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ENCIT 2016
16th Brazilian Congress of Thermal Sciences and Engineering
Experimental study on a closed-conduit flow perturbed by a two-dimensional hill
Submission Author:
Henrique Pelisson Chimetta , SP
Co-Authors:
Erick de Moraes Franklin
Presenter: Henrique Pelisson Chimetta
doi://10.26678/ABCM.ENCIT2016.CIT2016-0107
Abstract
We present here some results of an experimental study on the perturbation of a fully developed turbulent boundary layer by a two-dimensional asymmetric hill of low aspect ratio (O(0.1)). Perturbations in boundary layers are frequently encountered in nature and industry. Some examples are airflows over hills, water flows over river dunes, and liquid flows over sand ripples and dunes in closed conduits such as petroleum pipelines. With the boundary layer perturbed, the distributions of velocities and stresses change along the flow. These new distributions are important to understand the bed instabilities associated with sediment transport. In our experiments, water flows were imposed over an asymmetric hill, with a relatively small curvature, fixed on the bottom wall of a closed conduit. Particle image velocimetry (PIV) was used to measure the flow fields. For the flow upstream of the hill, we found some usual characteristics of a turbulent channel flow, such as logarithmic regions and typical profiles of the xy component of the Reynolds stress. Over the ripple, the maximum of the vertical component of the mean velocity is restricted to a narrow band, above the ripple surface, for every longitudinal position toward the crest. We found the region where the Reynolds stress is perturbed, and the turbulent kinetic energy production was also computed.
Keywords
Boundary Layer, Low Hill, Perturbation
