Eventos Anais de eventos
COBEM 2023
27th International Congress of Mechanical Engineering
DESTRUCTION AND REGENERATION PROCESS OF A LAMINAR SEPARATION BUBBLE UNDER FORCING CONDITIONS
Submission Author:
omar elias horna pinedo , RJ , Peru
Co-Authors:
omar elias horna pinedo, Igor Braga de Paula
Presenter: omar elias horna pinedo
doi://10.26678/ABCM.COBEM2023.COB2023-1790
Abstract
The destruction and regeneration transient process of a laminar separation bubble (LSB) under forcing conditions is experimentally studied. The experiments were carried out in a low turbulence and close return water Channel. An adverse pressure gradient was induced by a false wall, this wall created a convergent-divergent channel, the bubble was formed on the region of an adverse pressure gradient over a flat plane. Controlled broadband disturbances of high and low amplitude are introduced with a vibration ribbon located upstream of the LSB formation region. Velocity fields were acquired using the time-resolved two-dimensional particle image velocimetry technique. The bubble forcing consists in the excitation of a wave train with alternating periods of high and low amplitude upstream to the LSB. The wave packet contains the most unstable frequency estimated in the regime of unforced LSB. In the destruction case, the high amplitude forcing inhibits the boundary layer separation and hence the formation of the LSB. In the regeneration case, a sudden change from high to low forcing amplitude allows the bubble growth up to a limiting extend. Phase locked and ensemble average were used in data acquisition and post processing data respectively. The results show differences between the time of destruction and regeneration process of a LSB. The merging and ejection of vortices were evaluated, showing similar results with those reported in the literature. The results describe in high level of detail many features of the destruction and the regeneration transient process of a LSB.
Keywords
Laminar separation bubble, PIV time resolved, merging and ejection of vortices, controlled broadband perturbation.
