Open-Pit Mine Dewatering Based on Water Recirculation—Case Study with Numerical Modelling

The layout of the dewatering system in open-cast mining must be adapted to mining assumptions and to the size of expected inflows, which, in turn, depend on natural conditions and the operation of other mines and groundwater intakes, affecting the arrangement of the hydrodynamic field. This case study analyses possible dewatering solutions related to a change in the mining drainage system: decommissioning by flooding of a depleted deposit and dewatering of a new one located in the vicinity. As part of numerical modelling, a solution was sought to minimise the environmental impact of drainage. Forecast calculations for two drainage alternatives were made. One of the solutions follows the classic approach: independent dewatering of the new excavation. The second solution assumes the recirculation of waters from dewatering of the new mine through their discharge into a closed and flooded pit located in the vicinity. The results of the forecasts for both variants point to the modification of the hydrodynamic field resulting from expected volumes of inflows and different environmental effects. The use of numerical simulations assisted the selection of the optimal dewatering solution.

Simulation of the Hydrodynamic Field in Nhat Le Estuary, Quang Binh Province

Hydrodynamic field is the primary research problem of all studies on coastal estuarine areas. Over the years, there have been many studies on Nhat Le estuary's region (Quang Binh). Still, these studies have not focused on simulating the characteristics of the hydrodynamics of this area. This study will present the ability to apply a mathematical model to simulate hydrodynamic fields for the region of Nhat Le estuary and Quang Binh sea by constructing the MIKE 21 model set based on the actual measurement database by the Center for Environmental Fluid Dynamics implemented in 2018. Through the calculation scenarios under different conditions, the longshore current mainly consists of Southeast - Northwest (especially with NE waves, the current direction is Northwest - Southeast) with current speed mostly in the range of 0.1 - 0.4 m/s. In estuarine areas, river flows have complicated developments, including many component flows. In the dry season, the river flow is not strong and is dominated by changes in the tide phase, withdrawal in a day. There are days of high flood flow in the flood season, overwhelming the tidal currents; the maximum flow velocity at the door can reach more than 6 m/s. Waves in the southwest monsoon season are relatively small, about 0.25 - 0.6 m; while the waves in the Northeast monsoon season are quite large and very strong during the storm, but when the depth is about -3 to -4 m, the wave height decreases sharply, spreading to the door. In particular, when there are floods in the river, the waves that propagate through this depth will almost calm.

ELECTROPHORESIS IN THE TOTAL (CONSTANT AND ALTERNATING) ELECTRIC FIELD. II. PECULIARITIES OF THE COMBINED IMPACT OF ALTERNATING AND CONSTANT ELECTRIC FIELDS

The hydrodynamics of electrophoresis under the simultaneous impact of constant and alternating electric fields is considered. It has been shown that when the constant and alternating external fields are combined, the energy of the constant electric field is transferred into the alternating hydrodynamic field. An example is given of a dispersed medium in which a giant dispersion of the dielectric constant can arise, which in turn can contribute to an increase in the total electrophoresis rate. Analogies of the behavior of the considered dispersed medium with the action of an electroacoustic transducer based on the use of electrokinetic phenomena are given.

Analysis of an electroosmotic flow in wavy wall microchannels using the lubrication approximation

We present the analysis of an electroosmotic flow (EOF) of a Newtonian fluid in a wavy-wall microchannel. In order to describe the flow and electrical fields, the lubrication and Debye-Hückel approximations are used. The simplified governing equations of continuity, momentum and Poisson-Boltzmann, together with the boundary conditions are presented in dimensionless form. For solving the mathematical problem, numerical and asymptotic techniques were applied. The asymptotic solution is obtained in the limit of very thin electric double layers (EDLs). We show that the lubrication theory is a powerful technique for solving the hydrodynamic field in electroosmotic flows in microchannels where the amplitude of the waviness changes on the order of the mean semi-channel height. Approximate analytical expressions for the velocity components and pressure distribution are derived, and a closed formula for the volumetric flow rate is obtained. The results show that the principal parameters that govern this EOF are the geometrical parameter, ε, which characterizes the waviness of the microchannel and the ratio of the mean semi-channel height to the thickness of the EDL, κ.

Numerical Simulation of Scour Depth and Scour Patterns in Front of Vertical-Wall Breakwaters Using OpenFOAM

An advanced coupled numerical model was developed and implemented in the present work, describing the scour patterns and predicting the scour depth in front of vertical-wall breakwaters. It consists of two independent models, a hydrodynamic Computational Fluid Dynamics (CFD) Reynolds Averaged Navier–Stokes (RANS) model developed on the OpenFOAM (version 2.4.0) toolbox (CFD), describing the wave propagation and the associated hydrodynamic field, and a morphodynamic one (sediment transport model), which was developed in FORTRAN by the authors and yields the updated seabed morphology. The method used here is iterative. The hydrodynamic model is applied for any given initial seabed geometry and wave conditions, resulting in the hydrodynamic field of the flow, which is used as input by the second sediment transport model for the seabed morphology evolution. This process is repeated until the equilibrium profile is achieved. Model results are compared satisfactorily with experimental data for both scour patterns and prediction of scour depth.

Detection of Floating Objects Based on Hydroacoustic and Hydrodynamic Pressure Measurements in the Coastal Zone

The development of coastal infrastructure and related maritime transport necessitatesthe intensification of vessel traffic monitoring. Navigation systems used in this research are traditionally based on the information transmitted by radio waves. Marine traffic safety requires constant supervision carried out by dedicated systems, the operation of which may be limitedby difficult environmental conditions. The possibilities of supporting navigation systems with underwater observation systems are explored here. The research was carried out using an underwater measurement system. Local disturbances of the hydroacoustic and hydrodynamic field from the moving vessels were analysed. The potential for identifying a moving vessel, for example for offshore infrastructure security purposes, is demonstrated.