Eventos Anais de eventos
ENCIT 2016
16th Brazilian Congress of Thermal Sciences and Engineering
Stability Analysis of Incompressible Coaxial Jets Using Boundary Layer Theory
Submission Author:
Helio Ricardo Quintanilha Junior , RJ
Co-Authors:
Leonardo Santos de Brito Alves
Presenter: Helio Ricardo Quintanilha Junior
doi://10.26678/ABCM.ENCIT2016.CIT2016-0558
Abstract
A differential dispersion relations in a linear stability analysis concept is employed in order to identify the convective/absolute nature of the instability of a local base flow. In coaxial jets, curvature effects are neglected due to their momentum thickness that is much smaller than the jet diameter. The main goal is to identify the transition from convective to absolute instability as a function of the jet parameters. In order to do so, the zero group velocity conditions are applied directly to the differential dispersion relation and it becomes possible to search for arbitrary points of transition to absolute instability, as well as verify their causality. The case considered is where the inner nozzle wall separating both streams has non-negligible thickness. A base flow is created using boundary layer theory. Results obtained so far indicate an agreement with former cases analysed with matrix forming approach built with second-order finite differences.
Keywords
Linear Stability Analysis, Coaxial Jets, Linear stability theory, Convective Instability, Absolute Instability
