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Coupling effect of wall slip and spanwise oscillation on drag reduction in turbulent channel flow

Physical Review Fluids 2020年第12期5卷 124601-124601页

作者： Zexiang Li Songsong Ji Huiling Duan Shilong Lan Jinbai Zhang Pengyu Lv State Key Laboratory for Turbulence and Complex Systems Department of Mechanics and Engineering Science BIC-ESAT College of Engineering Peking University Beijing 100871 China Key Laboratory of High Energy Density Physics Simulation Center for Applied Physics and Technology Peking University Beijing 100871 China National Laboratory of Computational Fluid Dynamics Beihang University Beijing 100191 China

The coupling effect of the isotropic wall slip and the spanwise oscillation boundary conditions on the drag reduction and turbulence properties are studied by direct numerical simulations. As the slip length increases, the drag reduction gradually changes from the oscillation dominated to the slip dominated. The increase of slip length will decrease the maximum spanwise velocity of the fluid on the wall, which is responsible for the decreased ability of the oscillatory wall motion to reduce the skin-friction drag. The drag reduction decomposition shows that the contribution from the modifications of turbulent dynamics will undergo a shift from drag increase to drag reduction as the isotropic slip length increases. Compared with the respective no-slip reference flow, the drag reduction of wall slip in laminar and turbulent channel flows can be expressed in a unified form versus the outer scale slip length. Furthermore, many aspects of the turbulence properties are influenced by the coupling effect. First, the wall slip condenses the envelope range of the phase fluctuations caused by the oscillatory wall motion, as well as the magnitude of the periodic fluctuation of the phase-averaged friction coefficient. Second, an unexpected property of the coupled boundary condition is found that the existence of the Stoke layer delays the relaminarization process caused by the large slip length. Third, the wall slip would narrow the periodic inclination of the streaks and then inhibit the energy transfer process in the horizontal direction. Fourth, in terms of phase, the Stokes strain and the shear angle have the same lag phase with the spanwise velocity, while the hysteresis of turbulent dynamics leads to the larger lag phase of the streaks and phase-averaged friction coefficient. These new features are valuable for increasing knowledge on this topic.

关键词： Slip boundary effects Turbulence Wall slip

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Asymptotic critical behavior of holographic phase transition at finite topological charge - the spectrum of excited states becomes continuous at T = 0

arXiv

引用

arXiv 2021年

作者： Nguyen, Toan T. Phat, Tran Huu Key Laboratory for Multiscale Simulation of Complex Systems Department of Theoretical Physics University of Science Vietnam National University – Hanoi 334 Nguyen Trai street Thanh Xuan Hanoi100000 Viet Nam Vietnam Atomic Energy Commission 59 Ly Thuong Kiet street Hoan Kiem Hanoi100000 Viet Nam

Within the framework of AdS/CFT duality, excited states of the conformal field living at the global AdS boundary of a four-dimensional spacetime Einstein gravity are investigated analytically in the probe limit where the field equations are linearized. At asymptotically large values, the threshold chemical potential for the appearance of excited condensate states are discrete, equal spacing, with the gap approaches zero logarithmically in the limit T → 0. Remarkably, numerical results show that, this behavior applies even for states as low as for the first or the second excited state of the condensate. This is especially significant on the liquid side of the black hole van der Waals - like phase transition (small or zero topological charge) where there seems to be no gap between the ground state and the first excited state at zero temperature. We postulate that, at the exact limit T = 0 where the gap is zero, the spectrum of threshold chemical potentials becomes continuous, all excited states of the condensate are activated above a finite chemical potential, suggesting a new quantum phase transition as a function of the chemical potential. Previous studies have largely missed this continuous spectrum of excited states in the T → 0 limit. This fact should be taken into account carefully in AdS/CFT duality studies. Copyright © 2021, The Authors. All rights reserved.

关键词： Excited states

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On the triplet of holographic phase transition

arXiv

引用

arXiv 2021年

作者： Phat, Tran Huu Nguyen, Toan T. Vietnam Atomic Energy Commission 59 Ly Thuong Kiet street Hoan Kiem Hanoi100000 Viet Nam Key Laboratory for Multiscale Simulation of Complex Systems Department of Theoretical Physics University of Science Vietnam National University − Hanoi 334 Nguyen Trai street Thanh Xuan Hanoi100000 Viet Nam

We start from an Einstein − Maxwell system coupled with a charged scalar field in Anti−de Sitter space−time. In the setup where the pressure P is identified with the cosmological constant, the AdS black hole (BH) undergoes the phase transition from small to large BHs, which is similar to the transition from liquid to gas in the van der Waals theory. Based on this framework, we study the triplet of holographic superconducting states, consisting of ground state and two lowest excited states. Our numerical calculations show that the pressure variation in the bulk creates a mechanism in the boundary which causes changes in the physical properties of excited states, namely: a) when the pressure P is higher than the critical pressure Pc (P > Pc) of the phase transition from small to large BHs the ground state and the first excited state are superconducting states while the second excited state is the normal one. However, at lower pressure, P ≤ Pc, the ground state is solely the superconducting state. We conjecture that the precedent phenomena could take place when the scalar field in the bulk is replaced by other matter fields. Copyright © 2021, The Authors. All rights reserved.

关键词： Ground state

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Charged AdS black hole and the quantum tunneling from black hole to white hole

arXiv

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arXiv 2022年

作者： Phat, T.H. Anh, N.T. Nguyen, Toan T. Quyet, H.V. Vietnam Atomic Energy Commission 59 Ly Thuong Kiet Hanoi Viet Nam Faculty of Energy Technology Electric Power University 235 Hoang Quoc Viet Hanoi Viet Nam Key Laboratory for Multiscale Simulation of Complex Systems Department of Theoretical Physics University of Science Vietnam National University − Hanoi 334 Nguyen Trai street Thanh Xuan Hanoi100000 Viet Nam Department of Physics Hanoi Pedagogical University 2 Vinh Phuc Phuc Yen15000 Viet Nam

In this paper, we show that depending on the sign of the electric charge Q, the charged AdS black hole (BH) possesses two alternative facets when the cosmological constant is identified to the thermodynamic pressure P. It is discovered that: 1) the equation of state of BH corresponds to Q > 0 and when Q changes from Q > 0 to Q WH (T) which releases in this process equals with minus sign the latent heat of BH, too;3) Finally, the probability of the quantum tunneling from the BH to the WH is obtained. We suggest the perspective of application of the results above to the AdS/CFT duality. Copyright © 2022, The Authors. All rights reserved.

关键词： Gravitation

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The sQ¯ q¯ q (q = u, d;Q = c, b) tetraquarks in the chiral quark model

arXiv

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arXiv 2021年

作者： Yang, Gang Ping, Jialun Segovia, Jorge Department of Physics Zhejiang Normal University Jinhua321004 China Department of Physics Jiangsu Key Laboratory for Numerical Simulation of Large Scale Complex Systems Nanjing Normal University Nanjing210023 China Departamento de Sistemas Físicos Químicos y Naturales Universidad Pablo de Olavide SevillaE-41013 Spain

The low-lying sQq¯q¯ (q = u, d, Q = c, b) tetraquark states with JP = 0+, 1+ and 2+, and in the isoscalar and isovector sectors, are systematically investigated in the framework of real- and complex-scaling range of a chiral quark model, whose parameters have been fixed in advance describing hadron, hadron-hadron and multiquark phenomenology, and thus all results presented here are pure predictions. Each tetraquark configuration, compatible with the quantum numbers studied, is taken into account;this includes meson-meson, diquark-antidiquark and K-type arrangements of quarks with all possible color wave functions in four-body sector. Among the different numerical techniques to solve the Schrödinger-like 4-body bound state equation, we use a variational method in which the trial wave function is expanded in complex-range Gaussian basis functions, because its simplicity and flexibility. Several compact bound states and narrow resonances are found in both charm-strange csq¯q¯ and bottom-strange bsq¯q¯ tetraquark sectors, most of them as a product of the strong coupling between the different channels. The so-called X0,1(2900) signals, recently found by the LHCb collaboration, are unstable in our formalism with several candidates in the single-channel computations. Copyright © 2021, The Authors. All rights reserved.

关键词： Hadrons

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Hidden-charm tetraquarks with strangeness in the chiral quark model

arXiv

引用

arXiv 2021年

作者： Yang, Gang Ping, Jialun Segovia, Jorge Department of Physics Zhejiang Normal University Jinhua321004 China Department of Physics and Jiangsu Key Laboratory for Numerical Simulation of Large Scale Complex Systems Nanjing Normal University Nanjing210023 China Departamento de Sistemas Físicos Químicos y Naturales Universidad Pablo de Olavide SevillaE-41013 Spain

The hidden-charm tetraquarks with strangeness, ccs ¯ q¯ (q = u, d), in JP = 0+, 1+ and 2+ are systematically investigated in the framework of real- and complex-scaling range of a chiral quark model, whose parameters have been fixed in advance describing hadron, hadron-hadron and multiquark phenomenology. Each tetraquark configuration, compatible with the quantum numbers studied, is taken into account;this includes meson-meson, diquark-antidiquark and K-type arrangements of quarks with all possible color wave functions in four-body sector. Among the different numerical techniques to solve the Schrödinger-like 4-body bound state equation, we use a variational method in which the trial wave function is expanded in complex-range Gaussian basis functions, which is characterized by its simplicity and flexibility. This theoretical framework has already been used to study different kinds of multiquark systems, such as the hidden-charm pentaquarks, Pc+, and doubly-charmed tetraquarks, Tcc+. The recently reported Zcs states by the BESIII and LHCb collaborations are generally compatible with either compact tetraquark or hadronic molecular resonance configurations in our investigation. Moreover, several additional exotic resonances are found in the mass range between 3.8 GeV and 4.6 GeV. Copyright © 2021, The Authors. All rights reserved.

关键词： Hadrons

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Reanalysis of the most strange dibaryon within constituent quark models

引用

Physical Review C 2020年第3期101卷 034004-034004页

作者： Hongxia Huang Xinmei Zhu Jialun Ping Department of Physics and Jiangsu Key Laboratory for Numerical Simulation of Large Scale Complex Systems Nanjing Normal University Nanjing 210023 People's Republic of China Department of Physics Yangzhou University Yangzhou 225009 People's Republic of China

The most strange dibaryon ΩΩ with quantum numbers S=−6, I=0, and JP=0+,1−,2+,3− is reanalyzed in the framework of a quark delocalization color screening model (QDCSM) and chiral quark model (ChQM). The ΩΩ dibaryon with JP=0+ is bound, and the one with other quantum numbers JP=1−,2+,3− are all unbound in our calculation. The low-energy scattering phase shifts, the scattering length, and the effective range of the ΩΩ dibaryon with JP=0+ also support the existence of such strange dibaryon. This dibaryon is showed to be a shallow bound state in QDCSM, while the binding energy becomes much larger in the ChQM by including the effect of the hidden color channels coupling. And the scalar nonet meson exchange in the ChQM also provides more attraction for the ΩΩ system. Experimental search for such most strange dibaryon will provide much information for understanding the hadron-hadron interactions in different quark models.

关键词： Nucleon-nucleon interactions Quark model

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Query modeling for click data based image recognition using graph based propagation and sparse coding

Query modeling for click data based image recognition using ...

引用

9th International Conference on Internet Multimedia Computing and Service, ICIMCS 2017

作者： Wu, Weichen Tan, Min Zheng, Guangjian Yu, Jun Key Laboratory of Complex Systems Modeling and Simulation School of Computer Science and Technology Hangzhou Dianzi University Hangzhou310018 China

ISBN: (纸本)9789811085291

We address the fine-grained image recognition problem using user click data, wherein each image is represented as a semantical query-click feature vector. Usually, the query set obtained from search engines is large-scale and redundant. We propose a novel query modeling approach to merge semantically similar queries and construct a compact click feature. We represent each query as a click feature, and design a graph based propagation approach to predict the zero-clicks, ensuring similar images have similar clicks. Afterwards, using this feature, we formulate the problem as a sparse coding based recognition task, wherein the dictionary is discriminatively trained. We evaluate our method for fine-grained image recognition on the public Clickture-Dog dataset. It is shown that, the propagated click feature performs much better than the original one. Also, sparse coding performs better than K-means in query merging. © Springer Nature Singapore Pte Ltd. 2018.

关键词： Image recognition

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The ${ {\bar{\boldsymbol q}\boldsymbol q\bar{\boldsymbol s}\boldsymbol Q} \;\;{(\boldsymbol q {\bf =}\boldsymbol u,\,\boldsymbol d;\,\boldsymbol Q{\bf =}\boldsymbol c,\,\boldsymbol b)} }$ tetraquark system in a chiral quark model*

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Chinese Physics C 2024年第7期48卷 073106-073106页

作者： Gang Yang Jialun Ping Jorge Segovia Department of Physics Zhejiang Normal University Jinhua 321004 China Department of Physics and Jiangsu Key Laboratory for Numerical Simulation of Large Scale Complex Systems Nanjing Normal University Nanjing 210023 China Departamento de Sistemas Físicos Químicos y Naturales Universidad Pablo de Olavide E-41013 Sevilla Spain

The S-wave $\bar{q}q\bar{s}Q \;\; (q=u,\,d;\,Q=c,\,b)$ tetraquarks, with spin-parities $J^P=0^+$, $1^+$, and $2^+$, in both isoscalar and isovector sectors, are systematically studied using a chiral quark model. The

The S-wave $\bar{q}q\bar{s}Q \;\; (q=u,\,d;\,Q=c,\,b)$ $\bar{q}q\bar{s}Q \;\; (q=u,\,d;\,Q=c,\,b)$ tetraquarks, with spin-parities $ J^P=0^+ $ $J^P=0^+$, $ 1^+ $ $1^+$, and $ 2^+ $ $2^+$, in both isoscalar and isovector sectors, are systematically studied using a chiral quark model. The

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Study of Bs → K(∗)+− decays in the PQCD factorization approach with the lattice QCD input

arXiv

引用

arXiv 2020年

作者： Jin, Su-Ping Hu, Xue-Qing Xiao, Zhen-Jun Department of Physics and Institute of Theoretical Physics Nanjing Normal University Nanjing Jiangsu210023 China Jiangsu Key Laboratory for Numerical Simulation of Large Scale Complex Systems Nanjing Normal University Nanjing210023 China

In this paper, we studied systematically the semileptonic decays Bs → K(∗)+− with l− = (e−,µ−,τ−) by using the perturbative QCD (PQCD) and the "PQCD+Lattice" factorization approach, respectively. We first evaluated all relevant form factors Fi(q2) in the low q2 region using the PQCD approach, and we also take the available Lattice QCD results at the end point qmax2 as additional input to improve the extrapolation of the form factors to the high q2 region. We calculated the branching ratios and other twelve kinds of physical observables: AFB(l), PL, FLK∗ and the angular observables Pi and Pj′. From our studies, we find the following points: (a) for Bs → Kl+l− decays, the PQCD and "PQCD+Lattice" predictions for branching ratios (BRs) B(Bs → Kl+l−), the ratios of the BRs RKeµ,µτ and the longitudinal polarization asymmetry of the leptons PL agree well within errors;(b) the "PQCD+Lattice" prediction B(Bs → K∗µ+µ−) = (2.58+0−0..6960)×10−8 does agree well with the LHCb measured value (2.9 ± 1.1) × 10−8;(c) for the ratios RKeµ∗ and RKµτ∗, the PQCD and "PQCD+Latatice" predictions agree very well and have a small error less than 10% due to the cancellation of the theoretical uncertainties in the ratios of the branching ratios;(d) for the angular observables P1,2,3 and P4′,5,6,8 , our theoretical predictions for each lepton l− are consistent within errors;(e) the theoretical predictions of the angular observables P3 and P6′,8 are less than 10−2 in absolute value, but the magnitude of P1,2 and P4′,5 are larger than 0.2;and (f) the PQCD and "PQCD+Lattice" predictions of the binned values of all considered observables in the two q2-bins [0.1 − 0.98]GeV2 and [1.1 − 6]GeV2 generally agree with each other and also be consistent with the LCSR results within errors. We believe that above predictions could be measured by future LHCb and Belle-II experiments. Copyright © 2020, The Authors. All rights reserved.

关键词： Quantum theory

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