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In this work, we compare two different parameterisations for the wind velocity–component standard deviations. The first one is the (Hanna 1982) parameterisation, while the second is the (Scire et al. 2000) parameterisation, which provide the proper values and vertical structure for the wind standard deviations in the convective, neutral and stable layers, needed as input the Lagrangian stochastic model SPRAYWEB. The results of the model simulations carried out using the two parameterisations are compared, in terms of both mean concentration and concentration standard deviation, by evaluating some statistical indexes and trough scatter- and qq-plots. [ABSTRACT FROM AUTHOR]

Human–robot interaction has extended its application horizon to simplify how human beings interact with each other through a remotely controlled telepresence robot. The fast growth of communication technologies such as 4G and 5G has elevated the potential to establish stable audio–video-data transmission. However, human–robot physical interactions are still challenging regarding maneuverability, controllability, stability, drive layout, and autonomy. Hence, this paper presents a systematic design and control approach based on the customer's needs and expectations of telepresence mobile robots for social interactions. A system model and controller design are developed using the Lagrangian method and linear quadratic regulator, respectively, for different scenarios such as flat surface, inclined surface, and yaw (steering). The robot system is capable of traveling uphill (30 ∘ ) and has a variable height (600–1200 mm). The robot is advantageous in developing countries to fill the skill gaps as well as for sharing knowledge and expertise using a virtual and mobile physical presence. [ABSTRACT FROM AUTHOR]

Fast simulation tools for the prediction of transient particle transport are critical in designing the air distribution indoors to reduce the exposure to indoor particles and associated health risks. This investigation proposed a combined fast fluid dynamics (FFD) and Markov chain model for fast predicting transient particle transport indoors. The solver for FFD-Markov-chain model was programmed in OpenFOAM, an open-source CFD toolbox. This study used two cases from the literature to validate the developed model and found well agreement between the transient particle concentrations predicted by the FFD-Markov-chain model and the experimental data. This investigation further compared the FFD-Markov-chain model with the CFD-Eulerian model and CFD-Lagrangian model in terms of accuracy and efficiency. The accuracy of the FFD-Markov-chain model was similar to that of the other two models. For the two studied cases, the FFD-Markovchain model was 4.7 and 6.8 times faster, respectively, than the CFD-Eulerian model, and it was 137.4 and 53.3 times faster than the CFD-Lagrangian model in predicting the steady-state airflow and transient particle transport. Therefore, the FFD-Markov-chain model is able to greatly reduce the computing cost for predicting transient particle transport in indoor environments. [ABSTRACT FROM AUTHOR]

In the framework of the Urban Dispersion International Evaluation Exercise (UDINEE) project coordinated by the European Commission's Joint Research Centre, a case study was conducted of the Joint Urban 2003 (JU2003) experimental campaign in the central area of Oklahoma City, USA. The UDINEE project concerned the cases of puff dispersion of the JU2003 campaign, which are of special interest to scenarios related to security studies, such as explosions of radiological dispersal devices. Starting from the fact that puff-dispersion variability is substantial, especially in complex urban areas, even for puffs released under similar meteorological conditions, a methodology is presented for assessing this variability, which is applied to the dispersion of puffs in two of the intensive operation periods of the JU2003 campaign. Lagrangian and Eulerian dispersion models are applied for the simulations. For the Lagrangian model, variability is assessed by repeating the computations a large number of times. For the Eulerian model, variability is assessed by constructing probability density functions of concentrations on the basis of the dispersion-model results. Peak concentrations, dosages, puff-arrival times and puff durations are considered. Percentiles calculated by the Lagrangian model for all the above quantities and by the Eulerian model for peak concentrations and dosages are compared with the measurements. The results are encouraging since in several cases the measured and computed ranges of values overlap. [ABSTRACT FROM AUTHOR]

The motion of bedload particles is diffusive and occurs within at least three scale ranges: local, intermediate and global, each of which with a distinctly different diffusion regime. However, these regimes, extensions of the scale ranges and boundaries between them remain to be better defined and quantified. These issues are explored using a Lagrangian model of saltating grains over the uniform fixed bed. The model combines deterministic particle motion dynamics with stochastic characteristics such as probability distributions of step lengths and resting times. Specifically, it is proposed that a memoryless exponential distribution is an appropriate model for the distribution of rest periods while the probability that a particle stops after a current jump follows a binomial distribution, which is a distribution with lack of memory as well. These distributions are incorporated in the deterministic Lagrangian model of saltating grains and extensive numerical simulations are conducted for the identification of the diffusive behavior of particles at different time scales. Based on the simulations and physical considerations, the local, intermediate, and global scale ranges are quantified and the transitions from one range to another are studied for a spectrum of motion parameters. The obtained results demonstrate that two different time scales should be considered for parameterization of diffusive behavior within intermediate and global scale ranges and for defining the local-intermediate and intermediate-global boundaries. The simulations highlight the importance of the distributions of the step lengths and resting times for the identification of the boundaries (or transition intervals) between the scale ranges. [ABSTRACT FROM AUTHOR]

The Global Lagrangian Atmospheric Dispersion Model (GLADIM) is described. GLADIM is based on the global trajectory model, which had been developed earlier and uses fields of weather parameters from different atmospheric reanalysis centers for calculations of trajectories of air mass that include trace gases. GLADIM includes the parameterization of turbulent diffusion and allows the forward calculation of concentrations of atmospheric tracers at nodes of a global regular grid when a source is specified. Thus, GLADIM can be used for the forward simulation of pollutant propagation (volcanic ash, radionuclides, and so on). Working in the reverse direction, GLADIM allows the detection of remote sources that mainly contribute to the tracer concentration at an observation point. This property of Lagrangian models is widely used for data analysis and the reverse modeling of emission sources of a pollutant specified. In this work we describe the model and some results of its validation through a comparison with results of a similar model and observation data. [ABSTRACT FROM AUTHOR]

A new approach is proposed to predict concentration fluctuations in the framework of one-particle Lagrangian stochastic models. The approach is innovative since it allows the computation of concentration fluctuations in dispersing plumes using a Lagrangian one-particle model with micromixing but with no need for the simulating of background particles. The extension of the model for the treatment of chemically reactive plumes is also accomplished and allows the computation of plume-related chemical reactions in a Lagrangian one-particle framework separately from the background chemical reactions, accounting for the effect of concentration fluctuations on chemical reactions in a general, albeit approximate, manner. These characteristics should make the proposed approach an ideal tool for plume-in-grid calculations in chemistry transport models. The results are compared to the wind-tunnel experiments of Fackrell and Robins (J Fluid Mech, 117:1-26, ) for plume dispersion in a neutral boundary layer and to the measurements of Legg et al. (Boundary-Layer Meteorol, 35:277-302, ) for line source dispersion in and above a model canopy. Preliminary reacting plume simulations are also shown comparing the model with the experimental results of Brown and Bilger (J Fluid Mech, 312:373-407, ; Atmos Environ, 32:611-628, ) to demonstrate the feasibility of computing chemical reactions in the proposed framework. [ABSTRACT FROM AUTHOR]

The importance of particle-particle collisions in sediment saltation in the bed-load layer is analyzed herein by means of numerical simulation. The particle saltation theoretical/numerical model follows a Lagrangian approach, and addresses the motion of sediment particles in an open channel flow described by a logarithmic velocity profile. The model is validated with experimental data obtained from the literature. In order to evaluate the importance of the phenomenon, simulations with and without particle-particle collisions were carried out. Results for two different sediment concentrations are presented, namely 0.13% and 2.33%. For each concentration of particles, three different flow intensities were considered, and trajectories of two different particle sizes, within the sand range were computed. Changes in particle rotation, particle velocity, and angle of trajectory before and after particle-particle collisions appear to be relatively important at lower shear stresses, whereas they decrease in significance with increasing flow intensities. Analyses of the evolution in time of the second order moment of particle location suggest that inter-particle collisions introduce transverse diffusion in saltating particles in the span-wise direction. [ABSTRACT FROM AUTHOR]

A numerical study of the gas–liquid–solid multiphase flow in hydrocyclones is presented. Three models of turbulence, the RNG k–ε model, the Reynolds stress model and Large eddy simulation with the volume of fluid model (VOF) multiphase model for simulating air core are compared in order to predict axial and tangential velocity distributions. This presentation is mainly aimed at identifying an optimal method, used to study effective parameters, based on which, eventually, effect of inlet flow rate variations and body dimension variations such as underflow diameter, overflow diameter and cone angle on the separation performance and pressure drop are investigated. The results are then used in the simulation of particle flow described by the stochastic Lagrangian model. The results suggest that the predicted size classifications are approximately similar to those of RSM and LES methods. Predictions using the RSM model are found in agreement with experimental results with a marginal error within the range of 4 to 8%. Proceeding model validation, parametric studies have been carried out concerning the influence of velocity inlet, particle size and body dimension such as underflow and overflow diameter and cone angle. The predictions demonstrate that the flow fields in the hydrocyclones with different sizes and lengths are different, which yields different performances. [ABSTRACT FROM AUTHOR]

To efficiently simulate the advection-diffusion processes along and across density surfaces, we need to deal with a diffusivity tensor containing off-diagonal elements (Redi, J Phys Oceanogr, 12:1154–1158, 1982). In the present paper, the Lagrangian model, in case of a space-varying diffusivity tensor, is developed. This random walk model is applied for two idealized test cases for which the analytical solutions are known. Results of the testing show that the Lagrangian approach provides accurate and effective solutions of advection-diffusion problems for general diffusivity tensor. [ABSTRACT FROM AUTHOR]

We propose a two-dimensional Lagrangian analytical solution for relating source strength and concentration profiles within and above a plant canopy. The new solution describes passive scalar dispersion under conditions of local advection through a fetch correction function in a one-dimensional Lagrangian analytical dispersion model. The model is capable of predicting absolute concentration profiles of passive scalars for different fetches for situations in which the reference concentration is known or the background concentration is available. Tests of the model showed good agreement with measurements from field and wind-tunnel experiments. [ABSTRACT FROM AUTHOR]

Profiles of velocity variances based on observations in flat rural areas are well established, and are used for modelling turbulent dispersion in all types of regions including those of complex terrain and urban areas. Surface-based and balloon observations are used to assess the profiles in both rural and urban areas. It is shown that, with good meteorological inputs for the locality of friction velocity and surface sensible heat flux, the profiles are equally well suited to urban areas. The sensitivity of the profiles to the input meteorological data, in particular using numerical weather prediction (NWP) data, is discussed. This highlights the limitations of NWP data for dispersion modelling and stresses the importance of schemes for modelling urban meteorology. [ABSTRACT FROM AUTHOR]

An Eulerian model and a Lagrangian particle model are used to study the dispersion of a contaminant released from a low source in the Stable Boundary Layer (SBL) using two different turbulence parameterisations. The Eulerian model is based on the solution of the advection-diffusion equation by the Laplace transform technique. The Lagrangian model is based on a generalized form of the Langevin equation. The first parameterisation, Degraziaet al. (2000), is based on Taylor’s statistical diffusion theory and the observed spectral properties, supposes a linear combination between shear and buoyancy turbulence. The second, Hanna (1982), is based on observed spectral properties from Minnesota Planetary Boundary Layer (PBL) observations and is widely used in pollutant dispersion models. Considering that these simulations are in the SBL, the analysis of the results shows a reasonably good agreement between the values computed by the models against the experimental ones for the two turbulence parameterisations. [ABSTRACT FROM AUTHOR]

This study proposes a two-dimensional Lagrangian stochastic dispersion model for estimating spatial and temporal variation of scalar sources, sinks, and fluxes within a forest canopy. Carbon dioxide and heat dispersion experiments were conducted for field testing the model. These experiments also provided data for field testing a newly developed one-dimensional Lagrangian analytical dispersion model. It was found that these two models produce similar scalar source-sink and flux distribution patterns. Comparing with CO2 flux measurements, the one-dimensional model performed as well as the two-dimensional model even when the fetch is short (≈100 m). To drive these Lagrangian models, velocity statistics through the canopy volume must be specified a priori. The sensitivity of the computed sources, sinks, and fluxes to the description of the flow statistics was further examined. All in all, we found good agreement between model predicted and eddy-correlation measured CO2 and sensible heat fluxes. [ABSTRACT FROM AUTHOR]

High-resolution hydrodynamic models are a common tool to simulate water dynamics in estuaries. Results from these models are, however, difficult to interpret without the aid of additional parameters to integrate the information. In this paper a methodology to understand the transport patterns in the Tagus Estuary is proposed. It is based on the computation of two renewal time scales: residence time and integrated water fraction. This last parameter is used to build a dependency matrix that gives the integrated influence of each region of the estuary at a selected point. The parameters are computed using a Lagrangian transport model coupled to the hydrodynamic model. Results show that Tagus Estuary has two different types of regions: the central part of the estuary, with low renewal efficiency, and three regions with higher renewal efficiency. Renewal mechanisms are, however, different for each region as shown by the dependency matrix. Comparison of renewal time scales with results from a water-quality model revealed that residence time is not a limiting parameter for primary production in the Tagus Estuary. [ABSTRACT FROM AUTHOR]

Marine litter has been defined as solid materials of human origin discarded at sea, or reaching the sea through waterways. The effect of marine debris on wildlife, tourism and human health is well documented and there is considerable scientific literature about plastic litter in the sea and over the seabed, mostly highlighting the possible impact on marine mammals and tourism. Dispersal of marine and terrestrial organisms on floating objects has biogeographical and ecological interest. For some species, extension of their geographical range is more likely to be related to transport of mature individuals on floating rafts than to the active or passive dispersal of reproductive propagules. Variability and variety of rafting materials has increased dramatically in recent years and marine litter has been used widely as a raft by `hitch-hiking' species. This paper reports on the benthic invertebrates living on marine debris transported by wind and surface currents over the western Mediterranean Sea. Plastics accounted for the major item of debris because of poor degradability, however glass, cans, fishing nets and polyurethane containers, were also found. Macro-benthos living on raft material comprised mainly molluscs, polychaetes and bryozoans. Large fish were found commonly below large plastic bags. Estimations of the distances that may be covered by hitch-hiking species and the contribution of rafting to the theoretical dispersal of species is provided. [ABSTRACT FROM AUTHOR]

Aiming at providing numerical tools useful to assess the impacts of coastal development pressures on marine life, a Lagrangian model for population dynamics of pelagic eggs and larvae of the greasyback shrimp, Metapenaeus ensis, in Osaka Bay was developed and improved based on laboratory experiments. The model was combined with a 3-D Eulerian numerical model that predicts physical and biological conditions of the habitat. A series of numerical experiments was done to investigate their transport processes from the spawning grounds, and the concentration process of full-grown larvae towards the mouth of Yodo River that flows into the innermost basin. Model results revealed, as a general tendency, that the early larval developmental stages through nauplius to zoea continue to drift like a passive tracer, and begin to concentrate at the river mouth area after the mysis stage, mainly avoiding low saline environment in the surface layer. This suggests that the full-grown larvae may be favored with chance to take advantage of the river-induced gravitational circulation that dominates the innermost estuarine basin. In addition, it was found that tidal condition around the spawning period also exerts a considerable influence upon the fate of pelagic larvae. [ABSTRACT FROM AUTHOR]

A Lagrangian model was developed to predict the vertical distribution of pheromone in apple orchards treated with synthetic pheromone released from polyethylene tubing dispensers. Measurements of tree dimensions' dispenser heights, air temperature, and wind speed were used as inputs to the model. Data to test the model output were obtained by air sampling and capillary gas chromatography to determine atmospheric pheromone concentration. The model predicted highest concentrations of pheromone in the plane of the dispensers. Predicted and measured concentrations were in the range 0.5–5 ng/m3 for blocks treated with 1000 or 2000 dispensers/ha. Mean wind speed had a large influence on pheromone concentrations within the canopy with concentrations decreasing at higher wind speeds. Wind speeds <0.1 m/sec, which represent good flying conditions for moths, resulted in high levels of mean pheromone concentration. Dispenser height had only a small influence on the maximum pheromone concentration, with the peak concentrations decreasing with increasing application height. The lower peak concentration for an elevated dispenser occurred mainly because wind speeds were higher in the upper parts of the tree canopy. Air temperature, dispenser density, and pheromone release rate (as inferred by dispenser liquid length), also had a significant influence on pheromone concentration because of the linear relationship between these parameters and the corresponding flux of pheromone released into the treated orchards. We use known scaling relationships to demonstrate these effects. [ABSTRACT FROM AUTHOR]

The characteristics of turbulence within a forest are spatially heterogeneous and distinct from those associated with the surface boundary layer. Consequently, the size and probability distribution of ’flux footprints‘ emanating from sources below a forest canopy have the potential to differ from those observed above forests. A Lagrangian random walk model was used to investigate this problem since no analytical solution of the diffusion equation exists. Model calculations suggest that spatial characteristics of ’flux footprint‘ probability distributions under forest canopies are much contracted, compared to those evaluated in the surface boundary layer. The key factors affecting the statistical spread of the ’flux footprint‘, and the position of the peak of its probability distribution, are horizontal wind velocity and the standard deviations of vertical and horizontal velocity fluctuations. Consequently, canopies, which attenuate mean horizontal wind speed, or atmospheric conditions, which enhance vertical velocity fluctuations, will contract flux footprint distributions mostly near the floor of a forest. It was also found that the probability distributions of the ’flux footprint‘ are narrower when horizontal wind velocity fluctuations are considered, instead of the simpler case that considers only vertical velocity fluctuations and mean horizontal wind velocity. [ABSTRACT FROM AUTHOR]

The Lagrangian equations of motion of small solid particle in turbulent boundary layer flows, taking into account the effects of the drag force caused by the wall presence, the Saffman and the Magus lift forces et al., is studied. Using the spectral method, analytical expressions relating to the Lagrangian power spectra of particle velocity to that of the fluid are developed and the results are used to evaluate various response statistics. In this paper, the results clearly show that the turbulent diffusivity of the particle may be larger than that of the fluid for a period of long-time. [ABSTRACT FROM AUTHOR]

The purpose of this work is to develop a reliable numerical model for the spray dryer desulfurization system. The shape of the spray dryer requires that a body fitted orthogonal coordinate system be used for the numerical model. The governing equations are developed in the general orthogonal coordinates and discretized to yield a system of algbraic equations. A modified two-equation turbulence model is also included in the numerical program. The stability of QUICK scheme is investigated and the Absolutely Stable QUICK scheme is developed and included in the numerical model. The trajectory approach is used to simulate the flow of the dispersed phase. Two-way coupling phenomena is modeled by this sheme. The absorption of sulfur dioxide into lime slurry droplets is simulated by a model based on gas-phase mass transfer. The program is applied to a typical spray dryer desulfurization system. The reuslts show the capability of the program to predict the sensitivity of system performance to change in operational parameters. [ABSTRACT FROM AUTHOR]