Search results

A laboratory experiment was conducted in the soil laboratory in the Department of Environment and Environmental Pollution, Environment and Natural Resources Research Institute, National Centre for Research. The purpose of this paper is to study the movement of crude oil through soil column.

Polyvinyl chloride columns were filled with Shambat soil, amended with three concentrations of light crude oil (0.16, 0.32, and 1.28 ppm), obtained from Petrodar Oil Company. Soil samples were taken from 5 and 10 cm depths after two, 14 and 28 days from crude oil addition. At each sampling date, the recovery of petroleum hydrocarbons measured.

The results obtained indicated that high by significant differences among the different concentrations, different depths and different sampling durations. Moreover, the downward mobility of petroleum hydrocarbons decreased with increasing crude oil concentration.

Results of the experiment revealed the importance of studying the fate and mobility of total petroleum hydrocarbons (TPH) in soils in order to facilitate a proper reclamation practice specially in oil polluted sites.

This study aims at investigating two-dimensional laminar flow of power-law fluids around three unconfined side-by-side cylinders.

The numerical study is performed by solving the governing (continuity and momentum) equations using a finite volume-based code ANSYS Fluent. The numerical results have been presented for different combinations of the governing dimensionless parameters (dimensionless spacing, 1.2 = L = 4; Reynolds number, 0.1 = Re = 100; power-law index, 0.2 = n = 1.8). The dependence of the kinematic and macroscopic characteristics of the flow such as streamline patterns, distribution of the surface pressure coefficient, total drag coefficient with its components (pressure and friction) and total lift coefficient on these dimensionless parameters has been discussed in detail.

It is found that the separation of the flow and the apparition of the wake region accelerate as the dimensionless spacing decreases, the number of the cylinder increases and/or the fluid behavior moves from shear-thinning to Newtonian then to shear-thickening behavior. In addition, the distribution of the pressure coefficient on the surface of the cylinders presents a complex dependence on the fluid behavior index and Reynolds number when the dimensionless spacing between two adjacent cylinders is varied. At low Reynolds numbers, the drag coefficient of shear-thinning fluids is stronger than that of Newtonian fluids; this tendency decreases progressively with increasing of Re until a critical value; beyond the critical Re, the opposite trend is observed. The lift coefficient of the middle cylinder is null, whereas, the exterior cylinders experience opposite lift coefficients, which show a complex dependence on the dimensionless spacing, the Reynolds number and the power-law index.

The flow over bluff bodies is a practical engineering problem. In the literature, it can be seen that the previous studies on non-Newtonian fluids are limited to the flow over one or two cylinders (effect of an odd number of cylinders on each other). Besides that, the available results concerning the flow of Newtonian fluids over three cylinders are limited to the high Reynolds numbers region only. However, this work treats the flow of non-Newtonian power-law fluids past three circular cylinders in side-by-side arrangements under a wide range of Re. The outcome of the present study demonstrates that the augmentation of the geometry complexity to three cylinders (effect of pair surrounding cylinders on the surrounded ones in what concerns Von Karman Street phenomenon) causes a drastic change in the flow patterns and in the macroscopic characteristics. The present results may be used to predict the flow behavior around multiple side-by-side cylinders.

The purpose of this paper is to investigate the influence of two decomposition processes, namely, composting and vermicomposting, on the chemical composition of the finished products of a mixture of: cotton residues; soil and cotton residues; farmyard; soil.

Composting experiments were done over six months to prepare four different mixtures as follows: cotton residues+soil (C); cotton residues+soil+earthworms (C+E); cotton residues+soil+farmyard manure (C+F); and cotton residues+soil+farmyard manure+earthworms (C+F+E). Electrical conductivity, pH, nitrate-N, ammonium-N, ash, total phosphorus, total nitrogen, total organic carbon, carbon: nitrogen ratio, total potassium and trace elements (Mn, Fe, Cu and Zn) were determined on monthly-based samples.

Significant differences (p < 0.05) in organic carbon, nitrate-N, nitrogen, phosphorus, and potassium content were recorded in vermicompost compared to compost. In general, results indicated that vermicompost had a significant effect compared to compost and a positive effect on the chemical properties of the finished products.

This research work was carried out by four researchers from two institutions concerned with agricultural production and environmental aspects related to soil productivity. The paper emphasizes on production of organic fertilizers with good quality and monitoring of composting process for better management practices of agricultural wastes in Sudan.

This paper aims to introduce a new numerical approach based on the local weak form and the Petrov–Galerkin idea to numerically simulation of a predator–prey system with two-species, two chemicals and an additional chemotactic influence.

In the first proceeding, the space derivatives are discretized by using the direct meshless local Petrov–Galerkin method. This generates a nonlinear algebraic system of equations. The mentioned system is solved by using the Broyden’s method which this technique is not related to compute the Jacobian matrix.

This current work tries to bring forward a trustworthy and flexible numerical algorithm to simulate the system of predator–prey on the nonrectangular geometries.

The proposed numerical results confirm that the numerical procedure has acceptable results for the system of partial differential equations.