scholarly journals Multiscale Numerical and Experimental Analysis of Tribological Performance of GO Coating on Steel Substrates

Materials ◽  
2019 ◽  
Vol 13 (1) ◽  
pp. 41 ◽  
Author(s):  
Robin Hildyard ◽  
Mahdi Mohammadpour ◽  
Sina Saremi-Yarahmadi ◽  
Manuela Pacella
Keyword(s):  
Numerical Model ◽  
Numerical Modelling ◽  
Combustion Engine ◽  
Cylinder Liner ◽  
Tribological Behaviour ◽  
Surface Shear ◽  
Frictional Performance ◽  
Surface Measurements ◽  
Tribological Films ◽  
Steel Substrates

Herein, nano-tribological behaviour of graphene oxide (GO) coatings is evaluated by a combination of nanoscale frictional performance and adhesion, as well as macroscale numerical modelling. A suite of characterisation techniques including atomic force microscopy (AFM) and optical interferometry are used to characterise the coatings at the asperity level. Numerical modelling is employed to consider the effectiveness of the coatings at the conjunction level. The macroscale numerical model reveals suitable deposition conditions for superior GO coatings, as confirmed by the lowest measured friction values. The proposed macroscale numerical model is developed considering both the surface shear strength of asperities of coatings obtained from AFM and the resultant morphology of the depositions obtained from surface measurements. Such a multi-scale approach, comprising numerical and experimental methods to investigate the tribological behaviour of GO tribological films has not been reported hitherto and can be applied to real-world macroscale applications such as the piston ring/cylinder liner conjunction within the modern internal combustion engine.

scholarly journals THE USE OF ARRAY PROCESSORS FOR NUMERICAL MODELLING OF TIDAL ESTUARY DYNAMICS

1980 ◽  
Vol 1 (17) ◽  
pp. 142
Author(s):  
D. Prandle ◽  
E.R. Funke ◽  
N.L. Crookshank ◽  
R. Renner
Keyword(s):  
Numerical Model ◽  
Numerical Modelling ◽  
Hybrid Model ◽  
Numerical Models ◽  
Computer Time ◽  
Scale Model ◽  
Hybrid Modelling ◽  
Tidal Propagation ◽  
Physical Scale ◽  
Array Processors

The use of array processors for the numerical modelling of estuarine systems is discussed here in the context of "hybrid modelling", however, it is shown that array processors may be used to advantage in independent numerical simulations. Hybrid modelling of tidal estuaries was first introduced by fiolz (1977) and later by Funke and Crookshank (1978). In a hybrid model, tidal propagation in an estuary is simulated by dynamically linking an hydraulic (or physical) scale model of part of the estuary to a numerical model of the remaining part in a manner such that a free interchange of flow occurs at the interface(s). Typically, the elevation of the water surface at the boundary of the scale model is measured and transmitted to the numerical model. In return, the flow computed at the boundary of the numerical model is fed directly into the scale model. This approach enables the extent of the scale model to be limited to the area of immediate interest (or to that area where flow conditions are such that they can be most accurately simulated by a scale model). In addition, since the region simulated by the numerical model can be extended almost indefinitely, the problems of spurious reflections from downstream boundaries can be eliminated. In normal use, numerical models are evaluated on the basis of computing requirements, cost and accuracy. The computer time required to simulate one tide cycle is, in itself, seldom of interest except in so far as it affects the above criteria. However in hybrid modelling this parameter is often paramount since concurrent operation of the numerical and scale models requires that the former must keep pace with the latter. The earlier hybrid model of the St. Lawrence (Funke and Crookshank, 1978) involved a one-dimensional numerical model of the upstream regions of the river. However, future applications are likely to involve extensive two-dimensional numerical simulation.

scholarly journals Numerical modelling of agglomeration process in a granular bed containing melting particles

2021 ◽  
Vol 2057 (1) ◽  
pp. 012063
Author(s):  
I G Donskoy
Keyword(s):  
Thermal Decomposition ◽  
Porous Medium ◽  
Numerical Model ◽  
Numerical Modelling ◽  
Side Wall ◽  
Low Grade ◽  
Granular Bed ◽  
Agglomeration Process ◽  
Simulation Results ◽  
Implicit Numerical Method

Abstract The paper considers a numerical model of a flow in a porous medium containing particles of a melting component (polymer). For this, an implicit numerical method of splitting in directions is used. Calculations are carried out for two heating methods (through the side wall, or by the input gas). The simulation results qualitatively reproduce some of the experimentally observed features of the thermal decomposition of polymer-containing mixtures. The results obtained are of interest in the study of low-grade fuels processing, often accompanied by agglomeration, as well as in the development of methods by which agglomeration can be prevented.

Mutual influence of plateau roughness and groove texture of honed surface on frictional performance of piston ring–liner system

2016 ◽  
Vol 231 (7) ◽  
pp. 838-859 ◽  
Author(s):  
Yang Hu ◽  
Xianghui Meng ◽  
Youbai Xie ◽  
Jiazheng Fan
Keyword(s):  
Piston Ring ◽  
Cylinder Liner ◽  
Texture Features ◽  
Groove Depth ◽  
Mixed Lubrication ◽  
Operating Conditions ◽  
Friction Reduction ◽  
Lubrication Performance ◽  
Liner System ◽  
Frictional Performance

The cylinder liner surface finish, which is commonly produced using the honing technique, is an essential factor of engine performance. The characteristics of the texture features, including the cross-hatch angle, the plateau roughness and the groove depth, significantly affect the performance of the ring pack–cylinder liner system. However, due to the influence of the honed texture features, the surface roughness of the liner is not subject to Gaussian distribution. To simulate the mixed lubrication performance of the ring–liner system with non-Gaussian roughness, the combination of a two-scale homogenization technique and a deterministic asperities contact method is adopted. In this study, a one-dimensional homogenized mixed lubrication model is established to study the influence of groove parameters on the load-carrying capacity and the frictional performance of the piston ring–liner system. The ring profile, plateau roughness, and operating conditions are taken into consideration. The main findings are that for nonflat ring, shallow and wide groove textures are beneficial for friction reduction, and there exists an optimum groove density that makes the friction minimum; for flat ring, wide and sparse grooves help improving the tribological performance, and there exists an optimum groove depth that makes the friction minimum.

Validation of a Numerical Model for the Investigation of Tension Leg Platforms With Marine Energy Application Using REEF3D

2021 ◽  
Author(s):  
Christian Windt ◽  
Nils Goseberg ◽  
Tobias Martin ◽  
Hans Bihs
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Numerical Model ◽  
Numerical Modelling ◽  
Numerical Data ◽  
Wave Structure ◽  
Offshore Wind ◽  
High Resolution Data ◽  
Marine Energy ◽  
Mooring Dynamics

Abstract Exploiting the offshore wind resources using floating offshore wind systems at sites with deep water depths requires advanced knowledge of the system behaviour, including the hydro-, areo-, and mooring dynamics. To that end, high-fidelity numerical modelling tools, based on Computational Fluid Dynamics, can support the research and development of floating offshore wind systems by providing high-resolution data sets. This paper presents the first steps towards the numerical modelling of tension leg platforms for floating offshore wind applications using the open-source Computational Fluid Dynamics toolbox REEF3D. The numerical model of a taut-moored structure is validated against experimental reference data. Results from wave-only test cases highlight the simplicity and effectiveness of the wave generation method, implemented in REEF3D. For the considered wave-structure interaction cases, deviations between the experimental and numerical data can be observed for the surge and pitch displacements, while the heave displacement and the mooring forces are capture with sufficient accuracy. Overall, the numerical results indicate high potential of REEF3D to be used for the modelling of floating offshore wind systems.

Physical and numerical modelling of sediment guiding walls in an alpine river

2021 ◽  
Author(s):  
Jakob Siedersleben ◽  
Marco Schuster ◽  
Dennis Ties ◽  
Benjamin Zwick ◽  
Markus Aufleger ◽  
...  
Keyword(s):  
Numerical Model ◽  
Numerical Modelling ◽  
Power Plants ◽  
Sediment Management ◽  
Design Flow ◽  
Scale Model ◽  
Surface Measurement ◽  
Management Options ◽  
Erosion And Deposition ◽  
Alpine River

<p>The presented work is part of the optimization of the sediment management at the hydroelectric powerplants in Reutte/Höfen in Austria. The weirs of the two powerplants are situated at the alpine river Lech, located about 3 km upstream of the Lechaschau gauge (A=1012.2 km²). Totally five sluice gates and a fixed overflow weir are controlling the upstream reservoir, being subjected to high rates of coarse bed load material. In frame of a coupled approach of physical and numerical modelling, different options to (i) avoid/minimize sediment deposition and (ii) allow improved sediment flushing were tested and optimized. Besides a lowering of energy losses (reduced spilling times) the reduction of depositions downstream close to the turbine outlet were considered.</p><p>The physical model covers the hydropower and weir system of both power plants within a stretch of 400m / 150m using a model scale of 1:25. Investigated situations covered periods of reservoir sedimentation, flushing of the reservoir and typical flood flow situations (e.g. HQ1 and an unsteady HQ5 event). For model parametrization, sediment samples to quantify size distribution were taken in the field. Sediment inputs to the model were realized dynamically and were required (due to scaling effects) to exclude cohesive fractions having a minimum particle size of 0.5 mm. The full-area surface measurement of the river bed was made by means of airborne laser bathymetry and echo sounding.</p><p>As part of an optimization of the overall sediment management strategy, the focus of the presented research is on the western located runoff power plant Höfen. Via a lateral water intake, a maximum design flow of 15 m³/s is withdrawn causing that the intake structure is subjected to sediment depositions. Within the described scale model (1:25) and a partial scale model (1:15) covering the western side, several management options and configurations of sediment guiding walls were tested. Erosion and deposition as well as the transported material are assessed by 3D laser scanning and permanent monitoring of transported sediment load entering and leaving the scale model.</p><p>Complementary, a 2D hydro numerical model using a layer based multi fraction approach for sediment transport is set up for an extended area to simulate the morpho-dynamic behavior. The numerical model covers the whole weir system and 750 m of the upstream part of the Lech. The simulations made were realized at nature scale and allowed to mimic the erosion and deposition pattern obtained within the physical modelling for different tested options. Regardless of a chosen guiding wall setup, the results showed that each one is compromise between sediment defense and the effectiveness of the subsequent flushing processes.</p>

In-Situ Static and Dynamic Testing and Numerical Modelling of the Dome of the Siena Cathedral (Italy)

2015 ◽  
pp. 85-114
Author(s):  
Gianni Bartoli ◽  
Michele Betti ◽  
Saverio Giordano ◽  
Maurizio Orlando
Keyword(s):  
Numerical Model ◽  
Numerical Modelling ◽  
13Th Century ◽  
Structural Behaviour ◽  
Destructive Testing ◽  
Dynamic Vibration ◽  
Heritage Buildings ◽  
Siena Cathedral ◽  
Vibration Tests

The chapter reports on the in-situ experimental campaign and the numerical modelling that were performed to assess the static and dynamic behaviour of the Cupola of the Siena Cathedral in Italy: an irregular polygonal masonry structure built in the 13th century and composed of two domes. The research was motivated by the failure of some of the stone-trusses which connect the two masonry domes and consists of: a) single and double flat-jack tests in the internal dome, b) dynamic vibration tests on the Cupola under environmental (wind) and artificial (vibrodyne) loads and c) dynamic vibration tests on the double colonnade located below the Cupola (hammer impact tests). Results of tests were employed to identify a numerical model of the Cupola, which allowed to simulate its structural behaviour and to account for the failure of the stone-trusses between the two domes. The numerical model was later extended to the whole Cathedral. Through the discussion of an emblematic case study, the chapter shows a careful application of non-destructive testing (NDT) and numerical modelling in the field of assessment (and rehabilitation) of heritage buildings.

Fronts and shelf-circulation models

1981 ◽  
Vol 302 (1472) ◽  
pp. 597-604 ◽  
Keyword(s):  
Numerical Model ◽  
Numerical Modelling ◽  
Continental Shelf ◽  
Satellite Imagery ◽  
Three Dimensional ◽  
Shelf Circulation ◽  
Eddy Formation ◽  
Coastal Front

Satellite imagery shows that fronts and frontal eddies are widespread on the northwest European continental shelf. The implications for the numerical modelling of transports (for example, of pollutants) are discussed. A brief review of some models of shelf circulation is given. It is argued that to include fronts in models of shelf circulation requires a better understanding of dynamics on the frontal scale. A three-dimensional numerical model of eddy formation in a coastal front is then presented that reproduces many of the observed features.

Stability Analysis of Chatter System on Ultrasonic Honing

2013 ◽  
Vol 712-715 ◽  
pp. 1241-1247
Author(s):  
Yun Peng Shao ◽  
Xi Jing Zhu ◽  
Meng Liu ◽  
Zhen Liu
Keyword(s):  
Combustion Engine ◽  
Damping Ratio ◽  
Stability Limit ◽  
Cylinder Liner ◽  
Spindle Speed ◽  
Machining System ◽  
Motion Speed ◽  
The Stability ◽  
Stiffness And Damping

The chatter caused by the inner factors of the machining system in the ultrasonic honing process would seriously affect the surface quality of combustion engine. A dynamical model of ultrasonic honing chatter system was established, which involved with ultrasonic honing mechanism and dynamic honing depth, the relationship between the limit honing width and honing speed was deduced based on the theory of regenerative chatter; the simulation was carried out to obtain the effect of different parameters including stiffness coefficient, damping ratio, spindle speed and reciprocation motion speed on the stability limit curve of the chatter system. It can be concluded that the ultrasonic honing chatter system have better stability with low spindle speed, high stiffness and damping ratio, which providing foundation to eliminate ultrasonic honing system chatter in the precision machining of cylinder liner.

Tribological Behaviour of Gradient TiAlSiN Superhard Coatings

2016 ◽  
Vol 674 ◽  
pp. 207-212 ◽  
Author(s):  
Athanasios Mourlas ◽  
Pandora Psyllaki ◽  
Dimitrios Chaliampalias ◽  
George Vourlias ◽  
Lyliana Kolaklieva ◽  
...  
Keyword(s):  
Photoelectron Spectroscopy ◽  
Tribological Behaviour ◽  
Experimental Conditions ◽  
Tin Coatings ◽  
Cathodic Arc Deposition ◽  
Transmission Electron ◽  
Gradient Microstructure ◽  
Average Factor ◽  
Gradient Coatings ◽  
Steel Substrates

The present study addresses the influence of the gradient microstructure of nanocrystalline TiAlSiN coatings on their tribological behaviour. Cathodic arc deposition was applied to elaborate such coatings, with a total thickness of 3.5 μm, onto stainless steel substrates. Their microstructure has been characterised via Transmission Electron Microscopy (TEM) and X-ray Photoelectron Spectroscopy (XPS) and has been reported in detail previously. Since the main application of TiN-based coatings is the enhancement of the anti-wear resistance of metallic substrates, this work is focused on the tribological performance of gradient TiAlSiN coatings under dry sliding conditions. For this purpose, tests were carried out in a ball-on-disc apparatus, using an alumina ball as counterbody. The influence of the sliding velocity on the evolution of the friction coefficient and the wear lifetime of the gradient coatings has been evaluated in comparison to those of TiN coatings of the same thickness, tested under the same experimental conditions. It was found that the gradient microstructure results in an increase of the coatings’ mean lifetime by an average factor of three.

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