Turbulence Model Extension for Vortex Dominated Flows and Optimization with Experimental Data

This document provides information and instructions for preparing a Full Paper to be included in the Proceedings of 14th WCCM ­ ECCOMAS CONGRESS 2020

Ultrastable, high-repetition-rate attosecond beamline for time-resolved XUV-IR coincidence spectroscopy

The implementation of attosecond photoelectron-photoion coincidence spectroscopy for the investigation of atomic and molecular dynamics calls for a high-repetition-rate driving source combined with experimental setups characterized by excellent stability for data acquisition over time intervals ranging from a few hours up to a few days. This requirement is crucial for the investigation of processes characterized by low cross sections and for the characterization of fully differential photoelectron(s) and photoion(s) angular and energy distributions. We demonstrate that the implementation of industrial-grade lasers, combined with a careful design of the delay line implemented in the pump-probe setup, allows one to reach ultrastable experimental conditions leading to an error in the estimation of the time delays of only 12 as. This result opens new possibilities for the investigation of attosecond dynamics in simple quantum systems

Attosecond pulse shaping using a seeded free-electron laser

Attosecond pulses are central to the investigation of valence- and core-electron dynamics on their natural timescales1–3. The reproducible generation and characterization of attosecond waveforms has been demonstrated so far only through the process of high-order harmonic generation4–7. Several methods for shaping attosecond waveforms have been proposed, including the use of metallic filters8,9, multilayer mirrors10 and manipulation of the driving field11. However, none of these approaches allows the flexible manipulation of the temporal characteristics of the attosecond waveforms, and they suffer from the low conversion efficiency of the high-order harmonic generation process. Free-electron lasers, by contrast, deliver femtosecond, extreme-ultraviolet and X-ray pulses with energies ranging from tens of microjoules to a few millijoules12,13. Recent experiments have shown that they can generate subfemtosecond spikes, but with temporal characteristics that change shot-to-shot14–16. Here we report reproducible generation of high-energy (microjoule level) attosecond waveforms using a seeded free-electron laser17. We demonstrate amplitude and phase manipulation of the harmonic components of an attosecond pulse train in combination with an approach for its temporal reconstruction. The results presented here open the way to performing attosecond time-resolved experiments with free-electron lasers

Complex attosecond waveform synthesis at fel fermi

Free-electron lasers (FELs) can produce radiation in the short wavelength range extending from the extreme ultraviolet (XUV) to the X-rays with a few to a few tens of femtoseconds pulse duration. These facilities have enabled significant breakthroughs in the field of atomic, molecular, and optical physics, implementing different schemes based on two-color photoionization mechanisms. In this article, we present the generation of attosecond pulse trains (APTs) at the seeded FEL FERMI using the beating of multiple phase-locked harmonics. We demonstrate the complex attosecond waveform shaping of the generated APTs, exploiting the ability to manipulate independently the amplitudes and the phases of the harmonics. The described generalized attosecond waveform synthesis technique with an arbitrary number of phase-locked harmonics will allow the generation of sub-100 as pulses with programmable electric fields

Pre-combustion CO2 capture by MDEA process in IGCC based on air-blown gasification

AbstractThis work aims at assessing the performance of IGCC power plants with CO2 capture based on air-blown gasification, which is a field scarcely assessed in the open literature. The whole process is modelled and simulated, from coal gasification to syngas cooling and cleaning, to the syngas utilization in the power island. Particular attention is paid to the capture section, based on a two-stage H2S-CO2 selective separation using MDEA as solvent, which was accurately modelled with a rate based approach. The final results show competitive performance of the assessed plants in terms of efficiency and specific emissions with respect to more conventional IGCC systems based on oxygen-blown gasification

Assessment of MDEA absorption process for sequential H2S removal and CO2 capture in air-blown IGCC plants

This work deals with pre-combustion CO2 capture by Methyldiethanolamine (MDEA) scrubbing in air-blown integrated gasification combined cycles (IGCCs). Two types of coal, with low- and high-sulphur content, are considered as fuel input in power plants, as well as two combustion turbines, with different turbine inlet temperature, representative of state-of-the-art and advanced technologies. The gasification section and the power island are simulated by means of the proprietary code GS. Acid gas removal (AGR), consisting in the sequential H2S removal and CO2 capture from the syngas by MDEA solvent, is calculated with Aspen Plus®. MDEA concentration and solvent circulation are varied in each of the assessed cases to comply with the target CO2 capture efficiency and with the CO2 and H2S purity specifications. The resulting heat duties for H2S and CO2 stripping, the consumption of the auxiliaries in the AGR plants, as well as the CO2 compression work are used to calculate the energy and mass balances of the integrated gasification combined cycles. Sensitivity analysis on the temperature approach in the recuperative heat exchanger of the CO2 capture section and on the pressure of the CO2 stripping column have been performed to assess potential energy savings. Results are compared with benchmark IGCC plants without CO2 capture. Net electric efficiencies between 36.6% and 40.4%, with 95% of CO2 capture efficiency, are achieved depending on the coal quality (i.e. the sulphur content), the combustion turbine technology and the MDEA regeneration pressure and heat exchanger temperature difference. Correspondingly, a specific primary energy consumption for CO2 avoided (SPECCA) between 2.85 and 3.2 MJ/kgCO2 for the low-sulphur coal cases and between 3.2 and 3.7 MJ/kgCO2 for the high-sulphur coal cases have been calculated

Investigation of Additively Manufactured Wind Tunnel Models with Integrated Pressure Taps for Vortex Flow Analysis

Wind tunnel models are traditionally machined from high-quality metal material; this condition reduces the possibility to test different geometric variations or models as it corresponds to incremental cost. In the last decade, the quality of additive manufacturing techniques has been progressively increasing, while the cost has been decreasing. The utilization of 3D-printing techniques suggests the possibility to improve the cost, time, and flexibility of a wind tunnel model production. Possible disadvantages in terms of quality of the model finishing, stiffness, and geometric accuracy are investigated, to understand if the production technique is capable of providing a suitable test device. Additionally, pressure taps for steady surface pressure measurements are integrated during the printing procedure and the production of complex three-dimensional highly swept wings have been selected as targets. Computational fluid dynamics tools are exploited to confirm the experimental results in accordance with the best practice approaches characterizing flow patterns dominated by leading-edge vortices. The fidelity level of the experimental data for scientific research of the described flow fields is investigated. An insight of the most important guidelines and the possible improvements is provided as well as the main features of the approach