Numerical Flow Modeling of Artificial Ocean Upwelling

Artificial Upwelling (AU) of nutrient-rich Deep Ocean Water (DOW) to the ocean's sunlit surface layer has recently been put forward as a means of increasing marine CO2 sequestration and fish production. AU and its possible benefits have been studied in the context of climate change mitigation as well as food security for a growing human population. However, extensive research still needs to be done into the feasibility, effectiveness and potential risks, and side effects associated with AU to be able to better predict its potential. Fluid dynamic modeling of the AU process and the corresponding inorganic nutrient transport can provide necessary information for a better quantification of the environmental impacts of specific AU devices and represents a valuable tool for their optimization. Yet, appropriate capture of all flow phenomena relevant to the AU process remains a challenging task that only few models are able to accomplish. In this paper, simulation results obtained with a newly developed numerical solution method are presented. The method is based on the open-source modeling environment OpenFOAM. It solves the unsteady Reynolds-Averaged Navier-Stokes (RANS) equations with additional transport equations for energy, salinity, and inorganic nutrients. The method aims to be widely applicable to oceanic flow problems including temperature- and salinity-induced density stratification and passive scalar transport. The studies presented in this paper concentrate on the direct effects of the AU process on nutrient spread and concentration in the ocean's mixed surface layer. Expected flow phenomena are found to be captured well by the new method. While it is a known problem that cold DOW that is upwelled to the surface tends to sink down again due to its high density, the simulations presented in this paper show that the upwelled DOW settles at the lower boundary of the oceans mixed surface layer, thus keeping a considerable portion of the upwelled nutrients available for primary production. Comparative studies of several design variants, with the aim of maximizing the amount of nutrients that is retained inside the mixed surface layer, are also presented and analyzed.

Analyzing the impact of intake structure on the flow at low pressure SHPP

The structural parts of intake structures directly affect the flow velocity distribution in the turbine intake of small hydropower plants, where inhomogeneous flow leads to uneven load of the turbine units causing operational problems. A 2D numerical flow modeling was used for investigations of the flow in an intake structure of a low-head small hydropower plant. The effects of shape changes of the intake structure on the flow velocity distribution in the turbine intakes were investigated and assessed proving significant effect of the shapes of the intake structure on the flow homogeneity in turbine intakes.

Estudio del proceso de evaporación en el Salar Tres Quebradas por medio de medidas in situ y datos de satélite

<p>The calculation of evaporation (<em>Ev</em>) is a fundamental process on the planning of investment for nonmetallic mining in salt flats. Dispose to reliable estimates of evaporation allows to reduce one of the main uncertainties of the flow models in this type of basin. This paper focuses on the calculation of <em>Ev</em> in the Tres Quebradas salt flat, Catamarca (Argentina), applying Priestley-Taylor model whit satellite data. Study area comprises the Tres Quebradas and Verde lagoons, and a central evaporite zone. Satellite data (CERES and OLI-LandSat 8), meteorological information, brine density measurements, evaporation measurements, and spectral signatures to calculations were used. The lagoons evaporation was estimated and by means of a Class A evaporation pan validated. The evaporation control in evaporite zones also was studied using a phreatic level function. <em>Ev</em> values of 1302 mm year^–1 and 1249 mm year^–1 for the Tres Quebradas and Verde lagoons were obtained, respectively, similar to Class A evaporation pan values measured. In the case of evaporite zones, an average annual value of 152 mm year^–1 was estimated, regulated by the phreatic level. In summary, an average annual of system water loss by evaporation of 1.31±0.32 m³ s^–1 was obtained, where more than 80% corresponds to the Tres Quebradas and Verde lagoons, and the rest to the central evaporite zone. The results achieved are consistent and will be used as input data in the numerical flow modeling to the estimation of the lithium brine reserve of the salt flats.</p>

NUMERICAL FLOW MODELING AROUND OKINAWA FROM CORAL REEF AREA TO OPEN OCEAN

Coastal area along the Okinawa sea is formed from coral reefs. In the area, coastal flows are generated by various factors of tide, wave, wind, river discharge and so on. In the offshore areas, oceanic currents including the Kuroshio also influence the coastal flows, because of the openness. Thus, the flow pattern becomes complicated by such external forces. To simulate the flow pattern of the Okinawa sea by numerical flow modeling, the model needs to deal with the various external forces from shallow coral reef area to deep open ocean. Additionally, steep slope exists in the offshore end of coral reef. In such region, we have to be careful because flow simulation is likely unstable. This study intends to develop the numerical flow model which is applicable to the Okinawa sea, and its performance has been tested in the several sea areas. In addition, field observations were carried out to investigate the flow phenomena and to verify the model accuracy. The result of filed observation and its comparing with the simulation is shown.

Measuring Stand Tests of a Michell-Banki Waterturbine Prototype, Performedunder Natural Conditions

The article presents the result of tests of a single segment of a prototype water turbine, performed in order to determine its shaft power output as a function of rpm, and to verify the declared performance. The results have been compared with the outcomes of numerical calculations performed, for the same conditions, with the use of FLUENT software. The work presents information of crucial importance for presenting the process of testing the piece in question, such as: test environment, properties of the test piece, testing equipment used, as well as the methodology and the course of hydromechanical measurements, along with the characteristics of the results obtained. Then, the measurement results are discussed and analyzed. Conclusions are presented as well. Analysis of the results, taking into consideration the physical image of phenomena occurring in the case of flow-devices, such as water turbines, has made it possible to define other, important characteristics of the turbine, such as: output, shaft torque and efficiency, as a function of rpm and head of turbine. Test results have confirmed the expected mechanical and power-related properties of the turbine and have proved the numerical flow modeling model used effective. A brief description of the prospects concerning new applications of the turbine discussed has been presented as well

Rock glaciers on the run – understanding rock glacier landform evolution and recent changes from numerical flow modeling

Rock glaciers are landforms that form as a result of creeping mountain permafrost which have received considerable attention concerning their dynamical and thermal changes. Observed changes in rock glacier motion on seasonal to decadal timescales have been linked to ground temperature variations and related changes in landform geometries interpreted as signs of degradation due to climate warming. Despite the extensive kinematic and thermal monitoring of these creeping permafrost landforms, our understanding of the controlling factors remains limited and lacks robust quantitative models of rock glacier evolution in relation to their environmental setting. Here, we use a holistic approach to analyze the current and long-term dynamical development of two rock glaciers in the Swiss Alps. Site-specific sedimentation and ice generation rates are linked with an adapted numerical flow model for rock glaciers that couples the process chain from material deposition to rock glacier flow in order to reproduce observed rock glacier geometries and their general dynamics. Modeling experiments exploring the impact of variations in rock glacier temperature and sediment–ice supply show that these forcing processes are not sufficient to explain the currently observed short-term geometrical changes derived from multitemporal digital terrain models at the two different rock glaciers. The modeling also shows that rock glacier thickness is dominantly controlled by slope and rheology while the advance rates are mostly constrained by rates of sediment–ice supply. Furthermore, timescales of dynamical adjustment are found to be strongly linked to creep velocity. Overall, we provide a useful modeling framework for a better understanding of the dynamical response and morphological changes of rock glaciers to changes in external forcing.