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Numerical analysis of cavitation shedding flow around a three-dimensional hydrofoil using an improved filter-based model

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Journal of Hydrodynamics 2017年第2期29卷 361-375页

作者：张德胜施卫东张光建陈健 b.p.m.(bart)van esch Research Center of Fluid machinery Engineering and Technology Jiangsu UniversityZhenjiang 212013China Department of mechanical Engineering Eindhoven University of TechnologyEindhoven 5600MBTheNetherlands

The cavitation shedding flow around a 3-D Clark-Y hydrofoil is simulated by using an improved filter-based model （Fbm） and a mass transfer cavitation model with the consideration of the maximum density ratio effect between the liquid and the vapor. The unsteady cloud cavity shedding features around the Clark-Y hydrofoil are accurately captured based on an improved Fbm model and a suitable maximum density ratio. Numerical results show that the predicted cavitation patterns and evolutions compare well with the experimental visualizations, and the prediction errors of the time-averaged lift coefficient, drag coefficient and Strouhal number St for the cavitation number o- = 0.8, the angle of attack a= 8°at a Reynolds number Re = 7 x 10^5 are only 3.29%, 2.36% and 9.58%, respectively. It is observed that the cavitation shedding flow patterns are closely associated with the vortex structures identified by the Q- criterion method. The predicted cloud cavitation shedding flow shows clearly three typical stages：（1） Initiation of the attached sheet cavity, the growth toward the trailing edge. （2） The formation and development of the re-entrant jet flow. （3） Large scale cloud cavity sheds downstream. Numerical results also indicate that the non-uniform adverse pressure gradient is the main driving force of the re-entrant jet, which results in the U-shaped cavity and the 3-D bubbly structure during the cloud cavity shedding.

关键词： Cloud cavitation shedding flow filter-based model turbulent viscosity Clark-Y hydrofoil

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Numerical investigation on the mechanism of impeller hub corner separation flow and induced energy loss in the bulb tubular pump

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Journal of Hydrodynamics 2023年第2期35卷 252-267页

作者： Long-yue Sun Qiang pan De-sheng Zhang Rui-jie Zhao b.p.m.(bart)van esch Research Center of Fluid machinery Engineering and Technology Jiangsu UniversityZhenjiang212013China Wenling Fluid machinery Technology Institute of Jiangsu University Wenling317525China Department of mechanical Engineering Eindhoven University of TechnologyEindhovenThe Netherlands Shimge pump Industry(Zhejiang)Co. Ltd.Wenling317525China

Impeller hub corner separation flow(IHCS)has a significant influence on energy conversion of the bulb tubular pump,and its unsteady characteristics are investigated with CFD-based *** generation mechanism and power loss characteristics of IHCS are investigated by the entropy production method and pressure fluctuation *** main cause can be attributed to the large transverse pressure gradient near the hub at the trailing edge of the impeller,which is aggravated by the circumferential movement trend and the diffuser reverse flow,while the IHCS is significantly weakened with increased flow *** undesirable flow behavior is more likely to cause a significant increase in energy loss near the hub region compared to that in the rim *** relative vortex stretching induced by the velocity gradient is the main cause of the horn-like vortex(HLV),and its intensity and resulting energy loss tend to decrease along the vortex *** HLV changes the dominant frequency of the pressure fluctuations in the nearby flow field,the value of which increases from 1fr(the blade passing frequency)to 2fr with increased amplitude,mainly due to the lower pressure regions on the impeller suction surface(SS)and HLV vortex *** to the effect of rotor-stator interaction(RSI),the HLVs generated between two adjacent impeller blades are cut into several sections by the diffuser vanes and propagate and dissipate along the mainstream direction.

关键词： bulb tubular pump corner separation entropy production pressure fluctuation visualization analysis

Influence of curing conditions on the shrinkage behavior of three-dimensional printed concrete formwork

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Frontiers of Structural and Civil Engineering 2024年第8期18卷 1225-1236页

作者： m.bEKAERT K.van TITTELbOOm G.de SCHUTTER magnel-vandepitte Laboratory for structural Engineering and building materials Department of Structural Engineering and Building MaterialsFaculty of Engineering and ArchitectureGhent UniversityGhent 60 B-9052Belgium

The use of three-dimensional(3D)printed concrete as formwork is becoming more widely applied within the ***,the technology is still not optimized and there are many reports of preliminary cracking during the curing of cast *** is believed to result from differential shrinkage between the printed and cast *** cracks(in the printed concrete or at the interface between the infill and printed concrete)form a preferential path for aggressive substances and can reduce the durability of the combined concrete *** ensure the desired service life of the structure,it is important that the differential shrinkage between cast and printed concrete is *** study investigated the effect of curing conditions on the differential shrinkage behavior of 3D and cast *** influence of prewetting of the dry-cured 3D printed formwork was also *** the experimental program,a vibrated and self-compacting concrete were used as cast *** 3D printed formwork was produced and combined with cast concrete to simulate a concrete *** formwork was cured for 1,7,or 28 d exposed to the air(relative humidity:60%or 95%)or submerged in *** length change of the combined elements was observed over 56 d after concrete casting and throughout the thickness of the *** show that increasing the curing period in dry conditions of the printed concrete leads to an expansion of the formwork on the first day after *** expansion leads to a non-uniform strain evolution throughout the curing period of the combined *** concrete formwork stored in wet conditions does not expand after the casting process but tends to show a decreasing linear deformation within the whole elements.

关键词： 3D concrete printing formwork shrinkage curing

Numerical analysis of the unsteady behavior of cloud cavitation around a hydrofoil based on an improved filter-based model

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Journal of Hydrodynamics 2015年第5期27卷 795-808页

作者：张德胜王海宇施卫东张光建 van esch b.p.m.(bart) Research Center of Fluid machinery Engineering and Technology Jiangsu University Department of mechanical Engineering Eindhoven University of Technology

The unsteady cavitation evolution around the Clark-Y hydrofoil is investigated in this paper, by using an improved filter-base model（Fbm） with the density correction method（DCm）. To improve the prediction accuracy, the filter scale is adjusted based on the grid size. The numerical results show that a small filter scale is crucial for the unsteady simulations of the cavity shedding flow. The hybrid method that combines the Fbm and the DCm could help to limit the overprediction of the turbulent viscosity in the cavitation region on the wall of the hydrofoil and in the wake. The large value of the maximum density ratio ρ1 /ρv, clip promotes the mass transfer rate between the liquid phase and the vapor phase, which results in a large sheet cavity length and the vapor fraction rise inside the cavity. The cavity patterns predicted by the improved method are verified by the experimental visualizations. The time-average lift, the drag coefficient and the primary oscillating frequency St for the cavitation number σ= 0.8, the angle of attack, α= 8°, at a Reynolds number Re= 7×10^5 are 0.735, 0.115 and 0.183, respectively, and the predicted errors are 3.29%, 3.36% and 8.93%. The typical three stages in one revolution are well-captured, including the initiation of the sheet/attached cavity, the growth toward the trailing edge（TE） with the development of the re-entrant jet flow, and the large scale cloud cavity shedding. It is observed that the cloud cavity shedding flow induces the vortex pairs of the TE vortices in the wake and the shedding vortices. The positive vorticity vortex of the re-entrant jet and the TE vortices interacts and merges with the negative vorticity vortex of the leading edge（LE） cavity to produce the shedding flow.

关键词： filter-based model(Fbm) density correction method cloud cavitation hydrofoil unsteady behavior

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Clinical-based phenotypes in children with pediatric post-COVID-19 condition

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World Journal of pediatrics 2024年第7期20卷 682-691页

作者： Lieke C.E.Noij Jelle m.blankestijn Coen R.Lap marlies A.van Houten Giske biesbroek Anke-Hilse maitland-van der Zee mahmoud I.Abdel-Aziz Johannes b.van Goudoever mattijs W.Alsem Caroline L.H.brackel Kim J.Oostrom Simone Hashimoto Suzanne W.J.Terheggen-Lagro Department of pediatric pulmonology and Allergy Amsterdam UMCLocation AMCEmma Children’s HospitalAmsterdam University Medical CenterRoom G2-222Meibergdreef 91105AZAmsterdamThe Netherlands Department of pulmonary medicine Amsterdam UMCAmsterdamThe Netherlands Department of pediatrics Spaarne GasthuisHoofddorpThe Netherlands Department of pediatrics Emma Children’s HospitalAmsterdam University Medical CenterAmsterdamThe Netherlands Department of Rehabilitation medicine Amsterdam Movement SciencesMeibergdreef 9AmsterdamThe Netherlands Department of paediatric pulmonology Department of PaediatricsTergooi MCHilversumThe Netherlands Department of Child and Adolescent psychiatry and psychosocial Care Amsterdam UMCAmsterdam Reproduction and DevelopmentAmsterdamThe Netherlands

background pediatric post coronavirus disease 2019(COVID-19)condition(ppCC)is a heterogeneous syndrome,which can significantly affect the daily lives of *** study aimed to identify clinically meaningful phenotypes in children with ppCC,to better characterize and treat this *** participants were children with physician-diagnosed ppCC,referred to the academic hospital Amsterdam UmC in the Netherlands between November 2021 and march *** factors and information on post-COVID symptoms,comorbidities,and impact on daily life were *** clusters were identified using an unsupervised and unbiased approach for mixed data *** Analysis of 111 patients(aged 3–18 years)revealed three distinct clusters within *** 1(n=62,median age=15 years)predominantly consisted of girls(74.2%).These patients suffered relatively more from exercise intolerance,dyspnea,and smell *** 2(n=33,median age=13 years)contained patients with an even gender distribution(51.5%girls).They suffered from relatively more sleep problems,memory loss,gastrointestinal symptoms,and *** 3(n=16,median age=11 years)had a higher proportion of boys(75.0%),suffered relatively more from fever,had significantly fewer symptoms(median of 5 symptoms compared to 8 and 10 for clusters 1 and 2 respectively),and experienced a lower impact on daily *** This study identified three distinct clinical ppCC phenotypes,with variations in sex,age,symptom patterns,and impact on daily *** findings highlight the need for further research to understand the potentially diverse underlying mechanisms contributing to post-COVID symptoms in children.

关键词： Adolescents Clusters Long COVID pediatric phenotypes post-COVID syndrome

New insights into protein–polysaccharide complex coacervation:Dynamics,molecular parameters,and applications

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Aggregate 2024年第1期5卷 148-166页

作者： Jiabao Zheng paul van der meeren Weizheng Sun School of Food Science and Engineering South China University of TechnologyGuangzhouChina Department of Green Chemistry and Technology Faculty of Bioscience EngineeringGhent UniversityGhentBelgium Overseas Expertise Introduction Center for Discipline Innovation of Food Nutrition and Human Health(111 Center) GuangzhouChina

For more than a decade,the discovery of liquid–liquid phase separation within living organisms has prompted colloid scientists to understand the connection between coacervate functionality,phase behavior,and dynamics at a multidisciplinary *** the protein–polysaccharide was the first system in which the coacervation phenomenon was discovered and is widely used in food systems,the phase state and relaxation dynamics of protein–polysaccharide complex coacervates(ppCC)have rarely been discussed ***,this review aims to unravel the relationship between ppCC dynamics,thermodynamics,molecular architecture,applications,and phase states in past *** ahead,solving the way molecular architecture spreads to macro-functionality,that is,establishing the relationship between molecular architecture–dynamics–application,will catalyze novel advancements in ppCC research within the field of foods and biomaterials.

关键词： dynamics encapsulation liquid coacervate protein-polysaccharide complex coacervation solid precipitate

poisoning effect of polyvinyl chloride on the catalytic pyrolysis of mixed plastics over zeolites

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Science China Chemistry 2024年第7期67卷 2265-2273页

作者： Jiangchun Yuan Wenjie Wang Weixiao Sun Zhirong Yang Yueqiang Cao Wenyao Chen Xiaohu Ge Gang Qian Xiang Feng Xuezhi Duan Xinggui Zhou Kevin m.van Geem Jing Zhang State Key Laboratory of Chemical Engineering East China University of Science and TechnologyShanghai 200237China School of Chemical Engineering Zhengzhou UniversityZhengzhou 450001China Laboratory for Chemical Technology(LCT) Department of MaterialsTextiles and Chemical EngineeringFaculty of Engineering&ArchitectureGhent UniversityZwijnaarde B-9052Belgium State Key Lab of Heavy Oil processing China University of PetroleumQingdao 266580China

Nowadays,the chemical recycling is applied for only 1%of total waste plastics,largely due to contaminants in plastic waste and difficulty in product *** the major contaminant,polyvinyl chloride(pVC)often forms corrosive hydrogen chloride(HCl)during the chemical recycling,which may cause severe catalyst deactivation and equipment ***,the investigation on catalytic pyrolysis(the major route for plastics chemical recycling)of the pVC containing mixed plastics has been rarely ***,catalytic co-pyrolysis of pVC and polyethylene(pE)was studied over an aromatization catalyst,pt/ZSm-5,since the basic building block aromatics are desired products from plastics chemical *** poisoning effect of pVC vapor on the catalyst stability was explored by collective efforts of thorough product analysis and catalyst *** was found that the HCl evolving from pVC has an autocatalytic effect that promotes the scission of dehydrochlorinated pVC,resulting in the high yield of benzene and acetylene from *** the other hand,the presence of pVC suppressed the aromatics formation from pE,largely due to the poisoning effect of pVC-derived HCl on the pt/*** deactivation is irreversible as evidenced by the decreased zeolite crystallinity and the loss of strong acid sites that are key to the aromatization,possibly due to the removal of framework Al upon the interaction with *** modification with octadecylphosphonic acid only slightly alleviated the pVC poisoning *** insights on the pVC poisoning of zeolite catalysts provided in this work may guide the process design of chemical recycling of pVC containing waste plastics.

关键词： polyvinyl chloride polyethylene zeolite aromatics deactivation

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Improvement of the SST γ-Re_(θt) transition model for flows along a curved hydrofoil

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Journal of Hydrodynamics 2021年第3期33卷 520-533页

作者： Chang-liang Ye Chao-yue Wang Dan Zi Yuan Tang bart.p.m.van esch Fu-jun Wan College of Water Resources and Civil Engineering China Agricultural UniversityBeijing100083China Department of mechanical Engineering Eindhoven University of TechnologyEindhovenThe Netherlands beijing Engineering Research Center of Safety and Energy Saving Technology for Water Supply Network System Beijing100083China

The transition in the boundary-layer flow affects the hydrodynamic performances of hydraulic machineries,as the key components in the ship propulsion *** shear stress transfer(SST)γ-Re_(θt) transition model is an important prediction tool in the boundary layer simulation for *** present paper improves the prediction accuracy of the SST γ-Re_(θt) model for the boundary layers along a curved *** SST γ-Re_(θt) transition model for the flows along a curved hydrofoil is improved by introducing a correction to the transition onset Reynolds number Reθ***,the transition onset locations for the flows along the hydrofoils of different curvatures are obtained by the large eddy simulation and by using the SST γ-Re_(θt) ***,the transition onset Reynolds numbers Reθt in the SST γ-Re_(θt) model is modified to ensure that the predicted boundary layer parameters are consistent with the large eddy simulation(LES)*** correlation function between the curvature ratio and the modified transition onset Reynolds number is obtained and subsequently used as a correction function in the original SST γ-Re_(θt) *** test cases are used to evaluate the performance of the improved SST γ-Re_(θt) *** the NACA0035 hydrofoil with a large curvature,the predicted results obtained by using the improved SST γ-Re_(θt) model are quite consistent with the experimental data,which indicates the advantages of the improved model in predicting the boundary layer transition along a *** the test cases of the NACA0016 hydrofoil with a mild curvature and the NACA66(mod)-312 hydrofoil,the prediction results of the improved model are in good agreement with the experimental results in terms of the wake region and the boundary layer parameters,which indicates that the improved SST γ-Re_(θt) model can serve as a powerful tool in the design and the optimization of hydraulic machineries such as the waterjet pumps or the naval propellers.

关键词： Hydrodynamics transition model curvature effect hydrofoil boundary layer transition

Effect of Thermal Cycles on Creep behavior of bituminous binder in Hot Regions

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Journal of Civil Engineering and Architecture 2024年第7期18卷 334-339页

作者： bachir Glaoui mahdjoub bendjima m'hamed merbouh martin van de Ven Laboratoire de la Fiabilité des matériaux et Structures en Régions Sahariennes(FImAS) Université de Béchar B.P.417Béchar08000Algérie Laboratory of Road and Railway Engineering TU DelftP.O.Box 50482600 GA DelftThe Netherlands

This research is devoted to the study of creep behavior of asphalt binder in hot *** binder was subjected to thermal cycles due to the variation of temperature from day to *** cycles produce a heating-cooling *** evaluate the effect of climate change in laboratory,the DSR(dynamic shear rheometer)was used,and the results found with the nine samples were *** thermal cycles led to aging and therefore hardening of the ***,a rheological model was proposed that can represent the curves obtained experimentally,where it is able to describe the creep behavior of binders tested.A new model is proposed that correlates well with the experimental curves,which is called A+2 K.

关键词： bitumen temperature heating/cooling DSR bbR model