Global NEST Journal

Smoothed Particle Hydrodynamics (SPH) is a promising simulation technique in the family of Lagrangian mesh-free methods, especially for flows that undergo large deformations. Particle methods do not require a mesh (grid) for their implementation, in contrast to conventional Computational Fluid Dynamics (CFD) methods. Conventional CFD algorithms have reached a very good level of maturity and the limits of their applicability are now fairly well understood. In this paper we investigate the application of the SPH method in Poiseuille and transient Couette flow along with a free surface flow example. Algorithmically, the method is viewed within the framework of an atomic-scale method, Molecular Dynamics (MD). In this way, we make use of MD codes and computational tools for macroscale systems.

The aim of this work was the application and evaluation of a mathematical model for the simulation of anaerobic hydrolysis and acid production processes. For the description of the processes involved, the Anaerobic Digestion Model ADM1 was employed. The ADM1 implementation in prefermenters is relatively easy, but the estimation of its components concentrations, kinetic parameters and stoichiometric coefficients, remains a problem to be solved. This study provides useful results for the ADM1 implementation in acid digesters design and operation. Model calibration and verification was performed using experimental data from two bench scale acid digesters operating at different temperatures (12, 20, 27 and 34 °C) and retention times (1,2, 4 and 6 days). Model sensitivity analysis illustrated that the values of pH, disintegration kinetic parameter and aceticlastic methanogenesis specific rate, as well as biomass and inert soluble COD concentrations in the primary sludge exert a significant influence on soluble COD production. Model parameters (disintegration and hydrolysis kinetic parameters and specific rate of methane production) as well as the temperature dependency of these parameters are given in this paper.

The aim of the study was to determine cadmium influence on the lead phytotoxicity to spring barley (Hordeum vulgare L.). The seedlings of H. vulgare were treated with single Pb (ranging from 0.1 to 100 mg l-1) and Pb mixture with Cd. Plant biomass production, physiological response, induction of oxidative damage and metals accumulation in roots and shoots were evaluated. Single Pb and under the presence of cadmium impaired the growth of H. vulgare, altered the content of photosynthetic pigments and induced lipid peroxidation. The addition of Cd to the Pb treatments has led to additive or synergistic effects on H. vulgare shoot and root dry weight, oxidative damage and increased bioaccumulation. The interactive effect of these metals on the content of photosynthetic pigments was concentration range dependent. Additivity was detected when H. vulgare were exposed to low concentrations of Cd and Pb and high concentrations of these metals had lower than additive effect.

Currently, the ecosystem is being damaged in many rivers and subsequently the fish species living there are also facing decline or even extinction. This situation urges to model the habitat and to design suitable restoration strategies in order to increase the capabilities of ecological modeling. In this paper, we proposed a numerical model to assess the ecosystem habitat situation and investigated the impacts of two ecological restorations strategies for the target fish species. The model includes a hydrodynamic model, a habitat model and habitat restoration schemes. The hydrodynamic model simulated the flow properties while sediments in the riverbed were also surveyed. Based on these parameters and fish preference curves, the habitat suitability indices were calculated. In order to analyze the river habitat quality, the weighted usable areas and overall suitability index were also calculated and the effects of the restoration strategies on selected fish species (Freshwater Reeves shad - Tenualosa reevesii) in the Chin-sha River were evaluated. The two ecological restoration strategies: addition of side-channel (scheme I) and river bank reconstruction (scheme II) enhanced the Freshwater Reeves shad habitat suitability level, with the high suitability index proportion increasing from 19.5% to 33.1% for scheme I and to 36.1% for scheme II. Based on the modelling results, we concluded that our numerical model could potentially provide suitable scenarios for successful fish habitat restoration.