Search

Fast fluid dynamics (FFD) is an intermediate model between multi-zone models and computational fluid dynamics (CFD) models for indoor airflow simulations. The use of coarse grids is preferred with FFD in order to increase computing speed. However, by using a very large mesh cell to represent a heat source that could have a much smaller physical size than the cell, coarse-grid FFD would under-predict the thermal plume and thermal stratification. This investigation integrated a thermal plume model into coarse-grid FFD. The integration first used the plume model to calculate a source for the momentum equations and then corrected the temperature at the plume cell. The integration enabled coarse-grid FFD to correctly predict the plumes. When applied to displacement ventilation, coarse-grid FFD with the plume model can accurately predict the mean air temperature stratification in rooms as compared with experimental data from the literature. The improved model has also been used to calculate the ventilation rate for buoyancy-driven natural ventilation. The calculated ventilation rates agree well with the experimental data or predictions by CFD and analytical models. Coarse-grid FFD with the plume model used only a small fraction of the computing time required by fine-grid FFD, while the associated errors for the two grid sizes were comparable. [ABSTRACT FROM AUTHOR]

To analyze the deterrent effect and level of traffic electronic enforcement on inhibition of traffic violation, on the basis of the plume model, this paper built a quantitative analysis model of traffic electronic enforcement deterrence level. This model corrected and redefined the factor meaning and expression form of plume model, and calibrated constant values with data from traffic survey to analyze the characteristics of related factors which can influence the traffic electronic enforcement deterrence effect on the scope of time and space. The case studies showed that the calculation results of the model was consistent with the survey results of traffic violation rate, which indicated that this model can quantify the contribution degree of electronic enforcement on inhibition of traffic violation. By reasonable layout of location, direction and quantity of traffic electronic enforcement facilities, the traffic violation rate of the layout area can be effectively reduced. [ABSTRACT FROM AUTHOR]

The sources of groundwater pollution such as, industrial effluents, sewage and extensive farming have lead to agrochemical pollution. Mathematical modeling helps to analyze the existing situation, allows forecasting, and to evaluate the effects of changes in the surrounding water quality. The present research has been focused mainly towards understanding the various processes affecting the transport of chemicals in soils. Dispersion coefficient for the sandy loam soil was found to be 0.247 m²/d, 0.150 m²/d and 0.01 m²/d for nitrates, phosphates and Chlorpyriphos through column, and 0.3 37 m²/d, 0.217 m²/d and 0.077 m²/d for nitrates, phosphates and Chiorpyriphos through channel studies, respectively. For similar analysis of the breakthrough curves, dispersion coefficient for the clay soil was found to be 0.0835 m²/d, 0.0632 m²/d and 0.008 m²/d for nitrates, phosphates and Chlorpyriphos through column and 0.147 m²/d , 0.0848m²/d and 0.022 m²/d for nitrates, phosphates and Chlorpyriphos through channel studies, respectively. The one-dimensional analytical model has been used and validated with the experimental data obtained from column and channel studies in sandy loam and clay soils and compared with model output (in which total elimination rate "K" is considered as zero). From this a variation of about 40-60 percent in the leaching characteristics of pollutants was being observed (nitrates, phosphates and chlorpyriphos). [ABSTRACT FROM AUTHOR]

The potential of solar chimney in building ventilation has long been recognized. However, very few data have been reported on its ventilation performance in actual buildings. In this study, the field performance of a solar chimney attached to a test house was studied under Hangzhou climate conditions. The ventilation rates were determined by measuring the airflow rate in the chimney channel. The results show that the solar chimney provided relatively consistent air changing rates of about 2–5 h−1 on average 24 h a day despite that it was installed on the south-east wall. With the wind influence suppressed using a windproof net at the chimney outlet, the solar radiation and the temperature difference between the room and the outside were two major sources contributing to the stack flow. The inverse condition, higher room temperature than the outside, was the major driving force of stack flow during the absence of solar radiation. The limiting effect of the room inlet size was also demonstrated. The field data validated the plume model, which predicted all the data with reasonable accuracy. Our study indicates that a properly designed solar chimney can provide reliable ventilation round the clock during most time of the year in Hangzhou or cities with similar climate. Extra measures are only needed in summer times when neither the solar radiation nor the inverse condition is available. [ABSTRACT FROM AUTHOR]

As the oil activity outside the Norwegian coast moves towards north,the potential for conflict with the fishing industry increases. Reasons for this are the presence of spawning areas for important fish stocks like herring and cod, and also the technical development of subsurface solutions for the oil exploration, increasing the risks for the occurrence of subsurface blowouts. The paper explains how this potential for conflict can be described by means of numerical modelling techniques. The Haltenbanken area outside the western coast of Norway is selected as a field case. The modelling work involves underwater plume modelling as well as 3D modelling of ocean currents. The resultsfrom these modelling works are then combined with the modelling of the far-field transport and dilution of the underwater plume, and alsothe modelling of the spreading and transport of larvae from spawningareas. By combining the calculation of the concentration fields withthe spreading calculations of the larvae, the exposure of a total larvae population (one year stock) can be estimated. The paper concludes that under unfavourable conditions, the overlap between the hydrocarbon concentration fields and the geographical distribution of larvaeat its most vulnerable stage may cause a significant impact on a population level. [ABSTRACT FROM AUTHOR]

This paper presents a sub-sea blowout model designed with special emphasis on deep-water conditions. The model is an integral plume modelbased on a Lagrangian concept. This concept is applied to multiphasedischarges in the formation of water, oil and gas in a stratified water column with variable currents. The gas may be converted to hydrate in combination with seawater, dissolved into the plume water, or leaking out of the plume due to the slip between rising gas bubbles andthe plume trajectory. Non-ideal behaviour of the gas is accounted for by the introduction of pressure- and temperature-dependent compressibility z-factor in the equation of state. A number of case studies are presented in the paper. One of the cases (blowout from 100 m depth) is compared with observations from a field experiment conducted in Norwegian waters in June 1996. The model results are found to comparefavourably with the field observations when dissolution of gas into seawater is accounted in the model. For discharges at intermediate toshallow depths (100/250 m), the two major processes limiting plume rise will be: (a) dissolution of gas into ambient water, or (b) bubbles rising out of the inclined plume. These processes tend to be self-enforcing, i.e., when a gas is lost by either of these processes, plume rise tends to slow down and more time will be available for dissolution. For discharges in deep waters (700/1500 m depth), hydrate formation is found to be a dominating process in limiting plume rise. [ABSTRACT FROM AUTHOR]