Abstract Reduced order models are widely used to analyze density wave oscillations. The approximation methods of physical parameters in these models are essential to calculation precision. However, previous studies pay less attention to the effects of methods. In this paper, six kinds of approximation methods are investigated respectively, including the cubic approximation. These approximations are related to the axial position and time-dependent variables. Meanwhile, the density change in the single-phase section is considered. For high subcooling numbers, the computed values of most methods agree well with the experimental results. However, the values are various in conditions of low subcooling numbers. The deviations between the computed values of the linear/linear method and the experimental data are the smallest under the condition of uniform heat flux.

中文翻译：

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降阶模型的近似方法对密度波振荡的影响

摘要 降阶模型被广泛用于分析密度波振荡。这些模型中物理参数的近似方法对计算精度至关重要。然而，以往的研究较少关注方法的影响。本文分别研究了六种近似方法，包括三次近似。这些近似值与轴向位置和时间相关变量有关。同时，考虑了单相段的密度变化。对于高过冷数，大多数方法的计算值与实验结果非常吻合。然而，在低过冷数的条件下，这些值是不同的。