Efficiency Analysis of Savonius-Style Wind Turbine in Hydrodynamic Flow Field

The world’s population is going to surge past 10 billion by 2050. In order to cater to the energy demand of the ever-increasing posterity, scientists across the globe are working to harness power from renewable sources of energy. In pursuit of studying alternative energy sources, Savonius-style turbines (SSTs) have gained increased attention in the past few years. However, considering the low operational efficiency, design aspects of these turbines need to be improved. In this study, experimental investigations have been carried out using two designs of SSTs namely classical SST and elliptic shaped SST. The study has been carried out using an experimental setup that could produce a low head of < 1 m and water flow velocity within a range of 0.4 m/s to 1.2 m/s; the velocities at which perennial rivers flow. This study presents the comparison and analysis of the coefficients of power and torque measurements at various tip speed ratios. The study shows that there exists a local maximum when coefficient of performance is plotted with TSR. Out of the two profiles studied here, elliptic shaped SST generated a coefficient of power of 0.392 and a coefficient of torque of 0.538, when the water head was set at 1 m and flow velocity of 0.47 m/s. Experimental data reported here exhibit a gain of 16 % using an elliptic shaped SST over classical design.

Artisanal Mining Practice and Physical Impacts on the Environment in the Ity-Floleu Gold Region, Côte d'Ivoire

This paper describes artisanal gold mining practices and environmental impacts around the Ity-Floleu gold mine, in western Côte d'Ivoire. Interviews and field observations as well as measurements of turbidity and water flow velocity in the section of the river (Cavally) watering the study area, made it possible to identify 13 artisanal mining sites, housing 247 artisans, operating in groups made up mainly of 5 to 10 people. The activity is dominated by local populations from the villages of Ity and Floleu and the surrounding communities. Gold mined comes from alluvial and vein ores, with a predominance of alluvial ore, extracted in the sediments of the bed and the banks of the river and in the soils, inside forests. In the bed of the river, sediments are dredged using machines placed on boats, from where they are washed in mats and then dumped into the watercourse. On the other hand, on the banks of the river and in the forests, the material used consists of picks, dabas, mats, and shovels. In all cases, gold is recovered as a concentrate of gold powder. As regards vein ores, they are also extracted along with the soils of cultivable land, but in the form of blocks of stone which are crushed and washed. The gold is then recovered using mercury, followed by cyanidation. The techniques used lead to the silting up and the fall of the banks of the river, reduction of agricultural land, and the degradation of the environment by the tailings. The Cavally River appears to be strongly impacted in the midstream part of the Ity-Floleu axis, marked by a decrease in the bed and the river flow velocity (0.19 m/s) and higher turbidity (255.3 NTU). More effective policies are urgently needed to restore degraded ecosystems, both aquatic and terrestrial.

Numerical Simulation of Heat Transfer Tube Characteristics of Refrigeration and Air Conditioning Based on Mixed Fractional Model

The main parameters affecting the heat transfer performance of heat transfer tube heat exchanges include fin shape, fin spacing, fin thickness, tube row arrangement, tube diameter, dry and wet bulb temperature and flow rate. The air side heat transfer performance of heat transfer tube heat exchange and the influence of velocity field and temperature field distribution on heat transfer effect have been the focus of domestic and foreign scholars. In this paper, based on the mixed fraction model, CFD software is used to simulate the absorption process of gravity falling film outside the heat transfer tubes of refrigeration and air conditioning, and to study the flow and heat transfer characteristics of the process. The results show that, for the heat transfer tubes with the selected structure, the heat transfer capacity increases with the increase of water flow velocity, and the heat transfer enhancement effect of turbulence is enhanced. The heat transfer tubes have better comprehensive heat transfer performance than smooth tubes with the same diameter.

Influence of abiotic factors on incubation of Baikal omul eggs in the Selenga River (Lake Baikal Basin)

Abiotic factors affecting the choice of spawning sites for the Baikal omul (Coregonus migratorius) in the Selenga River over 27 years were studied. A total of 3,450 samples were collected using the Dulkeit scraper in Decembers of 1987-2014, at 24 trans-sections in the Selenga River channel over a total length of 410 km. At each sampling site we recorded omul egg density, substrate particle size, water depth, water flow velocity, and ice thickness. Omul eggs were found mainly on hard substrates (sand, gravel, pebbles, and pebble-cobbles combinations). Omul has been found to avoid spawning at depths less than 1.5 m and greater than 6.0 m. Water velocity and ice thickness did not strongly influence the choice of site. Omul eggs were found at flow rates of 0.05-0.7 m/s with a maximum at 0.1 m/s.

Study of Fluid Flow Movement by Using Self Potential Data

The Self-Potential (SP) method is passive method in geophysics which works based on the natural presence of an electric field on the surface due to anomalies below the surface. SP value on surface can be generated by fluid flow through rock pores or fractures. We study fluid flow movement in subsurface using the velocity value of fluid flow derived from SP values measured on surface. For that purpose, we carried out mathematical modelling, connecting the Helmholtz-Smoluchovsky’s electrokinetic potential gradient equation with Darcy’s law. The velocity of fluid flow depends on the intrinsic permeability of rocks, electrokinetic potential gradient and electrohydrolic conductivity constant. We tested derived velocity of fluid flow on the SP data from a pilot project test site. Study results show that fluid flow in vertical direction can be identified from SP data at locations where there are significant changes of positive and negative SP values. Fluid flows from a high SP value to a low SP value and this flow is opposite the positive SP gradient. The SP value at study site lie in the range -80mV to -160mV, whereas the value of the water flow velocity lie in the range 0.08 cm/s - 0.21 cm/s.

Dam Break Simulation with HEC-RAS and OpenFOAM

A dam break is a natural disaster that can cause significant property damage and loss of life. It's useful to identify potential flooding areas downstream in the event of a dam break. In this study both HEC-RAS and OpenFOAM are set up to simulate the inundation map downstream of the Dworshak dam in Idaho. Using the same topographical data from satellite observations, similar computational meshes are set up in both HEC-RAS and OpenFOAM. Where possible, identical or similar conditions are set up in HEC-RAS and OpenFOAM to model flooding patterns due to a dam break. The velocity of the water before reaching Ahsahka, the town located at the junction downstream from the dam, is 11.5% slower in HEC-RAS compared to OpenFOAM. The average velocity of water before reaching the end of the computational domain at Big Canyon Creek is about 20% slower in HEC-RAS compared to OpenFOAM. One notable discovery is that the water flow velocity in OpenFOAM appears to depend on the mesh resolution used in the simulation. A significant velocity difference is observed when water flows from one mesh refinement region to another mesh refinement region with a different resolution.

Technical Means and Methods for Studying the Fine Structure of a Water Flow using Video Registration

The article discusses developed technical means and methods allowing to obtain in situ spatial distribution of velocity of suspended particle movement by a water flow. A brief description is given of the developed measuring complex based on video recording of the aquatic environment. The method of performing full-scale experiments by the example of study of sea estuaries is described. The article presents measurement results and examples of spatial distributions of flow velocities required for solving various problems related to mass transfer, coast erosion and silting of water areas. Analysis of expedition research results obtained using the developed complex allowed to create methodical approaches to assess the current state of a water body and informative parameters of its state using a visualization method. Based on the created methods, data on the fine structure of the flow in the Chernaya River estuary area were obtained. Comparison of the averaged data on the water flow velocity with the measurement results obtained through standard technical means, namely a hydrometric current meter, showed minimal discrepancies not exceeding 11 %. The developed method and technical means make it possible to study the water flow dynamics and to describe the flow fine structure, which is necessary for studying the mechanisms of erosion, sediment accumulation and transport.

Analysis and calculation of sediment scouring rate at different locations of storm sewer

To explore the migration differences of sediments at the front, middle, and end sections of a storm sewer when scoured by water, and further evaluate the pollution load, the scouring process of sediments at different locations of a storm sewer was simulated and mathematical models were built to calculate the scouring rate. Results show that scouring rate is affected by sediment particle size, pipeline slope, sediment thickness, and water flow velocity. As the slope increased, scouring rate at the end section increased more obviously. The scouring rate at the front section slightly decreased with increasing sediment thickness, but opposite trends were observed at the middle and end sections. When the particle size (0.33 mm–0.83 mm) and flow velocity (0.15 m/s–0.65 m/s) increased within their ranges, scouring rate increased across all three locations. Models for calculating scouring rate were established via two data fitting. The calculated values were compared with measured values at a scouring time of 1 min. Under different particle sizes, the difference between the calculated and measured values at front, middle, and end sections were in the ranges of −0.63% to 0.63%, −0.01% to 0.02%, and −0.13% to 0.16%, respectively, all of which showed good consistency.

Modeling and Parametric Simulation of Microplastic Transport in Groundwater Environments

Efforts to reduce the toxic effects of microplastics (MPs) on the environment have increased globally in recent years. However, the existing models used for the simulation of contaminant transport in groundwater are meant for dissolved substances, which is not suitable for studying MPs. Therefore, in this study, the transport of MPs in a saturated porous medium was modeled by establishing governing equations. Simulations were performed using the finite element method to examine the effects of the parameters of the governing equations on the transport of MPs. The results suggest that it is necessary to reduce the diffusivity of MPs and increase the water flow velocity, porosity, and first-order attachment coefficient to effectively contain this environmental hazard. From the simulation results, it can be derived that a combination of low diffusivity, fast water flow velocity, and high soil porosity may reduce the amount of MPs that are leaked into groundwater environments. The modeling and simulations performed in this study provide a clear understanding of the transport phenomena of MPs with applications in combating water pollution.