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Cavitation research with computational fluid dynamics:From euler-euler to euler-Lagrange approach

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Journal of Hydrodynamics 2024年第1期36卷 1-23页

作者： Bin Ji Zi-yang Wang Huai-yu Cheng rickard e.bensow State Key Laboratory of Water Resources engineering and Management Wuhan UniversityWuhan430072China Department of Mechanics and Maritime Sciences Chalmers University of TechnologyGothenburgSweden

Unsteady cavitating flow often contains vapor structures with a wide range of different length scales,from micro-bubbles to large cavities,which issues a big challenge to precisely investigate its evolution mechanism by computational fluid dynamics(CFD)*** present work reviews the development of simulation methods for cavitation,especially the emerging euler-Lagrange ***,the progress of the numerical investigation of hot and vital issues is discussed,including cavitation inception,cloud cavitation inner structure and its formation mechanism,cavitation erosion,and cavitation *** is indicated that the euler-Lagrange method can determine cavitation inception point *** cloud cavitation,the euler-Lagrange method can reveal the source of microbubbles and their distribution law inside the shedding *** method also has advantages and great potential in assessing cloud cavitation-induced erosion and *** the ever-growing demands of cavitation simulation accuracy in basic research and engineering applications,how to improve the euler-Lagrange method’s stability and applicability is still an open *** further promote the application of this advanced CFD simulation technology in cavitation research,some key issues are to be solved and feasible suggestions are put forward for further work.

关键词： numerical simulation euler-euler method euler-Lagrange method bubble dynamicsgy,Gothenburg,Sweden

Hydrodynamic mechanisms of aggressive collapse events in leading edge cavitation

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Journal of Hydrodynamics 2020年第1期32卷 6-19页

作者： Mohammad Hossein Arabnejad Ali Amini Mohamed Farhat rickard ebensow Department of Mechanics and Maritime Sciences Chalmers University of TechnologyGothenburgSweden Laboratory for Hydraulic Machines EPFLLausanneSwitzerland

Transient cavities generated from unsteady leading-edge cavitation may undergo aggressive collapses which are responsible for cavitation *** this paper,we studied the hydrodynamic mechanisms of these events in the leading edge cavitation fonned over a modified NACA0009 hydrofoil using experimental and numerical *** the experimental investigation,high-speed visualization(HSV)and paint test are employed to study the behavior of the cavitating flow at σ=1.25,α=5°,U∞=20 m/*** the numerical part,the same cavitating flow is simulated using an inviscid density-based compressible solver with a barotropic cavitation *** numerical results are first compared with the experimental HSV to show that the simulation is able to reproduce the main features of the cavitating ***,as the compressible solver is capable of capturing the shock wave upon the collapse of cavities,the location of collapse events with high erosion potential are *** location of these collapse events are compared with the paint test results with a qualitatively good *** is clearly observed,in both the experiments and the numerical simulation,that there exists four distinct regions along the hydrofoil with higher risks of erosion:(1)A very narrow strip at the leading edge,(2)an area of accumulated collapses at around 60 percent of the sheet cavity maximum length,(3)an area around the closure line of the sheet cavity with the highest erosion damage,and(4)a wide area close to the trailing edge with dispersed collapse events.A combined analysis of the experimental and numerical results reveals that the small-scale structures generated by secondary shedding are more aggressive than the large-scale cloud cavities(primary shedding).It is also observed that the high risk of cavitation erosion in regions 2 and 3 is mainly due to the collapses of the small cavity structures that are formed around the sheet cavity closure line or the rolling cloud cavity.

关键词： Hydrodynamic mechanisms aggressive collapse events high-speed visualization(HSV) paint test compressible simulation of cavitating flows

Time-resolved, defect-hosted, trace element mobility in deformedWitwatersrand pyrite

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Geoscience Frontiers 2019年第1期10卷 55-63页

作者： Denis Fougerouse Steven M.Reddy Christopher L.Kirkland David W.Saxey William D.rickard Robert M.Hough School of earth and Planetary Sciences The Institute for Geoscience Research (TIGeR) Curtin University Geoscience Atom Probe Advanced Resource Characterisation Facility John de Laeter Centre Curtin University CSIRO Minerals Resources

The Pb isotopic composition of rocks is widely used to constrain the sources and mobility of melts and hydrothermal fluids in the earth's crust. In many cases, the Pb isotopic composition appears to represent mixing of multiple Pb reservoirs. However, the nature, scale and mechanisms responsible for isotopic mixing are not well known. Additionally, the trace element composition of sulphide minerals are routinely used in ore deposit research, mineral exploration and environmental studies, though little is known about element mobility in sulphides during metamorphism and deformation. To investigate the mechanisms of trace element mobility in a deformed Witwatersrand pyrite(FeS_2), we have combined electron backscatter diffraction(eBSD) and atom probe microscopy(APM). The results indicate that the pyrite microstructural features record widely different Pb isotopic compositions, covering the entire range of previously published sulphide Pb compositions from the Witwatersrand basin. We show that entangled dislocations record enhanced Pb, Sb, Ni, Tl and Cu composition likely due to entrapment and short-circuit diffusion in dislocation cores. These dislocations preserve the Pb isotopic composition of the pyrite at the time of growth(~3 Ga) and show that dislocation intersections, likely to be common in deforming minerals, limit trace element mobility. In contrast, Pb, As, Ni, Co, Sb and Bi decorate a highangle grain boundary which formed soon after crystallisation by sub-grain rotation *** isotopic composition within this boundary indicates the addition of externally-derived Pb and trace elements during greenschist metamorphism at ~2 Ga. Our results show that discrete Pb reservoirs are nanometric in scale, and illustrate that grain boundaries may remain open systems for trace element mobility over 1 billion years after their formation.

关键词： Atom probe microscopy Nanoscale Nanogeochronology Microstructure Isotope geochemistry Common Pb

Improved gastrointestinal health for irritable bowel syndrome with metagenome-guided interventions

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Precision Clinical Medicine 2020年第2期3卷 136-146页

作者： Cem Meydan ebrahim Afshinnekoo Nate rickard Guy Daniels Laura Kunces Theresa Hardy Loukia Lili Sarah Pesce Paul Jacobson Christopher e.Mason Joel Dudley Bodi Zhang Onegevity Health 152 W 57thNew YorkNY 10019USA Thorne Research 152 W 57thNew YorkNY 10019USA

Irritable bowel syndrome(IBS)is the most prevalent functional gastrointestinal disorder worldwide,and the most common reason for referral to gastroenterology ***,the pathophysiology is still not fully understood and consequently current management guidelines are very symptom-specific,leading to mixed *** we present a study of 88 individuals with IBS who had baseline sequencing of their gut microbiome(stool samples),received targeted interventions that included dietary,supplement,prebiotic/probiotic,and lifestyle recommendations for a 30-day period,and a follow-up sequencing of their gut *** study’s objectives were to demonstrate unique metagenomic signatures across the IBS phenotypes and to validate whether metagenomic-guided interventions could lead to improvement of symptom scores in individuals with *** subjects also completed a baseline and post-intervention questionnaire that assessed their symptom *** average symptom score of an individual with IBS at baseline was 160 and at the endpoint of the study the average symptom score of the cohort was *** mixed IBS subtype showed the most significant reduction in symptom scores across the different subtypes(average decrease by 102 points,P=0.005).The metagenomics analysis reveals shifts in the microbiome post-intervention that have been cross-validated with the literature as being associated with improvement of IBS *** the complex nature of IBS,further studies with larger sample sizes,more targeted analyses,and a broader population cohort are needed to explore these results further.

关键词： irritable bowel syndrome microbiome metagenomics

Forecasting Baltic Dirty Tanker Index by Applying Wavelet Neural Networks

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Journal of Transportation Technologies 2013年第1期3卷 68-87页

作者： Shuangrui Fan Tingyun Ji Wilmsmeier Gordon Bergqvist rickard 不详

Baltic exchange Dirty Tanker Index (BDTI) is an important assessment index in world dirty tanker shipping industry. Actors in the industry sector can gain numerous benefits from accurate forecasting of the BDTI. However, limitations exist in traditional stochastic and econometric explanation modeling techniques used in freight rate forecasting. At the same time research in shipping index forecasting e.g. BDTI applying artificial intelligent techniques is scarce. This analyses the possibilities to forecast the BDTI by applying Wavelet Neural Networks (WNN). Firstly, the characteristics of traditional and artificial intelligent forecasting techniques are discussed and rationales for choosing WNN are explained. Secondly, the components and features of BDTI will be explicated. After that, the authors delve the determinants and influencing factors behind fluctuations of the BDTI in order to set inputs for WNN forecasting model. The paper examines non-linearity and non-stationary features of the BDTI and elaborates WNN model building procedures. Finally, the comparison of forecasting performance between WNN and ARIMA time series models show that WNN has better forecasting accuracy than traditionally used modeling techniques.

关键词： BDTI Tanker Freight Rates Forecasting Wavelets Neural Networks Shipping Finance

Chemistry : structure and dynamics / James N. Spencer, George M. Bodner, Lyman H. rickard.

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