FLUENT能量方程：双温度模型（Two-Temperature Model）应用

Two-Temperature Model

enables/disables the Two-Temperature Model. Only available for the density-based solver.

双温度模型

启用/关闭双温度模型，双温度模型只能在密度基求解器中可用。

When using the density-based solver, a two-temperature model is available for simulating the thermal non-equilibrium phenomena in hypersonic flows. It models the energy relaxation process in the flow and provides a better prediction of the flow fields than the one-temperature model.

当使用基于密度的求解器时，双温度模型可用于模拟高超音速流动中的非平衡热现象。其模拟了流动中的能量弛豫过程，并提供了比单温度模型更好的流场预测。

The degree of thermal non-equilibrium is typically measured by a suitable Damkohler number, expressed as the ratio between the characteristic time for a fluid element to travel a characteristic length and the characteristic time for the energy modes to reach equilibrium. When the flow speed is relatively low, the Damkohler number is much larger than one, which means the number of molecular collisions is sufficient for the flow to reach the local thermodynamic equilibrium state. For the hypersonic flows, the Damkohler number is typical of the order of unity. This indicates that the fluid element does not reside at one location long enough to bring the local thermodynamic state to equilibrium, and therefore the flow is in thermal non-equilibrium. To properly address this effect, it is necessary to use a two-temperature model that assumes: the translational and rotational energy modes of species are in equilibrium with one temperature; and the vibrational and electronic energy modes of species are in equilibrium with another temperature. A system of conservation equations is solved that includes the Navier-Stokes equations and one additional transport equation that models the conservation of vibrational-electronic energy.

热不平衡度通常通过合适的Damkohler数来测量，Damkohler数表示为流体单元移动特征长度的特征时间与能量模式达到平衡的特征时间之间的比率。当流动速度相对较低时，Damkohler数远大于1，这意味着分子碰撞的次数足以使流动达到局部热力学平衡状态。对于高超声速流动，Damkohler数是典型的单位阶数。这表明流体单元在一个位置停留的时间不足以使局部热力学状态达到平衡，因此流动处于热非平衡状态。为了正确处理这种影响，有必要使用一个双温度模型，该模型假设：项的平移和旋转能量模式与一个温度平衡；项的振动和电子能量模式与另一个温度处于平衡状态。求解了一个守恒方程组，其中包括Navier-Stokes方程和另一个模拟振动电子能量守恒的输运方程。

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