Preliminary studies on jet flows from flat vane swirler: Effect of twist angle

AbstractTwisted bilayered systems such as bilayered graphene exhibit remarkable properties such as superconductivity at magic angles and topological insulating phases. For generic twist angles, the bilayers are truly quasiperiodic, a fact that is often overlooked and that has consequences which are largely unexplored. Herein, we uncover that twisted n-layers host intrinsic higher dimensional topological phases, and that those characterized by second Chern numbers can be found in twisted bi-layers. We employ phononic lattices with interactions modulated by a second twisted lattice and reveal Hofstadter-like spectral butterflies in terms of the twist angle, which acts as a pseudo magnetic field. The phason provided by the sliding of the layers lives on 2n-tori and can be used to access and manipulate the edge states. Our work demonstrates how multi-layered systems are virtual laboratories for studying the physics of higher dimensional quantum Hall effect, and can be employed to engineer topological pumps via simple twisting and sliding.

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Self-similarity of turbulent jet flows with internal and external intermittency

Journal of Fluid Mechanics ◽

10.1017/jfm.2021.399 ◽

2021 ◽

Vol 919 ◽

Author(s):

M. Gauding ◽

M. Bode ◽

Y. Brahami ◽

É. Varea ◽

L. Danaila

Keyword(s):

Turbulent Jet ◽

Jet Flows ◽

Self Similarity

Abstract

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A Simple Gas-Kinetic Model For Dilute and Weakly Charged Plasma Micro-Jet Flows

Fluids ◽

10.3390/fluids6070250 ◽

2021 ◽

Vol 6 (7) ◽

pp. 250

Author(s):

Shiying Cai ◽

Chunpei Cai

Keyword(s):

Simple Model ◽

Electric Fields ◽

Neutral Condition ◽

Jet Flows ◽

Far Field ◽

Convection Term ◽

Number Density ◽

Simulation Based ◽

Analytical Formulas ◽

Electric Field Force

This paper presents a simple model for slightly charged gas expanding into a vacuum from a planar exit. The number density, bulk velocity, temperature, and potential at the exit are given. The electric field force is assumed weaker than the convection term and is neglected in the analysis. As such, the quasi-neutral condition is naturally adopted and the potential field is computed with the Boltzmann relation. At far field, the exit degenerates as a point source, and simplified analytical formulas for flow and electric fields are obtained. The results are generic and offer insights on many existing models in the literature. They can be used to quickly approximate the flowfield and potential distributions without numerical simulations. They can also be used to initialize a simulation. Based on these results, more advanced models may be further developed.

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Spectroscopy of a tunable moiré system with a correlated and topological flat band

Nature Communications ◽

10.1038/s41467-021-23031-0 ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Xiaomeng Liu ◽

Cheng-Li Chiu ◽

Jong Yeon Lee ◽

Gelareh Farahi ◽

Kenji Watanabe ◽

...

Keyword(s):

Band Structure ◽

Twist Angle ◽

Bilayer Graphene ◽

Scanning Tunneling Spectroscopy ◽

Scanning Tunneling ◽

Flat Band ◽

Correlated Electron ◽

Partial Filling ◽

Valley Polarization ◽

Spectroscopic Signatures

AbstractMoiré superlattices created by the twisted stacking of two-dimensional crystals can host electronic bands with flat energy dispersion in which enhanced interactions promote correlated electron states. The twisted double bilayer graphene (TDBG), where two Bernal bilayer graphene are stacked with a twist angle, is such a moiré system with tunable flat bands. Here, we use gate-tuned scanning tunneling spectroscopy to directly demonstrate the tunability of the band structure of TDBG with an electric field and to show spectroscopic signatures of electronic correlations and topology for its flat band. Our spectroscopic experiments are in agreement with a continuum model of TDBG band structure and reveal signatures of a correlated insulator gap at partial filling of its isolated flat band. The topological properties of this flat band are probed with the application of a magnetic field, which leads to valley polarization and the splitting of Chern bands with a large effective g-factor.

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