Large Eddy Simulation of the Variable Density Mixing Layer

In this paper we perform large eddy simulations of variable density mixing layers, which originate from initially laminar conditions. The aim of this work is to capture the salient flow physics present in the laboratory flow. This is achieved through varying the nature of the inflow condition, and assessing the vortex structure present in the flow. Two distinct inflow condition types are studied; the first is an idealised case obtained from a mean inflow velocity profile with superimposed pseudo-white-noise, and the second is obtained from an inflow generation technique. The inflow conditions generated have matching mean and root mean squared statistics. Validation of the simulations is achieved through grid dependency and subgrid-scale model testing. Regardless of the inflow condition type used, the change in growth rate of the mixing layer caused by the density ratio is captured. It is found that the spacing of the large-scale spanwise structure is a function of the density ratio of the flow. Detailed interrogation of the simulations shows that the streamwise vortex structure present in the mixing layer depends on the nature of the imposed inflow condition. Where white-noise fluctuations provide the inflow disturbances, a spatially-stationary streamwise structure is absent. Where the inflow generator is used, a spatially stationary streamwise structure is present, which appears as streaks in plan-view visualisations. The stationary streamwise structure evolves such that the ratio of streamwise structure wavelength to local vorticity thickness asymptotes to unity, independent of the density ratio. This value is in agreement with previous experimental studies. Recommendations are made on the requirements of inflow condition modelling for accurate mixing layer simulations

MOESM1 of Reductive dissolution of As(V)-bearing Fe(III)-precipitates formed by Fe(II) oxidation in aqueous solutions

Additional file 1: Table S1. Total added Fe in individual replicates as derived from Fe(II) and Fe(tot) in filtered and Fe(tot) in unfiltered samples collected at the end of each experiment. Figure S1. UV-Vis calibration data. Figure S2. Comparison of UV-Vis data for dissolved Fe(II) with ICP-MS data for total Fe in 0.1-Âľm filtered solutions from 3 dissolution experiments. Figure S3. Comparison of dissolution data of wet and dried amorphous Fe(III)-phosphate formed in the presence of Ca or Na. Figure S4. Dissolution data for fresh and dried 2-line ferrihydrite synthesized by forced hydrolysis of a concentrated ferric nitrate solution

SORAS - a simple arsenic removal process

The serious threat to the health of millions of people through consumption of arsenic-rich groundwater in Bangladesh calls for immediate action on various levels. One of these actions is be the development of a low-cost and simple arsenic removal method available to every household. The development of alternative water sources and/or the installation of larger arsenic removal units will take more time due to logistic and financial constraints. Currently existing small-scale arsenic removal procedures require chemicals that are either not easily available and/or affect water taste and odour. Solar oxidation and removal of arsenic (SORAS) is a simple method that uses irradiation of water with sunlight in PET- or other UV-A transparent bottles to reduce arsenic levels from drinking water. The SORAS method is based on photochemical oxidation of As(III) followed by precipitation or filtration of As(V) adsorbed on Fe(III)oxides as shown in Fig. 1. Groundwater in Bangladesh naturally contains Fe(II) and Fe(III) and therefore, SORAS could reduce arsenic contents and would be available to everyone at virtually no cost. It could be a water treatment method used at household level to treat small quantities of drinking water

SORAS - a simple arsenic removal process

The serious threat to the health of millions of people through consumption of arsenic-rich groundwater in Bangladesh calls for immediate action on various levels. One of these actions is be the development of a low-cost and simple arsenic removal method available to every household. The development of alternative water sources and/or the installation of larger arsenic removal units will take more time due to logistic and financial constraints. Currently existing small-scale arsenic removal procedures require chemicals that are either not easily available and/or affect water taste and odour. Solar oxidation and removal of arsenic (SORAS) is a simple method that uses irradiation of water with sunlight in PET- or other UV-A transparent bottles to reduce arsenic levels from drinking water. The SORAS method is based on photochemical oxidation of As(III) followed by precipitation or filtration of As(V) adsorbed on Fe(III)oxides as shown in Fig. 1. Groundwater in Bangladesh naturally contains Fe(II) and Fe(III) and therefore, SORAS could reduce arsenic contents and would be available to everyone at virtually no cost. It could be a water treatment method used at household level to treat small quantities of drinking water

Cationically Charged Mn^IIAl^III LDH Nanosheets by Chemical Exfoliation and Their Use As Building Blocks in Graphene Oxide-Based Materials

We report on the synthesis and exfoliation of MnIIAlIII sulfonate and sulfate layered double hydroxides (LDHs) and their combination with graphene oxide by charge-directed self-assembly. The synthesis of the LDH compounds has been accomplished either directly by coprecipitation of the respective hydroxides with sulfonate anions or by ion-exchange of the chloride-containing LDH with sodium dodecylsulfate. Exfoliation of the bulk material in formamide yields colloidal suspensions of positively charged nanosheets with lateral dimensions of tens to hundreds of nanometers and thicknesses down to 1.3 nm, ascertained by TEM and AFM. Flocculation of the LDH nanosheets with an aqueous graphene oxide suspension yields a hybrid material that can be converted to a reduced graphene oxide/LDH composite by hydrazine reduction. The hybrid materials were tested for pseudocapacitive electrochemical storage capacity and electrocatalytic oxygen evolution reactions and showed significant increases compared to the pristine materials

Lithium Charge Storage Mechanisms of Cross-Linked Triazine Networks and Their Porous Carbon Derivatives

Redox active electrode materials derived from organic precursors are of interest for use as alternative cathodes in Li batteries due to the potential for their sustainable production from renewable resources. Here, a series of organic networks that either contain triazine units or are derived from triazine-containing precursors are evaluated as cathodes versus Li metal anodes as possible active materials in Li batteries. The role of the molecular structure on the electrochemical performance is studied by comparing several materials prepared across a range of conditions allowing control over functionality and long-range order. Well-defined structures in which the triazine unit persists in the final material exhibit very low capacities at voltages relevant for cathode materials (<10 mA·h g^–1). Relatively high, reversible capacity (around 150 mA·h g^–1) is in fact displayed by amorphous materials with little evidence of triazine functionality. This result directly contradicts previous suggestions that the triazine unit is responsible for charge storage in this family of materials. While the gently sloping discharge and charge profiles suggest a capacitive-type mechanismfurther confirmed by the trend of increasing capacity with increasing surface areaelectron paramagnetic resonance (EPR) spectroscopy studies show that the materials exhibiting higher capacities also display substantial EPR signals, potentially implicating unpaired spins in a charge storage mechanism that could involve charge transfer