高温化学非平衡计算中源项处理方法

Calculation method of source terms in high temperature chemical nonequilibrium flows

高超声速三维化学非平衡绕流流场的数值模拟中 ,在计算初期容易发生组元密度出现负值的非物理现象 ,另外源项的刚性是影响计算稳定性和收敛速度的主要原因。根据源项线性化理论 ,采用 2种源项线性化方法处理化学反应源项 .一种为根据流场内化学反应物理规律构造的线性化方法 ,该方法能抑制在计算过程中组元密度出现负值现象 ,提高了计算稳定性 ,加速了收敛速度 .同时采用了时间预处理矩阵的线性化方法 ,较好地解决了非平衡化学反应与流场耦合的刚性问题。证明了所构造源项线性化方法相容性 .数值实验表明该方法有效地避免了源项计算中密度出负的问题 ,加快了计算的收敛速度 。

In the numerical simulation of hypersonic chemical nonequilibrium flows, species density may become negative at the beginning of calculation, chemical stiffness is the main reason that affects the calculating stability and convergence. Based on the basic theory of source term linearization, two linearization methods were chosen. One is based on the physical rules of chemical reaction flows. The advantage is that it can improve the calculating stability and avoid the species density to become negative during the calculation. The other method is the time preconditioner method, which has the function of diminishing the stiffness of the source term. The method was proved to be well approximated to the partial differential equations. The calculation result shows that this method can avoid negative density appearance and accelerate the calculation convergence.