Numerical Analysis of the Influence of the Impinging Distance on the Scouring Efficiency of Submerged Jets

Water jet technology is widely used in submerged buried pipes as a non-traditional trenching process,often invol-ving a complex sediment response.An important adjustable and influential engineering variable in this technol-ogy is represented by the impinging distance.In this study,the FLOW-3D software was used to simulate the jet scouring of sand beds in a submerged environment.In particular,four sets of experimental conditions were con-sidered to discern the relationship between the maximum scour depth and mass and the impinging distance.As shown by the results,a critical impinging distance h0 exists by which the static scour depth can be maximized;the scour mass ratio between dynamic and static conditions decreases as the impinging distance increases.Moreover,the profile contours are similar when the erosion parameter Ec is in the range 0.35<Ec<2.Empirical equations applicable for predicting the jet trenching contour under both dynamic and static scour modes are also provided in this study.

Simulation of two-phase debris flow scouring bridge pier

Debris flows are typical two-phase flows, which commonly accompany erosion in mountainous areas, and may destroy bridge engineering by scouring. In this study, a physically-based two-phase model is applied for the simulation of debris flow scouring of bridge pier. In this model, the shear stress of debris flow on an erodible bed is considered to be a function of the solid shear stress, fluid shear stress, and volume fraction; accordingly, the erosion is incorporated into the two-phase model. Using a highaccuracy computational scheme based on the finite volume method, the model is employed for simulating a dynamic debris flow over an erodible bed. The numerical results are consistent with the experimental data, and verify the feasibility of the two-phase model. Moreover, a simple numerical test is performed to exhibit the fundamental behaviour of debris flow scouring of bridge pier, which shows that the degree of erosion on each side of the pier is higher compared to other areas. The scouring depth is influenced by the variations of solid volume fraction and velocity of debris flow and pier width.

Experimental Study on the Effect of the Inclination Angle on the Scouring Efficiency of Submerged Water Jets

The effects of oblique submerged scouring jets on sand beds with various particle sizes have been studied experimentally.In particular,a total of 25 experiments have been carried out to explore the influences of the jet angle and application time on the considered submerged sand beds.Test results conducted with a specially-designed device have shown that the scouring efficiency attains a maximum when the inclination angle is in the range between 15°and 20°and then it decreases when the inclination angle becomes higher.

The analysis on reservoir sediment deposition and downstream river channel scouring after impoundment and operation of TGP

According to the measured data after impoundment and operation of the Three Gorges Reservoir,the reservoir sediment deposition and downstream river channel scouring are described briefly and compared with the research results achieved in the demonstration stage.It is indicated through analysis that the reservoir sediment deposition and downstream river channel scouring during 8-year impoundment and operation are still within the original forecast,so the original forecasting results are feasible.The further observation and comparison should be conducted because the comparison between the observed data and the original forecast is not so sufficient in time and the prototype observation and related research work should be strengthened in the future.

Investigation of Scouring Mechanism Around A Circular Pier

In the present study, the flow field around a circular pier is investigated with experimental measurements and numerical simulations. The transient flow patterns during erosion are studied in detail. The results show that the traditional equations of particle motion are not perfect for the calculation of the sand motion under this complex flow situation. The scouring agents, such as turbulent intensity, the fluctuating pressure and the vertical pressure gradient, having many effects on the sand motion with the increasing scouring depth, need to be considered in modifying the traditional model.

Experimental Study on Scouring and Silting Deformation of Artificial Beach Under Storm Surge−Wave Coupling

With the increasing construction of artificial beach in coastal areas, it is of practical significance to study the beach surface deformation of artificial beach profile. Previous studies only focus on a single wave dynamic factor, and it is difficult to predict the beach deformation of artificial beach profile under the storm surge-wave co-action. To solve this problem, the cross-section physical model test method was used to study the beach surface deformation of a typical artificial beach profile in Shuangdao Bay, Weihai, Shandong Province, after continuous wave actions till they stabilize. The characteristics of beach surface deformation under the conditions of constant water levels, laddershaped water level combined with corresponding wave elements and storm surge-wave co-action are compared and analyzed. A beach profile model which satisfies the theory of Bruun model is proposed. The test results show that the maximum scour depth of beach under storm surge-wave co-action is smaller and the scour range is obviously larger than that under the condition of constant water levels or ladder-shaped water level. The evaluation of the maximum scour depth by traditional model test tends to be conservative while the evaluation of the scour range is insufficient.The research results can provide scientific reference for designing artificial beaches.

Surfactant scouring wastewater modified bentonites—promising material for unmanageable wastewater treatment

Trimeric quaternary ammonium surfactants are newly developed surfactants, their widespread synthesis and utilization results in a great amount of scouring wasterwater of high COD, which is unmanageable. The present investigation aims to fred a new type of organo-bentonites modified by the scouring wastewater and to treat the scouring wastewater at the same time. Results of adsorption experiments of phenol and formaldehyde by the modified bentonite show that, at the optimal ratio 24% （W/V） of modified bentonite to scouring wastewater, the removal rate of phenol and formaldehyde by FTAT scouring wastewater modified bentonite is 3.53 times and 2.48 times higher than that of Na-bentonite, and the COD of treated scouring wastewater reduces to below 200 mg/L, meeting the second level of Standards for Discharge of Water Pollutants from the Ammonia Industry of China.

Applications of Enzyme-simulating Copper Complex Catalyst in Low-temperature Scouring/Bleaching of Cotton Knits

An enzyme-stimulating catalyst( PTL) with copper ions( Cu^(2+)) as the activation center and aminophosphonate as ligand was developed and applied in low-temperature scouring/bleaching of cotton knits. The optimal weight ratio of Cu^(2+) to aminophosphonate was 1 ∶75. Via orthodox and single-factor experiments,the most efficient formula for low-temperature scouring/bleaching was composed of 0. 4 g/L high-efficiency degreaser DM-1130,1. 5 g/L PTL,2. 0 g/L sodium hydroxide( NaOH),and 7. 0 g/L 30% hydrogen peroxide( H_2O_2). The PTL could not only increase the whiteness of cotton knits,but also remove pectin to enhance capillary effect.

Scouring Process of Natural Color Cotton Products

In order to improve the absorbency of color cotton products, alkali and pectase scouring processes under different conditions were tested, by comparing the actual results of two different scouring processes. It was considered that the pectase scouring process more suits color cotton products.

Bed Load Transport Rate in Scouring and Armoring Process of Non-uniform Sediment River Bed

Flume experiments were carried out to study bed load transport rate during rive bed scouring and ar- moring.A theoretical differential equation linking the transport rate to the probability of incipient motion of non-uniform sediment is solved.The transport rate is shown to decrease exponentially with time,according to the theory,which is in good agreement with the experiment data.

The Effect of Desizing and Scouring with Enzyme on Grooved Polyester/Cotton Denim

The denim woven by cotton and grooved polyester fiber (Coolcool) is desized by amylase and scouring enzyme. The technological parameters are discussed,such as concentrations of amylase and compound enzyme HK,time,temperature,and pH value. The technical conditions are optimized through experimental analysis. This eco-finishing process is very helpful to improve the denim production and the performance of moisture absorption and sweat transmission function.

Enzyme Assisted Ultrasound Scouring of Raw Wool Fibres

Scouring of raw wool is a chemical treatment that needs a high amount of detergents, alkalis and water. Effluents produced by this treatment are extremely polluted with chemicals and impurities washed out from the fibers. It is well known that the ultrasound washing can remove effectively different substances from the textile surfaces even without surfactants due to the cavitations occurring at certain parameters of the ultrasound field. On the other side water treatments of wool combined with mechanical agitation provoked felting which can impair the quality of wool materials. Felting itself depends not only on the parameters of water treatments but also on the structure of wool cuticle. Partial hydrolysis of the cuticle with some proteases can decrease considerably the wool felting. The aim of this work is to study the possibility of applying the ultrasound at the process of raw wool scouring and the influence of proteases on the felting properties of wool at these conditions. It has been found out that ultrasound environment applied does not impair the specific activity of enzyme auxiliaries used and leads to increasing of their effect on the surface of wool fibers. Thus the scouring process studied could be used for developing of a technology producing lower amount and less polluted effluents.

Bed Load Transport Rates during Scouring and Armoring Processes

Dambreak-induced bed scouring may undermine the foundation of bridge piers and other structures,and that destruction can pose a serious threat.Consequently,this paper aims at exploring the mechanisms of scouring and armoring.Firstly,the incipient velocity for nonuniform sediment particles was studied,and a formula was derived based on the angle of repose of nonuniform sediment.The results showed that the mechanism of incipient motion for sand and fine gravel differed from that for coarse gravel and cobbles.Also,comparison between experimental and field data shows that the results from the proposed formula agree well with those observed for all conditions.Secondly,a birth-death,immigration-emigration Markov process was developed to describe the bed load transport rate associated with scouring and armoring.The comparison between experimental data and computed results shows that our model can predict the bed load transport rate,although there may be some limitations,the chief of which is that there are many variables in the model to be determined through experiment.This makes its application in river engineering inconvenient.

Application of Gamma Test and Neuro-Fuzzy Models in Uncertainty Analysis for Prediction of Pipeline Scouring Depth

The process involved in the local scour below pipelines is so complex as to make it difficult to establish a general empirical model to provide accurate estimation for scour. This paper describes the use of an adaptive neuro-fuzzy inference system (ANFIS) and a Gamma Test (GT) to estimate the submerged pipeline scour depth. The data sets of laboratory measurements were collected from published literature and used to train the network or evolve the program. The developed networks were validated by using the observations that were not involved in training. The performance of ANFIS was found to be more effective when compared with the results of regression equations and GT Network modelling in predicting the scour depth of pipelines.

Bioscouring Knitted Cotton Fabric with an Experimental Pectate Lyase

An experimental pectate lyase enzyme was used to scour knitted cotton fabric and the emphasis was on pectin removal.Using an enzyme dosage of 0.2 g/L at temperature 55℃ and pH 6.35 for 30 min,good scouring properties were obtained.When appropriate concentrations of 1-Hydroxy Ethylidene-1,1-Diphosphonic Acid(HEDP)and CaCl2 were added,the percentage pectin removal improved significantly.

Effect of Mutual Interference of Bridge Piers on Scouring in Meandering Channel

Local scour is the reduction of original bed level around any hydraulic structure.Bridge failure due to scouring has made researchers study the cause of scouring and predict the scour depth and pattern around bridge piers and foundations.Several investigators have extensively studied local scour around isolated bridge pier,but modern designs of the bridges comprise of wide span and thus group of piers rather than a single pier.The flow and scour pattern around group of piers are different from the case of a single pier due to the interaction effect.The objective of present study is to investigate the effect of mutual interference of bridge piers on local scour experimentally around two piers in non-cohesive bed.Experiments were carried out on model bridge piers of circular cross section in a meandering channel.It was observed that when front and rear piers were placed at an angular displacement ofθ=40°and 80°respectively,maximum depth of scour is maximum.Hereθis the angle the line drawn at the inlet of bend to the line joining the centre of curvature and any point on the outer portion of the bend.

Linkage between riverbed scouring or deposition and the evolution of central bars:Case study in the Yangzhong reach of the Yangtze River

Understanding the relationship between unbalanced riverbed scouring or deposition and the evolution of central bars in natural conditions and human activity is useful for river regime control and waterway improvement projects.Toward this end,we utilized the Yangzhong reach in the lower reaches of the Yangtze River as a case study and evaluated runoff,sediment content,and topographical data measured over the past 70 years(1951–2021).With the decrease in the amount of incoming sediment in the river basin,the Yangzhong reach exhibited a continuous state of scouring.The cumulative riverbed scouring volumes of the low-water and flood channels from 1981 to 2021 were 3.97×10^(8)and 4.14×10^(8)m^(3),respectively,with the riverbed scouring volume of the low-water channel accounting for 95.9%of that of the flood channel.Under quasi-natural runoff–sediment conditions,the evolution of the central bars in the Yangzhong reach was highly correlated with the amount of scouring or deposition.In particular,the Luochengzhou reach could be characterized as a meandering river with scouring on concave riverbanks and deposition on convex riverbanks.In the context of reduced incoming sediment,the beach area of the Yangzhong reach decreased by approximately 9.9%(from 2003 to 2021)and the central bars of the straight section areas decreased.Moreover,following operation of the Three Gorges Reservoir,both the Luocheng central bar and Jiangyin beach areas could be characterized as meandering rivers with convex riverbanks and beaches.In the quasi-natural period before the implementation of the waterway improvement project,the trend of high scouring intensity and increased fluid diversion ratio in the right branch of the Luocheng central bar was in accordance with the law that the short branch of the length is in a developing state under the condition of decreasing river sediment volume.With the control of riverbank protection and the construction of waterway improvement projects in the Yangzhong reach,the shapes of the riverbanks and central bars were effectively stabilized,and the linkage relationship formed in the quasi-natural period was interrupted.Overall,these findings provide a strong foundation for understanding riverbed scouring or deposition and the evolution of central bars under the influence of natural conditions and human activities,and will inform future river management and waterway dimension planning.

Numerical study on local scour characteristics around submarine pipelines in the Yellow River Delta silty sandy soil under waves and currents

Due to their high reliability and cost-efficiency,submarine pipelines are widely used in offshore oil and gas resource engineering.Due to the interaction of waves,currents,seabed,and pipeline structures,the soil around submarine pipelines is prone to local scour,severely affecting their operational safety.With the Yellow River Delta as the research area and based on the renormalized group(RNG)k-εturbulence model and Stokes fifth-order wave theory,this study solves the Navier-Stokes(N-S)equation using the finite difference method.The volume of fluid(VOF)method is used to describe the fluid-free surface,and a threedimensional numerical model of currents and waves-submarine pipeline-silty sandy seabed is established.The rationality of the numerical model is verified using a self-built waveflow flume.On this basis,in this study,the local scour development and characteristics of submarine pipelines in the Yellow River Delta silty sandy seabed in the prototype environment are explored and the influence of the presence of pipelines on hydrodynamic features such as surrounding flow field,shear stress,and turbulence intensity is analyzed.The results indicate that(1)local scour around submarine pipelines can be divided into three stages:rapid scour,slow scour,and stable scour.The maximum scour depth occurs directly below the pipeline,and the shape of the scour pits is asymmetric.(2)As the water depth decreases and the pipeline suspension height increases,the scour becomes more intense.(3)When currents go through a pipeline,a clear stagnation point is formed in front of the pipeline,and the flow velocity is positively correlated with the depth of scour.This study can provide a valuable reference for the protection of submarine pipelines in this area.

Clear-water local scouring around three piers in a tandem arrangement

Experiments of local scouring around three piers were carried out under steady clear-water conditions. We investigated the role of pier spacing and flow rate in scour depth and progression. The scour-hole depth around the upstream pier was the same as that for single piers and independent of pier spacing. The scour behavior of the middle and downstream piers progressed through a synchronous scouring region, a transition region, and a radical deviation region as the fluid velocity increased. The critical velocity from the synchronous scouring region to the transition region for the middle and downstream piers was the same, which linearly increased with pier spacing. The degree of deviation in the radical deviation region for the middle and downstream piers was dependent on the pier spacing. The critical velocity from the transition region to the radical deviation region for the middle pier increased with the pier spacing. When the spacing was larger than 11 times the diameter of a pier, the scour depths of the three-pier configuration were the same as for the single piers, which indicates the limit of inter-pier fluid–structure interaction. Finally, the data from this study are used to derive adjustment factors to predict the local scour depth around three piers.

Numerical simulation of scouring funnel in front of bottom orifice

The scouring funnel in front of a bottom orifice under the condition of fixed water levels is simulated by using an Eulerian two-phase model, with onsideration of the flow-particle and particle-particle interactions. The predictions of the scouting funnel shape agree well with laboratory measurements. The flow-field characteristics of the two phases and the influences of the hydraulic and geometric parameters on the shape of the scouring funnel are analyzed on the basis of the computation results. It is revealed that the non-dimensional maximum scour hole parameters, the depthdm / do, the length l,. / do, and the half-width w / do, are linearwith the densimetric Froude number Fro , the main parameter describing the scour hole, the centerline scour depth Dc and the half-scour width Wr vary according to a power law, and the transverse scour profiles exhibit strong similarities, the velocity distribution of the water is confined within the sink-like area near the orifice, and the mutual impact of the flows at the azimuthal sections and the resistances of the walls and the sand layer produce a vortex in the scour hole, that makes the sand particles to be suspended in the water, the exchanging water in the pore water is the main contributor in forcing the sand to move, and transporting the sand in the same direction as the pore water along azimuthal sections.