Effects of approximation methods for reduced order models on density wave oscillations

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. [Display omitted] •The cubic approximation is introduced in reduced order models.•Effects of six kinds of approximation methods on calculation accuracy are investigated.•The linear/linear method has a better performance under the condition of constant heat flux.