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While many stepped spillways geometry design guidelines were developed for flat steps, designing pooled steps might be an appropriate alternative to spillways working more efficiency. This paper aims to deal with the inception point of air-entrainment and void fraction in the different height of the pools. Following that, pressure distribution was evaluated in aerated and non-aerated regions under the effect of different heights of the pools and slopes through the use of the FLOW-3D software. Comparison of obtained numerical results with experimental ones was in good agreement for all discharges used in this study. Pools height had the insignificant effect on the inception point location. The value of void fraction was more affected in lower discharges in comparison with higher ones. Negative pressure was not seen over the crest of spillway (non-aerated region), and the maximum pressure values were obtained for pools with 15 cm height along the crest in each discharge. In all slopes, negative pressure was not formed near the step bed in the pooled and flat stepped spillways. However, negative pressure was formed in more area near the vertical face in the flat stepped spillway compared with the pooled stepped spillway which increases the probability of cavitation phenomenon in the flat stepped chute.

A pooled stepped spillway was used in order to evaluate pressure, void fraction, and inception point. Also, different height of the pools was used. Numerical simulation of this study was fulfilled through Flow-3D software. The obtained results indicated that pools can affect two-phase flow characteristics including pressure, void fraction and inception point.

Over the crest, negative pressure was not seen. Pressure values were different for all used heights and the maximum ones obtained for 15 cm height. Also, pooled stepped played a more effective role in reducing the negative pressure points compared with flat cases. Inception point location was more affected in nappe and transition flow regimes in comparison with skimming flow regime particularly for 9 and 15 cm heights.

The research results of Felder et al. (2012a) from the University of Queensland were used to numerically simulate the flow over the pooled stepped spillway.

The purpose of this paper is to experimentally and numerically investigate the interference characteristics between two ski-jump jets on the flip bucket in a large dam spillway when two floodgates are running.

The volume of fluid (VOF) method together with the Realizable k-ε turbulence model were used to predict the flow in two ski-jump jets and the free surface motion in a large dam spillway. The movements of the two gates were simulated using a dynamic mesh controlled by a User Defined Function (UDF). The simulations were run using the prototype dam as the field test to minimize errors due to scale effects. The simulation results are compared with field test observations.

The transient flow calculations, accurately predict the two gate discharges compared to field data with the predicted ski-jump jet interference flow pattern similar to the observed shapes. The transient simulations indicate that the main reason for the deflected nappe is the larger opening difference between the two gates as the buttress side gate closes. When both gates are running, the two ski-jump jets interfere in the flip bucket and raise the jet nappe to near the buttress to form a secondary flow on this jet nappe surface. As the gate continues to close, the nappe surface continues to rise and the surface secondary flow become stronger, which deflects the nappe over the side buttress.

A dynamic mesh is used to simulate the transient flow behavior of two prototype running gates. The transient flow simulation clarifies the hydraulics mechanism for how the two ski-jump jets interfere and deflect the nappe.

The purpose of this paper is to evaluate the possibilities of the particle finite element method for simulation of free surface flows.

A numerical simulation of a number of examples for which experimental data are available is performed. The simulations are run using the same scale as the experiment in order to minimize errors due to scale effects. Some examples are chosen from the civil engineering field: a study of the flow over a flip bucket is analyzed for both 2D and 3D models, and the flow under a planar sluice gate is studied in 2D. Other examples, such as a 2D and 3D “dam break” with an obstacle are taken from the smooth particle hydrodynamics literature.

Different scenarios are simulated by changing the boundary conditions for reproducing flows with the desired characteristics. Different mesh sizes are considered for evaluating their influence on the final solution.

Details of the input data for all the examples studied are given. The aim is to identify benchmark problems for future comparisons between different numerical approaches for free surface flows.

Kumarkhera in Narendra Nagar township of Lesser Himalaya (Tehri Garhwal district of Uttarakhand in India) is showing signs of an impending disaster. The potential mass wastage zone may take toll of human lives in the near future and cause damage to residential and commercial area and infrastructure, namely road, telephone and electric lines and water supply lines. This paper aims to document the strategy for managing this potential disaster.

Study of satellite images and field investigations were carried out in order to probe the possibility of potential landslides in the near future and to find out the risk enhancing anthropogenic activities. Furthermore, the elements at risk were also assessed in order to evolve a disaster management strategy.

It is suggested that a series of prevention and mitigation measures (both structural and non‐structural) with the involvement of the local community are required to avoid an impending disaster in the study area.

This paper highlights the need for reading the signs of landslides and identifying the elements at risk and also calls for timely initiatives, including structural and non‐structural mitigation measures, so that the impact of the disaster can be minimized.

This paper presents a two‐dimensional finite element model for convection‐dominated melting and freezing problems. The enthalpy‐porosity approach is utilized to account for the physics of the evolution of the melt velocity at the solid/liquid phase change interface. Penalty formulation is employed to treat the incompressibility constraint in the momentum equations. The streamline upwind/Petrov Galerkin method is used in combination with primitive variables to solve the governing equations. Simulations are carried out for melting of a pure phase change material in a rectangular cavity heated from below. Sample results are presented and discussed.

The Rayleigh‐Benard‐Marangoni problem for natural convection in a rectangular cavity with thermocapillary forces on a free surface is investigated using a stream function‐vorticity formulation. The nonlinear system is iteratively decoupled and high‐degree p finite elements are used for the discretization of the physical domain. The linear systems arising from the discretization at each iteration are solved using a spectral multilevel scheme, which is a natural preconditioner for high‐p (spectral) elements. The spectral multilevel solver lends itself to parallelization in an element‐by‐element (EBE) framework. Simulation results are presented and compared to previously published results. The multilevel efficiency is compared to previous results for the driven cavity problem. Parallel performance studies are presented for the Cray T3E distributed memory architecture.

The purpose of this paper is to determine the thermo-gravitational convective state of a non-Fourier fluid layer of the single-phase-lagging type, heated from below. Unlike existing methodologies, the spectral modes are not imposed arbitrarily. They are systematically identified by expanding the spectral coefficients in terms of the relative departure in the post-critical Rayleigh number (perturbation parameter). The number and type of modes is determined to each order in the expansion. Non-Fourier effects become important whenever the relaxation time (delay in the response of the heat flux with respect to the temperature gradient) is of the same order of magnitude as process time.

In the spectral method the flow and temperature fields are expanded periodically along the layer and orthonormal shape functions are used in the transverse direction. A perturbation approach is developed to solve the nonlinear spectral system in the post-critical range.

The Nusselt number increases with non-Fourier effect as suggested in experiments in microscale and nanofluid convection.

Unlike existing nonlinear formulations for RB thermal convection, the present combined spectral-perturbation approach provides a systematic method for mode selection.

The purpose of this paper is to analyze two-dimensional steady-state Rayleigh–Bénard convection within rectangular enclosures in different aspect ratios filled with yield stress fluids obeying the Herschel–Bulkley model.

In this study, a numerical method based on the finite element has been developed for analyzing two-dimensional natural convection of a Herschel–Bulkley fluid. The effects of Bingham number Bn and power law index n on heat and momentum transport have been investigated for a nominal Rayleigh number range (5 × 10³ < Ra < 10⁵), three different aspect ratios (ratio of enclosure length:height AR = 1, 2, 3) and a single representative value of nominal Prandtl number (Pr = 10).

Results show that the mean Nusselt number Nu¯ increases with increasing Rayleigh number due to strengthening of convective transport. However, with the same nominal value of Ra, the values of Nu¯ for shear thinning fluids n < 1 are greater than shear thickening fluids n > 1. The values of Nu¯ decrease with Bingham number and for large values of Bn, Nu¯ rapidly approaches unity, which indicates that heat transfer takes place principally by thermal conduction. The effects of aspect ratios have also been investigated and results show that Nu¯ increases with increasing AR due to stronger convection effects.

This paper presents a numerical study of Rayleigh–Bérnard flows involving Herschel–Bulkley fluids for a wide range of Rayleigh numbers, Bingham numbers and power law index based on finite element method. The effects of aspect ratio on flow and heat transfer of Herschel–Bulkley fluids are also studied.

The post-critical convective state for Rayleigh-Benard (RB) convection is studied using a nonlinear spectral-amplitude-perturbation approach in a fluid layer heated from below. The paper aims to discuss these issues.

In the spectral method the flow and temperature fields are expanded periodically along the layer and orthonormal shape functions are used in the transverse direction. A combined amplitude-perturbation approach is developed to solve the nonlinear spectral system in the post-critical range, even far from the linear stability threshold. Also, to leading order, the Lorenz model is recovered.

It is found that very small Prandtl numbers (Pr < 0.1) can change the Nusselt number, when terms to O(ε5/2) and higher are considered. However, to lower orders the Prandtl number does not affect the results. Variation of the Nusselt number to different orders is found to be highly consistent. Comparison with experimental results is made and a very good qualitative agreement is observed, even far from the linear threshold.

Unlike existing nonlinear formulations for RB thermal convection, the present combined spectral-perturbation approach provides a systematic method for mode selection. The number and type of modes to be included are directly related to the post-critical Rayleigh number. The method is not limited to the weakly nonlinear range.

The present study is undertaken in the region of Guelma that is located in North-Eastern Algeria. Guelma’s agricultural plain is irrigated from the Seybouse ephemeral river (wadi). The latter collects the entire domestic and industrial wastewaters of the region that are discharged without prior treatment. Hence, the organic and biological or what so ever contributions to the wadi are capable of initiating a significant degradation of its waters’ quality and challenging their use for irrigation. The paper aims to discuss these issues.

The interpretation of the results of three sampling campaigns for chemical and bacteriological analyzes was carried out in terms of the indices’ method (organic pollution index (OPI) and microbiological quality index (MQI)). The results were statistically assessed through the use of the principal component analysis (PCA). The OPI was calculated according to the method of Leclercq and Maquet (1987) whose principle is to classify the contents for the polluting elements into 5 classes each class corresponding to a given range for the considered parameter, and then to calculate the overall average class number for each sample. The MQI depends on the water concentrations in: the total coliforms, the fecal coliforms, and fecal streptococci. One defines five classes of concentrations for each of these parameters. The MQI is again the overall mean of the numbers for the classes for every parameter.

The OPI reflects a moderate pollution for most sampling stations. The PCA indicates that the variables controlling salinity are mainly Cl⁻, Na⁺ and SO₄²⁻. In August 2016, El-Fedjoudj pumping station shows a very strong fecal contamination. According to the recommendations of World Health Organization (1989), waters from wadi Seybouse cannot be used for the irrigation of vegetable crops if they were to be consumed raw.

This study has an environment impact as it reveals the need to protect surface waters used for irrigation and therefore protect consumers of raw vegetables that are to be consumed uncooked.