Eventos Anais de eventos
ENCIT 2022
19th Brazilian Congress of Thermal Sciences and Engineering
Analysis of the boundary layer transition process caused by a gap.
Submission Author:
Felipe Oliveira Aguirre , SP
Co-Authors:
Felipe Oliveira Aguirre, Marlon Sproesser Mathias, Marcello Augusto Faraco de Medeiros
Presenter: Marcello Augusto Faraco de Medeiros
doi://10.26678/ABCM.ENCIT2022.CIT22-0158
Abstract
The interaction of the boundary layer with small surface irregularities has been studied in several contexts. Several studies reveal that some configurations of gaps, also called small cavities, can induce boundary-layer distur- bances due to the presence of unstable hydrodynamic modes. The literature presents results where, in some scenarios, the presence of gaps can induce boundary layer transition through the bypass transition phenomenon. To better understand this scenario, a representative case was chosen, where the transition occurs near the gap. For this case, it was analyzed how the unsteady modes predicted in linear stability theory behave in the flow. Initially, it was investigated how these modes behave inside the cavity, interacting and subsequently being convected out of the cavity. Subsequently, the con- vected structures were followed along the domain, to understand if there is memory of the flow structures present inside the cavity. We observed the presence of unstable two-dimensional modes in the mixing layer, known as Rossiter modes, and unstable three-dimensional modes inside the cavity, known as centrifugal modes, which are subsequently convected into the boundary layer downstream of the cavity. Analyzing the transition region, where the flow changes from laminar to turbulent, it was possible to notice that the Rossiter and Centrifugal modes are present in this region, interacting with each other. Finally, through the analysis of the turbulent region, it is possible to note the presence of memory of the centrifugal modes present in the cavity, as well as the presence of residual modes with a frequency close to the Rossiter modes.
Keywords
Boundary Layer, Flow instability, transition to turbulence, DNS, open cavity
