[1] This study was part of the international field measurement Campaigns of Air Quality Research in Beijing and Surrounding Region 2006 (CAREBeijing-2006). We investigated a new particle formation event in a highly polluted air mass at a regional site south of the megacity Beijing and its impact on the abundance and properties of cloud condensation nuclei (CCN). During the 1-month observation, particle nucleation followed by significant particle growth on a regional scale was observed frequently (~30%), and we chose 23 August 2006 as a representative case study. Secondary aerosol mass was produced continuously, with sulfate, ammonium, and organics as major components. The aerosol mass growth rate was on average 19 μg m -3 h -1 during the late hours of the day. This growth rate was observed several times during the 1-month intensive measurements. The nucleation mode grew very quickly into the size range of CCN, and the CCN size distribution was dominated by the growing nucleation mode (up to 80% of the total CCN number concentration) and not as usual by the accumulation mode. At water vapor supersaturations of 0.07-0.86%, the CCN number concentrations reached maximum values of 4000-19,000 cm -3 only 6-14 h after the nucleation event. During particle formation and growth, the effective hygroscopicity parameter κ increased from about 0.1-0.3 to 0.35-0.5 for particles with diameters of 40-90 nm, but it remained nearly constant at ~0.45 for particles with diameters of ~190 nm. This result is consistent with aerosol chemical composition data, showing a pronounced increase of sulfate.

Rapid aerosol particle growth and increase of cloud condensation nucleus activity by secondary aerosol formation and condensation: A case study for regional air pollution in northeastern China

The article aims at providing an up-to-date review on several latest advancements related to particle methods with applications in coastal and ocean engineering. The latest advancements corresponding to accuracy, stability, conservation properties, multiphase multi-physics multi-scale simulations, fluid-structure interactions, exclusive coastal/ocean engineering applications and computational efficiency are reviewed. The future perspectives for further enhancement of applicability and reliability of particle methods for coastal/ocean engineering applications are also highlighted.

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On the state-of-the-art of particle methods for coastal and ocean engineering

The δplus-SPH model: Simple procedures for a further improvement of the SPH scheme

Atti del convegno

Long-crested wave generation and absorption for SPH-based DualSPHysics model

SPH numerical modeling of wave–perforated breakwater interaction

Solitary wave-induced forces on horizontal circular cylinders: Laboratory experiments and SPH simulations

This paper deals with a two-dimensional numerical model based on the smoothed particle hydrodynamics (SPH) technique for the evaluation of the concentration field of pollutants in water. A SPH model is formulated to solve the fickian diffusion equation applied to pollutants with the same density as the water. A lagrangian SPH formalism of the advective diffusion equation is also developed for pollutant-water, taking into account the effects of molecular diffusion and natural advection induced by differences between the fluid densities. These equations are coupled with the fluid mechanics equations. Attention is paid to the numerical aspects involved in the solution procedure and to the optimization of the model parameters. Environmental engineering problems concerning diffusion and natural advection phenomena occur in the presence of a pollutant in still water. Numerical tests referring to a strip and a bubble of contaminant in a water tank with different initial concentration laws have been carried out. The results obtained by the proposed SPH models are compared with other available SPH formulations, showing an overall better agreement with standard analytical solutions in terms of spatial evolution of the concentration values. Capabilities and limits of the proposed SPH models to simulate advective diffusion phenomena for a wide range of density ratios are discussed.

Two-phase SPH modelling of advective diffusion processes

Lo stato dei litorali italiani.

This paper deals with the development of a 2D weakly compressible SPH
model to simulate wave pressures acting on vertical and slotted coastal
structures. Attention is devoted to investigate the diffusive term in the
continuity equation in order to smooth out the high-frequency numerical
noise in the pressure field. A hybrid formulation based on two literature
diffusive models is proposed. The interaction between regular waves with
vertical and perforated breakwaters is analyzed in time, space, and frequency
domain. Numerical results are compared with laboratory experiments and
other diffusive SPH formulations, varying the magnitude of the adopted
diffusive term. On the basis of an error analysis, the results show that the
hybrid formulation gives a better agreement with the experimental data for
the majority of the investigated cases. Moreover, SPH simulations highlight
nonlinear trends of dynamic pressures in correspondence with geometrical
singularities, such as the holes of slotted walls, due to strong pressure drops
induced by the flow motion.

https://downloads.hindawi.com/journals/mpe/2015/305028.pdf

Paolo Veltri

Papers

SPH numerical modeling of wave–perforated breakwater interaction

Solitary wave-induced forces on horizontal circular cylinders: Laboratory experiments and SPH simulations

Two-phase SPH modelling of advective diffusion processes

Lo stato dei litorali italiani.

Assessment of Dynamic Pressures at Vertical and Perforated Breakwaters through Diffusive SPH Schemes