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Advances on numerical and experimental investigation of ship roll damping

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水动力学研究与进展B辑:英文版 2023年第3期35卷 431-448页

作者： Patrick Sumislawski Moustafa Abdel-Maksoud Institute for Fluid Dynamics and Ship Theory Hamburg University of Technology (TUHH) Hamburg Germany

This paper presents recent developments towards efficient and reliable methods for roll damping estimation based on numerical simulations as well as model tests using the harmonic excited roll motion(HERM)technique.A newly designed automatic roll damping estimation procedure shows the advantage of a just-in-time post processing of experimental measurement results.Real-time analysis of the measured roll damping values permits a considerable shortening of the test times.Thus,a large number of investigations can be carried out with relatively manageable effort in order to determine the roll damping behavior of different keel configurations or at operating conditions,e.g.,different sized keels or Froude numbers.In addition,HERM measurement method is applied to investigate the memory effect.For this purpose,different excitation schemes are introduced and the results are analyzed.Moreover,a study of the scale effect on the roll damping properties is conducted,in which experimental and numerical investigations are performed for two scales of a ship model.Furthermore,a method is developed that significantly reduces the effort of Reynolds average Navier-Stokes(RANS)-based simulations of roll motion.The reduction of simulation time is achieved by introducing an artificial damping.The obtained results show that the developed method is very well applicable for numerical as well as in experimental investigations.During the model tests using HERM technique,the model is free and the rudder is used to keep the straight-ahead course.The analysis of the numerical and experimental results shows that the influence of the rudder induced force and moment during HERM tests is not negligible and the contribution of the rudder must be taken into account by estimating the roll damping.Finally,a new concept is developed to investigate the parametric roll behavior of ships,which allows neglecting the consideration of the complex modelling of free surface waves in the simulations.During the RANS computations,a potential-based method is appli

关键词： Roll damping harmonic excited roll motion rudder HERM experimental fluid dynamics(EFD) CFD

MP-PIC simulation of circulating fluidized beds using an EMMS based drag model for Geldart B particles

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Particuology 2021年第6期19卷 76-90页

作者： Timo Dymala Tom Wytrwat Stefan Heinrich Hamburg University of Technology Institute of Solids Process Engineering and Particle TechnologyDenickestr.1521073 HamburgGermany

In this study the multiphase particle-in-cell(MP-PIC)method is used for the simulation of two pilot-scale circulating fluidized beds(CFBs)with quartz sand belonging to Geldart’s group B as bed material.The simulations were performed using a homogeneous drag model as well as a structure dependent drag model based on the energy minimization multi-scale method(EMMS).The results are compared with experimental data from literature as well as experiments.The simulations with the EMMS based drag model show a good agreement of the time-averaged axial solids concentration,circulation rate and riser pressure drop.Furthermore,a lower grid sensitivity is observed compared to the homogeneous drag model.In contrast to the conventional drag model a dense bottom zone is predicted by the EMMS based drag model.An overprediction of the solid concentration in the dense bottom zone is presumably due to an overprediction of the cluster diameter that is calculated using an empirical cluster diameter correlation.This shows the necessity for a new meso-scale cluster correlation for the simulation of Geldart B particles.Furthermore,the results of the time-averaged radial solids concentration differ from the expectations of a core-annulus flow indicating that a mesh refinement at the walls is necessary.Finally,the importance of using a realistic particle size distribution is identified.

关键词： 3D-CFD simulation Circulating fluidized bed(CFB) Multiphase particle-in-cell method(MP-PIC) Energy minimizing multi-scale theory(EMMS) Validation study

Attritor-milling of poly(amide imide) suspensions

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Particuology 2014年第6期12卷 92-96页

作者： M.F.H.Wolff S.Antonyuk S.Heinrich G.A.Schneider Hamburg University of Technology Institute of Solids Process Engineering and Particle Technology Hamburg University of Technology Institute of Advanced Ceramics

The milling behavior of poly(amide imide),which serves as a prototypical hydrophilic high-performance polymer with a high glass transition temperature,was investigated.Various milling conditions(milling times up to 7h,stirrer tip speeds of 3.4-4.9 m/s,and mass concentrations of 5-20%) were tested,and particle sizes as low as d50,33μm were obtained.The milling was performed at 11℃ in an attritor.Differential scanning calorimetry and thermogravimetric analysis were performed before and after milling to investigate the effect of milling on the glass transition temperature and on the decomposition behavior of the polymer.The suspension obtained after milling was observed to be stable without the addition of stabilizers or the adjustment of the pH value,and no negative effect of milling on the polymer properties was observed.The attritor technique proved to be an adequate and efficient milling tool for the production of micrometer-sized high-performance polymer suspensions.

关键词： Attritor Polymer Grinding Suspension

Slice Thickness Optimization for the Focused Ion Beam-Scanning Electron Microscopy 3D Tomography of Hierarchical Nanoporous Gold

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Nanomanufacturing and Metrology 2022年第2期5卷 112-118页

作者： Alexander Shkurmanov Tobias Krekeler Martin Ritter Electron Microscopy Unit Hamburg University of Technology(TUHH)Eißendorfer Straße 4221073HamburgGermany

The combination of focused ion beam (FIB) with scanning electron microscopy (SEM), also known as FIB-SEM tomography, has become a powerful 3D imaging technique at the nanometer scale. This method uses an ion beam to mill away a thin slice of material, which is then block-face imaged using an electron beam. With consecutive slicing along the z-axis and subsequent imaging, a volume of interest can be reconstructed from the images and further analyzed. Hierarchical nanoporous gold (HNPG) exhibits unique structural properties and has a ligament size of 15–110 nm and pore size of 5–20 nm. Accurate reconstruction of its image is crucial in determining its mechanical and other properties. Slice thickness is one of the most critical and uncertain parameters in FIB-SEM tomography. For HNPG, the slice thickness should be at least half as thin as the pore size and, in our approach, should not exceed 10 nm. Variations in slice thickness are caused by various microscope and sample parameters, e.g., converged ion milling beam shape, charging effects, beam drift, or sample surface roughness. Determining and optimizing the actual slice thickness variation appear challenging. In this work, we examine the influence of ion beam scan resolution and the dwell time on the mean and standard deviation of slice thickness. After optimizing the resolution and dwell time to achieve the target slice thickness and lowest possible standard deviation, we apply these parameters to analyze an actual HNPG sample. Our approach can determine the thickness of each slice along the z-axis and estimate the deviation of the milling process along the y-axis (slow imaging axis). For this function, we create a multi-ruler structure integrated with the HNPG sample.

关键词： Focused ion beam Scanning electron microscopy Tomography Hierarchical nanoporous gold

Production of composites with high relative permittivity using the spouted bed technique

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Particuology 2019年第1期17卷 184-189页

作者： E. Eichner P.-K. Fischer S. Heinrich GA Schneider Institute of Solids Process Engineering and Particle technology Denickestr1521073 HamburgGermany Institute of Advanced Ceramics Hamburg University of TechnologyDenickestr1521073 HamburgGermany

This contribution presents a new application of the spouted bed technique. The developed production process involves coating fine copper particles with a polymer in a spouted bed plant and then hot pressing the produced granules to form a compact consisting of a copper–polymer composite with a high filling degree. The fabricated composites possess high relative permittivity, which is advantageous for the production of effective capacitors. With increasing filling degree of copper, the relative permittivity of the composites increased, with a maximum relative permittivity of 214 obtained for the composite containing 78.1 vol% copper. Such a high filling degree can be achieved with conductive particles without obtaining a conductive composite by using the spouted bed technology in the production process. The high relative permittivity results from the high filling degree of particles isolated by a polymer coating.

关键词： Spouted bed High relative permittivity Fine particles Coating Metal-polymer composite

Particle formulation of hydroalcoholic rosemary (Rosmarinus officinalis L.) extracts using a spouted bed

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Particuology 2020年第4期18卷 26-34页

作者： D.Peshev E.Eichner M.Goslinska S.Pietsch Y.Trambabova T.Terzieva N.Georgieva S.Heinrich Department of Chemical Engineering University of Chemical Technology and Metallurgy1576 SofiaBulgaria Institute of Solids Process Engineering and Particle technology Hamburg University of Technology21073 HamburgGermany Department of Biotechnology University of Chemical Technology and Metallurgy1576 SofiaBulgaria

In this study,spouted bed technology was applied to the protection and functionalization of polyphenolic rosemary extracts.First,solid-liquid extraction was performed at 25℃with ethanol-water.The ethanol-water ratio was chosen to obtain high phenolic acid and diterpene concentrations in the extract.The selected solvent composition gave liquid extracts that could be directly added to a coating mixture for feeding into a spouted bed apparatus.Thus,no preliminary solvent exchange or evaporation of the extraction solvent to dryness was required.Food grade Paselli MD 6 maltodextrin and HiCap 100 modified starch were used as inert core and shell materials in the spouted bed encapsulation process under mild operating conditions.The antioxidant activity of the fresh extract was retained during processing,which indicated that the active constituents were preserved and quantitatively transferred into the encapsulated formulations,which were readily soluble in water.The obtained powders were composed of nearly spherical particles.Their compositions,water solubilities,and particle morphologies make them a strong candidate for food and beverage applications as natural antioxidants,preservatives,or functional ingredients.

关键词： Particle Polyphenolic rosemary extract Encapsulation Spouted bed Bioactive Antioxidant

Enhancing 3D Reconstruction Accuracy of FIB Tomography Data Using Multi‑voltage Images and Multimodal Machine Learning

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Nanomanufacturing and Metrology 2024年第1期7卷 48-60页

作者： Trushal Sardhara Alexander Shkurmanov Yong Li Lukas Riedel Shan Shi Christian J.Cyron Roland C.Aydin Martin Ritter Institute for Continuum and Material Mechanics Hamburg University of TechnologyHamburgGermany Electron Microscopy Unit Hamburg University of TechnologyHamburgGermany Institute of Materials Physics and technology Hamburg University of TechnologyHamburgGermany Institute of Materials Mechanics Helmholtz-Zentrum HereonGeesthachtGermany Research Group of Integrated Metallic Nanomaterials Systems Hamburg University of TechnologyHamburgGermany Institute of Material Systems Modeling Helmholtz-Zentrum HereonGeesthachtGermany

FIB-SEM tomography is a powerful technique that integrates a focused ion beam(FIB)and a scanning electron microscope(SEM)to capture high-resolution imaging data of nanostructures.This approach involves collecting in-plane SEM imagesand using FIB to remove material layers for imaging subsequent planes,thereby producing image stacks.However,theseimage stacks in FIB-SEM tomography are subject to the shine-through effect,which makes structures visible from theposterior regions of the current plane.This artifact introduces an ambiguity between image intensity and structures in thecurrent plane,making conventional segmentation methods such as thresholding or the k-means algorithm insufficient.Inthis study,we propose a multimodal machine learning approach that combines intensity information obtained at differentelectron beam accelerating voltages to improve the three-dimensional(3D)reconstruction of nanostructures.By treatingthe increased shine-through effect at higher accelerating voltages as a form of additional information,the proposed methodsignificantly improves segmentation accuracy and leads to more precise 3D reconstructions for real FIB tomography data.

关键词： Multimodal machine learning Multi-voltage images FIB-SEM Overdeterministic systems 3D reconstruction FIB tomography

Novel technique for measurement of coating layer thickness of fine and porous particles using focused ion beam

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Particuology 2019年第1期17卷 190-198页

作者： M. Goslinska I. Selmer C. Kleemann U.Kulozik I. Smirnova S. Heinrich Hamburg University of Technology Institute of Solids Process Engineering and Particle TechnologyDenickestr1521073 HamburgGermany Hamburg University of Technology Institute of Thermal Separation ProcessesEiJ^endorfer Str. 3821073 HamburgGermany Technical university of Munich Chair of Food and Bioprocess EngineeringWeihenstephaner Berg 185354 FreisingGermany

A novel technique for the measurement of the coating layer thickness of fine particles was developed in this work based on cross-sectioning of micrometre-sized single coated particles using focused ion beam (FIB) milling. This technique was tested on two batches of aerogel particles coated with thin coatings in a spouted bed. The FIB milling procedure consisted of two steps. First, the desired part of the coated particle was removed using a high ion beam current. The resulting cross-sectioned area was then polished using a lower ion beam current to make the cross-section clearly visible. The FIB milling process was controlled with simultaneous scanning electron microscopy (SEM). Afterwards, the coating layer thickness was evaluated using the SEM images. The coating layer was successfully applied on the porous aerogel microparticles in the spouted bed. The coating uniformity of the highly porous particles increased with increasing sprayed coating solution amount, with up to 91% of the particle pores being covered. The FIB-cross-sectioning technique using an ion beam of 2.50 nA for the first milling and 0.43 nA for polishing of the surface resulted in successful generation of cross-sections of representative particles with a visible particle core and coating layer. A coating layer thickness of approximately 700 nm was achieved on particles with sizes of below 45 μm.

关键词： Coating layer thickness Focused ion beam Microparticle Aerogel Spouted bed Dilute spouting

Shear assessment of compression flanges of structural concrete T-beams

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Frontiers of Structural and Civil Engineering 2014年第4期8卷 354-361页

作者： Bjorn SCHUTTE Viktor SIGRIST Institute of Concrete Structures Hamburg University of Technology Hamburg 21073 Germany

In T-beams the force transfer from the web into the flange has to be studied. The general design procedure is based on a strut-and-tie （or a stress field） model which comprises spreading compressive and transverse tensile forces. As is known, strut-and-tie models represent the force flow within a structural member at ultimate. This procedure is sufficient for design purposes and in general, leads to safe results. For the assessment of a structure it may be worthwhile to improve the accuracy. For this purpose both web and flange have to be looked at more in detail. An advanced method for the analysis of webs in shear is the Generalized Stress Field Approach [1]. This approach can be utilized for treating flanges, where the classical assumptions have to be adapted; in particular by considering the strain dependence of the concrete compressive strength and thus, defining a representative strain value. In the present contribution background and details of these aspects are given, and the corresponding calculation procedure is described. Theoretical results are compared with experimental data and show a reasonably good agreement. However, as the number of sufficiently documented tests is very limited no concluding findings are attained.

关键词： concrete structures structural assessment stress field analysis shear