Journal of Hydraulic Engineering

Laboratory flume experiments were conducted to study the flow field and sediment dynamics in a mobile-bed channel bend with and without the presence of stream barbs (upstream-angled submerged groynes). This paper presents spatial distributions of the vorticity field and the turbulent Reynolds shear stresses, kinetic energy, and integral scales. The objectives of the present paper were to (1) advance understanding of the role that vorticity and turbulence play in the erosion process in channel bends with and without barbs, and (2) optimize barb design for reducing erosion along the outer bank regions of channel bends through consideration of flow-field turbulence and vorticity. Results indicate that (1) increased $z$-vorticity occurred in the outer bank scour zone for all runs with and without barbs; (2) for the runs without barbs and with moderately sized barbs, increased streamwise-cross-stream Reynolds stress (${\tau }_{\mathrm{uv}}$) was found to coincide with locations of scour; and (3) for the run with large barbs, all three Reynolds shear stresses increased, but ${\tau }_{\mathrm{vw}}$ was most consistently associated with scour locations. In general, local scour near the barbs was associated with increased $z$-vorticity, tke, and nonprincipal Reynolds stresses (${\tau }_{\mathrm{uv}}$ and ${\tau }_{\mathrm{vw}}$). Furthermore, it was observed that the outer bank region (particularly between adjacent barbs) may be susceptible to increased erosion if stream barbs, due to their size and layout, generate excessive turbulence and secondary velocities.

The flow characteristics around two partially buried objects, a short cylinder (SC) and a truncated cone (TC) were examined experimentally and numerically. Experiments were conducted in a large tilting flume with vertical walls made of acrylic plastic and steel floor covered by a 24-m long sand pit. For each experiment, the object was placed on a flat sandy bed, the flume was filled to a water depth of 41 cm, and a steady unidirectional current was established at high Reynolds numbers while sinking of the object was tracked over time. Velocity records were taken with an acoustic Doppler velocimeter (ADV) probe at the final stage of burial and scour hole evolution. The flow structure around each object was further investigated using a model that solves the Reynolds-averaged Navier-Stokes (RANS) equations coupled with a $\kappa \text{-}\epsilon$ turbulence closure model, and results were compared to the experimental measurements. Measurements and numerical simulations allowed identification of regions of high and low velocity and turbulent kinetic energy accounting for zones of potential sediment erosion and deposition that dictate the burial of the object. The $\kappa \text{-}\epsilon$ turbulence closure model was shown to reproduce the experimental mean flow velocity and turbulent kinetic energy with acceptable accuracy.

This paper presents a new model for unsteady flow routing through dendritic and looped river networks based on performance graphs. The model builds on the application of a hydraulic performance graph (HPG) to unsteady flow routing introduced in a previous study and adopts the volume performance graph (VPG) introduced in another study. The HPG of a channel reach graphically summarizes the dynamic relation between the flow through and the stages at the ends of the reach under gradually varied flow (GVF) conditions, and the VPG summarizes the corresponding storage. Both the HPG and VPG are unique to a channel reach with a given geometry and roughness and can be computed decoupled from unsteady boundary conditions by solving the GVF equation for all feasible conditions in the reach. Hence, in the proposed approach, the performance graphs can be used for different boundary conditions without the need to recompute them. Previous models based on the performance graph concept were formulated for routing through single channels or channels in series. The new approach expands on the use of HPG/VPGs and adds the use of rating performance graphs for unsteady flow routing in dentritic and looped networks. The applicability of the proposed model to subcritical unsteady flow routing is exemplified through a looped network, and its simulation results are contrasted with those from the well-known unsteady Hydrologic Engineering Centers River Analysis System model. The results show that the present extension of application of the HPG/VPGs appears to inherit the robustness of the HPG routing approach in a previous study. The unsteady flow model based on performance graphs presented in this paper can be extended to include supercritical flows.

The dynamics of the Grand River plume, a major tributary of Lake Michigan, was studied in the vicinity of the Grand Haven coast on the east side of the lake. The river spread laterally from the mouth and formed a thin surface buoyant plume with various shapes that have not been previously reported. To understand the influence of different driving forces, primarily wind, buoyancy, and ambient currents, extensive field experiments were carried out over four periods in August and June 2006, and June and July 2007. They included aerial photography over the plume, acoustic Doppler current profiler (ADCP) deployments, meteorological buoys, drifters, SF6 and Rhodamine WT tracer releases, three-dimensional (3D) CTD profiling over the plume, and CTD casts at the river mouth. The results showed more flow classes than included in previous studies. A modified classification scheme based on the relative magnitude of the plume-crossflow length scale and a Richardson number were devised that includes longshore current components and onshore-offshore wind effects. A ratio of length scales and the Richardson number could predict whether the plume was shore attached or unattached, and how the onshore wind can spread the unattached plume offshore, deflect it back to shore, or diffuse it.

The application of inverse transient analysis (ITA) to estimate the location and magnitude of lost lining and internal corrosion of metal pipelines is demonstrated for a field pipeline. The method uses a transient model and inverse search algorithm to analyze patterns of measured pressure reflections obtained after a transient pressure wave is induced in a pipeline. The method is applied in the field on a 6 km long section of a 750 mm nominal diameter steel pipeline with internal cement mortar lining. The equipment used for generating hydraulic transients and measuring pressure responses in the pipeline is described. Results of the field tests are analyzed to estimate the location and extent of internal wall damage along the pipeline. Extensive ultrasonic thickness survey results are used to corroborate the approximate location and magnitude of predicted pipeline wall damage.

The objective of this study is to estimate, model, and parameterize the form drag due to vegetated weirlike obstacles. An experimental study has been carried out for validation purposes. The prototype weirlike structure (in the form of a dike or groyne) has been modeled as a weir with various downstream slopes ($1:4$, $1:7$, $1:15$), and vegetation has been represented in various shapes placed on top of the crest of the weir with 25% blockage area inside the vegetated region. Measurements for energy head losses are carried out for a range of discharges and downstream water levels covering submerged and subcritical flow conditions. The energy head loss attributable to submerged vegetated dikes and groynes can be modeled well by an expansion loss form drag model, which is based on a one-dimensional energy and momentum conservation equations.

This paper presents a discussion on the application and accuracy of roughness height formulas from a practical point of view. Such formulas have been proposed to describe the equivalent roughness height for plane bed conditions on the basis of the Shields parameter. The application of these relationships requires an iterative solution technique. However, as this paper demonstrates, the roughness estimates are not always reliable because the application of the formulas yields large discrepancies in the results.

The characterization of sediment transport is an important problem that has been actively studied for some time. Numerous approaches have been demonstrated in the literature, including mechanistic models, probabilistic arguments, machine learning algorithms, and empirical formulations. Most implementations of sediment transport relations are deterministic in nature and require the specification of model parameters. These parameters are traditionally assumed fixed (i.e., a single value), and subsequent predictions are not necessarily representative because of uncertainty because they are fixed (i.e., a line). In this paper, a Bayesian statistical sediment transport model is presented, and its ability to infer critical shear values from observations to nonlinear regression is compared. This approach provides several advantages, namely (1) parameters are not constrained to be normally distributed as is required in many traditional approaches; (2) estimates of parameter variability are easily obtained and interpreted from distributions that arise naturally from the estimation and prediction process; and (3) predictive distributions, or probability densities of predictions, are easily obtained through Bayesian methods and provide a robust way to sediment transport probabilistically centered on a deterministic formulation.

Negative surges can be caused by a sudden change in flow resulting from a decrease in water depth. In the present study, some physical experiments were conducted in a rectangular channel to characterize the unsteady free-surface profile and longitudinal velocity beneath a negative surge propagating upstream. The physical observations showed that, during the first initial instants, the celerity of the surge leading edge increased rapidly with time, while later the negative surge propagated upstream in a more gradual manner with a celerity decreasing slowly with increasing distance. The velocity data highlighted some relatively large turbulent fluctuations beneath the negative surge. The physical results were used to test the analytical solution of the Saint-Venant equations and some numerical models. The findings suggested that the negative surge propagation appeared relatively little affected by the boundary friction within the investigated flow conditions.