Advanced breakup-nucleon enhancement of deuteron-induced reaction cross sections

Following the EUROfusion PPPT-programme action for an advanced modeling approach of deuteron-induced reaction cross sections, as well as specific data evaluations in addition of the TENDL files, an assessment of the details and corresponding outcome for the latter option of TALYS for the breakup model has been carried out. The breakup enhancement obtained in the meantime within computer code TALYS, by using the evaluated nucleon-induced reaction data of TENDL-2019, is particularly concerned. Discussion of the corresponding results, for deuteron-induced reactions on $$^{58}$$ 58 Ni, $$^{96}$$ 96 Zr, and $$^{231}$$ 231 Pa target nuclei up to 200 MeV incident energy, includes limitations still existing with reference to the direct-reaction account.

LES of Particle-Laden Flow in Sharp Pipe Bends with Data-Driven Predictions of Agglomerate Breakage by Wall Impacts

The breakage of agglomerates due to wall impact within a turbulent two-phase flow is studied based on a recently developed model which relies on two artificial neural networks (ANNs). The breakup model is intended for the application within an Euler-Lagrange approach using the point-particle assumption. The ANNs were trained based on comprehensive DEM simulations. In the present study the entire simulation methodology is applied to the flow through two sharp pipe bends considering two different Reynolds numbers. In a first step, the flow structures of the continuous flow arising in both bend configurations are analyzed in detail. In a second step, the breakage behavior of agglomerates consisting of spherical, dry and cohesive silica particles is predicted based on the newly established simulation methodology taking agglomeration, fluid-induced breakage and breakage due to wall impact into account. The latter is found to be the dominant mechanism determining the resulting size distribution at the bend outlet. Since the setups are generic geometries found in dry powder inhalers, important knowledge concerning the effect of the Reynolds number as well as the design type (one-step vs. two-step deflection) can be gained.

Numerical investigation of soot emission sources in a direct-injection spark-ignition engine based on comprehensive breakup model validation

Direct injection system is widely adopted in spark-ignition engines to achieve higher thermal efficiency, but it accompanies a penalty in particulate emission, especially when engine is not fully warmed-up. Split injection strategy is known to be an effective measure to reduce engine-out particulate emissions. To better understand the role of split injections, this study aims to analyze the effect of split injection strategy on the sources of soot formation using computational fluid dynamics simulation. To accurately predict changes in particulate mass and number associated with split injection strategy, it is vital that spray models be carefully validated against the experimental data since spray dynamics govern the formation of soot emission sources, such as local fuel-rich mixtures and wall-deposited fuel-films. To this end, a set of spray experiments for free sprays is performed to measure liquid penetration length and droplet size distribution, and hence a comprehensive validation is conducted for spray breakup models. Then, engine simulations are carried out to predict the change in soot sources according to split injection, and the trend of simulation results is compared against the measured engine-out particulate mass and number. Simulation results indicate that breakup model validation using both penetration length and droplet size data is critical for predicting fuel spray dynamics and formation of sources of soot emission. It is also revealed that the piston wetting decreases as the number of injections increases because less amount of fuel is injected when piston is closer to the injector. Lastly, the late evaporation of heavy gasoline components from fuel-film appears to be a significant contributor to soot precursors formation.

Tuning of NASA Standard Breakup Model for Fragmentation Events Modelling

The continuous growth of space debris motivates the development and the improvement of tools that support the monitoring of a more and more congested space environment. Satellite breakup models play a key role to predict and analyze orbital debris evolution, and the NASA Standard Breakup Model represents a widely used reference, with current activities relevant to its evolution and improvements especially towards fragmentation of small mass spacecraft. From an operational perspective, an important point for fragmentation modelling concerns the tuning of the breakup model to achieve consistency with orbital data of observed fragments. In this framework, this paper proposes an iterative approach to estimate the model inputs, and in particular, the parents’ masses involved in a collision event. The iterative logic exploits the knowledge of Two Line Elements (TLE) of the fragments at some time after the event to adjust the input parameters of the breakup model with the objective of obtaining the same number of real fragments within a certain tolerance. Atmospheric re-entry is accounted for. As a result, the breakup model outputs a set of fragments whose statistical distribution, in terms of number and size, is consistent with the catalogued ones. The iterative approach is demonstrated for two different scenarios (i.e., catastrophic collision and non-catastrophic collision) using numerical simulations. Then, it is also applied to a real collision event.

Numerical Investigation of Droplet Properties of a Liquid Jet in Supersonic Crossflow

The atomization process of a liquid jet in supersonic crossflow with a Mach number of 1.94 was investigated numerically under the Eulerian-Lagrangian scheme. The droplet stripping process was calculated by the KH (Kelvin-Helmholtz) breakup model, and the secondary breakup due to the acceleration of shed droplets was calculated by the combination of the KH breakup model and the RT (Rayleigh-Taylor) breakup model. In our research, the existing KH-RT model was modified by optimizing the empirical constants incorporated in this model. Moreover, it was also found that the modified KH-RT breakup model is applied better to turbulent inflow of a liquid jet than laminar inflow concluded from the comparisons with experimental results. To validate the modified breakup model, three-dimensional spatial distribution and downstream distribution profiles of droplet properties of the liquid spray in the Ma = 1.94 airflow were successfully predicted in our simulations. Eventually, abundant numerical cases under different operational conditions were launched to investigate the correlations of SMD (Sauter Mean Diameter) with the nozzle diameter as well as the airflow Mach number, and at the same time, modified multivariate power functions were developed to describe the correlations.

A CFD-PBM coupled model under entire turbulent spectrum for simulating a bubble column with highly viscous media

To account for the effect of liquid viscosity, the bubble breakup model considering turbulent eddy collision based on the inertial subrange turbulent spectrum was extended to the entire turbulent spectrum that included the energy-containing, inertial, and energy-dissipation subranges. The computational fluid dynamics-population balance model (CFD-PBM) coupled model was modified to include this extended bubble breakup model for simulations of a bubble column. The effect of turbulent energy spectrum on the bubble breakup and hydrodynamic behaviors was studied in a bubble column under different liquid viscosities. The results showed that when the liquid viscosity was < 80 mPas, the bubble breakup and hydrodynamics were almost independent on the turbulent spectrum. At liquid viscosity > 80 mPas, the bubble breakup rate and gas holdup were significantly under-predicted when the inertial turbulent spectrum was used, and when using the entire turbulent spectrum the predictions were more consistent with experimental data.