Eventos Anais de eventos
ENCIT 2018
Brazilian Congress of Thermal Sciences and Engineering
Boundary Layer Transition From Smooth To Rough Walls
Submission Author:
Gabriel Maltese de Oliveira Meletti , Brandenburg
Co-Authors:
Gabriel Maltese de Oliveira Meletti, Erick de Moraes Franklin
Presenter: Erick de Moraes Franklin
doi://10.26678/ABCM.ENCIT2018.CIT18-0004
Abstract
This paper presents an experimental study on the channel flow transition from smooth to rough walls, and also the transition back to the smooth region. Different water flow rates were imposed in a closed conduit of rectangular cross section, where rough elements consisting of cavities of d- and k-type covered part of the bottom wall of the test section. These transitions cause a shift on flow velocity profiles that changes their parameters when compared to the flow over a smooth wall. Reynolds numbers based on the channel half-height were moderate, varying between 7800 and 9600, and the regime upstream of the rough elements was hydraulically smooth. Experimental data for this specific case remain scarce and the physics involved rests to be better understood. The flow field was measured using low frequency PIV (particle image velocimetry). From the instantaneous fields measured with PIV, the mean velocities, fluctuations, shear stresses and turbulence production were computed. The results show the presence of oscillations in Reynolds stress and turbulence production, that are higher for the k-type roughness, and were not shown in previous experimental works.
Keywords
Transition Region, Turbulence, Roughness, Bounday Layer
