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A better understanding of oil droplet formation, degradation, and dispersal in deep waters is needed to enhance prediction of the fate and transport of subsurface oil spills. This research evaluates the influence of initial droplet size and rates of biodegradation on the subsurface transport of oil droplets, specifically those from the Deepwater Horizon oil spill. A three-dimensional coupled model was employed with components that included analytical multiphase plume, hydrodynamic and Lagrangian models. Oil droplet biodegradation was simulated based on first order decay rates of alkanes. The initial diameter of droplets (10–300 μ m) spanned a range of sizes expected from dispersant-treated oil. Results indicate that model predictions are sensitive to biodegradation processes, with depth distributions deepening by hundreds of meters, horizontal distributions decreasing by hundreds to thousands of kilometers, and mass decreasing by 92–99% when biodegradation is applied compared to simulations without biodegradation. In addition, there are two- to four-fold changes in the area of the seafloor contacted by oil droplets among scenarios with different biodegradation rates. The spatial distributions of hydrocarbons predicted by the model with biodegradation are similar to those observed in the sediment and water column, although the model predicts hydrocarbons to the northeast and east of the well where no observations were made. This study indicates that improvement in knowledge of droplet sizes and biodegradation processes is important for accurate prediction of subsurface oil spills.

Highlights: [•] This article presents a family of macroscopic higher order traffic flow models, which encompasses many current macroscopic models. [•] The Lagrangian expression of this family, following a partial integration, can be recast as a Hamilton–Jacobi equation and admits a variational interpretation. [•] The variational methods, notably the inf-morphism and Lax–Hopf formulas, can be suitably extended to this family of models. [Copyright &y& Elsevier]

A computational framework for dynamic three-phase pipe flow is presented and compared with some severe liquid slugging experiments with air–oil–water flow in an S-shaped riser. The model is based on a hybrid slug capturing and slug tracking formulation, in which a full two-fluid formulation is used in the stratified flow regions. A tracking scheme based on a single liquid momentum balance over the length of the liquid slug is used for the slug region. Slug fronts and bubble noses are tracked with a moving computational grid. This allows for correct reproduction of bubble nose velocities and eliminates numerical diffusion. A mixture liquid momentum formulation for the oil–water mixture is applied, and demonstrated with a simplistic liquid–liquid slip velocity model which includes a gradual transition from separated to mixed oil–water flow. The simulations compare well with the severe slugging experiments, both with respect to pressure amplitude and slugging period. [ABSTRACT FROM AUTHOR]

Abstract: A novel Lagrangian algebraic slip mixture model (LASMM) has been developed to study multiphase flows. In this model, the slip velocity between continual and dispersed phases was developed through the bubble Lagrangian movement equation. According to the Lagrangian equation, the various interfacial forces at interface of the continual and dispersed phases were considered. Through the connection of the slip velocity, the Lagrangian equation was induced into the governing Eulerian equations of the two-phase mixture flow. This model therefore realized the connection between Eulerian model and Lagrangian model. Through the comparisons of the numerical simulations to the experiments in horizontal pipe, this model was validated. [Copyright &y& Elsevier]

Abstract: A new method for the buoyant plume rise computation is proposed. Following Alessandrini and Ferrero (Phys A 388:1375–1387, 2009) a scalar transported by the particles and representing the temperature difference between the plume and the environment air is introduced. As a consequence, no more particles than those inside the plume have to be released to simulate the entrainment of the background air temperature. A second scalar, the vertical plume velocity, is assigned to each particle. In this way the entrainment is properly simulated and the plume rise is calculated from the local property of the flow. The model has been tested against data from two laboratory experiments in neutral and stable stratified flows. The comparison shows a good agreement. Then, we tested our new model against literature analytical formulae in a simple uniform neutral atmosphere, considering either the case of a single plume or the one of two plumes from adjacent stacks combining during the rising stage. Finally, a comparison of the model against an atmospheric tracer experiment (Bull Run), characterized by vertically non-homogeneous fields (wind velocity, temperature, velocity standard deviations and time scales), was performed. All the tests confirmed the satisfactory performance of the model. [Copyright &y& Elsevier]

Highlights: [•] A model was developed to simulate the transport and dispersion of Asian carp eggs. [•] The performance of FluEgg was evaluated against data obtained from published flume experiments. [•] FluEgg outputs provide valuable insights into egg suspension and settlement. [•] FluEgg predicts drifting behaviors of Asian carp eggs based on stream properties. [•] FluEgg provides useful information about the location of potential spawning grounds. [Copyright &y& Elsevier]

Delpeche-Ellmann, N.C., Soomere, T., 2013. Using Lagrangian models to assist in maritime management of Coastal and Marine Protected Areas Several previous attempts to mitigate current-driven environmental risks to the nearshore via a concealed structure of surface Lagrangian transport have assumed a constant value to the entire nearshore. We extend these attempts towards more realistic accounting for the Coastal and Marine Protected Areas (MPA). We investigate the effects shifting the present fairway would have on the amount of current-driven pollutants the MPA may receive. The Rossby Centre Ocean circulation model, the TRACMASS Lagrangian trajectory model and statistical methods were employed to identify patterns of current-driven transport in the Gulf of Finland, the Baltic Sea, for the period 1987-1991. Pollution point sources were assumed to occur along the fairway. An analysis was made on how much of the pollution travelled to each of the MPA and the time frame involved. The existing fairway passes extremely close to one of the MPA. Shifting the fairway by a small distance to the south leads to a huge decrease in the amount of pollution. However deciding to shift a fairway requires several other factors to be considered, for this may also increase the risk of pollution for other MPAs or be incompatible with the national legislation. [ABSTRACT FROM AUTHOR]

The research described in this article concerns contaminant intrusion into a water distribution system associated with transient events. A Lagrangian-based contaminant transport model was coupled with an Eulerian-based transient hydraulic model to study contaminant intrusion and its propagation in a water distribution system. The hydraulic model was used to detect negative pressures during normal system operations. The Lagrangian-based contaminant transport model reduced simulation time and avoided numerical dissipation and dispersion errors that often occur with Eulerian-based modeling. The proposed water quality model was used to evaluate two systems described in the literature for their potential vulnerability to contaminant intrusion. The new transient water quality model realistically simulated intrusion events and contaminant propagation in both systems. [ABSTRACT FROM AUTHOR]

Abstract: Jellyfish blooms are generally attributed to a biological response to the environment, neglecting the role of transport patterns in redistributing existing populations. Here, we use high-resolution (1.25km) ocean modeling to examine the role of transport in the onshore arrival and abundance of the pelagic stinging jellyfish Pelagia noctiluca on the Ligurian Sea coast. Jellyfish are modeled as Lagrangian particles with a 0–300-m diel vertical migration typical of P. noctiluca. Over the course of a year, onshore arrivals are not restricted to the summer. Arrivals are concentrated at capes, but abundance can reach maxima in bays and in the lee of capes. Two factors impact jellyfish arrivals at the coast: the position of the Northern Current and the wind. A comparison of summer 2006 and available onshore jellyfish observations suggests a correct capture of the main stranding events by the model. These results have implications for understanding long-term fluctuations. [Copyright &y& Elsevier]

Abstract: A Lagrangian model of a surface-advected river plume is developed. The model combines the deterministic approach resulting from the momentum budget with a random-walk scheme. We validated and applied the model to the conditions of the region adjacent to the Mzymta River estuary in the Black Sea. Further, using the model, we investigated the dependencies between the spatial extent of the plume and the wind stress τ. The character of these dependencies proved to depend critically on the wind direction with respect to the geometry of the coast and the river mouth. With the offshore and “downwelling favorable” alongshore winds, the plume area initially grows with the increase of τ, and then starts to decrease when τ exceeds a certain critical value. With the onshore wind, the area decreases steadily (though not linearly) as τ increases. The most complex behavior is observed for the “upwelling favorable” alongshore wind: the plume area initially decreases until the wind stress exceeds a certain critical value, then starts to increase with τ and attains a maximum, and then eventually drops to zero as τ continues to increase. As expected, the increase of the inflow velocity, i.e., discharge rate, resulted in the growth of the plume area, while the patterns of the dependencies between the plume area and the wind stress configurations were robust in the broad range of intermediate discharge values. We also investigated the dependence of the plume area on the latitude, with all other conditions kept fixed. This dependence exhibited a distinct “M-shaped” pattern, with minima corresponding to the equatorial and polar regions, and maxima in the tropics. However, even moderate wind stress largely offsets the effect of the changing Coriolis parameter and strongly distorts the shape of the curve. [Copyright &y& Elsevier]

Abstract: It is important to accurately model person-to-person particle transport in mechanical ventilation spaces to create and maintain a healthy indoor environment. The present study introduces a hybrid DES-Lagrangian and RANS-Eulerian model for simulating transient particle transport in enclosed environments; this hybrid model can ensure the accuracy and reduce the computing cost. Our study estimated two key time constants for the model that are important parameters for reducing the computing costs. The two time constants estimated were verified by airflow data from both an office and an aircraft cabin case. This study also conducted experiments in the first-class cabin of an MD-82 commercial airliner with heated manikins to validate the hybrid model. A pulse particle source was applied at the mouth of an index manikin to simulate a cough. The particle concentrations versus time were measured at the breathing zone of the other manikins. The trend of particle concentrations versus time predicted by the hybrid model agrees with the experimental data. Therefore, the proposed hybrid model can be used for investigating transient particle transport in enclosed environments. [Copyright &y& Elsevier]

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]

Abstract: Particulate matter remains a challenging pollutant for air pollution control in the UK and across much of Europe. Particulate matter is a complex mixture of which secondary inorganic compounds (sulphates, nitrates) are a major component. This paper is concerned with taking a basic version of the UK Photochemical Trajectory Model and enhancing a number of features in the model in order to better represent boundary layer processes and to improve the description of secondary inorganic aerosol formation. The enhancements include an improved treatment of the boundary layer, deposition processes (both wet and dry), attenuation of photolysis rates by cloud cover, and inclusion of the aerosol thermodynamic model ISORROPIA II to account both for chemistry within the aerosol and between the particles and gas phase. Emissions inventories have been updated and are adjusted according to season, day of the week and hour of the day. Stack emissions from high level sources are now adjusted according to the height of the boundary layer and a scheme for generating marine aerosol has been included. The skill of the improved model has been evaluated through predictions of the concentrations of particulate chloride, nitrate and sulphate and the results show increased accuracy and lower mean bias. There is a much higher proportion of the values lying within a factor of 2 of the observed values compared to the basic model and Normalised Mean Bias has reduced by at least 89% for nitrate and sulphate. Similarly, the Index of Agreement between calculated and measured values has improved by ∼10%. Considering the contribution of each enhancement to the improvement in the performance metrics, the most significant enhancement was the replacement of the parameterisation of the boundary layer height, relative humidity and temperature by HYSPLIT values calculated for each trajectory. The second most significant enhancement was the parameterisation of the photolysis rates by values calculated by an off line database accounting for the dependence of photolysis rates on zenith angle, cloud cover, land surface type and column ozone. The inclusion of initial conditions which were dependent on the starting point of the trajectory and the modulation of stack emissions made the most significant improvement to sulphate. Furthermore, in order to assess the model''s response to abatement scenarios, 30% abatements of either NH3, NOx or SO2 showed a reduction in the sum of chloride, nitrate and sulphate of between 3.1% and 8.5% (with a corresponding estimated reduction of 1.6–3.7% reduction in PM10). The largest reduction in this contribution is due to the abatement of NOx. [Copyright &y& Elsevier]

The article presents a study which uses the Modelo Hidrodinâmico (MOHID) model system to assess the health, specifically of bacteria Escherichia coli contamination, of marine water bodies along the inner part of Bahía Blanca estuary. The concept of lagrangian tracers is cited to be used in evaluating the spatial-temporal evolution of pollution plume. Variability and means indicator organism counts are presented to be accurately predicted by the fate models. The model results are suggested as a useful tool for reducing pollution in the estuary.

Abstract: A numerical model (TurbSeed) is described which calculates explicitly the dispersal of plant seeds by wind, especially the fraction of seeds, which are transported more than 100m starting at the inflorescence. Such rare events are called here long-distance dispersal. The framework of TurbSeed includes three main modules: [(1)] A turbulence model (TM) for a specified location and time period using meteorological parameters from publicly available mesoscale weather models or simulated climate data. [(2)] A Lagrangian model (LM) which calculates the seed transport in the turbulent boundary layer and [(3)] A module which considers the effect of weather conditions on release of seeds (RS). In this approach the turbulent field is prescribed by a coarse wind field derived from the mesoscale climate simulations superimposed by a random velocity component. Similar approaches are known as Eulerian–Lagrangian approaches. The main difference in this new approach (TM) lies in the construction of the turbulent structure of the wind field. The introduction of such a random velocity component uses the Monin–Obukhov similarity theory. An inverse random phase Fast-Fourier-Transformation reconstructs the time structure of turbulence using a parameterized power spectrum of turbulence which is accepted as standard in micro meteorology. In the LM module Monte-Carlo-Simulations for numerous trajectories are used to incorporate the effects of turbulence. The RS module takes into account various conditions of release of plant seeds, such as the date of maturity of the seeds and the effect of wind speed on the release of seeds. This model can be driven not only with data from observed weather conditions, but also with output of mesoscale climate scenarios. Thus, TurbSeed can study the effect of climate change on wind dispersal of seeds. [Copyright &y& Elsevier]

Abstract: We describe a backward-time Lagrangian air quality model based on time-reversed, stochastic particle trajectories. The model simulates the transport of air parcels backward in time using ensembles of fictitious particles with stochastic motions generated from the Stochastic Time-Inverted Lagrangian Transport model (STILT). Due to the fact that STILT was originally developed out of the HYSPLIT lineage, the model leverages previous work () that implemented within HYSPLIT a chemical scheme (CB4). Chemical transformations according to the CB4 scheme are calculated along trajectories identified by the backward-time simulations. This approach opens up several key advantages: 1) exclusive focus upon air parcels that affect the receptor''s air quality; 2) the separation of transport processes—elucidated by backward-time trajectories—from chemical reactions that enables implications of multiple emission scenarios to be probed; 3) the potential to incorporate detailed sub-gridscale mixing and transport phenomena that are not tied to Eulerian gridcells. The model was used to simulate concentrations of air quality-relevant species (O3 and NO x ) at eight measurement sites in the Canadian province of Ontario. The model-predicted concentrations were compared with observations, and comparisons show that simulated O3 concentrations usually agree well with observations across sites in rural areas, small towns, and big urban regions. Furthermore, the backward-time model showed improved performance over the previous approach involving forward-time particle trajectories, especially for O3. However, the model under-estimated NO x at sites away from the big cities, possibly due to the inability of the coarsely gridded emission grids to resolve fine-scale NO x sources. Influences of cross-border transport of U.S. emission sources on the test sites were investigated using the model by turning off anthropogenic and natural U.S. emission sources. The model results suggest that total U.S. emissions contributed more than 30% of O3 concentrations at the target sites and that over half of all hours during the simulation period were affected either by anthropogenic or natural emissions from the U.S. sources, indicating the importance of U.S. sources for air quality across Ontario. [Copyright &y& Elsevier]

The transport of particles in turbulent flows is a common problem in hydraulic engineering. In this paper, the focus is set on a numerical model used to simulate the transport of small bodies (debris, algae, etc.) along a coastline. In this problem, the particles are larger than the small turbulent eddies, but smaller than the large turbulent eddies, and sufficiently diluted within the flow so that each particle does not affect the flow or the motion of other particles. A mixed Eulerian–Lagrangian approach was chosen in order to model a large flow area with sufficient information for the turbulent diffusion. This model is validated through an experiment on particles released into a partially obstructed channel flow. The measurements are then compared with simulations using two Eulerian industrial codes, Telemac-2D and OpenFoam. Finally, an application to algae bloom transport in a harbour is presented. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, we are interested in the numerical treatment of a nonlinear model describing phytoplankton aggregation. The model consists in an integro-differential diffusion equation, with a chemotaxis term responsible for self-attraction of phytoplankton cells. We develop and implement a numerical scheme to solve this nonlinear PDE and present numerical solutions for parameters values corresponding to real conditions in nature. The numerical results emphasize the role of the nonlinear chemotaxis term in producing aggregating patterns and further, they are used to explore the asymptotic behavior of the model. [Copyright &y& Elsevier]

Abstract: Wire and Arc Additive Layer Manufacturing (WAALM) is gaining increasing popularity as the process allows the production of large custom-made metal workpieces with high deposition rates. The high power input of the welding process, causes significant residual stress and distortion of the workpiece. This paper describes the thermo-mechanical behaviour of the multi-layer wall structure made by the WAALM process. A 3D thermo-elastic–plastic transient model and a model based on an advanced steady-state thermal analysis are employed in this study. This modelling approach shows a significant advantage with respect to the computational time. The temperature simulations and distortion predictions are verified by comparing with the experimental results from thermo-couples and laser scanners, while the residual stresses are verified with the neutron diffraction strain scanner ENGIN-X. The stress across the deposited wall is found uniform with very little influence of the preceding layers on the following layers. The stress redistributed after unclamping with a much lower value at the top of the wall than at the interface due to the bending distortion of the sample. [Copyright &y& Elsevier]

Abstract: This paper introduces a numerical simulation model for investigating the influence of moving subjects on the dispersion and deposition of expiratory droplets, rather than on the dispersion of surrogate gaseous counterparts generally adopted in related research works. In our work, the Lagrangian discrete trajectory model is used for tracing the motion of droplets, the Eulerian RANS method is used for solving the airflow field, and the dynamic mesh model for describing the human movement. The model validation was performed through result comparisons with published data from literatures. A case study on the influence of human walking on the dispersion and deposition of expiratory droplets in an airborne infection isolation room (AIIR) is then presented. Our findings show that the human walking disturbs the local velocity field with wake formation. The increase of walking speed could effectively reduce the overall number of suspended droplets, which may have a positive impact on releasing the infection risk of health workers in AIIR. [Copyright &y& Elsevier]

Abstract: The Canary Upwelling System (CUS), a major eastern boundary upwelling system, sustains large cross-border fisheries of small pelagic fish, which poses the question of stock connectivity. Studies suggest that ichthyoplankton transport from the northwest African coast to the Canary Islands (CI) is facilitated by coastal-upwelling associated filaments. Here we analyze connections between larval supply to the CI and sardine and anchovy populations that spawn over the continental shelf. For both species, ichthyoplankton observations (1) at the shelf and (2) near the island of Gran Canaria (GC) are used. Predictions of ichthyoplankton transport to GC are obtained from the Ichthyop Lagrangian transport model, which is forced by a high-resolution hydrodynamic model (ROMS) that reproduces the regional circulation. Results show that upwelling filaments play an important role in the transport of larvae to GC. However, (1) filaments are not the only mechanism, and (2) filament presence does not necessarily imply larval transport. Anchovy and sardine larval presence at GC appears to be independent of the respective adult spawning seasonality. Combining of observed and modeled data does not succeed in reproducing the observed larval patterns at GC. Various hypotheses are proposed to explain this discrepancy in larval transport to GC. [Copyright &y& Elsevier]

Abstract: This paper presents a numerical study of a gas-particle flow in three inclined rectangular jets in crossflow. The predicted gas phase velocities and particle phase velocities are validated against previously reported experimental data. Two turbulence models, the standard k–ɛ model and Shear Stress Transfer (SST) model, are used to model the gas phase turbulence. This work shows that both models provide acceptable predictions of the gas flow and mixing generated by the three jets. Neither model could accurately reproduce the jet core and the flow near bottom wall. The particle phase in this flow comprises a large number of small particles. Thus particles follow the gas phase flow closely and any errors in the turbulence model and gas flow predictions are passed on to the particle phase simulation. This paper also includes a literature review on rectangular jets in crossflow and gas-particle laden jets in crossflow. [Copyright &y& Elsevier]

The effect of particle-particle collision on the trajectories of saltating grains in open-channel flows is investigated. The vertical distributions of saltating particles are also analysed. A stochastic particle-particle collision model was designed to determine the collision probability along a particle trajectory, based on the assumption that inter-particle collision frequency may be described by the formula of kinetic gas theory. This parameter is the key quantity for the calculation of collision probability. The Monte Carlo simulation method is used to obtain the velocity and concentration of saltating particles. It is the first attempt to apply a probabilistic inter-particle collision approach to Lagrangian modelling of saltating grains. Trajectories of different particles with and without particle-particle collision are compared with available data. The proposed procedure allows verification of the hypothesis regarding the effect of the particle-particle collision on sediment transport. The described mechanism affects the vertical particle concentration and therefore may play an essential role in bed-load sediment transport. [ABSTRACT FROM AUTHOR]

Abstract: This paper considers the behaviour of mono-disperse coarse glass particles in a pneumatic conveying experiment which consists of a curved and straight rectangular duct. Thus, the flow situation comprises the formation of a particle strand in the curved section as well as its dispersion in the subsequent straight horizontal channel. Thereby, from a physical point of view the effects of inter-particle collisions, particle rotation and wall roughness are of crucial importance. Based on this experimental setup six numerical models for the granular phase are applied in order to picture these physical phenomena. While the first set of three models – the (a) Lagrangian Discrete Phase (DP) model, the (b) Discrete Element Method (DEM) and the (c) ‘standard’ Eulerian-granular (EUgran) model – is readily available in commercial codes the remaining three models represent in-house developments. As a first modification the standard DP model is enhanced by sub-models accounting for inter-particle collisions, wall roughness and particle rotation in order to get an (d) enhanced Discrete Phase (DP+) model. Next, two combinations between the Eulerian and Lagrangian models, the (e) Dense Discrete Phase Model (DDPM), and a (f) Eulerian based hybrid model (EUgran+) are presented and discussed. Thus, all in all six numerical models are evaluated by qualitatively checking the main flow pattern, subsequently by a quantitative validation of dedicated profiles of particle velocity and concentration and finally, by qualitatively comparing the computational effort of each numerical model. While all ‘out of the box’ models fail in predicting even basic flow patterns the remaining enhanced models agree well with the experimental results. Nevertheless, their required computational effort is significantly different. [ABSTRACT FROM AUTHOR]

Abstract: Models of harmful algal blooms (HABs) need to include autecological characteristics of the HAB species because the bloom dynamics can only be successfully described if relevant life cycle aspects (in particular en- and excystment) are included in some way. This study presents an overview on how the life cycle is considered in current Lagrangian and Eulerian models. Examples of the latter are given, which range from crude parameterizations in one-compartment models, to stage-resolving twelve-compartment models. Advantages and disadvantages of the different approaches are highlighted. A generalized model classification is presented which may be used as a framework for further phytoplankton life cycle modeling studies. [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]

Abstract: Humidification of chicory root cold stores helps in maintaining the quality and extending the postharvest storage time of chicory roots. Low evaporation rate of the sprayed droplets at such sub-zero temperatures (−2°C to −1°C) favours surface deposition that could have an adverse effect on the efficiency of the storage room. A three-dimensional computational fluid dynamics (CFD) model was developed and used to predict the storage room air velocity, temperature and humidity distributions, and fate of the water droplets that were sprayed for humidifying the storage room. The humidification system in a chicory root cold store was then optimized. The efficiency of the humidification system was affected by length of cold air deflector, stack height, number of nozzles and duration of humidification. Elongating the air deflector, reducing the stack height, reducing the number of nozzles and shortening the humidification time increased the amount of droplet evaporated and decreased the amount of droplet deposited on the stack. The following combinations of room design and operating parameters could clearly give the best performance of the humidification system: deflector length of 0.8m, two nozzles with an interval humidification of 1.5min on and 2min off cycle and stack height of 3.4m. [Copyright &y& Elsevier]

Abstract: In this paper, a Lagrangian-extended finite-element (FE) method is presented in modeling large-plasticity deformations and contact problems. The technique is used to model arbitrary interfaces in two-dimensional (2D)/three-dimensional (3D) large deformations. The material interfaces are represented independent of the FE mesh and the process is accomplished by integrating enriched elements with a larger number of Gauss points, whose positions are fixed in the element. The large elasto-plastic deformation formulation is employed within the eXtended Finite-Element Method (X-FEM) framework to simulate the nonlinear behavior of materials. The interface between two bodies is modeled by using the X-FEM technique and applying modified level set and Heaviside enrichment functions. Finally, several numerical examples of arbitrary material interfaces are modeled to demonstrate the efficiency of the Lagrangian X-FEM technique in large deformation of plasticity and contact problems. [Copyright &y& Elsevier]

Abstract: Satellite-derived sea surface temperature (SST) and chlorophyll ([Chl]) concentration maps are used together with numerical models to study the advection patterns observed during a summer upwelling event off central Portugal, a region characterized by a complex coastline and bathymetry. It is shown that the model solutions realistically reproduce the main patterns of spatial and temporal SST variability, namely the decrease in the active upwelling areas during the wind intensification phase, the 1-day lag between the peak of the northerlies and minimum SST, and the small SST variability in the sheltered embayments. The expected circulation features are reproduced in the model solutions: the strong along-slope flows, the development of filaments and separated jets, shadow areas downstream of main capes, frontal-scale instabilities and the rapid onset of coastal counter currents along the inshore zone during relaxation. The evolution of the oceanographic conditions, specifically the mixed layer depth and horizontal velocity, and the advection patterns obtained from a Lagrangian model are compared with the observed SST and [Chl] variability. The results imply that the potential phytoplankton accumulation/growth (PPAG) areas are characterized by surface temperatures lower than , mixed layer depth and horizontal velocity less than 30m and 0.3m/s, respectively. It is shown that remotely-sensed [Chl] concentration patterns, namely its asymmetric distribution relative to SST during the intense wind phase, is primarily related to the mixed layer depth and secondly to the horizontal velocity. The trajectories obtained with the Lagrangian model confirmed earlier suggestions of the presence of recirculation cells, downstream of the capes where the coastal jet separates from the coast, and revealed that significant vertical displacements occur in these cells. [Copyright &y& Elsevier]

Abstract: Humidification during long-term cooled storage of fruits is being introduced into practice to prevent excessive moisture loss and quality degradation. High pressure fogging is one of the few systems that can be used in ultra low oxygen (ULO) storage rooms. For system design and optimization, a CFD based multiscale model was used. At the smallest scale, the flow through stacked products in boxes was predicted using a direct model that combined discrete element (DE)-CFD modelling. At larger scale, a loaded cool room model that predicts the storage room air velocity, temperature and humidity distributions and fate of the water droplets was developed. The loaded product was considered as a porous medium, where the anisotropic loss coefficients were determined from a combined DE-CFD simulation. A Lagrangian particle tracking multiphase flow model was used. An interval humidification of 1min on and 15min off with a water pressure of 80bar (3.59Lh−1) for a ULO storage room at −1°C on average gave a relative humidity of 96.3%. The amount of sprayed water deposited on the stack and room surfaces depend on the application pressure and nozzle position and direction. Good agreement was found between measured and predicted results. [Copyright &y& Elsevier]

The prediction of the present and future impact of radioactivity release is important. However, there are several models and options to choose from. An integrated approach is proposed in this study and it is implemented to Istanbul Technical University (ITU) TRIGA Mark II Research Reactor. The procedure was divided into six steps including quantification of the source term, specification of meteorological data, atmospheric dispersion model selection, atmospheric dispersion and deposition calculation, biosphere and geosphere transport calculation, and finally dose and risk calculation. The acquisition of data and parameters for these steps were discussed in detail to provide insight to users of the integrated method. The evaluation of wind direction and speed defined in the safety analysis report of the reactor showed that the average wind direction at the reactor site altered from NE direction to NE-NNE over time but speed stayed almost the same. The maximum-total cloudshine and groundshine as a result of annual exposure rate were found as 21.1 μSv/yr at ITU Ayazağa Campus. For inhalation, Ba-140 and I-131 were found to have the highest risk in mortality and morbidity, respectively. The same is true for Sr-90 and I-131 in the lifetime intake of food while in the lifetime intake of tap water, Sr-90 is the leading radioisotope for both mortality and morbidity risks. However, all calculated values are quite low considering the survival rates. Moreover, the results of the study provides useful insight into the understanding of necessities while shedding light on limitations. [Display omitted] • Integrated methodology for radionuclide atmospheric dispersion and corresponding health risks. • Investigation of contamination of plants considering foliar and root uptake mechanisms. • Description of pathways of radionuclides to groundwater reservoirs and performance of related calculations. • Clarification of mortality and morbidity risk prediction methods due to consumption of contaminated food and water. [ABSTRACT FROM AUTHOR]