Study of a Hydraulic Jump in an Asymmetric Trapezoidal Channel with Different Sluice Gates

In this study,the main properties of the hydraulic jump in an asymmetric trapezoidal flume are analyzed experimentally,including the so-called sequent depths,characteristic lengths,and efficiency.In particular,an asymmetric trapezoidal flume with a length of 7 m and a width of 0.304 m is considered,with the bottom of the flume transversely inclined at an angle of m=0.296 and vertical lateral sides.The corresponding inflow Froude number is allowed to range in the interval(1.40<F1<6.11).The properties of this jump are compared to those of hydraulic jumps in channels with other types of cross-sections.A relationship for calculating hydraulic jump efficiency is proposed for the considered flume.For F1>5,the hydraulic jump is found to be more effective than that occurring in triangular and symmetric trapezoidal channels.Also,when■mes>8 and■>5,the hydraulic jump in the asymmetrical trapezoidal channel downstream of a parallelogram sluice gate is completely formed as opposed to the situation where a triangular sluice is considered.

水流和电解质对黏性泥沙絮凝沉降影响试验

为探索河口海岸地区水流和盐度共同作用对黏性泥沙絮凝沉降的影响,以泥沙浓度和絮团粒径为参数,采用自制的同轴旋转双筒产生运动水流和外加电解质的方法,研究6个水流强度(0 s^(-1)、1.38 s^(-1)、2.54 s^(-1)、4.67 s^(-1)、7.19 s^(-1)、13.2 s^(-1)和20.3 s^(-1))和3种电解质(NaCl、CaCl_2、AlCl_3)作用下的黏性泥沙絮凝沉降过程。试验结果表明:1水流对黏性泥沙絮凝沉降的影响与其强度相关。低强度水流(水流强度小于4.67 s^(-1))表现为初期促进、中后期阻碍的规律;高强度水流则由于强水流剪切力和自上而下的紊动掺混作用始终起阻碍作用。2电解质的存在将分别增强和减弱高、低强度水流所起作用;相同浓度下,当阳离子化合价从+1价变成+3价时,水流的影响作用更明显,尤其体现在稳定段。

Theoretical Analysis of A Buoyant Jet Interacting with Small Amplitude Waves

A new theoretical solution is presented here for the dynamic characteristics of a buoyant jet due to opposing small amplitude waves. The conservation equations of mass, tangential moment^n and vertical momentum are solved by the integral method which encompasses the Gaussian profiles of velocity and density. The action of waves is incorporated into the equations of motion as an external force and a new exact solution is obtained to predict the trajectory, velocity distribution and boundary thickness of the buoyant jet over an arbitrary lateral cross section. It is found that the velocity along the centerline is inversely proportional to the ratio of the momentum of the wave to the buoyant jet. The averaged bound- ary width varies with the fluctuation of the boundary width, the distance from the orifice and the velocity correction function. Owing to the motion of waves, the fluctuation of the boundary width is proportional to the wave steepness.

Interactions of nonlinear gravity waves and uniform current in Lagrangian system

The particle trajectory on a weakly nonlinear progressive surface wave obliquely interacting with a uniform current is studied by using an Euler-Lagrange transformation.The third-order asymptotic solution is a periodic bounded function of Lagrangian labels and time,which imply that the entire solution is uniformly-valid.The explicit parametric solution highlights the trajectory of a water particle and mass transport associated with a particle displacement can now be obtained directly in Lagrangian form.The angular frequency and Lagrangian mean level of the particle motion in Lagrangian form differ from those of the Eulerian.The variations in the water particle orbits resulting from the oblique interaction with a steady uniform current of different magnitudes are also investigated.

A third-order asymptotic solution of nonlinear standing water waves in Lagrangian coordinates

Asymptotic solutions up to third-order which describe irrotational finite amplitude standing waves are derived in Lagrangian coordinates. The analytical Lagrangian solution that is uniformly valid for large times satisfies the irrotational condition and the pressure p = 0 at the free surface, which is in contrast with the Eulerian solution existing under a residual pressure at the free surface due to Taylor＇s series expansion. In the third-order Lagrangian approximation, the explicit parametric equation and the Lagrangian wave frequency of water particles could be obtained. In particular, the Lagrangian mean level of a particle motion that is a function of vertical label is found as a part of the solution which is different from that in an Eulerian description. The dynamic properties of nonlinear standing waves in water of a finite depth, including particle trajectory, surface profile and wave pressure are investigated. It is also shown that the Lagrangian solution is superior to an Eulerian solution of the same order for describing the wave shape and the kinematics above the mean water level.

Modeling nonstationary extreme wave heights in present and future climates of Greek Seas

In this study the generalized extreme value （GEV） distribution function was used to assess nonstationarity in annual maximum wave heights for selected locations in the Greek Seas, both in the present and future climates. The available significant wave height data were divided into groups corresponding to the present period （1951-2000）, a first future period （2001-2050）, and a second future period （2051-2100）. For each time period, the parameters of the GEV distribution were specified as functions of time-varying covariates and estimated using the conditional density network （CDN）. For each location and selected time period, a total number of 29 linear and nonlinear models were fitted to the wave data, for a given combination of covariates. The covariates used in the GEV-CDN models consisted of wind fields resulting from the Regional Climate Model version 3 （RegCM3） developed by the International Center for Theoretical Physics （ICTP） with a spatial resolution of 10 km ×10 km, after being processed using principal component analysis （PCA）. The results obtained from the best fitted models in the present and future periods for each location were compared, revealing different patterns of relationships between wind components and extreme wave height quantiles in different parts of the Greek Seas and different periods. The analysis demonstrates an increase of extreme wave heights in the first future period as compared with the present period, causing a significant threat to Greek coastal areas in the North Aegean Sea and the Ionian Sea.

Migration of total chromium and chloride anion in the Rocha River used for estimating degradation of agricultural soil quality at the Thiu Rancho zone

The Rocha River is a receptor to receive wastewater from household,hospital and industry,from where contaminants are transported in the river,affecting biodiversity and the ecosystem of the area.In this paper we estimated the maximum transport of total chromium and chloride anion by applying the analytical model of Ogata&Banks(1961),and the results obtained are grouped into three zones:Contaminated,transition,and uncontaminated.The analytical model was applied with 13 samples collected from the river piezometers installed near Rocha,where they are arranged in two lines,i.e.RH-1 to RH-6 as the first line and RH-9 to RH-12 as the second line.The total chromium concentrations range from 0.16 mg/L(RH-1)and 0.11 mg/L(RH-9)at the closest points to Rocha River,to 0.13 mg/L(RH-7)and 0.03 mg/L(RH-12)at the most remote points to the river.The advance of the pollutants does not exceed 50 meters with respect to the axis of the Rocha River.

Population Structures and Diets of Two Species of <i>Pisodonophis</i>(Ophichthidae) from the Southwest Coast of Taiwan

This study was used to lift nets and trap net fishing at intertidal zone of lagoon and estuarine regions of southern Taiwan. From July 2013 to July 2018, a total 420 specimens of Pisodonophis were analyzed, the average total body length (TL) and average body weight (W) of P. boro eels are 68.4 ± 11.9 cm and 140.4 ± 86.1 g (N = 194), respectively. Typically, P. cancrivorus eels are smaller (TL = 52.8 ± 9.2 cm) and lighter (W = 107.9 ± 73.7 g [N = 119]) than P. boro eels. The natural logarithmic linear relationships between the TL and W of P. boro and P. cancrivorus are respectively expressed as ln(W)b = 2.4405 ln(TL) − 5.4448 (R2 = 0.796, N = 194) and ln(W)c = 3.2168 ln(TL) − 8.2027, (R2 = 0.934, N= 119). P. cancrivorus typically preys on shrimp, crab, and fish;lab assessment revealed that the frequencies of occurrence of these foods in their guts were 49%, 21%, and 15%, respectively (N = 100). The main catch months of P. boro were during the rainy season, and that of P. cancrivorus were the winter season in Taiwan. The average W values of P. boro from Jhuoshuei and Puzih estuaries were 343.2 ± 218.8 g (N = 91) and 140.4 ± 86.1 g (N = 194), respectively. Furthermore, the results of the study revealed that the Puzih estuary is overfished. We suggest that fishery management units should develop some protection measures for the conservation of aquatic ecosystems in estuarine regions. For example, the P. boro weighing less than 113 g will be released back to the estuary.

Delaware Method Improvement for the Shell and Tubes Heat Exchanger Design

In this paper the Delaware Method published in 1963 is analyzed and upgraded with using correction factors which take into account the undesirable currents of the mean flow. However, this method presents graphically these correction factors which imply an impediment to fulfill the software calculations. Thus, the equations corresponding to the correction factor equations and a Fortran 77 numerical program were established. This system is given to explore different design alternatives in order to find the optimal solution to each proposed problem. The results of this work was a simple software that can perform calculations with the introduction of parameters depending only on the geometry of the heat exchanger, i.e., geometry, temperature and fluid characteristics eliminating the human errors and increasing the calculations speed and accuracy.

Fractal characteristics of filamentous bacteria in activated sludge and its significance

On the basis of fractal theory, the fractal characteristics of filamentous bacteria in activated sludge are studied by image dissector system. The results show that the spatial distribution structure of filamentous bacteria in activated sludge has high self similarity in statistics and the filamentous bacteria have clear phenomenon of fractal growth. The critical fractal dimension values of filamentous bacteria bulking such as Eikelboom 021N, Eikelboom 1701, Sphaerotilus natans and Eikelboom 0041 are determined initially. The fractal dimensions can be taken as a parameter to describe filamentous bacteria of activated sludge quantitatively and bring to light the disorder in appearance and the rule in inherence of filamentous bacteria system.

Air-vent layouts and water-air flow behaviors of a wide spillway aerator

A spillway aerator should guarantee favorable flow conditions in the coupled water-air system even if the aerator is unconventionally wide. Eight air-vent configurations are devised and incorporated into a 35-m wide chute aerator for a generalized study. Computational fluid dynamics(CFD) simulations are performed to explore their effects on water-jet and air-cavity features. The Re-normalisation group(RNG) k-ε turbulence model and the two-fluid model are combined to predict the two-phase flow field. The results demonstrate appreciable influences of the vent layouts on the water-air flow. The air vents stir the air motion and re-distribute the cavity air pressure. Once the vent layout is modified, reciprocal adjustments exist between the jet behavior and air-pressure field in the cavity, thus leading to considerable differences in air-flow rate, jet-trajectory length, vent air-flow distribution across the chute, etc. The large width plays a discernable role in affecting the aerated flow. Telling differences exist between the near-wall region and the central part of the chute. To improve the duct pressure propagation, a gradual augment of the vent area should be assigned towards the chute center. Relative to single-slot vents across the flow, the layouts with segregated vents gain by comparison. A designer should see to it that a vented aerator operates satisfactorily for a given range of flow discharges.

Theoretical and Experimental Study of Breaking Wave on Sloping Bottoms

This paper studies the continuous evolution of breaking wave for the surface water waves propagating on a sloping beach. A Lagrangian asymptotic solution is derived. According to the solution coupled with the wave breaking criteria and the equations of water particles motion, the wave deformation and the continuous wave breaking processes for the progressive water waves propagating on a sloping bottom can be derived. A series of experiments are also conducted to compare with the theoretical solution. The results show that the present solution can reasonably describe the plunging or spilling wave breaking phenomenon.

Particle Trajectories in Nonlinear Water Wave on Uniform Current

The study in this paper is focusing on trajectories of particles in the irrotational progressive water waves coexisting with uniform current. The parametric equations of particle trajectories over a range of levels in a Lagrangian type of description are developed analytically via the Euler-Lagrange transformation. The Lagrangian wave period of particle motion differing from the Eulerian wave period and the mass transport can also be obtained directly. The third-order solution of particle trajectory exhibits that they do not move in closed orbital motion but represent a net movement that decreases exponentially with the water depth. Uniform current is found to have significant effect on the trajectories and drift velocity of gravity waves. Overall, the influence of increased uniform current is to increase the relative horizontal distance traveled by a particle, as well as the magnitude of the time-averaged drift velocity on the free surface. For adverse current cases, a reverse behavior is found. The obtained third-order solutions satisfy the irrotational condition contrasted to the Gerstner waves and are verified by reducing to those of two-dimensional gravity waves in Lagrangian coordinates.

Hydrodynamic dispersion of reactive solute in a Hagen–Poiseuille flow of a layered liquid

An analysis of the solute dispersion in the liquid flowing through a pipe by means of Aris–Barton's ‘method of moments', under the joint effect of some finite yield stress and irreversible absorption into the wall is presented in this paper. The liquid is considered as a three-layer liquid where the center region is Casson liquid surrounded by Newtonian liquid layer. A significant change from previous modelling exercises in the study of hydrodynamic dispersion, different molecular diffusivity has been considered for the different region yet to be constant. For all time period, finite difference implicit scheme has been adopted to solve the integral moment equation arising from the unsteady convective diffusion equation. The purpose of the study is to find the dependency of solute transport coefficients on absorption parameter, yield stress, viscosity ratio, peripheral layer variation and in addition with various diffusivity coefficients in different liquid layers. This kind of study may be useful for understanding the dispersion process in the blood flow analysis.

Experimental Study on Excavation Characteristics of Rockmass by Triaxial Test

Applying MTS rock stiffness test machine, tests under triaxial condition were carried out for rockmass under loading and unloading. By measuring and analyzing such mechanical properties as stress, strain, elastic modulus, Poisson ratio and elastic wave velocity during the whole test process, the differences of mechanical characteristics under loading and unloading conditions were revealed, to provide some useful references for excavation.

Model for Predicting the Transport and Dispersal of Contaminants Incoming with Submarine Groundwater: Case Study for the Southwestern Taiwan Coastal Zone

As was recognized recently, the submarine groundwater transports a significant amount of various contaminants into the coastal ocean. An assessment of the impact of intruded pollutants in the coastal ecosystems requires understanding fate of the pollutants and processes of their dispersal in ambient waters. In this paper, we proposed a 3-D coupled ocean circulation/particle-tracking model for predicting the transport and dispersal of pollution-containing groundwater discharged into a coastal environment of the southwestern Taiwan. The particle-tracking model takes currents and turbulent diffusivities predetermined by the ocean circulation model and uses the Lagrangian approach to predict the motion of individual droplets, the sum of which constitutes a contaminant plume in result of discharge of contaminant-rich submarine groundwater. The ocean circulation model was forced by tides and seasonal favorable winds for the south-western coast of Taiwan. The initialization of the coupled model was set using field data obtained in 2009 on the Ping-tung shelf where shallow aquifer seepages were discovered. Several types of numerical experiment scenarios were set up to elucidate the transport and dispersal of conservative and nonconservative (nitrate) contaminants in the shallow coastal zone. The comparison of obtained numerical results with observations performed by other researches was discussed.

Simulating Long Waves in a Coifs Harbour 3D Physical Model Using Short Wave Spectra

This paper presents examples of field data of extreme seiche waves measured at Coffs Harbour by MHL and describes the generation and measuring methodology to detect and reduce seiche agitation in the Coifs Harbour boat ramp using a 3D physical model. The paper also discusses the techniques in investigating a short wave problem of stability in the same model where a long wave is simulated. Waves offshore of Coffs Harbour at 80 m depth have been recorded by MHL for a period of over 30 years. Long waves have been simultaneously measured in the harbour over a period of a decade. These data enabled the model to be verified on two dates （4/6/12, 5/9/14） when high long waves were recorded at the boat ramp harbour under storm and non-storm conditions. Long waves are generated in harbours due to group bounded long wave and surf beat or edge waves. The paper presents methodologies of generating long waves both numerically and by using physical models, and discusses the advantages and disadvantages of these generation techniques. Numerical modelling carried out using long period regular waves in a previous investigation predicted reductions up to 50% due to change of planform of the boat ramp harbour where an area next to the boat ramp was excavated and roughness elements introduced to dampen long periods. The 3D physical model simulated a 25% decrease in the long wave energy in the boat ramp when a suitable change in the planform was made. A 3D undistorted model of scale 1：58 was used in the investigation.

Characterization and Valorization of Two Algerian Bentonites in the Waterproofing Systems

The interest in environment has recently considerably grown, and its protection is now included in the continuous action of the governments and the industries. In Algeria, the different types of waste are currently produced in almost 3.000 illegal dumps, occupying approximately 150.000 hectares. To overcome this problem, waterproofing sites prove the most appropriate solution. It is a geotechnical method to guard against the action of water by narrowing the flow of water through a surface in a given time. The site’s waterproofing technique, in the landfills sites, is nowadays a very necessary condition to protect the environment, which requires the use of appropriate materials. This work deals within the valorization of local materials (sand and bentonite), in the waterproofing technique of the technical landfills site “TLS”. To this end, two types of bentonites from the west of Algeria are used. In order to achieve an optimal mixture, ensuring good performance in terms of hydraulic conductivity, durability and shear strength, mixtures based of sand at different concentrations of bentonite, at compact state are prepared and studied. This study showed that a low permeability of mixture (sand/bentonite) can be achieved with introducing 8% of a calcium bentonite, against 6% of a sodium bentonite. The latter presents a great adsorption capacity and a self healing ability, compared to calcium bentonite. This gives a good sustainability against climate variations of mixture based on sodium bentonite. This mixture has also confered a good mechanical behavior, expressed by the recorded, reduction of the friction angle (Φ) and the increase of the cohesion (C). Therefore it represents an optimal mixture for waterproofing systems, due to its economical and ecological advantages.

Sand Grain Size and Organic Matter Concentration in the Intertidal Zones on the Southwest Coast of Taiwan

From April 2013 to April 2014, the average pH and water temperature of the Taisi oyster cultivation area (TS, Yunlin County, Taiwan) were 8.05 (7.35 - 8.45) and 24.7˚C (13.7˚C - 32.8˚C) (N = 8226) The average organic matter (OM) concentration at sites TS-A and TS-B were 6.9% ± 1.3% and 6.9% ± 1.2%, and the weight of drift sand was 40.3 ± 19.1 g/d/m2 and 28.5 ± 34.3 g/d/m2 (N = 27). Considerable sand drifting typically occurs during the southwest monsoon season in summer. The average OM concentration at five dunes from Zhuoshui estuary to Zengwun estuary was 23.9 ± 4.5 g/kg. The percentage of sand grain weight of 0.15 - 0.25 mm and 0.25 - 0.60 mm was 82.5% ± 14.2% and 10.5% ± 12.0%. In the spring and autumn of 2015, the average OM concentration at the eight intertidal zones from Hanbao to Cigu was 49.8 ± 34.1 g/kg (N = 177), and the OM concentrations at Huwei estuary and Hanbao and Fangyuan intertidal zones were relatively high. The OM concentration (95.3 ± 75.7 g/kg) of the low tide zone of Huwei estuary was the highest among all tidal zones. The OM concentration during spring (59.4 ± 41.7 g/kg, N = 95) was higher than that in autumn (39.1 ± 17.8 g/kg, N = 84). For sand grain size ranges 0.15 - 0.25 and 0.063 - 0.15 mm, the weight ratio of intertidal sediment was 39.4% ± 26.9% and 27.6% ± 20.1%, respectively. The broad and flat intertidal zone was marked by fine sand and long intertidal zone;the weight ratio of SGSs < 0.25 mm exceeded 65%, and the OM concentration was between 20 and 30 g/kg. Coastal habitat diversity creates differences in biological communities, especially among crabs and benthic organisms. A greater understanding of coastal environments can aid in the management of coastal wetlands.

Sexual Dimorphism, Length-Weight Relationships, Fecundity, and Diet of the Striped Eel Catfish Plotosus lineatus (Plotosidae) on Taiwan’s Southwest Coast

This study of feeding guild fish from the same coast of subtropics helps to suggest conservation of fishery resources. A total of 2,537 specimens of Plotosus lineatus (Plotosidae) were collected from July 2013 to March 2019 on the coast of Taiwan. The average total body length (TL) was 23.7 cm ± 4.7 cm and 20.3 cm ± 2.9 cm, and the average body weight (W) was 94.1 g ± 59.6 g and 56.6 g ± 30.8 g among 174 males and 630 females, respectively. The LWRs of male and female were ln(W)M = 3.2914 × ln (TL) −6.0395, and ln(W)F = 3.0917 × ln(TL) −5.3629. The male specimens were large than female in TL and W. The average OSW/TL ratios were 0.722 ± 0.044 and 0.649 ± 0.029 among 41 male and 49 female specimens, respectively. The OSW of the male head was wider than that of the female head (F = 91.5;p < 0.001), and the head widths of the male fish were significantly more than those of their female counterparts, causing the OSs to form granular protrusions. The average CFW/TL ratios were 0.198 ± 0.034 and 0.252 ± 0.032 among the male and female specimens, respectively. The CFW of the male specimens was narrower than that of the female specimens (F = 58.9;p < 0.001), and the CF gap of the male fish was narrower than that of the female fish. The P. lineatus exhibits significant sexual dimorphism. The average eggs number of each female was 2375.6 eggs/individual ± 1140.9 eggs/individual (N = 161). The major prey of P. lineatus were shrimps, crabs, and fishes;the total relative frequencies of occurrence of the prey were 57.1%, 32.6%, and 37.2%, respectively (N = 282), and their total relative abundance levels were 40.2%, 26.3%, and 25.8%, respectively (N = 445). Proper scientific knowledge management will improve the development of fisheries.