Jose Douglas da Gama Melo

This study investigates the numerical modeling of a high-velocity circular free-water jet impinging into a plunge pool, focusing on the simulation and validation of mean and fluctuating dynamic pressures on the pool floor. Numerical simulations were performed using two different computation methods, two-phase volume-of-fluid and Euler–Euler, under conditions replicating experimental data obtained at a jet velocity of 7.4 m/s and plunge pool depth of 0.8 m. The models, based respectively on the Volume of Fluid (VoF) and Euler–Euler methods, were evaluated for accuracy in replicating experimentally measured pressures and air concentration values. The Euler–Euler solver, coupled with the k-Omega SST turbulence model, demonstrated mesh independence for mean dynamic pressures with a mesh resolution of 24 cells across the jet diameter. In contrast, two-phase volume-of-fluid exhibited mesh dependency, particularly near the jet stagnation point and pressure values higher than the experimental ones. While the Euler–Euler accurately captured mean pressures and air concentration in close agreement with experimental data, its Reynolds-Averaged Navier–Stokes (RANS) formulation limited its ability to simulate pressure fluctuations directly. To approximate these fluctuations, turbulent kinetic energy values were used to derive empirical estimates, yielding results consistent with experimental measurements. This study demonstrates the efficacy of the Euler–Euler method with the k-Omega SST model in accurately capturing key dynamic pressures and air entrainment in plunge pools while highlighting opportunities for future work on pressure fluctuation modeling across a broader range of jet conditions.

Spillways are a requirement for dams’ safety, mainly preventing overtopping during floods. A common spillway solution involves plunging jets, which dissipate a considerable flow energy in the plunge pool. Energy dissipation has to occur in a controlled manner to avoid endangering the dam foundation and river slopes. Indeed, a scouring process in the downstream riverbed will inevitably develop until equilibrium is reached, otherwise a suitable pre-excavated or concrete lined plunge pool has to be provided. This paper focuses on experimental studies in which particular attention was paid to the dynamic pressures in the plunge pool floor at the vicinity of the jet stagnation zone sampled at 2.4 kHz. A rectangular experimental facility, 4.00 m long and 2.65 m wide, was used as plunge pool. Tests involved a vertical circular plunging jet with velocity ranging from 5 to 18 m/s and plunge pool depth ranging from 4.2 to 12.5 jet diameters. Differences in dynamic pressure measurements are highlighted between transducers located in the inner and outer regions of the jet diameter footprint. Several parameters characterizing the dynamic pressures evidence trends tied with the jet velocity that, to the authors’ knowledge, were not dealt in previous research. These can derive from the coupling effects of consequent recirculating motions and air entrainment in the limited-size plunge pool. Both effects, increasing with velocity, cause an reduction in the efficiency of the diffusing jet shear layer. This aspect deserves further investigation to achieve a better understanding and more complete characterization.

Simplified methods are useful alternatives for prior analysis of the effects of dam rupture and can guide the decision-making process for carrying out more complete studies. In this context, a new simplified approach is presented, which enables the analysis of aspects from dam rupture of earthen dams that failed due to overtopping, considering dam height and reservoir volume as input data. Hypothetical cases were analyzed applying dam-break hydrodynamic simulations, which results allowed the development of equations capable of estimating peak flow attenuation and peak discharge arrival time along the downstream valley. The proposed approach was applied in a hypothetical case study (15 m high dam and 17 hm3 reservoir volume), obtaining results close to those achieved through other methods, especially in case of estimating the maximum discharges throughout the downstream valley, where the average differences between the results of the methods were of the order of 15%.

Este trabalho propôs-se a avaliar a qualidade do leite cru, produzido na região de Xinguara Pará, considerando como ferramenta importante a geotecnologia associada a análises físico-químicas e microbiológicas. Foram coletados no primeiro trimestre de 2019 o leite in natura de quatro locais, fornecedores de laticínios no município de Xinguara – Pará. No laboratório de Tecnologia de Alimentos da Universidade do Estado do Pará, Campus Redenção-PA, foram avaliados parâmetros físico-químicos e microbiológicos. Apesar dos baixos índices zootécnicos do estado do Pará, fica evidente que a área analisada aleatoriamente, no sudeste do estado, o leite apresentou boa qualidade para ser utilizado pela indústria, estando a maioria dos parâmetros dentro das exigências estabelecidas pela Instrução Normativa nº 76 de 2018.

The capability of two different OpenFOAM^® solvers, namely interFoam and twoPhaseEulerFoam, in reproducing the behavior of a free water jet was investigated. Numerical simulations were performed in order to obtain the velocity and air concentration profiles along the jet. The turbulence intensity was also analyzed. The obtained results were compared with published experimental data and, in general, similar velocity and air concentration profiles were found. InterFoam solver is able to reproduce the velocity field of the free jet but has limitations in the simulation of the air concentration. TwoPhaseEulerFoam performs better in reproducing the air concentration along the jet, the results being in agreement with the experimental data, although the computational runs are less stable and more time consuming. The sensitivity analysis of the inlet turbulent intensity showed that it has no influence in the characteristics of the jet core. With this research it is possible to conclude that: interFoam with k-Epsilon (k-ε) turbulence model is the best choice if the goal of the numerical simulations is the simulation of the velocity field of the jet. Meanwhile, twoPhaseEulerFoam with mixturek-Epsilon (mk-ε) shall be considered if the objective is the simulation of the velocity field and the air concentration.

The effect of jet aeration on the mean hydrodynamic forces applied on plunge pool floors was investigated. A mathematical expression is proposed to estimate the buoyancy coefficient reflecting the aeration effect, including contributions from previous authors. A correction of the theoretical values resulting from this expression based on data obtained in an experimental setup with vertical submerged rectangular (two-dimensional) aerated jets is proposed. The effect of the buoyancy coefficient is introduced in the integration of the hydrodynamic pressures over slabs of the plunge pool floor. Dimensionless forces on the upper faces of the slabs are determined for different air concentrations of the impinging jet. The effect of jet aeration entering the plunge pool on the uplift force applied in the lower faces of the slabs in the case where a waterstop failure occurs is also analysed.