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This research proposes a novel nature-based design of a new concrete armour unit for the cover layer of a rubble-mound breakwater. Armour units are versatile with respect to shape, orientation, surface condition details, and porosity. Therefore, a detailed analysis is required to investigate the exact state of their hydraulic interactions and structural responses. In this regard, the performance results of several traditional armour units, including the Antifer cube, Tetrapod, X-block and natural stone, are considered for the first step of this study. Then, the related observed results are compared with those obtained for a newly designed (artificial coral) armour unit. The research methodology utilizes the common wave flume test procedure. Furthermore, several verified numerical models in OpenFOAM code are used to gain the extra required data. The proposed armour is configured to provide an effective shore protection as an environmental-friendly coastal structure. Thus it is designed with a main trunk including deep grooves to imitate the typical geometry of a coral type configuration, so as to attain desirable performance. The observed results and an analytic hierarchy process (AHP) concept are used to compare the hydraulic performance of the studied traditional and newly proposed (artificial coral) armour units. The results indicate that the artificial coral armour unit demonstrates acceptable performance. The widely used traditional armour units might be replaced by newer designs for better wave energy dissipation, and more importantly, for fewer adverse effects on the marine environment.

ABSTRACTInvestigation of the effects of sloping dry and wet immobile beds on downstream dam-break flows is of great importance given the destructive power of these flows. Such investigation can lead to the adoption of appropriate measures and timely control strategies. In this study, numerical simulations of experimental wave propagation were carried out using four models, i.e. -SST-RANS, realizable -RANS, Smagorinsky-LES, and -SST-DES on sloped beds, for the first time as its novelty, with respect to upstream water and different downstream tail-water depths. The -SST-DES exhibited the best performance in the simulation of wave peak patterns and mean velocities. Taylor diagrams showed that all models were similar in estimating the highest R values and lowest centered root-mean-square errors for dry beds. However, for wet beds with higher downstream tail-water depths, the CRMSE were higher. For lower depths, the standard deviations of the models were generally closer to those of the flume experimental measurements conducted by the experimental study. The present study has shed light on the levels of turbulence models’ accuracy in simulation of dam-break flows on dry and wet sloping beds, and can be taken as a basis for further understanding of the flood flow behavior in future studies.

ABSTRACTWall jets are important hydraulic flows that occur in relation to many civil engineering structures. Researchers have made efforts to study wall jet hydraulics in an unconfined field that can be described by the self-similarity theory. Herein, a highly turbulent submerged wall jet entering a confined basin was considered to investigate numerically. Attempts were made to give details of the flow structure in the confined basin using OpenFOAM, employing five turbulence closures: standard k–ε, realizable k–ε, RNG k–ε, standard k–ω, and k–ω SST. The simulated vertical profiles of velocity were compared with laboratorial measurements available in the literature to determine the best performance. It was found that, while dealing with cases of the wall jet entering a confined basin, the self-similarity hypothesis, which is widely used to describe wall jets in unconfined domain, failed to predict the evolution of the wall jet further downstream. In the regions near the jet entering, in which self-similarity dominated, all the turbulence models simulated the wall jet successfully and computed the same results. On the other hand, in the transition stage, which shows the evolution of wall jet profile to uniform profile, the k–ω SST turbulence model predictions had better agreement with experimental data.

A new approach for predicting the mixing properties of a rosette dense jet group in crossflow ambient conditions based on multi-gene genetic programming (MGGP) is presented. Explicit MGGP formulations for the dimensionless terminal rise height (yt/dF), the dimensionless impact distance (xi/dF), and the impact dilution (Si/F) are developed. Experimental data are used for training and testing the models. The performances of the MGGP models are found to be superior to the existing empirical equations, which are not sufficiently accurate to be used in conceptual rosette diffuser design. A confidence analysis is also conducted for the developed models. The results demonstrate that the MGGP technique is a promising tool to evolve an explicit, accurate and relatively compact mathematical model to predict a rosette dense jet group. The developed MGGP models can facilitate accurate estimation of the primary mixing characteristic parameters of a rosette dense jet group in crossflow ambient conditions for the investigated data range, and they could be continuously and quickly improved or extended with the availability of more training data.

The variables describing the merging and mixing properties of multiple vertical buoyant jets in stationary ambient water have not been generally formulated and reported. This work develops new evolutionary-based models to predict such variables, including for the non-dimensional vertical displacement of the merging point (ym/D), the non-dimensional centerline concentration (Cm/C0) where the jets start merging, the non-dimensional vertical displacement of the well-mixed location (yw/D), and the non-dimensional concentration where the jets are well mixed (Cw/C0). These parameters are crucial in the design of outfall systems and for environmental impact assessments. A fully three-dimensional (3D) computational fluid dynamics model that solves the Navier–Stokes equations and uses the re-normalisation group (RNG) k-ε turbulence closure is validated against the available experimental data. The validated numerical model is further utilized to carry out additional computations for 100 different cases to enrich the data sets. The data are employed to develop and evaluate the evolutionary-based models, and the model networks are optimized using multigene genetic programming. The proposed models can serve to compute the mentioned jet characteristic variables as a function of non-dimensional port spacing (Sp) and jet densimetric Froude number (Fr). Partial derivative sensitivity analysis is also conducted to assess how the varying input variables affect the jet characteristic parameters. An uncertainty analysis is also performed for the proposed models. The proposed explicit equations and codes facilitate easy estimation of the merging and mixing properties of vertical buoyant jets discharged from multiport diffusers.

Although several experiments have been done on inclined dense jets in shallow water where inclined dense jet interacts with the water surface, the jet trajectory and minimum dilution at the return point (Sr) and water surface (SS) have not been generally formulated and reported. In this paper, new evolutionary-based models are developed to predict variables describing jet trajectory and dilution, including the non-dimensional horizontal displacement of the return point (xr/D), non-dimensional horizontal displacement of the minimum surface dilution point (xs/D), dilution at the return point (Sr) and minimum dilution at the water surface (SS). These parameters are essential in brine discharge system design. Two sets of experimental data are applied to develop and evaluate the models, and the model networks are optimized using gene expression programming (GEP). The mentioned parameters serve to compute dilution and displacement at the return point and water surface as a function of discharge angle (θ), non-dimensional ambient depth (H/D) and jet densimetric Froude number (F). Partial derivative sensitivity analysis is also carried out to examine the effect of each dimensionless input variable on the target parameters. The explicit equations and pseudo codes reported facilitate easy estimation of the trajectory maximum impact point distance as well as dilutions for dense jets at different angles from the horizontal.

This paper evaluates the effect of receiving water conditions on offset buoyant jet behavior. Several experiments on the discharge of thermal and nonthermal horizontal buoyant offset jets into stagnant ambient water are conducted. Particle Image Velocimetry (PIV) is used to measure the time history of the jet velocity distribution. Various characteristics of the jet flow, such as the centerline jet trajectory, jet growth rate and jet velocity decay, are discussed. All comparative experiments are conducted with the same densimetric Froude numbers (Frd, ranging from 9.9 to 29.8) and density differences ∆ρ, ranging from 5.1 to 17.41). The results show that the trajectories of thermal jets are not the same as those of nonthermal jets, which suggests that thermal jets travel farther than nonthermal jets. The experimental results were then compared to predictions of three Reynolds-averaged Navier-Stokes (RANS) turbulence models: the standard k-ε, realizable k-ε, and buoyancy-modified k-ε. The best prediction of the centerline jet trajectory was found to be obtained from realizable k-ε. The study results revealed that the source of buoyancy (salinity versus temperature for the same values of Frdand same ∆ρ) affects the trajectory and mixing properties of the jet.

ABSTRACTOgee spillway is one of the most common types of the spillway. Researchers have attempted to investigate the hydraulics of ogee structure under hydraulic heads near the design head. Herein, an ogee-crested spillway is studied at heads significantly greater than the design head. The efforts are undertaken to study the hydrodynamic field under high head ratio conditions by conducting a numerical simulation using OpenFOAM with five turbulence closures including standard k–ε, realizable k–ε, RNG k–ε, k–ωSST and LRR. The comparisons of flow parameters under different head ratios with the experimental data demonstrated that the LRR model had the best performance, which shows its strength in cases dealing with flow separation or significant streamline curvature. It is found that with increasing hydraulic head, up to seven times that of the design head, the flow separation zone grows linearly. Discharge coefficients are studied for a wide range of head ratios. It is concluded that increasing head ratio up to five leads to an increase in the discharge coefficient due to decreasing pressure on the ogee crest. As head ratio increases to greater values, the discharge coefficient drops suddenly due to some changes in the pressure field.

To compare heavy metal (HM) adsorption capabilities between fixed and suspended morphologies of bacteria, batch adsorption tests of Cu(II) and Pb(II) were performed. Adsorption experiments were performed at 22°C, neutral pH (7–7.5), and low concentrations of HMs (2.5–25mg/l). A mixed bed bioreactor (MBBR) and a batch reactor were used to develop the fixed and suspended bacteria, respectively. The dominant bacteria were identified by 16s RNA sequencing as Enterobacter ludwigii, Zoogloea ramigeraisand Comamonas testosteroni.The two morphologies exhibited significant differences in percent dry weight and in extracellular polymeric substances (EPS) content. The fixed bacteria displayed 29% EPS content by weight compared to 9.5% EPS found on the suspended bacteria.

The purpose of this experimental study was to investigate the effects of a rectangular canal on the hydrodynamics of turbulent surges before and after the canal by implementing a series of physical experiments. A dam-break wave model was used to simulate the tsunami-like turbulent waves passing over a smooth and horizontal surface, in the presence and absence of a canal. Three canal depths of d=0.05, 0.10 and 0.15m were used to model shallow, moderate and deep conditions and three canal widths of w=0.60, 1.60 and 3.0m were selected to model narrow to wide canals. The front velocity of the dam-break induced surges were controlled by rapidly releasing upstream impounded set volumes of water with depths of do=0.20, 0.30 and 0.40m. The dam-break wave propagation over a horizontal, dry and smooth bed revealed four regimes describing the variations of surge height with time. The arrival time to reach the maximum surge height and the quasi steady-state regime was correlated with each impoundment depth and an empirical formulation was proposed to estimate the onset of the quasi steady-state flow. The maximum surge heights measured before and after the mitigation canal location were compared with those recorded in the corresponding tests without the presence of the canal. It was found that the peak surge height upstream of the canal could increase up to 40% compared to the test without the presence of the canal in relatively small impoundment depth and in presence of a narrow canal due to momentum dissipation. The wave height downstream of the canal increased between 10% and 50% of the wave height without the presence of the canal and the minimum change in the wave height occurred for the canal width to depth ratio of 20. The time-history of surge velocity after the mitigation canal indicated a significant decay of between 40% and 60% in the presence of a canal due to the bed friction changes and momentum dissipation.