An experimental study with four different types of bed conditions was carried out to understand the effect of roughness in open channel flow at two different Reynolds numbers. The bed conditions include a smooth surface and three different roughness conditions, which were generated using sand grains with a median diameter of 2.46 mm. The three rough conditions include a surface with distributed...

abstract for investigating the effect of bed form in alluvial channels on the amount of bed load transport, a set of experiments was carried out in a tilting flume under unsteady flow conditions (hydrograph). the produced hydrographs were in triangular form with a maximum discharge of 30 to 45 lit/s/m. three size of sediment particles were used with equal to 1.5, 2.1 and 3.0mm, clear water with...

movement of sediment in the river causes many changes in the river bed. these changes are called bedform. river bedform has significant and direct effects on bed roughness, flow resistance, and water surface profile. thus, having adequate knowledge of the bedform is of special importance in river engineering. several methods have been developed by researchers for estimation of bed form dimensio...

[1] We explored the dependence of experimental bedrock erosion rate on shear stress, bed load sediment flux, alluvial bed cover, and evolving channel morphology. We isolated these variables experimentally by systematically varying gravel sediment flux Qs and water discharge Qw in a laboratory flume, gradually abrading weak concrete “bedrock.” All else held constant, we found that (1) erosion ra...

density or gravity currents have been always one of the main causes for sedimentation along many of the dam reservoirs. so controlling this phenomenon is very important for increasing useful life of such reservoirs. in this research study the effect of a combination of rough bed and obstacle on the control of sedimentary density current has been investigated. experiments were conducted in a til...

Field studies of forest gravel-bed rivers in northwestern Washington and southeastern Alaska demonstrate that bed-surface grain size is responsive to hydraulic roughness caused by bank irregularities, bars, and wood debris. We evaluate textural response by comparing reach-average median grain size (D50) to that predicted from the total bank-full boundary shear stress (t0bf), representing a hypo...

The effect of bed roughness on an iso-kinetic chemical plume released into the logarithmic region of the bed boundary layer of an open channel flow is examined. The bed roughness is varied systematically to generate flows in the smooth (painted polyethylene sheets), transitional rough (2.5-mm and 11.5-mm gravel beds), and fully rough (21.0-mm gravel bed) regimes. Concentration fields are measur...

Hydrodynamic river models are applied to design and evaluate measures for purposes such as safety against flooding. The modeling of river processes involves numerous uncertainties, resulting in uncertain model results. Knowledge of the type and magnitude of these uncertainties is crucial for a meaningful interpretation of the model results. The aim of this study is to quantify the uncertainty d...

A physically realistic roughness closure method for the simulation of turbulent open-channel flow over natural beds within the framework of large-eddy simulation LES is proposed. The description of bed roughness in LES is accomplished through a roughness geometry function together with forcing terms in the momentum equations. The major benefit of this method is that the roughness is generated f...