction is improved, but device complexity increases due to coupling of multi-scale simulations
Solution Approach 1:
The patent introduces intermediary coupling layers between macro and micro simulations. The macro CFD simulation provides boundary conditions (temperature, pressure, flow velocity) to the micro MD simulation, and the micro simulation returns detailed interface reaction data and effective heat transfer coefficients. These intermediaries enable precise heat prediction while managing system complexity through structured information exchange.
Solution Approach 2:
The complex micro-scale molecular dynamics simulation is applied locally only at the gas-solid interface where heterogeneous reactions occur, rather than throughout the entire domain. The bulk flow field uses efficient macro-scale CFD methods. This local application of complex simulation reduces overall device complexity while maintaining high precision where needed.
3Measurement precision
If multi-scale coupled numerical simulation method is developed to represent heterogeneous reaction mechanism, then measurement precision of heat prediction is improved, but loss of time increases due to comprehensive multi-scale coupling
Solution Approach 1:
The patent applies partial action by conducting micro-scale molecular dynamics simulation only at critical gas-solid interface regions where heterogeneous reactions significantly impact heat transfer, rather than throughout the entire domain. This selective application reduces simulation time while maintaining high precision for the most critical heat prediction zones.
Solution Approach 2:
The macro-scale CFD simulation is performed first to establish boundary conditions and bulk flow properties before conducting the more computationally intensive micro-scale MD simulation. This preliminary action allows the micro simulation to focus only on interface phenomena with pre-defined boundary conditions, reducing total simulation time.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method enhances the precision of surface heat prediction for ablation heat resistant systems by accurately representing the evolution mechanism of gas-solid interface materials, facilitating a more integrated and precise design of heat resistant systems for hypersonic aircraft.
Implementation Method 1
performing a numerical simulation of a non-deformation hypersonic aircraft external flow field by using a macro computational fluid dynamics (CFD) solver
Implementation Method 2
performing numerical simulation on the micro model through a micro RMD solver, wherein the heating temperature is consistent with the average temperature of the wall surface
Implementation Method 3
the heating temperature is consistent with the average temperature of the wall surface of the high-temperature area obtained by the CFD calculation
Implementation Method 4
impacting the solid-phase atomic model in the micro model by taking the average mass fraction of the wall surface components obtained by the macro CFD calculation as the incidence ratio of molecules and atoms
Implementation Method 5
calculating a system diffusion coefficient by means of a mean square displacement (MSD) method
Implementation Method 6
obtaining a mass loss rate by means of the Fick's law, wherein the ratio of the mass loss rate to the original density of the heat resistant material is the ablation retreating rate
Data Source
AI summary
A multi-scale prediction method for an ablation behavior of a hypersonic aircraft heat resistant structure, includes inputting hypersonic inflow far field boundary conditions into a macro CFD solver to perform numerical simulation of the external flow field of a hypersonic aircraft; extracting the mass fraction and temperature distribution of wall surface components; obtaining an msd.txt file and an atomic path file recording the mean square displacement data through a micro RMD solver; obtaining the ratio of mass loss rate to material density, namely, the ablation retreating rate using the MSD method and Fick's law; inputting it into a CFD solver for performing grid reconstruction and transient calculation to obtain the transient variation in the external flow field of a hypersonic aircraft along the ablation retreating of the aircraft wall surface.