Resumen de Modeling Double Concentric Jets Using Linear and Non-linear Approaches
Juan A. Martín, Adrián Corrochano, Javier Sierra, David Fabre, Soledad Le Clainche Martínez
This article models the wake interaction between double concentric jets. The configuration is formed by a rounded jet surrounded by an external annular jet and is defined in a two-dimensional domain imposing axi-symmetric conditions. The flow is studied at laminar conditions (low Reynolds number) in three different cases based on the velocity of the two jets defined as Ui and Ue: case (i) Ui = Ue, case (ii) 2Ui = Ue and case (iii) Ui = 2Ue. Linear stability theory (LST) predicts the most unstable modes identifying a steady and an unsteady mode, both localized in the near field in the empty area between the two jets, forming a bubble. Neutral stability curves identify the critical Reynolds number for each test case, showing that this value is larger in case (iii) than in case (i), although the velocity of the inner jet in case (iii) is twice the velocity in case (i), suggesting that the flow bifurcation is delayed in case (iii). Finally, dynamic mode decomposition is applied to create a model for the non-linear solution of the concentric jets in case (i). The method retains the modes predicted by LST plus some other modes. Using these modes is possible to extrapolate the solution from the transitory of the numerical simulations to the attractor with error ∼2%, resulting in a reduction of the computational time in the numerical simulations of 50%.
