Exact regularized point particle method for multi-phase flows in the two-way coupling regime

Particulate flows have been largely studied under the simplifying assumptions of one-way coupling regime where the disperse phase do not react-back on the carrier fluid. In the context of turbulent flows, many non trivial phenomena such as small scales particles clustering or preferential spatial accumulation have been explained and understood. A more complete view of multiphase flows can be gained calling into play two-way coupling effects, i.e. by accounting for the inter-phase momentum exchange between the carrier and the suspended phase, certainly relevant at increasing mass loading. In such regime, partially investigated in the past by the so-called Particle In Cell (PIC) method, much is still to be learned about the dynamics of the disperse phase and the ensuing alteration of the carrier flow. In this paper we present a new methodology rigorously designed to capture the inter-phase momentum exchange for particles smaller than the smallest hydrodynamical scale, e.g. the Kolmogorov scale in a turbulent flow. In fact, the momentum coupling mechanism exploits the unsteady Stokes flow around a small rigid sphere where the transient disturbance produced by each particle is evaluated in a closed form. The particles are described as lumped, point masses which would lead to the appearance of singularities. A rigorous regularization procedure is conceived to extract the physically relevant interactions between particles and fluid which avoids any "ah hoc" assumption. The approach is suited for high efficiency implementation on massively parallel machines since the transient disturbance produced by the particles is strongly localized in space around the actual particle position. As will be shown, hundred thousands particles can therefore be handled at an affordable computational cost as demonstrated by a preliminary application to a particle laden turbulent shear flow.Comment: Submitted to Journal of Fluid Mechanics, 56 pages, 15 figure

The vertical gradient of Electro-Atmospheric potential at Macerata (Italy) (Central East Apennines)

This work studies eleven years of measures of the gradientof electro-atmospheric potential carried out in the Observatory ofMacerata (East Central Apennines). The medium yearly and monthlyvalues as well as the medium hourly values have been calculated. Thecalculations are based on the values of five calm days chosen with probabilisticmethods from all the calm days of the month considered. The equation lias also been found from the medium hourly curve bymeans of harmonic analysis. Then the harmonics have been examinedstopping at the third, and it has been found that these reflected the differentgeneral and local components such as that due to the masses of air of maritimeorigin and that due to the masses of continental air operating alternativelyin the region of observation. The general minimum of the local hours"> a. m. (4 TU) is clearly shown by the first harmonic, and it is also presentin the medium hourly curve but appears in this less accentuated than whatwe would expect it to be.Finally the behaviours of the vertical gradient in clear, cloudy andcalm days have been studied and the different results compared.The behaviour of the parameter of the atmospheric electricity in relationto the solar phenomena has also been studied and in particular with thebehaviour of the sunspots during the eleven years of observations

Non-radial oscillation modes as a probe of density discontinuities in neutron stars

A phase transition occurring in the inner core of a neutron star could be associated to a density discontinuity that would affect the frequency spectrum of the non-radial oscillation modes in two ways. Firstly, it would produce a softening of the equation of state, leading to more compact equilibrium configurations and changing the frequency of the fundamental and pressure modes of the neutron star. Secondly, a new non-zero frequency g-- mode would appear, associated to each discontinuity. These discontinuity g--modes have typical frequencies larger than those of g--modes previously studied in the literature (thermal, core g-- modes, or g--modes due to chemical inhomogeneities in the outer layers), and smaller than that of the fundamental mode; therefore they should be distinguishable from the other modes of non radial oscillation. In this paper we investigate how high density discontinuities change the frequency spectrum of the non-radial oscillations, in the framework of the general relativistic theory of stellar perturbations. Our purpose is to understand whether a gravitational signal, emitted at the frequencies of the quasi normal modes, may give some clear information on the equation of state of the neutron star and, in particular, on the parameters that characterize the density discontinuity. We discuss some astrophysical processes that may be associated to the excitation of these modes, and estimate how much gravitational energy should the modes convey to produce a signal detectable by high frequency gravitational detectors.Comment: submitted to MNRA

Impact of reconfiguration on the flow downstream of a flexible foliated plant

This paper explores the impacts of reconfiguration and leaf morphology on the flow downstream of a flexible foliated plant. 3D acoustic Doppler velocimetry and particle image velocimetry were used to experimentally investigate the hydrodynamic interaction between a foliated plant and the flow, testing two plants with different leaves morphology under different bulk flow velocities. The model vegetation was representative of riparian vegetation species in terms of plants hydrodynamic behavior and leaf to stem area ratio. To explore the effects of the seasonal variability of vegetation on the flow structure, leafless conditions were tested. Reconfiguration resulted in a decrease of the frontal projected area of the plants up to the 80% relative to the undeformed value. Such changes in plant frontal area markedly affected the spatial distributions of mean velocity and turbulence intensities, altering the local exchanges of momentum. At increasing reconfiguration, the different plant morphology influenced the mean and turbulent wake width. The leafless stem exhibited a rigid behavior, with the flow in the wake being comparable to that downstream of a rigid cylinder. The study revealed that the flexibility-induced reconfiguration of plants can markedly affect the local distribution of flow properties in the wake, potentially affecting transport processes at the scale of the plant and its subparts

Inhaled sodium cromoglycate to treat cough in advanced lung cancer patients.

C-fibres probably represent the common final pathway in both ACE inhibitors and neoplastic cough. A recent report demonstrated that inhaled sodium cromoglycate is an effective treatment for ACE inhibitors' cough; this effect might be due to the suppression of afferent unmyelinated C-fibres. We tested the hypothesis that inhaled sodium cromoglycate might also be effective in lung cancer patients who presented with irritative neoplastic cough. Twenty non-small-cell lung cancer (NSCLC) patients complaining of cough resistant to conventional treatment were randomised to receive, in a double-blind trial, either inhaled sodium cromoglycate or placebo. Patients recorded cough severity daily, before and during treatment, on a 0 to 4 scale. The efficacy of treatment was tested with the Mann-Whitney U-test for non-parametric measures, comparing the intergroup differences in the measures of summary of symptom scores calculated in each patient before and after treatment. We report that inhaled sodium cromoglycate can reduce cough, also in NSCLC patients and that such reduction, observed in all patients treated, is statistically significant (P < 0.001). Inhaled sodium cromoglycate appears to be a cost-effective and safe treatment for lung cancer-related cough

Quantum-classical dynamical distance and quantumness of quantum walks

We introduce a fidelity-based measure $\text{D}_{\text{CQ}}(t)$ to quantify the differences between the dynamics of classical (CW) and quantum (QW) walks over a graph. We provide universal, graph-independent, analytic expressions of this quantum-classical dynamical distance, showing that at short times $\text{D}_{\text{CQ}}(t)$ is proportional to the coherence of the walker, i.e. a genuine quantum feature, whereas for long times it depends only on the size of the graph. At intermediate times, $\text{D}_{\text{CQ}}(t)$ does depend on the graph topology through its algebraic connectivity. Our results show that the difference in the dynamical behaviour of classical and quantum walks is entirely due to the emergence of quantum features at short times. In the long time limit, quantumness and the different nature of the generators of the dynamics, e.g. the open system nature of CW and the unitary nature of QW, are instead contributing equally.Comment: 6 pages, 3 figures, largely rewritte