Three-dimensional numerical investigation on micro-meter droplet impact and penetration into the porous media with different velocities

Droplets impacting and penetration into porous media is commonly seen in natural and engineering processes, in which the kinetics and capillary effect are of great importance to the lateral spreading and vertical penetration. In this study, a three-dimensional numerical simulation method was proposed to study the micro-meter droplet impact and penetration into the porous media. It is found that both the lateral spread and vertical penetration occur on the millisecond timescale and larger velocity will enhance the lateral spreading but have little influence on the penetration time and depth. The direct numerical method proposed in this study can be applied to predict the actual spreading and penetration status in the droplet-powder system and further insight into the droplet-powder interaction.

EFFECTIVENESS EVALUATION OF THE STRUCTURAL COMPACT MATRIX METHOD FOR CALCULATING THE COMPACTNESS COEFFICIENT

The article examines the efficiency of the structural compact-matrix numerical method in comparison with the classical direct numerical method for calculating the spatial packing density of the simplest hexagonal lattice. The theoretical results of a comparative analysis of the considered numerical meth-ods, as well as a computational experiment, carried out to quantitatively assess their effectiveness, are presented.

Crystal fractionation by crystal-driven convection

<p>In the last two decades, improved fine scale analysis in crystalline profiles has improved our understanding of igneous processes, while opening our sight to more complexities. As an example, plagioclase crystal profiles in Holyoke flood-basalt flow revealed that the crystals got exposured to different melt environments as the layer underwent fractional crystallization. Fractional crystallization is an essential process for determining the compositional evolution of magmatic systems. The process requires a reactive segregation process, where crystals precipitate from the melt and segregate from their residual melt. In this study, we are motivated by the subtleties in the crystalline record to model the segregation component of fractional crystallization, or crystal fractionation.</p><p> </p><p>We build a numerical model with individually resolved, denser-than-melt crystals in a convective flow. We test the low to intermediate crystallinity regime, where the physical processes leading to efficient fractionation are less clear than at high crystallinity. We simulate the physical segregation of crystals from their residual melt at the scale of individual crystals using a direct numerical method. By resolving each of the crystals, we do not require a priori parameterization of crystal-melt interactions. We use tracers in the melt to track the different melts around the crystals.</p><p> </p><p>We find that collective sinking of crystal-rich clusters dominate settling at low particle Reynolds numbers. The relatively rapid motion of this cluster strips away the residual melt around the cluster. Compared to individual settling, the resulting crystal fractionation is efficient but heterogeneous at the crystalline scale. Similar to the Holyoke flood-basalt plagioclase profiles, the crystals in our analysis show exposure to different melt environments as they drive crystal fractionation. Our results suggest that cluster driven fractional crystallization will vary in efficiency. At the system scale, this result would suggest a bell curve compositional abundance distribution in volcanic systems.</p><p><br><br><br></p><p> </p>

The flow-to-sliding transition in crystalline magma

<p>Magmatic flows are rarely, if ever, entirely free of crystals. If these crystals distribute in an approximately homogeneous way, their impact on flow can be captured by defining a suitable effective viscosity for the suspension. A spatially heterogeneous crystal distribution, however, can build up to the degree that the flow behavior of the crystal-bearing magma becomes substantially different from that of a pure melt. One example is the transition from flow to sliding, in which the deformation in the crystalline magma is concentrated almost entirely in a thin interfacial layer as opposed to being distributed in a typical flow profile throughout the domain. The transition is particularly consequential for the large-scale dynamics of the system, because it can be associated with transport rates increasing by orders of magnitudes.</p><p> </p><p>Most conduit models associate the flow-to-sliding transition with a critical crystal fraction, often in the 60% range. Here, we hypothesize that the flow to sliding transition can occur at crystal fraction as low as a few percents under certain conditions. We test our hypothesis by numerically reproducing existing laboratory measurements of the effective viscosity of plagioclase-bearing basalt in a rotational viscometer. We utilize a direct numerical method to resolve the interactions between the crystals and the magmatic melt at the scale of individual interfaces in 2D. Our numerical approach only requires assumptions about the pure phase including the crystal fraction and crystal shape. All phase interactions and their aggregate effect on the flow emerge self-consistently from the simulation itself. </p><p> </p><p>Our simulations suggest that the behavior of multiphase suspensions at low fluid Reynolds number is highly variable and depends sensitively on the characteristics of the immersed phases and the geometry of the flow domain. We show that there is no meaningful dilute limit in which the phase interactions can be neglected or captured by adjusting the effective rheology of the suspension in a way that removes dependencies on the properties of the immersed phase. Since our models operate at the scale of individual crystals, our model results are testable in both field and laboratory settings. In fact, they suggest that observations of microstructure provide valuable constraints on the large scale flow dynamics at the time. Particularly important is the degree of preferential crystal alignment and the existence of force chains or crystal clusters.</p>

Radiation Spectrum of Sequence of Electrons Moving in Spiral in Medium

Integral expressions for spectral-angular and spectral distributions of the radiation power for the sequence of electrons moving in magnetic fields in isotropic transparent medium are investigated using the improved Lorentz`s self-interaction method. Special attention is given to the research of the fine structurre of the spectral distribution of the synchrotron-Cherenkov radiation of one, two, three and four point electrons moving along the spiral in medium. The effects of coherent radiation of harmonics and oscillations in spectrum of the synchrotron-Cherenkov radiation of two, three and four point electrons are established and investigated using the direct numerical method for calculation the function of spectral distributions of the radiation power.

Analyzing the Departure Runway Capacity Effects of Integrating Optimized Continuous Climb Operations

Performing Continuous Climb Operation (CCO) procedures enable the reduction of the environmental footprint and the improvement of the trajectory efficiency when individually operated. However, its operation may affect negatively the overall operational efficiency at Terminal Manoeuvring Areas (TMAs). The estimation of capacity is a matter of paramount importance to all airport planning and analyzing the capacity effects of this particular operational technique on a certain scenario will definitely help on evaluating its potential applicability. In this paper, departure runway capacity at the Adolfo Suárez Madrid-Barajas airport was operationally evaluated when introducing CCOs. The considered trajectories consisted of multiobjective optimized CCOs based on the optimal control theory, using the pseudospectral direct numerical method. These scenarios allowed addressing of the incremental variations of CCOs versus conventional departures, through fast time simulation, with the objective to assess the effects on the operations.