Author(s): Rocio Luz Fernandez
Linked Author(s): Rocío Luz Fernández
Keywords: Bedforms; Turbulence; Flow separation; Energy budget; Turbulentdiffusion; Dissipation; Production
Abstract: The present work studies the structure of turbulence and coherent events documented in laboratory runs simulating three different stages of bedform amalgamation across the ripple-dune transition. Processing of the experimental data includes the mean velocity field, classical turbulence statistics, evaluation of contributions from different coherent events to the total Reynolds stresses as well as local deviations from the mean pressure caused by dynamical effects. The mechanisms maintaining the turbulence in different flow regions are appropriately explained by the terms in the turbulent kinetic energy budget. In this context, results clearly show that the energy produced in the recirculation region is only partially converted locally into heat through the dissipation, whereas the rest is transported by turbulent diffusion due to fluctuations towards other regions of the flow. Finally, the existence of low levels of communication between the wall and the outer regions in tourbulent boundary layer is verified for the periodic train of simulated ripples through the validation of the hypothesis of i°wall similarityi±.
Year: 2001