The literature abounds with apparently conflicting relations for predicting the reference near‐bed concentration of suspended sediment or entrainment rate noncohesive bed into suspension. Most these have been developed uniform material. In this paper, seven such are compared against a common set experimental data which direct measurements available. put forward by Van Rijn and Smith McLean found to perform best. A new relation material, having similar predictive capabilities, is using same...

Experiments were conducted to determine the behaviour of turbidity currents laden with non-cohesive silt (silica flour) moving down a slope bed which is covered similar silt. Each current was sustained constant inlet conditions for six eight minutes. The motion head not studied; measurements concentrated on continuous part that essentially in time but developing space. Only supercritical studied. free erode sediment from, and deposit on, bed. Measurements vertical profiles downstream...

The ability of turbulence models, based on two equation closure schemes (the k-ε and the k-ω formulations) to compute mean flow structure in open channels with rigid, nonemergent vegetation is analyzed. procedure, developed by Raupach Shaw (1982), for atmospheric flows over plant canopies used transform 3D problem into a more tractable 1D framework averaging conservation laws space time. With this methodology, form/drag related terms arise as consequence do not need be introduced...

The spreading and sediment deposit of a two-dimensional, unsteady, laminar mud flow from constant-volume source on relatively steep slope is studied theoretically experimentally. under consideration has the rheological properties Herschel–Bulkley fluid. low-Reynolds-number type well-formed wave front moving substantial distance downslope. Due to nonlinear characteristics, set partial differential equations needed for this transient problem. Depth-integrated continuity momentum are derived by...

A high-speed video system was used to study the interaction between sediment particles and turbulence in wall region of an open channel flow with both smooth transitionally rough beds. In flows, immersed within viscous sublayer were seen accumulate along low-speed streaks; apparently due presence quasi-streamwise vortices region. Larger did not tend group streaks, however their velocity observed respond streaky structure flows particle sorting observed. Coherent structures form shear layers...

Experiments on the entrainment of bed sediment into suspension by density underflows are described. The were created allowing saline water to move as a steady, continuous current under body essentially stagnant fresh water. slope was set at 0.08. Two grades fine crushed coal, with geometric mean sizes 100 μm and 180 μm, placed in trough length 2 m, over which currents passed. Measurements profiles flow velocity concentration suspended allowed for back calculation boundary shear stress rate...

A two‐equation turbulence model, based on the k ‐ϵ closure scheme, was used to determine mean flow and structure of open channels through simulated vegetation, thus providing necessary information estimate suspended sediment transport processes. Dimensional analysis allowed identification dimensionless parameters that govern in presence vegetation helped design numerical experiments investigate role different properties, characteristics, upon capacity. reduction averaged streamwise momentum...

A layer‐averaged model for steady, spatially developing turbidity currents laden with poorly sorted sediment is presented together laboratory experiments conducted to test several assumptions involved in the development and gather basic information about such flows deposits that they generate. Measured flow velocity concentration profiles displayed a good degree of similarity facilitated evaluation shape factors. The amount deposition grain size were found decrease monotonically distance...

Highly resolved three-dimensional and two-dimensional simulations of gravity currents in planar cylindrical configurations are presented. The volume release the heavy fluid is varied different phases spreading, namely acceleration, slumping, inertial viscous phases, studied. incompressible Navier–Stokes equations solved assuming that Boussinesq approximation valid for small density difference. performed three Reynolds numbers ( Re ): 895, 3450 8950 (this particular choice corresponds to...

Laboratory experiments were conducted to observe the behavior of turbidity currents in vicinity a slope transition. Both sediment‐laden and saline hydraulic jumps produced. The vertical structure was found depend on flow regime. turbid showed similar characteristics. amount water entrained by flows through jump small. change regime caused marked reduction bed shear stress downstream jump. In nature, current experiencing will drop most its bedload immediately from jump, while suspended load...

ABSTRACT Laboratory observations regarding the limit conditions for particle entrainment into suspension are presented. A high‐speed video system was used to investigate of sediment particles and glass beads lying over a smooth boundary as well rough bed. The results extend experimental previous studies towards finer sizes. criterion is proposed which function ratio between flow shear velocity settling velocity. Observations indicate that totally immersed within viscous sublayer can be...

The capability of acoustic Doppler velocimeters to resolve flow turbulence is analyzed. Acoustic velocimeter performance curves (APCs) are introduced define optimal and sampling conditions for measuring turbulence. To generate the APCs, a conceptual model developed which simulates different as well instrument operation. Different scenarios simulated using synthetic time series water velocity corresponding sampled signals. Main statistics synthetically generated, sampled, nonsampled plotted...

Laboratory observations of the saltation natural gravel particles in a steep, movable‐bed channel are reported. Standard video‐imaging techniques were used to measure and analyze particle motion. The is described terms statistical properties trajectories, such as mean values standard deviations length, height, streamwise velocity. results obtained compared with available empirical data, general good agreement obtained. Particle collision bed also analyzed, friction restitution coefficients...

A numerical model for local sediment scour with free surface and automatic mesh deformation is constructed results are compared experimental results. For the turbulence closure, two equation k–ε used. Two interfaces (water air, water sediment) in domain captured different approaches. The of flow simulated volume fluid (VOF) scheme, which an Eulerian approach. new method VOF scheme proposed to reduce computational time while retaining relative accuracy. behavior water-sediment interface (bed)...

The point at which a submarine canyon debouches on its associated abyssal fan is generally characterized by drop in channel slope. Turbidity currents of the kind responsible for genesis and should display an internal hydraulic jump near slope transition. No direct field observations any such appear, however, to have been made. Experiments nature resulting sedimentary deposits indicate that thickness just downstream tends increase as ratio bed shear velocity immediately behind particle fall decreases.

Turbidity currents in the ocean and lakes are driven by suspended sediment. The vertical profiles of velocity excess density shaped interaction between current bed as well ambient water above. We present results a set 74 experiments that focus on characteristics fractional saline turbidity flowing over mobile bed. gravity flows include flows, hybrid saline/turbidity pure current. use dissolved salt is surrogate for mud so fine it does not settle out readily. Thus, all can be considered to...

A Lagrangian model for the saltation of sand in water is proposed. Simulated trajectories neglecting particle rotation and turbulence effects compare fairly well with experimental observations. The motion coupled a stochastic collision bed, such that number realizations process can be simulated numerically. Model predictions mean values standard deviations height, length streamwise velocity agree dynamic friction coefficient are also good agreement observations, but they underestimate value...

Rapidly decelerating sediment-laden flows typically emplace confined sedimentary deposits. In the fluvial environment, when rivers reach lakes flow emplaces a subaerial delta with distinctive topset, foreset, and bottomset submarine turbidity currents undergoing rapid deceleration commonly wedges (i.e., deposits thinning in downstream direction). Froude-supercritical have an intrinsic self-regulating mechanism for deceleration, that faster they flow, more incorporate ambient sea water...

Experiments carried out under flat smooth bed condition in a periodic, asymmetric, Kinoshita meandering channel showed that bend skewness controls the three‐dimensional mean flow (e.g., primary and secondary flow) turbulence structure location of shear layers turbulent stresses). In this paper, similar hydraulic conditions are used to perform movable‐bed experiments with uniform sediment size order study effect orientation on morphodynamics. Two main differences between upstream‐...

Meandering rivers exhibit complex planform patterns with both upstream and downstream valley oriented meander bends. In order to describe the effects of bend orientation on long‐term river evolution, it is great importance be able (curvature) hydrodynamics flow as a first approximation. Mean turbulence characteristics were investigated experimentally in periodic, asymmetric, meandering channel herein called “the Kinoshita channel”. The configuration retains high‐order harmonic modes....

A Lagrangian model for the motion of a sediment particle in water flow is proposed. The equation averaged over turbulence, specialized to case coarse particles saltating water, and coupled with stochastic collision bed. Model predictions statistics gravel saltation generally agree well experimental observations. As an application model, bed load transport rates are estimated from modeled mean streamwise velocity dynamic friction coefficient. results obtained compare favorably typical...