The Impact of Nonequilibrium Flow on the Structure of Turbulence Over River Dunes

摘要: Most past experimental investigations of flow over river dunes have focused on conditions that match semiempirical flow‐depth scaling laws, yet such equilibrium are limited value because they rarely occur in natural channels. This paper quantifies the structure mean and turbulent fixed 2‐D laboratory across a range nonequilibrium within dune regime. The field was quantified using particle imaging velocimetry for 12 conditions, including flows too deep, shallow, fast, or slow size dunes. results demonstrate major departures patterns turbulence when compared to formed under conditions. length reattachment scales linearly with ratio depth‐averaged streamwise velocity shear at crest ( urn:x-wiley:00431397:media:wrcr23540:wrcr23540-math-0001), which provides new predictive measure length. Depth‐averaged vertical velocities urn:x-wiley:00431397:media:wrcr23540:wrcr23540-math-0002) show parabolic relationship urn:x-wiley:00431397:media:wrcr23540:wrcr23540-math-0003, peaking urn:x-wiley:00431397:media:wrcr23540:wrcr23540-math-0004 ~0.60 m/s, matches aspect transport stage present mobile bed spatial location wake found vary depth velocity, lower urn:x-wiley:00431397:media:wrcr23540:wrcr23540-math-0005 greater depths causing rise toward free surface. Deeper likely less convergence crests due reduced interaction surface, resulting reduction stage.