THE INTERNATIONAL JOURNAL OF COMPUTATIONAL METHODS AND EXPERIMENTAL MEASUREMENTS最新文献

{"title":"Fully and sparsely supported radial basis functions","authors":"E. Kansa, P. Holoborodko","doi":"10.2495/cmem-v8-n3-208-219","DOIUrl":"https://doi.org/10.2495/cmem-v8-n3-208-219","url":null,"abstract":"The central idea of this paper is that computer mathematics is not identical to ideal mathematics because computer numbers only have finite precision. All functions, especially the positive definite transcendental functions, are truncated and the expansion coefficients have finite precision and all branching operations require time to complete. Of all the known methods used to obtain numerical solutions to integral and partial differential equations, the global continuously differential radial basis functions (RBFs) that are implemented on computers closely resemble many aspects of ideal mathematics. The global RBFs have the attributes required to obtain very accurate numerical results for a variety of partial differential and integral equations with smooth solutions. Without the need for extremely fine discretization, the global RBFs have their spline properties and exponential convergence rates. The resulting system of full equations can be executed very rapidly on graphical processing units and fieldprogrammable gate arrays because, with full systems, there is no branching and full systems solvers are very highly vectorized, optimizing the usage of very fast processors.","PeriodicalId":22520,"journal":{"name":"THE INTERNATIONAL JOURNAL OF COMPUTATIONAL METHODS AND EXPERIMENTAL MEASUREMENTS","volume":"100 1","pages":"208-219"},"PeriodicalIF":0.0,"publicationDate":"2020-08-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80624311","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Visualization of stratified flows aro und a vertical plate: laboratory experiment and numerical simulation","authors":"Y. Chashechkin, Ya. V. Zagumennyi","doi":"10.2495/cmem-v8-n2-148-161","DOIUrl":"https://doi.org/10.2495/cmem-v8-n2-148-161","url":null,"abstract":"On the basis of the fundamental system, which includes equations of continuity, momentum, and substance transfer with a linearized equation of state, methods of experimental and numerical study are developed for visualizing the flow perturbation fields generated by uniform horizontal movement of a vertical plate in a stratified medium. The stratified flows were visualized in the laboratory tank by the high-sensitive and high-resolution Schlieren instrument Iab-458 at the stand ‘laboratory Mobile Tank’ of the unique research facility ‘hPC IPMech raS’ and numerically calculated within the frame of the open source CfD utility OpenfOaM using computing resources of cluster systems and supercomputers. both the computation results and the laboratory visualization data show that a vertical plate uniformly moving in a stratified fluid generates flow patterns which contain complex systems of internal waves, including upstream, attached and short ones, and thin interfaces, such as ligaments, formed due to the combined influence of the stratification and dissipation effects. Increase in the velocity of the plate movement leads to an essential restructuring of the wake flow past the plate, where typical vortex elements, such as vortex dipoles and ‘vortex bubbles’, are formed in the divergence zones of the phase surfaces of internal waves. all the flow structural components evolve and actively interact with each other and with the free stream. The observation and calculation results are in a good qualitative and quantitative agreement with each other.","PeriodicalId":22520,"journal":{"name":"THE INTERNATIONAL JOURNAL OF COMPUTATIONAL METHODS AND EXPERIMENTAL MEASUREMENTS","volume":"104 1","pages":"148-161"},"PeriodicalIF":0.0,"publicationDate":"2020-04-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80500981","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Development of unified framework for microstr ucture, residual stress, and crack propensity prediction using phase-field simulations","authors":"A. Staroselsky, Ranadip Acharya, B. Cassenti","doi":"10.2495/cmem-v8-n2-111-122","DOIUrl":"https://doi.org/10.2495/cmem-v8-n2-111-122","url":null,"abstract":"The approach to obtain a specific user-defined/as-desired or conformal/epitaxial microstructure in additive manufacturing (aM) is a challenging and expensive iterative process. Modeling and validation of solidification microstructure and residual stresses can be leveraged to reduce iteration cost in obtaining as-desired microstructure, minimize residual stress and prevent hot cracking. In the present study, computational fluid dynamics analysis is used to predict melt pool characteristics, and phase-field modeling is employed to simulate solidification with corresponding microstructure evolution in the as-deposited state for laser powder bed fusion (lPBf) process. Different features of lPBf microstructure such as segregation of secondary elements, dendrite sizes, dendritic orientation and dendritic morphology are predicted. The methods are further extended to predict orientation change as a function of number of layers. a constitutive materials model coupled to solidification is used to predict the stress in as-built part as well as the effect of stress on microstructural features. The model encompasses the effect of thermo-mechanical and shrinkage stresses and considers creep flow due to the presence of liquid phases in the mushy region. a phase-field-based methodology is proposed that can solve for hot cracking starting from the intrinsic defects such as porosity in lPBf process. Depending on the residual stress, crack propagation can be predicted from the unified model. The model was incorporated in a finite element code and used to predict crack growth phenomena such as values of critical stress, crack path, etc. Phase-field models of crack growth reduce the computational complications associated with singularities and allow finite element predictions of crack propagation without remeshing. This work intends to develop a unified phase-field framework that can sequentially predict solidification microstructure, residual stresses and structural cracking.","PeriodicalId":22520,"journal":{"name":"THE INTERNATIONAL JOURNAL OF COMPUTATIONAL METHODS AND EXPERIMENTAL MEASUREMENTS","volume":"57 1","pages":"111-122"},"PeriodicalIF":0.0,"publicationDate":"2020-04-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83483247","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Experimental investigation of fire resistance of GLT beams","authors":"Lucie Kucíková, T. Janda, M. Šejnoha, J. Sýkora","doi":"10.2495/cmem-v8-n2-99-110","DOIUrl":"https://doi.org/10.2495/cmem-v8-n2-99-110","url":null,"abstract":"Mechanical and fire loading play together with geometric and material properties of glued laminated timber beams a decisive role in theoretical investigation into the time-dependent fire resistance of these elements. This is a multidisciplinary problem including heat conduction, water evaporation, internal gas pressure evolution, pyrolysis, volume change, etc. If properly calibrated, such complex models should allow us to forecast the evolution and shape of the charred or zero strength layer. It is doubtless that the calibration and validation steps require experiments. In particular, the results of large-scale fire experiment are discussed in this contribution focusing on the influence of fire intensity and duration on the temperature and the charred layer evolution. The influence of fire on stiffness and strength will also be addressed through the results of Pilodyn measurements of wood elastic modulus and three-point bending tests of original and fire-exposed beams.","PeriodicalId":22520,"journal":{"name":"THE INTERNATIONAL JOURNAL OF COMPUTATIONAL METHODS AND EXPERIMENTAL MEASUREMENTS","volume":"15 1","pages":"99-110"},"PeriodicalIF":0.0,"publicationDate":"2020-04-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85243502","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Oil/water flow in a horizontal pipe—dispersed flow regime","authors":"D. S. Sanstos, F. Garcia, M. Rasteiro, P. Faia","doi":"10.2495/cmem-v8-n2-123-134","DOIUrl":"https://doi.org/10.2495/cmem-v8-n2-123-134","url":null,"abstract":"In multiphase fluid flow, the formation of dispersed patterns, where one of the phases is completely dispersed in the other (continuous medium) is common, for example, in crude oil extraction, during the transport of water/oil mixture. In this work, experimental and numerical studies were carried out for the flow of an oil/water mixture in a horizontal pipe, the dispersed liquid being a paraffin (oil with density 843 kg m−3 and viscosity 0.025 Pa s) and the continuous medium a water solution doped with NaCl (1000 μS. cm−1). The tests were made for oil concentrations of 0.01, 0.13 and 0.22 v/v and velocities between 0.9 and 2.6 ms−1 of the mixture. Experimental work was performed in a pilot rig equipped with an electrical impedance tomography (EIT) system. Information on pressure drop, EIT maps, volumetric concentrations in the vertical diameter of the pipe and flow images were obtained. Simulations were performed in 2dimensional geometry using the Eulerian–Eulerian approach and the k-ε model for turbulence modelling. The model was implemented in a computational fluid dynamics platform with the programme COMSOL Multiphysics version 5.3. The simulations were carried out using the Schiller–Neumann correlation for the drag coefficient and two equations for the viscosity calculation: Guth and Simba (1936) and Pal (2000). For the validation of the simulations, the pressure drop was the main control parameter. The simulations predicted the fully dispersed flow patterns and the pressure drop calculated when using the Pal (2000) equation for the viscosity calculation showed the best fit. The results of the images of the flows obtained by the photographs and simulations were in good agreement.","PeriodicalId":22520,"journal":{"name":"THE INTERNATIONAL JOURNAL OF COMPUTATIONAL METHODS AND EXPERIMENTAL MEASUREMENTS","volume":"53 1","pages":"123-134"},"PeriodicalIF":0.0,"publicationDate":"2020-04-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89633597","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Correction of wet gas flow measurements applying standard orifice","authors":"Barbara Tomaszewska-Wach, M. Rząsa","doi":"10.2495/cmem-v8-n2-175-185","DOIUrl":"https://doi.org/10.2495/cmem-v8-n2-175-185","url":null,"abstract":"","PeriodicalId":22520,"journal":{"name":"THE INTERNATIONAL JOURNAL OF COMPUTATIONAL METHODS AND EXPERIMENTAL MEASUREMENTS","volume":"64 1","pages":"175-185"},"PeriodicalIF":0.0,"publicationDate":"2020-04-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74028763","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"SO2 and NO2 simulation and validation in Metropolitan Lima using WRF-Chem model","authors":"A. Luna, H. Navarro, A. Moya","doi":"10.2495/cmem-v8-n2-135-147","DOIUrl":"https://doi.org/10.2495/cmem-v8-n2-135-147","url":null,"abstract":"In recent times, air pollution in Peru is attracting the attention of the population and the government as well, who finally makes the policies that help us to preserve good air quality. In this research, we used the chemical-meteorological model Weather research and Forecasting coupled with Chemical (WrF-Chem v3.8) to predict pollution scenarios. We studied and analyzed three 2017 months of summer (January, February and March) and three months of winter (July, august and September) to evaluate and forecast two pollutants concentration, sulfur dioxide (SO2) and nitrogen dioxide (NO2) over the city of lima. We also considered the meteorological variables such as the wind speed and its direction, average temperature, relative humidity and atmospheric pressure. besides, we used fixed industrial sources inventory as emission data and the global Forecast System (gFS) as border data for the meteorological components. Within the WrF-Chem model, we implemented the grell-Freitas parameterization of convection to represent the clouds; we used rrTMg for the shortwave/longwave radiation scheme, and the Monin-Obukhov for the processes in the surface layer, among others. On the other hand, for the gas phase chemistry, we used the raDM2 scheme, for the aerosol module we utilized the MaDE-SOrgaM, and finally, we employed the Fast-j photolysis scheme. We finally compared the results with the data provided by the ten monitoring stations that belong to the National Service of Meteorology and hydrology (SENaMhI) which are located in strategic zones in lima. lastly, we showed that the variables studied are within the environmental quality standard authorized by the Ministry of the Environment, and we also demonstrated that the simulations given by the model are, in general, overlapping the values measured experimentally in all of the monitoring stations evaluated.","PeriodicalId":22520,"journal":{"name":"THE INTERNATIONAL JOURNAL OF COMPUTATIONAL METHODS AND EXPERIMENTAL MEASUREMENTS","volume":"26 1","pages":"135-147"},"PeriodicalIF":0.0,"publicationDate":"2020-04-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80046785","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Corrosion of historic grey cast irons: indicative rates , significance, and protection","authors":"M. Sýkora, K. Kreislová, P. Pokorný","doi":"10.2495/cmem-v8-n2-162-174","DOIUrl":"https://doi.org/10.2495/cmem-v8-n2-162-174","url":null,"abstract":"In Europe many buildings and machinery in industrial sites are recognised as cultural heritage. These structures, often made from various types of irons or historic steels, have been for decades or centuries exposed to aggressive atmospheric environments and suffered from corrosion attack. The contribution discusses corrosion rates, the effects of corrosion on structural reliability, and the efficiency of surface treatments. The model for corrosion rates of historic metals cannot be based on the degradation model for mild steels even though specific features of historic alloys such as increased content of carbon and different chemical composition would be taken into account. realistic estimates of corrosion rates need additionally account for different micro-structure with inputs and different surface properties of historic alloys. This is why the presented model is based on a limited experimental data, considering the corrosivity of environment. The model assumes no corrosion during first seven years of service life and the same type of regression function for the progress period as is provided in ISO 9224 for mild steels and other metals. The effects of repeated applications of paintings are discussed. four principal strategies to the corrosion protection of industrial heritage structures include ‘leave as it is’, apply temporary protection to reduce degradation progress, apply long term protection, or undertake a complex restoration with replacement of damaged elements. Numerical example indicates that corrosion is normally insignificant for load-bearing iron structures, but may lead to severe problems for thin secondary structural and non-structural members such as railing or decorative elements. The proposed model estimates degradation progress in a mid-term perspective and supports decisions on maintenance of industrial heritage structures.","PeriodicalId":22520,"journal":{"name":"THE INTERNATIONAL JOURNAL OF COMPUTATIONAL METHODS AND EXPERIMENTAL MEASUREMENTS","volume":"9 1","pages":"162-174"},"PeriodicalIF":0.0,"publicationDate":"2020-04-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78441617","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Reduced order model of glass plate loaded by low-velocity impact","authors":"T. Janda, A. Zemanová, P. Hála, Petr Konrád, Jaroslav Schmidt","doi":"10.2495/cmem-v8-n1-36-46","DOIUrl":"https://doi.org/10.2495/cmem-v8-n1-36-46","url":null,"abstract":"This article concerns a reduced order model of unconstrained glass plate exposed to low-velocity impact. First, three-parametric model consisting of two masses connected with elastic spring is introduced, its calibration procedure is described, and the simulation of its response to force impulses with different duration is shown. Then a five-parametric variant of the reduced order model is presented, calibrated and tested. Combined with the Hertzian theory of non-adhesive contact, the model allows us to determine the time evolution of contact force for arbitrary mass, stiffness and initial velocity of the impactor. The simulated results are compared to experimentally obtained data and observations about the model properties and accuracy are made.","PeriodicalId":22520,"journal":{"name":"THE INTERNATIONAL JOURNAL OF COMPUTATIONAL METHODS AND EXPERIMENTAL MEASUREMENTS","volume":"29 1","pages":"36-46"},"PeriodicalIF":0.0,"publicationDate":"2020-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85134524","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"CFD based determination of sublimation mass flux for lyophilization inside a vial","authors":"M. Zadravec, J. Ravnik, Ziga Casar, M. Hriberšek","doi":"10.2495/CMEM-V8-N1-47-60","DOIUrl":"https://doi.org/10.2495/CMEM-V8-N1-47-60","url":null,"abstract":"In the case of computational models of lyophilization in a vial, the intensity of drying is to a large extent controlled by the pressure conditions above the drying surface, as the drying driving force is the pressure difference between the saturation vapour pressure at the sublimation interface and the vapour partial pressure above the drying substance. In majority of studies, the effect of the vial and the rubber stopper geometry on the pressure conditions inside the vial is either neglected or taken into account by an estimated additional vapour pressure increase inside the vial. As the pressure conditions depend on the flow of sublimated solvent inside the vial-stopper conduit geometry, but are experimentally difficult to determine, a dedicated CFD analysis of flow conditions inside the vial-stopper channel was performed. The influence of imposing of the no-slip and slip conditions on the solid surfaces on the pressure drop in the system was studied and the effect of the increased partial pressure of the solvent on the sublimation rate was evaluated for the starting phase of the lyophilization by implementing the Stefan’s one sided diffusion model. The computational results show, that the effect of the additional flow resistance due to the vial conduit and the stopper is most significant at lowest system temperatures, with as much as 30% increase in vapour pressure inside the vial.","PeriodicalId":22520,"journal":{"name":"THE INTERNATIONAL JOURNAL OF COMPUTATIONAL METHODS AND EXPERIMENTAL MEASUREMENTS","volume":"52 1","pages":"47-60"},"PeriodicalIF":0.0,"publicationDate":"2020-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75561625","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}