Active Hydrodynamic Regime Research Articles

Regional and Seasonal Inputs of Mercury into Lake St. Pierre (St. Lawrence River), a Major Commercial and Sports Fisheries in Canada

Lake St. Pierre (LSP), constituted of a 120 km2 stretching of the St. Lawrence River (Southern Quebec), hosts the largest freshwater fishery industry in Canada. The lake drains, through its main tributaries, an important area of agrarian land and was subjected to intense industrial activities in the past century. In this paper, we present (1) an estimation of the seasonal aquatic mercury (Hg) inputs to LSP from the St-Lawrence River and two major tributaries; (2) a reconstruction, by the analysis of sediment cores, of the historic inputs of Hg into LSP and in a large riparian wetland, Bay St. Francois. Our results indicate that the aquatic Hg inputs to LSP (290 kg Hg between April 2003 and April 2004) are moderately elevated with most of the inputs occurring from the St. Lawrence River, either in spring or early winter, during high flow episodes. The sediment profiles suggest a recent decrease in Hg inputs, likely attributable to improvements of industrial practices. The observed perturbation of the surface sediments give evidence of an active hydrodynamic regime, suggesting that LSP could only act as a transitory system for suspended sediment and Hg, with seasonal accumulation and recurrent re-suspension resulting from changes in the hydrodynamic regime. Finally, we observed positive MeHg fluxes from the sediment to the water at different seasons in Bay St. Francois. However, Hg levels in fish like walleyes of LSP are reported to be low, which could be explained by faster fish growth rates following in part intense fishing pressure in LSP.

Reconstruction of paleohydrodynamic conditions during the formation of Upper Jurassic conglomerates of the Crimean Peninsula

Conglomerates and sandstones related to Upper Jurassic division of Mesozoic rocks make up the Main Range of the Crimean Mountains. Grain size and structural features testify to active hydrodynamic regime of depositional environments. Conglomerates contain a small quantity of exotic granite-granodiorite pebbles and boulders probably transported from the Ukrainian Crystalline Shield situated 400 km north of the Crimean Peninsula. Paleohydrodynamic parameters and transportation mechanisms of debris were modeled with the help of different methods used in geoengineering computations. The results obtained demonstrated satisfactory convergence of the data. The calculations showed that the rocks under investigation were formed during a short (from geological standpoint) but very intense episode of sedimentation related to active tectonic processes that were responsible for the activation of hydrodynamic and sedimentation processes in the paleobasin.

Hydrodynamics and petroleum migration in the Upper Ordovician Red River Formation of the Williston Basin

Simulations of petroleum migration within the Red River petroleum system of the Williston Basin show that petroleum generation and secondary migration preceded the onset of an active hydrodynamic regime that persists to the present day. Furthermore: (1) a better understanding of the eastern limit of the mature source rock area, which is largely facies controlled, is required to reduce exploration risk east of the Nesson Anticline, (2) the Red River play types that have been prosperous in southeastern Saskatchewan should extend considerable distances to the north, as well as throughout central Saskatchewan and western Manitoba, Canada, and (3) accumulations that may have developed in the southwest of the basin have likely been flushed and redistributed subsequent to the onset of hydrodynamics.

Long-term effects of a toxic algal bloom on subtidal soft-sediment macroinvertebrate communities in Wellington Harbour, New Zealand

The long-term effects (>1 year) of a naturally occurring toxic plankton bloom ( Karenia brevisulcata) on subtidal benthic macroinvertebrate communities were investigated in Wellington Harbour, a semi-enclosed temperate embayment in New Zealand. For 3 years communities were sampled at three different sites in the harbour. Analyses revealed that community recovery following the bloom was site-specific. Multivariate analyses indicated that at one site community composition was approaching recovery ∼3 years post-bloom. At the second site, a sequential recovery process was indicated, whereas at the third site the community composition oscillated from year to year, but did not show any signs of a sequential recovery process. The nature of the hydrodynamic regime was identified as a major factor influencing the observed recovery processes. Communities exposed to an active hydrodynamic regime were less affected by the bloom and differed little in their composition pre- and post-bloom, as they were naturally in a perpetual state of recovery as indicated by a dominance of r-selected species. The community at the hydrodynamically less active site was more affected by the bloom and exhibited temporal differences in composition consistent with successional models. Complete recovery to a pre-disturbance climax community dominated by K-selected species is likely to take 4–5 years, if not interrupted by other disturbances. Given the increased occurrence of harmful algal blooms worldwide, more monitoring and manipulative studies are needed to further evaluate the effects of such disturbances on macrobenthic communities.

Heat Exchange under Beneficiation by Condensation Methods

The all-inclusive use of the resources of geothermal heat-carriers needs the devices with active hydrodynamic regimes and optimal design parameters. The complex investigations into the heat exchange under steam condensation are conducted on models with different structures of flows in working volumes. The heat exchange coefficients depending on the regime parameters are obtained, and the basic procedures to calculate processing equipment are developed.

A Quasi-stationary Approach to Drying Kinetics of Fluidized Particulate Materials

A modified quasi-stationary method has been proposed to describe drying kinetics of particulate materials dried in convective dryers with active hydrodynamic regimes. Both our own results and literature data were used. These include sliced celery, cranberry, diced carrot, wheat and polystyrene granules dried in four types of dryers: pulsed fluid bed dryer, fluid bed dryer with a mixer, spouted bed dryer with a draft tube, and vortex dryer. The method was validated by comparing experimental data with results of modeling in terms of a reduced moisture content and material temperature. A new form of the generalized drying curve has been proposed with the reduced time and the index of hydrodynamic intensity as parameters. The equations developed can be used to calculate the total drying time and determine the temporal variation of the moisture content and material temperature.

Hydrodynamics and mass exchange in active hydrodynamic regimes

The interaction between a liquid film and a gas flow is one of the widespread contact processes realized in highly effective and highly productive heat-exchange vessels. Film heat-exchange vessels are widely used to conduct such chemico-production and physical processes as adsorption (desorption), evaporation (condensation), fractional distillation, etc. Let us examine methods of calculating mass efficiencies in active hydrodynamic regimes - during wave formation, gravitational flow of a turbulent film, and a ascending companion film flow of liquid and gas

Prospects for commercial utilization of lean and nontraditional types of mineral raw material

1. The changeover to the production and processing of lean and nontraditional raw materials is requiring the use of new engineering processes or the improvement of existing processes. In this connection, processes of drying, heat-treatment, adsorption, vaporization, and fusion are becoming traditional in the mining industry; in order to implement these processes efficiently as the raw material becomes leaner, it is necessary to involve the use of devices with active hydrodynamic regimes.

Problems in activating the hydrodynamic situation in technological apparatus

-- As active hydrodynamic regimes (AHR) we may consider only those regimes at which by means of hydrodynamics an intensification of the process is obtained at high economic indices and at good finished product quality.