Journal of Hydraulic Engineering

Data related to floodplain inundation by fast-rising floods are limited and needed. Eighteen data sets are provided from experiments conducted in a symmetrical compound channel that has a trapezoidal main channel. Three flood types were investigated: long, moderate, and short duration floods (LDF, MDF, and SDF). The data include water depths, velocities, and bed shear stresses measured in straight and meandering reaches. Data show that a flat portion occurred in the MDF and LDF hydrographs when the floodplain was being inundated. Flood peaks stretch exponentially along the channel and are more pronounced in the meandering reach. An SDF has the fast decay rate, followed by MDF and LDF. Overbank front speeds of the SDF and MDF can be predicted by the moving speed of a surge, with the surge height being the difference of the bankfull depth from that of the base flow. The tail of a synthetic hydrograph should be modified according to the channel storage so that it can be used as an inflow boundary condition.

This paper characterizes the temporal behavior of uplift force generated by turbulent pressure fluctuations in spillway stilling basins. Theoretical and experimental analyses are presented that define the magnitude and temporal evolution of the maximum uplift acting on the lining of such basins. Analyses for the dynamic behavior of anchored floor slabs are also investigated. It is concluded that the applicability of the equivalent thickness criterion based on the balance of the forces acting on the slabs in static condition is unsafe for anchored slabs, because this criterion yields an inadequate area for the anchor steel. The results lead to a recommendation to double the area of anchor steel as computed by the equivalent thickness criterion for the design of slabs in stilling basins.

The angular momentum principle is employed to locate the trajectories of wastewater plumes. This momentum-based method differs from the traditional approach where a perturbation analysis, based on the centerline velocities, is employed for locating discharges. Evidence of the latter can be found in existing Eulerian-integral and length-scale models. The momentum-based method is incorporated into the hybrid model SD3D, where the regional flow solutions are modified to incorporate the influences of relatively small components of momentum on the discharge trajectory. This method provides a clear understanding of the factors that influence the location of the discharge. The momentum-based approach yields analytical trajectory solutions in many cases, and it eliminates the need to arbitrarily select the appropriate characteristic velocity for locating the flow. Comparisons are made with available experimental data, and they show that the momentum-based method provides accurate predictions of the flow trajectories under a variety of discharge conditions. Comparisons are also made with predictions from the CORMIX1 and JETLAG models. In general the predictions are consistent, but some important discrepancies are highlighted. The use of the momentum-based method for locating discharges is discussed in light of recent experimental studies.

A new methodology, named DisPar, based on a discrete probability distribution for a particle displacement, was developed to solve 1D advection-diffusion transport problems in water bodies. The discrete probability distribution for the particle displacement was developed as an average and variance function. These probabilities were used to predict the deterministic mass transfer between cells in one time step, and therefore the particle concentration in each cell was considered the state variable. The state equation was found to be similar to an explicit finite-difference formulation with a Eulerian grid. The model stability, positivity, and mass conservation are guaranteed by the probability distribution concept. DisPar produces solutions without numerical dispersion for constant velocity, diffusion coefficient, and cross-sectional area. In these conditions, DisPar was also developed as a function of space and time for an instantaneous mass spill. When the stability and positivity restrictions were respected, the model produced excellent results when compared to analytical solutions and other methods. The discrete particle displacement distribution concept differs from other numerical formulations, and therefore it represents a new modeling technique.

Laboratory experiments related to open channel hydraulics are generally intended to be carried out in the fully developed flow region of a rectangular flume. The developing region, in channels as well as in ducts, is a complex three-dimensional flow region influenced by secondary circulation and free surface effects, and is therefore not amenable to analytical solution. Laboratory data and a numerical model have been used to study the variation of the length of flow establishment in rectangular channels.

A dynamically consistent method of locating the rough wall origin y₀ is presented that is applicable to large- and small-scale rib roughness elements, where scale is defined relative to the depth of flow. Using the results of Reynolds-averaged computational fluid dynamics (CFD) calculations, a near-standard resistance law is derived in which k_s, the equivalent sand roughness parameter, for large-scale roughness is flow-depth dependent. It is postulated that the relationship with depth of both y₀ and k_s, when scaled appropriately, is independent of rib roughness height and spacing. For k_s this is supported by the CFD results.

The deposition of the instantaneously released sediment into a gravel matrix and the hydraulic resistance induced by the rapid siltation are investigated herein. The experimental results reveal that the depositional patterns of the sediment are governed by the gravel-sediment size ratio, the amount of sediment released, and the seepage flowrate. The observations also indicate that the stable stage of sediment deposition is reached shortly after the occurrence of sudden slump. A regression relation is developed to quantify the stable-stage hydraulic resistance with the major governing factors. Given the hydraulic resistance, one can use the siltation equation to evaluate the hydraulic conductivity of the silted porous medium. With such information, planning of the engineering alternatives to meet the seepage flow requirements is made possible.