Abstract The present study reveals the turbulence dynamics and morphological adjustments of mobile dune-shaped bedforms in an alluvial stream. Results demonstrate acceleration of flow over the dune crest enhancing streamwise velocity, while the initial and the lee side sections of the dune experience flow circulation. The near-bed regions of the initial and lee sections experience peak Reynolds shear stress, marking zones of higher momentum exchange and active sediment entrainment. Turbulence is dominated by streamwise fluctuations, with spanwise and vertical components reinforcing lateral mixing and particle suspension. Octant analysis indicates that sweep events dominate in the near-bed regions of the initial, crest and lee sections of the dune, driving bedform migration and intensifying scour development on the lee side. Probability distribution functions highlight strong non-Gaussian behaviour and intermittency at crest and lee sections, linked to vortex shedding and flow separation. Higher-order structure functions further confirm the presence of intense turbulent bursts in the near-bed region, underscoring the role of coherent structures in driving sediment motion. Morphological analysis shows progressive scour development at the lee side and downstream crest erosion, resulting in continuous dune migration. These findings advance understanding of turbulence–morphology interactions and their control on sediment transport in alluvial channels.
Behera et al. (Wed,) studied this question.