Broken Symmetries, Hydrodynamics and Rare Fluctuations

A special issue of Symmetry (ISSN 2073-8994). This special issue belongs to the section "Life Sciences".

Deadline for manuscript submissions: closed (31 October 2019) | Viewed by 8990

Special Issue Editors


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Guest Editor
Física Teórica, Departamento de Física Atómica, Molecular y Nuclear, Universidad de Sevilla, Apartado de Correos 1065, E-41080 Sevilla, Spain
Interests: non-equilibrium statistical mechanics; stochastic thermodynamics; control theory; granular systems; mathematical physics

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Guest Editor
Universidad Carlos III de Madrid, Madrid, Spain

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Guest Editor
University of Granada, Granada, Spain

Special Issue Information

Dear Colleagues,

Unravelling the role of fluctuations is a major problem in statistical mechanics, mainly in nonequilibrium states. Indeed, fluctuations encode relevant information and become large and prominent when the system is “small”.  Here, small means that the number of degrees of freedom is large, but much smaller than Avogadro’s, as is the case in granular systems or many biological systems. In fact, thanks to the development of new high-resolution experimental techniques, the study of fluctuations in microscopic biological systems constitutes a main research field in this direction.

In addition, understanding the emergent macroscopic behavior of nonequilibrium systems (i.e., the hydrodynamic or thermodynamic description) from the underlying microscopic dynamics is a topical subject both in classical and quantum systems. In this regard, unveiling critical phenomena in the fluctuations of many-body driven systems, such as dynamical phase transitions (DPTs) accompanied by spontaneous symmetry breaking, is one of the current challenges in theoretical physics.

Prof. Antonio Prados
Dr. Antonio Lasanta Becerra
Dr. Carlos Pérez Espigares
Guest Editors

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Keywords

  • fluctuations
  • hydrodynamics
  • large deviations
  • phase transitions
  • symmetry breaking
  • granular media
  • biophysics

Published Papers (2 papers)

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Research

13 pages, 9753 KiB  
Article
Effect of Stall Cells on Pressure Fluctuations Characteristics in a Centrifugal Pump
by Peijian Zhou, Jiacheng Dai, Chaoshou Yan, Shuihua Zheng, Changliang Ye and Xiang Zhang
Symmetry 2019, 11(9), 1116; https://doi.org/10.3390/sym11091116 - 4 Sep 2019
Cited by 18 | Viewed by 2371
Abstract
Rotating stall is an unsteady flow phenomenon, which always leads to instability and efficiency degradation. In order to reveal pressure fluctuations in the impeller of centrifugal pump induced by stall cells, the flow structures in a volute-type centrifugal pump were calculated using Large [...] Read more.
Rotating stall is an unsteady flow phenomenon, which always leads to instability and efficiency degradation. In order to reveal pressure fluctuations in the impeller of centrifugal pump induced by stall cells, the flow structures in a volute-type centrifugal pump were calculated using Large Eddy Simulation (LES) method. The predicted results of the numerical model were compared with experimental flow-head curve. The simulation results were in good agreement with the experimental results. The stall phenomenon occurred when the flow rate dropped to 70% of design flow rate. Three stall cells located at the entrance of passages could be observed, which remained stationary relative to the rotating impeller. With the decrease of flow rate, the area occupied by stall cells gradually increased. The peak value of pressure fluctuation at 25% of design flow rate is obviously larger than that at 50% of design flow rate. For the unstalled or stalled passage, the impeller-volute interaction played a leading role in the pressure fluctuations of the impeller. For the stalled passage, the amplitude of the low frequency induced by stall cell is relatively insignificant. Full article
(This article belongs to the Special Issue Broken Symmetries, Hydrodynamics and Rare Fluctuations)
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11 pages, 4853 KiB  
Article
Anti-Cavitation Design of the Symmetric Leading-Edge Shape of Mixed-Flow Pump Impeller Blades
by Di Zhu, Ran Tao and Ruofu Xiao
Symmetry 2019, 11(1), 46; https://doi.org/10.3390/sym11010046 - 3 Jan 2019
Cited by 17 | Viewed by 6242
Abstract
Mixed-flow pumps compromise large flow rate and high head in fluid transferring. Long-axis mixed-flow pumps with radial–axial “spacing” guide vanes are usually installed deeply under water and suffer strong cavitation due to strong environmental pressure drops. In this case, a strategy combining the [...] Read more.
Mixed-flow pumps compromise large flow rate and high head in fluid transferring. Long-axis mixed-flow pumps with radial–axial “spacing” guide vanes are usually installed deeply under water and suffer strong cavitation due to strong environmental pressure drops. In this case, a strategy combining the Diffusion-Angle Integral Design method, the Genetic Algorithm, and the Computational Fluid Dynamics method was used for optimizing the mixed-flow pump impeller. The Diffusion-Angle Integral Design method was used to parameterize the leading-edge geometry. The Genetic Algorithm was used to search for the optimal sample. The Computational Fluid Dynamics method was used for predicting the cavitation performance and head–efficiency performance of all the samples. The optimization designs quickly converged and got an optimal sample. This had an increased value for the minimum pressure coefficient, especially under off-design conditions. The sudden pressure drop around the leading-edge was weakened. The cavitation performance within the 0.5–1.2 Qd flow rate range, especially within the 0.62–0.78 Qd and 1.08–1.20 Qd ranges, was improved. The head and hydraulic efficiency was numerically checked without obvious change. This provided a good reference for optimizing the cavitation or other performances of bladed pumps. Full article
(This article belongs to the Special Issue Broken Symmetries, Hydrodynamics and Rare Fluctuations)
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