Time-domain linear and non-linear studies on density wave oscillations

Linear stability analysis of flow instabilities with a nodalized reduced order model in heated channel

“…In Fig. 6a and b, comparison between the results obtained with the presented model and models prescribed by Papini et al [22] with different friction factor multipliers calculations, Ambrosini et al [27] and experimental data [41] have been shown. Here also, in both these figures it has been observed that, the results are in good agreement with density variant model (N s ¼ 2, N t ¼ 2) and density invariant model with N-nodes assumption.…”

“…6. Comparison of stability boundaries with a) model prescribed by Papini et al [22], b) experimental data of water [41].…”

“…Hence it raises the requirement of accurate prediction of these forces which includes the predictions of mixture density, void fraction and friction factor multipliers. Several studies have been carried out [15,22,42] to calculate the aforementioned quantities. However, the present study is done to delineate the effects of different two-phase friction factor multipliers on the stability characteristics of the system.…”

“…The frequency domain approach [21] is associated with control-theory techniques, where transfer functions are obtained using Laplace transformation of the linearized model of governing equations. The stability of the system (linear stability characteristics with small perturbation) is then determined by the analyses of roots of the obtained transfer functions [9,10,12,13,15,22]. However, it is pointed out that this technique is not very useful for analyzing the nonlinear stability characteristics (for large perturbation) of the system due to the presence of linearized equations.…”

Effect of inlet pressure and temperature on density wave oscillations in a horizontal channel

“…This aspect has been particularly relevant for the validation of linear system codes. However with the growing development and use of nonlinear system codes (Papini et al, 2012;Narayanan et al, 1997), more detailed data bases are required for code validation.…”