Bridge Abutment Protection against Scouring for Unsteady Flow Conditions

The bridge abutment is one of the main parts of a bridge and significantly contributes to bridge stability. This study experimentally investigated the effect of the unsteadiness characteristics of hydrographs on the scouring phenomenon around the bridge abutment under clear water conditions. The ability of the permeable and impermeable spur dikes and their distances from the abutment at its upstream on the control of scouring around the bridge abutment was also investigated. The experimental observations imply that the effect of unsteady flow on the scouring process is relatively similar to the steady flow conditions. The results showed that the base time of hydrographs, the type of spur dikes, and the distance of spur dikes from the bridge abutment were the dominant parameters among the considered parameters in this study on the scouring process around the abutment. The results also revealed that the impermeable spur dike was able to completely eliminate scouring around the bridge abutment for two distances of 2L and 3L (where L is the abutment length) for both steady and unsteady flow conditions.

Experimental investigation of scouring around a single spur under clear water conditions

This study presents the effect of different parameters on scouring process around spur dikes. Our research group's stated objective was to evaluate the effects of sediment gradation, flow depth, spur angle and spur length on scouring process. Since most existing studies generally employed uniform sediment; in this study uniform and non-uniform sediment were selected. Experiments were made in a rectangular open channel in uniform flow conditions. Results showed that the effect of the spur dike length and the orientation angle on sediment scour varies with the type of sediment used. Scour volumes were 40% greater in uniform sediments than in non-uniform sediments. Measured scour depth was maximum at spurs perpendicular to the flow, whereas the scour volume was maximum at spurs directed upstream. The scour depth increased with an increase in the spur length; however, effect of spur length on scouring varied at a contraction rate of 0.29 for uniform sediments and 0.36 for non-uniform sediments. A multiple regression analysis was also performed, and four equations were suggested to predict the scour depth and scour volume. Comparisons were made with the literature equations applicable for clear-water scouring to check the suggested equation. Because of a wide range of contraction ratios considered in this study, the equations which considered the contraction effect yielded better estimates.

Analysis and calculation of sediment scouring rate at different locations of storm sewer

To explore the migration differences of sediments at the front, middle, and end sections of a storm sewer when scoured by water, and further evaluate the pollution load, the scouring process of sediments at different locations of a storm sewer was simulated and mathematical models were built to calculate the scouring rate. Results show that scouring rate is affected by sediment particle size, pipeline slope, sediment thickness, and water flow velocity. As the slope increased, scouring rate at the end section increased more obviously. The scouring rate at the front section slightly decreased with increasing sediment thickness, but opposite trends were observed at the middle and end sections. When the particle size (0.33 mm–0.83 mm) and flow velocity (0.15 m/s–0.65 m/s) increased within their ranges, scouring rate increased across all three locations. Models for calculating scouring rate were established via two data fitting. The calculated values were compared with measured values at a scouring time of 1 min. Under different particle sizes, the difference between the calculated and measured values at front, middle, and end sections were in the ranges of −0.63% to 0.63%, −0.01% to 0.02%, and −0.13% to 0.16%, respectively, all of which showed good consistency.

Exploring 3D Wave-Induced Scouring Patterns around Subsea Pipelines with Artificial Intelligence Techniques

Subsea pipelines carry oil or natural gas over long distances of the seabed, but fluid leakage due to a failure of the pipeline can culminate in huge environmental disasters. Scouring process may take place beneath pipelines due to current and/or wave action, causing pipeline suspension and leading to the risk of pipeline failure. The resulting morphological variations of the seabed propagate not only below and normally to the pipeline but also along the pipeline itself. Therefore, 3D scouring patterns need to be considered. Mainly based on the experimental works at laboratory scale by Cheng and coworkers, in this study, Artificial Intelligent (AI) techniques are employed to present new equations for predicting three dimensional current- and wave-induced scour rates around subsea pipelines. These equations are given in terms of key dimensionless parameters, among which are the Shields’ parameter, the Keulegan–Carpenter number, relative embedment depth, and wave/current angle of attach. Using various statistical benchmarks, the efficiency of AI-models-based regression equations is assessed. The proposed predictive models perform much better than the existing empirical equations from literature. Even more interestingly, they exhibit a clear physical consistence and allow for highlighting the relative importance of the key dimensionless variables governing the scouring patterns.

Study on the interference of pier on the channel bed

Scoring and sedimentation are two continuous processes which take place in river bed. These two phenomena have significant impact over the overall behavior of river. Scoring and sedimentation process get affected due the construction of structures like Bridges. Piers of bridge alter the natural flow of rivers. Due to this scouring process increases near to the pier. The scouring process gets affected due to the other activities like sand mining or filling. Also any obstruction like some construction can also affect the scouring. In this study laboratory tests were conducted to understand the nature of scouring near to the pier. For this purpose, model test were conducted in a straight channel with a model concrete pier. The impact of the obstruction in flow, mining of sand and filling of the sand is investigated through this investigation. The finding of this study can be utilized in understanding and development of techniques of controlling scouring near the pier

Numerical Simulation of Scouring in Overtopping Dam-break Flow

<p>Overtopping dam-break flow has great harm to the earthen embankments due to the hydraulic erosion. Some researchers have carried out relevant model experiments, but it is difficult to achieve the experimental conditions for the actual situation. The common numerical simulation is to express the scouring process through the empirical relationship, which obviously could not reflect the real scouring process. In this paper, a new overtopping erosion model using Smoothed Particle Hydrodynamics (SPH) is proposed. When the shear stress on the sediment SPH particle exceeds the critical stress, the erosion process begins. Then, when a sediment SPH particle is completely eroded, it will begin to move and is described as a non-Newtonian fluid. The un-incipient sediment particles are treated as boundary. This model is well validated with plane dike-breach experiment, and has also achieved a good agreement with erodible bed dam-break experiment.</p>

Quantification and evaluation of chemical footprint of woollen textiles

The chemical pollutants discharged in the production processes of textile products cause severe impact on the environment. The chemical footprint (ChF) methodology provides a new way to quantify the toxicity impacts caused by chemical pollutants. ChF does well in identifying priority chemical pollutants and helping enterprises to select greener chemicals to reduce the environment impacts. In this study, the ChF of woollen yarn were assessed with the data that collected from the production processes. The results showed that the ChF of dyeing process (4.10E+06 l) accounted for the largest proportion, because a large number of auxiliaries were used in the dyeing process to prevent uneven dyeing and colour difference, followed by scouring (7.79E+05 l) and finishing (8.11E+03 l). Among all the discharged chemical pollutants, polyoxyethylene nonyl phenyl ether (1.37E+06 l) caused the most ecotoxicity severe impact on the environment due to its high bioaccumulation and high toxicity to ecosystem, followed by sulfuric acid (1.03E+06 l). Sodium chloride and hydrogen peroxide were the two substances that caused the least environmental load. The overall uncertainty caused by toxicity prediction data accounting for 20.2% of the total ChF, and the uncertainty of the scouring process was the most. The results are referable for wool textiles producers to enhance the textile chemicals management.

EFFECT OF INORGANIC ALTERNATIVE SCOURING AGENTS ON STRUCTURE OF CELLULOSE/POLYESTER BLEND FABRIC

In this research, a structural modification for a cellulose/polyester blend has been carried out using NH4OH, (NH4)2C2O4 and liquid NH3 which are environmentally friendly alternative scouring agents with NaOH as control. The scouring process was carried out on the samples with these alternative agents. Investigation into structural modification of cellulose/polyester blend fabric using NH4OH, (NH4)2C2O4 and liquid NH3 and its structural characterization with X-ray diffraction was carried. The results showed the inferences variation in the crystallinity index of scoured samples from (3.21-65.30%), the crystallite size of scoured samples (1.9-15 nm) in the crystalline region and (7-20 nm) in the amorphous region, inter-planar spacing of the scoured samples (0.340-0.350 nm) of the crystalline region and (0.350-0.340 nm) of the amorphous region and number of crystalline planes of the scoured samples is (3-11) of the cellulose/polyester blend fabric samples via X-ray diffraction studies. Among these alternative agents (NH4)2C2O4 and NH4OH showed better interaction with both amorphous and crystalline regions of the cellulose/polyester blend fabric samples without loss in crystallinity when used as scouring agents, and the possibilities of being a superior alternative with significant effect on the structures of the cellulose/polyester blend, while the other samples showed possibilities of being highly competitive with the conventional agent.

Numerical investigation on the effect of bluntness factor on scouring mechanism by using lenticular geometry piers

Local scour and flow field around cylinders with lenticular geometry and different bluntness factors under the clear-water state were investigated numerically. To examine the scouring, large eddy simulation with a WMLES-Omega sub-grid model incorporating the sediment transport and morphodynamic model was applied. Streamlined geometry of the pier significantly affected the scour pattern and flow field in the lenticular model with length to width ratio of 5 and bluntness factor of zero. In the mentioned case, a very small scoured region was estimated at the sides of the pier, so it can be concluded that scour depth and scoured region decreases as the length to width ratio increases. Investigation of the scouring process and the flow field revealed that, the flow separation can affect the scour mechanism more in comparison to down-flow.

Turbulent Flow Field around Horizontal Cylinders with Scour Hole

This study presents the results of an experimental investigation on the flow-structure interactions at scoured horizontal cylinders, varying the gap between the cylinder and the bed surface. A 2D Particle Image Velocimetry (PIV) system was used to measure the flow field in a vertical plane at the end of the scouring process. Instantaneous and ensemble-averaged velocity and vorticity fields, viscous and Reynolds stresses, and ensemble-averaged turbulence indicators were calculated. Longitudinal bed profiles were measured at the equilibrium. The results revealed that suspended and laid on cylinders behave differently from half-buried cylinders if subjected to the same hydraulic conditions. In the latter case, vortex shedding downstream of the cylinder is suppressed by the presence of the bed surface that causes an asymmetry in the development of the vortices. This implies that strong turbulent mixing processes occur downstream of the uncovered cylinders, whereas in the case of half-buried cylinders they are confined within the scour hole.