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Seminars 05/5/2022

Seminars of the Institute for Computational Science (INCOS) & Advanced Institute of Materials Science (AIMaS) will be organized online at 9.00 AM on Thursday, 05th May 2022

9.00 AM – 10.00 AM: Dr. Nguyen Van Luc (INCOS, TDTU) presents the topic: "Oblique collision and reconnection of a vortex ring and a vortex tube" 

Abstract

The oblique collision and reconnection of a vortex ring and a vortex tube are numerically investigated using a sixth-order accurate vortex-in-cell method. At the oblique collision angle (α) of 0°, the reconnection occurs, in which half of the ring joins with a part of the tube to create a reconnected ring, and another half of the ring links to the rest of the tube to establish a new reconnected tube. At α = 15°, 30°, and 45°, two reconnections take place, where the first one generates a distorted reconnected tube, and then this tube reconnects itself to construct a new ring and a tube. The secondary vortex structures only appear surrounding the reconnected ring at α = 0°, while they are around both the reconnected ring and tube at α = 30° and 45°. As α increases, the time interval τ between two reconnections rises, and it is determined by a quadratic function as τ(α)=0.0037α2+0.0853α+0.975. The energy spectrum of the flow at the wavenumber (k) from 3 to 10 obeys the k−5/3 slope of a fully turbulent flow, and it is independent of α. However, the energy spectrum at the high wavenumber from 10 to 60 depends on α. This energy spectrum approaches the k−5/3 slope after the second reconnection for whole investigated cases.

 

10.00 AM - 11.00 AM: Dr. Le Thi Cam Tu (AIMaS, TDTU) presents the topic: "Manifestation Of Multiple Returns In Continuum Harmonics From Co Molecules"

Abstract

We theoretically study the manifestation of multiple returns in the high-order harmonic spectra from CO molecules by solving numerically the time-dependent Schroedinger equation within the single-active electron approximation. Based on the analysis of time-frequency profile [1] and classical simulation [2], we justify the multiple return effect and periodicity of harmonic spectra from CO. Furthermore, the time-frequency spectra show that the high-order returns not only are asymmetric regarding the molecular rotation of 180 degrees but also correlate with the first-order returns.

References

[1] Y.-l. Sheu, L.-Y. Hsu, H.-t. Wu, P.-C. Li and S.-I. Chu, AIP Advances 4, 117138 (2014).
[2] P. B. Corkum, Phys. Rev. Lett. 71, 1994 (1993).