CFD-PBM Simulation of Nickel-Manganese-Cobalt Hydroxide Co-precipitation in CSTR

The co-precipitation of Ni 0.8 Mn 0.1 Co 0.1 (OH) 2 in a pilot-scale CSTR is simulated by adopting the CFD-PBM approach combined with the operator-splitting method. It is shown that the excessive total computational time can affect the applicability of the approach, hence necessity of using massive parallel calculations. However, the effectiveness of the parallel calculation is limited unless an algorithm is implemented to balance the load of the source integration across computing processors

Wing Tip Vortices from an Exergy-Based Perspective

The lens of exergy is used to investigate a wingtip vortex in the near wake over a range of angles of attack. Exergy is the measure of thermodynamically “available” energy as determined through the more discriminating second law of thermodynamics. Experiments were conducted in a water tunnel at Institute of Aerospace Systems at Aachen. The data were taken three chord lengths downstream in the Trefftz plane of an aspect ratio 5 Clark-Y wing with a square-edged wing tip using particle image velocimetry. Intuitively, the minimum available energy state is expected to correspond to the maximum lift-to-drag ratio angle of attack. This, however, is not the case here. Most interestingly, although only two-dimensional Trefftz plane data were used to obtain the exergy distribution across the individual wing-tip vortices, the crossover point for the out-of-plane change from wakelike to jetlike wing-tip vortex core axial flow (indicating the peak lift-to-drag ratio) is identified by the in-plane exergy distribution. This crossover point is not identifiable in the evaluation of any other characteristics calculated from in-plane quantities. Consequently, the exergy method holds promise as a metric for the improvement of aircraft performance through the reduction of lift-induced drag

CFD-PBE modelling of continuous Ni-Mn-Co hydroxide co-precipitation for Li-ion batteries

A modelling framework is proposed to simulate the co-precipitation of Ni-Mn-Co hydroxide as precursor of cathode material for lithium-ion batteries. It integrates a population balance equation with computational fluid dynamics to describe the evolution of the particle size in (particularly continuous) co-precipitation processes. The population balance equation is solved by employing the quadrature method of moments. In addition, a multi-environment micromixing model is employed to consider the potential effect of molecular mixing on the fast co-precipitation reaction. The modelling framework is used to investigate the co-precipitation of Ni0.8Mn0.1Co0.1(OH)2 in a multi-inlet vortex micromixer, as a suitable candidate for the study of fast co-precipitation processes in continuous mode. Finally, the simulation results are discussed, and the role of the different phenomena involved in the formation and evolution of particles is identified by inspecting the predicted trends

Simulation of high Schmidt number fluids with dissipative particle dynamics: Parameter identification and robust viscosity evaluation

Dissipative particle dynamics (DPD) is a widely used coarse-grained technique for the simulation of complex fluids. Although the method is capable of describing the hydrodynamics of any fluid, the common choice of DPD parameters, such as friction coefficient γ, dissipative cutoff radius , coarse-graining factor Nm and weighting function exponent s, unrealistically leads to the simulation of liquid water with a low Schmidt number Sc at standard pressure and temperature. In this work we explored the influence of these parameters, finding the set of parameters needed to properly simulate liquid water. Particular attention was devoted to the numerical techniques to calculate the transport properties from equilibrium simulations, especially in the calculation of the viscosity, comparing the most commonly adopted techniques and formulating a recipe that can be used for further investigations

Landslides on Ceres: Diversity and Geologic Context.

Landslides are among the most widespread geologic features on Ceres. Using data from Dawn's Framing Camera, landslides were previously classified based upon geomorphologic characteristics into one of three archetypal categories, Type 1(T1), Type 2 (T2), and Type 3 (T3). Due to their geologic context, variation in age, and physical characteristics, most landslides on Ceres are, however, intermediate in their morphology and physical properties between the archetypes of each landslide class. Here we describe the varied morphology of individual intermediate landslides, identify geologic controls that contribute to this variation, and provide first-order quantification of the physical properties of the continuum of Ceres's surface flows. These intermediate flows appear in varied settings and show a range of characteristics, including those found at contacts between craters, those having multiple trunks or lobes; showing characteristics of both T2 and T3 landslides; material slumping on crater rims; very small, ejecta-like flows; and those appearing inside of catenae. We suggest that while their morphologies can vary, the distribution and mechanical properties of intermediate landslides do not differ significantly from that of archetypal landslides, confirming a link between landslides and subsurface ice. We also find that most intermediate landslides are similar to Type 2 landslides and formed by shallow failure. Clusters of these features suggest ice enhancement near Juling, Kupalo and Urvara craters. Since the majority of Ceres's landslides fall in the intermediate landslide category, placing their attributes in context contributes to a better understanding of Ceres's shallow subsurface and the nature of ground ice

Numerical and Experimental Analysis of the Daughter Distribution in Liquid-Liquid Stirred Tanks

The drop size distributions (DSDs) of a dilute immiscible liquid-liquid mixture were measured in a fully turbulent stirred tank operating at different impeller speeds. The results were used to infer the best daughter distribution function (DDF) leading to the best reproduction of the shape of the DSD. Bell-shaped, U-shaped, M-shaped, and uniform statistical DDFs were studied, producing from two to four daughters from each breakup event. A simplified approach from the literature was adopted to solve the population balance equation that considers the spectrum of the turbulence inside the tank obtained from computational fluid dynamics simulations. The U-shaped distribution producing four fragments better reproduces the shape of the experimental DSD in the studied system

CFD-DEM characterization and population balance modelling of a dispersive mixing process

This work investigates the breakup dynamics of solid agglomerates in a polymer compounding operation, by using computational fluid dynamics (CFD) simulations together with discrete element method (DEM) simulations. CFD simulations are used to compute the flow field and the shear stress distribution inside a 2D section of a typical internal mixer for polymer compounding. DEM simulations are instead used to predict the mechanical response of the agglomerates and to detect the critical viscous shear stress needed to induce breakup. DEM breakup data and viscous stress distributions are correlated by a first–time passage–statistics and used to calibrate a population balance model. The work returned detailed insights into the flow field characteristics and into the dispersive mixing kinetics. The simulation strategy herein reported can be adapted to study generic solid–liquid disperse flows in which the breakup of the solid phase is found at the core of the system behaviour