scholarly journals BDS PPP/INS Tight Coupling Method Based on Non-Holonomic Constraint and Zero Velocity Update

IEEE Access ◽  
2020 ◽  
Vol 8 ◽  
pp. 128866-128876
Author(s):  
Wei Sun ◽  
Yihan Yang
Keyword(s):  
Coupling Method ◽  
Tight Coupling ◽  
Holonomic Constraint ◽  
Zero Velocity

Flutter Study on High Speed Train External Windshield by a Tight Coupling Method

2019 ◽  
Author(s):  
Qian Jiang ◽  
Guannan Zheng ◽  
Guilin Zhao
Keyword(s):  
Information Transfer ◽  
High Speed ◽  
Stable State ◽  
Coupling Method ◽  
Coupling Scheme ◽  
Displacement Curve ◽  
High Speed Train ◽  
Tight Coupling ◽  
Time Step ◽  
Train Speed

Abstract Flutter is a complex problem caused by the interaction between the elastic structure and the flow field around that. In this paper a study of flutter on high speed train external windshield is presented. Here, a coupling scheme of computational fluid dynamics (CFD) and computational structure dynamics (CSD) is applied to simulate the flutter problems. Specifically, some key technologies like tight coupling method, information transfer and mesh deformation strategy are involved. Repeatedly exchanging information in the sub-iteration of physical time step is basically typical of tight coupling method, which is a second-order accuracy method. This flutter methodology has been applied for standard model AGARD 445.6 wing and other engineering examples, with lots of excellent results obtained. In this high speed train external windshield flutter research, eight train speed conditions are chosen to simulate the flutter issue, including 250km/h, 300km/h, 350km/h, 400 km/h, 450 km/h, 500 km/h, 550 km/h and 600 km/h. As for structural model, the first 30 order modes of elastic windshield are taken into consideration for CFD/CSD coupling simulation. In addition, it is defined to be the flutter boundary once the generalized displacement curve performing as persistent oscillation, which is the critical stable state for the vibration of external windshield. According to the research, under a specific train speed condition, adjustment of modal eigenfrequency can lead to the change of vibration stability. Furthermore, it is found that there is a positive correlation between train speed and modal eigenfrequency. So the optimal windshield scheme under different operating speeds is proposed that in order for the convergent vibration, a measure of changing eigenfrequency can be taken to ensure the vibration convergent and flutter cannot occur.

scholarly journals Numerical simulation of aircraft thermal anti-icing system based on a tight-coupling method

2020 ◽  
Vol 148 ◽  
pp. 119061 ◽  
Author(s):  
Xueqin Bu ◽  
Guiping Lin ◽  
Xiaobin Shen ◽  
Zhongliang Hu ◽  
Dongsheng Wen
Keyword(s):  
Numerical Simulation ◽  
Coupling Method ◽  
Tight Coupling

scholarly journals EFFICIENT CFD/CSD COUPLING METHODS FOR AEROELASTIC APPLICATIONS

2016 ◽  
Vol 42 ◽  
pp. 1660162 ◽  
Author(s):  
LONG CHEN ◽  
TIANHAO XU ◽  
JING XIE
Keyword(s):  
Numerical Simulation ◽  
Stokes Equations ◽  
Grid Method ◽  
Simulation Method ◽  
Mapping Method ◽  
Implicit Scheme ◽  
Coupling Method ◽  
Loose Coupling ◽  
Implicit Methods ◽  
Tight Coupling

A fast aeroelastic numerical simulation method using CFD/CSD coupling are developed. Generally, aeroelastic numerical simulation costs much time and significant hardware resources with CFD/CSD coupling. In this paper, dynamic grid method, full implicit scheme, parallel technology and improved coupling method are researched for efficiency simulation. An improved Delaunay graph mapping method is proposed for efficient dynamic grid deform. Hybrid grid finite volume method is used to solve unsteady flow fields. The dual time stepping method based on parallel implicit scheme is used in temporal discretization for efficiency simulation. An approximate system of linear equations is solved by the GMRES algorithm with a LU-SGS preconditioner. This method leads to a significant increase in performance over the explicit and LU-SGS implicit methods. A modification of LU-SGS is proposed to improve the parallel performance. Parallel computing overs a very effective way to improve our productivity in doing CFD/CFD coupling analysis. Improved loose coupling method is an efficiency way over the loose coupling method and tight coupling method. 3D wing's aeroelastic phenomenon is simulated by solving Reynolds-averaged Navier–Stokes equations using improved loose coupling method. The flutter boundary is calculated and agrees well with experimental data. The transonic hole is very clear in numerical simulation results.

scholarly journals On the Root Causes of the Fukushima Daiichi Disaster from the Perspective of High Complexity and Tight Coupling in Large-Scale Systems

Symmetry ◽  
2021 ◽  
Vol 13 (3) ◽  
pp. 414
Author(s):  
Atsuo Murata ◽  
Waldemar Karwowski
Keyword(s):  
Nuclear Power ◽  
Power Plants ◽  
Large Scale ◽  
High Complexity ◽  
Tight Coupling ◽  
Large Scale Systems ◽  
Safety Issues ◽  
Loss Of Coolant ◽  
Station Blackout ◽  
Fukushima Daiichi

This study explores the root causes of the Fukushima Daiichi disaster and discusses how the complexity and tight coupling in large-scale systems should be reduced under emergencies such as station blackout (SBO) to prevent future disasters. First, on the basis of a summary of the published literature on the Fukushima Daiichi disaster, we found that the direct causes (i.e., malfunctions and problems) included overlooking the loss of coolant and the nuclear reactor’s failure to cool down. Second, we verified that two characteristics proposed in “normal accident” theory—high complexity and tight coupling—underlay each of the direct causes. These two characteristics were found to have made emergency management more challenging. We discuss how such disasters in large-scale systems with high complexity and tight coupling could be prevented through an organizational and managerial approach that can remove asymmetry of authority and information and foster a climate of openly discussing critical safety issues in nuclear power plants.

scholarly journals Genes encoding putative bicarbonate transporters as a missing molecular link between molt and mineralization in crustaceans

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Shai Abehsera ◽  
Shmuel Bentov ◽  
Xuguang Li ◽  
Simy Weil ◽  
Rivka Manor ◽  
...  
Keyword(s):  
Calcium Carbonate ◽  
Molecular Mechanisms ◽  
Ph Control ◽  
Functional Genomic ◽  
Single Event ◽  
Tight Coupling ◽  
Molt Cycle ◽  
Mineral Deposition ◽  
Bicarbonate Transporters ◽  
Genes Encoding

AbstractDuring their life, crustaceans undergo several molts, which if theoretically compared to the human body would be equivalent to replacing all bones at a single event. Such a dramatic repetitive event is coupled to unique molecular mechanisms of mineralization so far mostly unknown. Unlike human bone mineralized with calcium phosphate, the crustacean exoskeleton is mineralized mainly by calcium carbonate. Crustacean growth thus necessitates well-timed mobilization of bicarbonate to specific extracellular sites of biomineralization at distinct molt cycle stages. Here, by looking at the crayfish Cherax quadricarinatus at different molting stages, we suggest that the mechanisms of bicarbonate ion transport for mineralization in crustaceans involve the SLC4 family of transporters and that these proteins play a key role in the tight coupling between molt cycle events and mineral deposition. This discovery of putative bicarbonate transporters in a pancrustacean with functional genomic evidence from genes encoding the SLC4 family—mostly known for their role in pH control—is discussed in the context of the evolution of calcium carbonate biomineralization.

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