p-DSMC METHOD OF RADIATION EFFECT OF RAREFIED GAS ATOMIC WITH EXTREMELY SUPERSONIC
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摘要: 极高超声速流动激波层内的高温导致内能模态的激发并伴随热辐射发生, 过高的温度使得空气分子完全解离, 原子组分对辐射热的贡献将达到80%以上. 本文基于优化的原子辐射模型, 提出追踪光子−直接模拟蒙特卡罗(p-DSMC)方法, 研究了稀薄流区不同马赫数下的高超声速二维圆柱绕流的壁面辐射加热, 获得了有无激发辐射效应的壁面压力和热流以及沿驻点线变化的平动、振动和转动温度. 在不考虑激发辐射效应的情况下, 得到的壁面压力和热流与已有的模拟结果符合的非常好, 误差均在5%以内, 尤其是在驻点位置, 误差在1%以内; 获得的平动、振动以及转动温度均与文献结果符合的很好. 在相同的来流条件下, 考虑辐射效应后发现, 来流速度低于10 km/s时, 辐射加热不明显, 在驻点区域, 辐射加热占对流加热比重在7%左右; 来流速度大于10 km/s时, 在驻点区域, 辐射加热占对流加热比重将超过30%. 考虑辐射效应后, 对非平衡区的平动、转动和振动温度的最大值影响不大. 此外, 另一个重要结论是, 流场中原子的浓度是影响壁面辐射热流大小的一个重要因素.Abstract: The high temperature behind the extremely supersonic flow shock layer leads to the excitation of internal energy mode and accompanied by thermal radiation. The high temperature makes the air molecules completely dissociated, and the contribution of atomic components to radiation will reach more than 80%. Based on the optimized atomic radiation model and using the photon tracing direct simulation Monte Carlo (PDSMC) method, the wall radiation heating of hypersonic two-dimensional cylinder at different Mach numbers in the rarefied flow region is studied. The wall pressure and heating with or without excited radiation effect and the translational, vibrational and rotational temperatures along the stagnation line are obtained. Without considering the excitation radiation effect, the wall pressure and heating obtained are in good agreement with the previous simulation results and the error is less than 5%. Especially at the stagnation point, the error is less than 1%. The translation, vibration and rotation temperatures obtained are also in good agreement with the literature results. Under the same flow conditions, considering the radiation effect, it is found that when the flow velocity is lower than 10 km/s, the radiative heating is not obvious. While the flow velocity is greater than 10 km/s, the proportion of radiative heating to convective heating will exceed 30% in the stagnation point. After considering the radiation effect, the maximum values of translational, rotational and vibrational temperatures in the non-equilibrium region have little effect. In addition, another important conclusion is that the concentration of atoms in the flow field is an important factor affecting the magnitude of the radiative heat flow on the wall.
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Key words:
- extremely supersonic /
- radiation effect /
- DSMC method /
- photon tracking /
- aerodynamic heating
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表 1 N、O原子群组能级的能量和简并度
Table 1. Energy and degeneracy of energy levels of N and O atomic groups
Atom Group Energy/J Degeneracy N 1 0 4 2 3.820 E-19 10 3 5.730 E-19 6 4 1.688 E-18 18 5 1.907 E-18 54 6 2.073 E-18 108 7 2.127 E-18 54 Atom Group Energy/J Degeneracy O 1 0 9 2 3.16 E-19 5 3 6.71 E-19 1 4 1.49 E-18 8 5 1.73 E-18 24 6 1.93 E-18 78 7 2.04 E-18 128 表 2 N(上)、O(下)原子群组激发态的辐射寿命和跃迁辐射几率
Table 2. Radiation lifetime and transition radiation probability of excited states of N (upper) and O (lower) atomic groups
atom transiton lifetme/s probability O 2→1 0.50 3→1 0.50 4→1 0.10 5→4 3.3 × 10−8 0.60 6→1 2.5 × 10−8 0.10 6→4 2.0 × 10−6 0.01 6→5 2.5 × 10−8 0.50 7→1 0.4 × 10−8 0.10 7→5 1.0 × 10−7 0.40 atom transiton lifetme/s probability N 2→1 0.70 3→1 0.50 3→2 0.50 4→1 0.5 × 10−8 0.50 4→2 0.2 × 10−8 0.25 4→3 0.5 × 10−8 0.25 5→2 0.2 × 10−8 0.15 5→4 6.0 × 10−8 0.08 6→2 1.0 × 10−8 0.10 6→3 1.0 × 10−8 0.10 6→5 5.0 × 10−8 0.70 7→4 1.0 × 10−6 0.10 表 3 流场的初始参数
Table 3. Initial parameters of flow field
stream parameter value N0 1.447 × 1020 1/m3 T0 187.0 K Ma 24.58/30.0/37.0 Twall 1000 K ρ 6.958 × 10−6 kg/m3 -
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