| 11. |
- Minelli, Guglielmo, 1988, et al.
(författare)
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Numerical Investigation of the Actuated Flow on a Bluff Body
- 2016
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Ingår i: Springer Proceedings in Physics. - Cham : Springer International Publishing. - 0930-8989 .- 1867-4941. ; 185, s. 295-302
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Konferensbidrag (refereegranskat)abstract
- Large Eddy Simulations (LES) are conducted to study the Active Flow Control (AFC) of the separation of the boundary layer on a rounded leading edge frontstep. This bluff body imitates the flow around a section of a simplified truck cabin and focuses on the separation arising at the front rounded corner, the so called A-pillar. The LES data show the connection between the actuation and drag reduction. The actuated and unactuated flows are analysed using modal decomposition and frequency analysis. Different configurations are tested and a strong influence of the actuation on both drag reduction and separation mechanism was observed. Relevant results, in terms of drag coefficient and recirculation bubble reduction, are achieved when the flow is actuated. LES shows an increased unsteadiness in the flow, introduced by the actuation. An analysis that investigates the connection between actuation and induced unsteadiness is presented.
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| 12. |
- Mirzaei, Maryam, 1982, et al.
(författare)
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Large Eddy Simulations of Flow Around Two Generic Vehicles in a Platoon
- 2016
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Ingår i: Springer Proceedings in Physics. - Cham : Springer International Publishing. - 0930-8989 .- 1867-4941. - 9783319306025 ; 185, s. 283-288
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Konferensbidrag (refereegranskat)abstract
- A detailed analysis of the effect of inter-vehicle distance on the flow structure of a two-model platoon is presented. Simulations are made for two Ahmed bodies with a slant angle of 25 degrees and for three inter-vehicle distances, d/L = 0.3, 0.5 and 1. The Reynolds number based on the body height was 30000. A drag increase was observed for the follower with d/L = 0.5, compared to the drag value of a single body in isolation. To explain the underlying reasons for the increase in drag, various instantaneous and time-averaged plots are presented and compared for different distances, and a significant change in flow structure was found in flows between the set-ups with d/L = 0.5 and d/L = 1.
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| 13. |
- Mirzaei, Maryam, 1982, et al.
(författare)
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Numerical Study of Aerodynamic Interactions in a Homogeneous Multi-vehicle Formation
- 2016
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Ingår i: Springer Proceedings in Physics. - Cham : Springer International Publishing. - 0930-8989 .- 1867-4941. - 9783319306025 ; 185, s. 289-294
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Konferensbidrag (refereegranskat)abstract
- An accurate and affordable method to study the flow features associated with vehicles in a homogeneous platooning is presented in this paper. It was found that only one pitch of a long-line periodic platoon would provide a sufficiently accurate observation of the flow interaction in the inter-vehicle region of the vehicles offering a significant reduction of the computational effort. The simulations of flow at Reynolds number of 30000 are made for a periodic platoon including slanted-back Ahmed bodies with a slant angle of 25 degrees and for four inter-vehicle distances, d/L = 0.1, 0.3, 0.5 and 1.
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| 14. |
- Richter, Steffen, et al.
(författare)
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Spectral and polarization properties of VUV-mirrors for experiments at a HHG beamline
- 2020
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Ingår i: Springer Proceedings in Physics. - Cham : Springer International Publishing. - 0930-8989 .- 1867-4941. ; 241, s. 175-179, s. 175-179
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Konferensbidrag (refereegranskat)abstract
- For polarization-resolved reflection experiments such as ellipsometry, not only is high reflectivity in a wide spectral range required for mirrors but also the quality of their polarization response is important. Furthermore, for VUV ellipsometry, optimal angles of incidence at the sample are between 45° and 60° with respect to the surface normal. In the best case, a setup should even allow variable angles. This requires reflective optics working at non-grazing incidence. In this theoretical study, a selection of potentially relevant materials and mirror designs for broadband use in the VUV is investigated. Based on the available tabulated databases of optical constants, we performed transfer-matrix calculations to obtain reflectance as well as polarization-response spectra in the desired VUV range up to 50 eV. From the variety of materials, we discuss metals that are otherwise commonly used at grazing incidence, Si, SiC, and as representatives for coating layers MgF2, SiO2, and Al2O3. While SiC is most universal, Si with only native oxide layer performs well especially below 25 eV. Aluminum has good properties but oxide layers are very detrimental, as protective coatings are in general.
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| 15. |
- Sahoo, Baidyanath, et al.
(författare)
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Simulation Studies of R2(Δ η, Δ ϕ) and P2(Δ η, Δ ϕ) Correlation Functions in pp Collisions with the PYTHIA and HERWIG Models
- 2022
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Ingår i: Proceedings of the 24th DAE-BRNS High Energy Physics Symposium, 2020. - Singapore : Springer Nature Singapore. - 1867-4941 .- 0930-8989. - 9789811923531 ; 277, s. 349-352
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Konferensbidrag (refereegranskat)abstract
- We presented a study of charge-independent (CI) and charge-dependent (CD) two-particle differential number correlation functions R2 and transverse momentum correlation functions P2 in pp collisions at s=2.76 TeV with the PYTHIA and HERWIG models.Calculations were presented for unidentified hadrons in three pT ranges 0.2 < pT≤ 2.0 GeV/c, 2.0 < pT≤ 5.0 GeV/c, and 5.0 < pT≤ 30.0 GeV/c.PYTHIA and HERWIG both qualitatively reproduce the near-side peak and away-side ridge correlation features reported by experiments.At low pT, both models produce narrower near-side peaks in P2 correlations than in R2 as reported by the ALICE collaboration in p–Pb and Pb–Pb collisions.This suggests that the narrower shape of the P2 near-side peak is largely determined by the pT dependent angular ordering of hadrons produced in jets.Both PYTHIA and HERWIG predict widths that decrease with increasing pT.Widths extracted for P2 correlators are typically significantly narrower than those of the R2 counterparts [1].
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| 16. |
- Seres, J., et al.
(författare)
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Attosecond dynamics of parametric amplification at 11 nm
- 2016
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Ingår i: X-Ray Lasers 2014 - Proceedings of the 14th International Conference on X-Ray Lasers. - Cham : Springer International Publishing. - 1867-4941 .- 0930-8989. - 9783319195209 ; 169, s. 173-178
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Konferensbidrag (refereegranskat)abstract
- X-ray parametric amplification is a high order parametric process with the capability to amplify ultrashort laser pulses with broad spectrum ranging from the extreme ultraviolet to the soft x-ray. In this contribution, the dynamics of this broadband amplification schema is studied with sub-20-as temporal resolution by seeding the amplifier with a train of 200-as-long pulses at 11 nm central wavelength.
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| 17. |
- Sukhareva, O. M., et al.
(författare)
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Validity of Quasi-classical Approaches to True Three-Body Decays
- 2020
-
Ingår i: Springer Proceedings in Physics. - Cham : Springer International Publishing. - 0930-8989 .- 1867-4941. ; 238, s. 283-286
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Konferensbidrag (refereegranskat)abstract
- Within the hyperspherical harmonics (HH) method the three-body problem is reduced to a motion of one effective particle in a “strongly deformed” field, which is described in the coupled-channel formalism. This method is well suited to studies of so-called true three-body decays. The reduction of the hyperspherical equations set to a single-channel approximation provides the basis of standard quasi-classical (QC) expression for width evaluation. We demonstrate that by itself the quasi-classical approach is quite precise in application to typical three-body effective potentials. However, the reduction to a single channel leads to a significant overestimation of the width.
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| 18. |
- Tavani, Francesco, et al.
(författare)
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Insights into the Structure of Reaction Intermediates Through Coupled X-ray Absorption/UV-Vis Spectroscopy
- 2021
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Ingår i: Springer Proceedings in Physics. - Cham : Springer International Publishing. - 0930-8989 .- 1867-4941. ; 220, s. 141-154
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Konferensbidrag (refereegranskat)abstract
- In this work, we propose a method for the structural characterization of chemical reaction intermediates. It allows one to analyze time-resolved coupled energy dispersive X-ray absorption spectroscopy (EDXAS) and UV-Vis reaction data through a matricial approach. Concentration profiles for the reaction key species are derived from the UV-Vis data and are used as mathematical constraints to extract their associated X-ray absorption near edge structure (XANES) spectra. The obtained XANES spectra are then quantitatively characterized by full multiple scattering (MS) calculations. We demonstrate the capabilities of this approach by applying it over a series of coupled EDXAS/UV-Vis spectra acquired in the reaction between FeII (tris(2-pyridylmethyl)amine) ([FeII(TPA)(CH3CN)2]2+ ) and H2O2. As a result, structural information for the elusive reaction key intermediate [ FeIII (TPA)(OOH)(X)]2 + is derived and it is suggested that X = CH3CN in opposition to X = H2O.
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| 19. |
- Yang, Zaihong, et al.
(författare)
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Study of Multi-neutron Systems with SAMURAI Spectrometer
- 2020
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Ingår i: Recent Progress in Few-Body Physics, FB22 201. - Cham : Springer International Publishing. - 0930-8989 .- 1867-4941. - 9783030323561 - 9783030323578 ; 238, s. 529-534
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Bokkapitel (refereegranskat)abstract
- The tetraneutron has been drawing the attention of the nuclear physics community for decades, but a firm conclusion on its existence and properties is still far from being reached despite many experimental and theoretical efforts. New measurements have recently been performed at RIBF with the SAMURAI spectrometer by applying complementary reaction probes, which will help to pin down the properties of this four-neutron system.
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| 20. |
- yilmas, I, 1980, et al.
(författare)
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Application and Comparison of Two Different DNS Algorithms for Simulating Transition to Turbulence in Taylor-Green Vortex Flow
- 2012
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Ingår i: Springer Proceedings in Physics. - Berlin, Heidelberg : Springer Berlin Heidelberg. - 0930-8989 .- 1867-4941. ; 141, s. 91-94
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Konferensbidrag (refereegranskat)abstract
- An all-Mach number, fully implicit, non-dissipative DNS algorithm and an incompressible, dissipative DNS algorithm were applied for simulating transition to turbulence in TGV flow to assess their behavior for this flow regime. The all-Mach number solver was developed and parallelized. A method was also adopted to remove oscillating pressure corrections in time. In order to compare the behavior of the algorithms, various flow diagnostics were calculated. The results were also compared to results given in the literature. The development of the flow and the peak structures show some differences due to different dissipative and energy conserving properties of the algorithms. However the physics of TGV flow are well captured by both, even though the grid is not fully resolved.
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