On the evolution of the turbulent boundary layer induced by a bedform transition

FERNANDEZ, ROCIO LUZ

Beijing

Congreso; XXIX Congreso Internacional de la IAHR; 2001

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. In addition, the validity of the hypothesis of "wall similarity" is verified for the periodic train of simulated ripples and using a methodology based on this hypothesis the mean shear velocity is estimated, which agrees with values computed by traditional methods.