Open-channel flows through emergent rigid vegetation: Effects of bed roughness and shallowness on the flow structure and surface waves

Free-surface flows through a staggered cylinder array were investigated in an open-channel flume. The cylinders simulated rigid emergent vegetation. Specifically, we studied four flow cases with two-factor design comprising rate (7 and 13 l s−1) bed-surface state (hydraulically rough smooth). We have primarily assessed the effects of bed roughness shallowness on time-averaged structure transverse fluctuating motion wake. Secondarily, former vortex-shedding-induced surface waves quantified. To gain further insight into effect structure, conducted transient simulations using hybrid Reynolds-Averaged Navier–Stokes/Large Eddy Simulation turbulence model. For all cases, downstream cylinder, upward occurs two counterrotating secondary current cells develop. bring high-momentum fluid from high-speed region wake, resulting near-bed streamwise velocity-bulge. measured velocity-bulge are greater for rough-bed than smooth-bed cases. increase increasing height, while currents decay faster longitudinal direction. is hindered by induced over whole water column, irrespective level. Coupled motion, observed three noticeable oscillations (termed “seiche waves”), whose amplitude decreases decreasing depth. Under combined strong bed, seiche vanished.