International Journal of Computational Methods and Experimental Measurements最新文献

{"title":"Coupling method for internal nozzle flow and the spray formation for viscous liquids","authors":"R. Ravendran, B. Endelt, J. Christiansen, P. Jensen, Martin Theile, I. Najjar","doi":"10.2495/CMEM-V7-N2-130-141","DOIUrl":"https://doi.org/10.2495/CMEM-V7-N2-130-141","url":null,"abstract":"Understanding the disturbances introduced by cavitation inside spray nozzles is important, when simulating the spray formation of highly viscous liquids. In this paper, a new model for cavitation-induced primary break-up is proposed, which is able to map the influence of cavitating nozzle flow on spray formation. Detailed experimental and numerical investigations of the viscous nozzle flow have been performed in order to develop an improved primary break-up model [1]. The proposed model describes the transition from the flow inside the nozzle, modelled using a homogeneous equilibrium model (HEM) method, to the first primary droplets modelled using a Eulerian–Lagrangian method. Thus, providing the boundary conditions for the calculation of the secondary break-up and spray formation. The nozzle exit is divided into a definite number of patches. Liquid momentum and vapor volume fraction from each patch are used to initialize the primary droplets. The model has been implemented in the open-source CFD software package OpenFOAM and validation has been done using high-speed shadow graphic imaging. The simulated spray tip penetration and spray cone angle at the near-nozzle region show a good agreement with the experiment results.","PeriodicalId":36958,"journal":{"name":"International Journal of Computational Methods and Experimental Measurements","volume":"11 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-03-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81457387","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":"The effect of numerical parameters on eddies in oceanic overflows: a laboratory and numerical study","authors":"Shanon M. Reckinger, Thomas H. Gibson, Fred Hohman, T. Morrison, Scott J. Reckinger, M. Carvalho","doi":"10.2495/CMEM-V7-N2-142-153","DOIUrl":"https://doi.org/10.2495/CMEM-V7-N2-142-153","url":null,"abstract":"Overflows in the ocean occur when dense water flows down a continental slope into less dense ambient water. It is important to study idealized and small-scale models, which allow for confidence and control of parameters. The work presented here is a direct qualitative and quantitative comparison between physical laboratory experiments and lab-scale numerical simulations. Physical parameters are varied, including the Coriolis parameter, the inflow density, and the inflow volumetric flow rate. Laboratory experiments are conducted using a rotating square tank and high-resolution camera mounted on the table in the rotating reference frame. Video results are digitized in order to compare directly to numerical simulations. The MIT General Circulation Model (MITgcm), a three-dimensional ocean model, is used for the direct numerical simulations corresponding to the specific laboratory experiments. It was found that the MITgcm was not a good match to laboratory experiments when physical parameters fell within the high eddy activity regime. However, a more extensive resolution study is needed to understand this fully. The MITgcm simulations did provide a good qualitative and quantitative match to laboratory experiments run in a low eddy activity regime. In all cases, the MITgcm simulations had more eddy activity than the laboratory experiments.","PeriodicalId":36958,"journal":{"name":"International Journal of Computational Methods and Experimental Measurements","volume":"8 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2019-03-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78553502","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":"An analytical study of the early stages of unsteady free convective flow from a differentially heated rotating sphere at large Grashof numbers","authors":"S. D’Alessio","doi":"10.2495/CMEM-V7-N1-57-67","DOIUrl":"https://doi.org/10.2495/CMEM-V7-N1-57-67","url":null,"abstract":"This research investigates the unsteady free convective flow of a viscous incompressible fluid from a differentially heated rotating sphere. The flow is assumed to remain laminar and to possess equatorial and azimuthal symmetry. The governing Navier-Stokes and energy equations are posed in terms of a scaled stream function vorticity formulation and are solved subject to no-slip and specified surface temperature conditions. At t = 0 an impulsive heat flux is applied in the form of a jump in surface temperature. An asymptotic solution valid for large Grashof numbers and small times following the impulsive startup is constructed. Two small parameters have been identified and based on this the flow variables are expanded in a double series in powers of these parameters. The non-zero leading-order terms in the asymptotic expansions have been determined analytically and the corresponding heat transfer coefficient has been found. Future work will involve obtaining numerical solutions.","PeriodicalId":36958,"journal":{"name":"International Journal of Computational Methods and Experimental Measurements","volume":"61 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2018-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86821239","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":"Micro/nano flows: vorticity generation","authors":"T. Moulden","doi":"10.2495/CMEM-V7-N1-68-78","DOIUrl":"https://doi.org/10.2495/CMEM-V7-N1-68-78","url":null,"abstract":"Vortical structures have been observed to develop in electrically driven fluid motion at the micro/nano scale, but no coherent theory has been put foreword in the literature to explain such a development. The present paper gives several results in a theory based upon the classical field equations. In particular, it is shown that the origin of vorticity production resides in the applied electric field interacting with any ion concentration gradients present in the fluid as defined by the vorticity equation. This is in addition to any viscous layer vorticity diffusion that may also exist in the flow.","PeriodicalId":36958,"journal":{"name":"International Journal of Computational Methods and Experimental Measurements","volume":"12 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2018-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88013945","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":"Non-linear behaviour of structural walls","authors":"Salima Djehaichia, R. Lassoued","doi":"10.2495/CMEM-V7-N1-14-21","DOIUrl":"https://doi.org/10.2495/CMEM-V7-N1-14-21","url":null,"abstract":"The vulnerability of reinforced concrete structures, which were built in the 1970s, under the effects of an earthquake is one of the major concerns of researchers, because the designs of these structures have been based on regulations, which are no longer valid. The parameters taken into account in this study to idealize the regulatory shortcomings are: low ratio of reinforcement, type of reinforcement and moderate resistance of concrete. The analysis to test these altered structures with one or both of the above parameters is carried out in the non-linear domain from the perspective of analysing their behaviour in an earthquake. In this paper, the modelling strategy is based on finite elements combined with a discretization of the shear wall most stressed by successive thin layers. The estimation of level of performance is achieved using capacity curves under increasing incremental loads; a non-linear characteristic force-displacement relationship can be determined. The results of the numerical model are compared with those of the Algerian seismic code (RPA). Through this comparison, it was found that there is an improvement in terms of displacement, shearing action and ductility. The introduction of confining as a local model makes it possible to refine the numerical model and improve the total behaviour of the structure. A parametric analysis is carried out to highlight the obvious weakness of structures designed and built in the 1970s.","PeriodicalId":36958,"journal":{"name":"International Journal of Computational Methods and Experimental Measurements","volume":"148 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2018-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85363314","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":"Assessment of complex variable basis functions in the approximation of ideal fluid flow problems","authors":"B. Wilkins, T. Hromadka, A. Johnson, Randy Boucher, H. D. McInvale, S. Horton","doi":"10.2495/CMEM-V7-N1-45-56","DOIUrl":"https://doi.org/10.2495/CMEM-V7-N1-45-56","url":null,"abstract":"Solving potential problems, such as those that occur in the analysis of steady-state heat transfer, electrostatics, ideal fluid flow, and groundwater flow, is important in several fields of engineering, science, and applied mathematics. Numerical solution of the relevant governing equations typically involves using techniques such as domain methods (including finite element, finite difference, or finite volume), or boundary element methods (using either real or complex variables). In this paper, the Complex Variable Boundary Element method (“CVBEM”) is examined with respect to the use of different types of basis functions in the CVBEM approximation function. Four basis function families are assessed in their solution success in modeling an important benchmark problem in ideal fluid flow; namely, flow around a 90 degree bend. Identical problem domains are used in the examination, and identical degrees of freedom are used in the CVBEM approximation functions. Further, a new computational modeling error is defined and used to compare the results herein; specifically, M = E / N where M is the proposed computational error measure, E is the maximum difference (in absolute value) between approximation and boundary condition value, and N is the number of degrees of freedom used in the approximation.","PeriodicalId":36958,"journal":{"name":"International Journal of Computational Methods and Experimental Measurements","volume":"9 7 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2018-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74494246","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":"35 years of advancements with the complex variable boundary element method","authors":"N. Demoes, G. Bann, B. Wilkins, T. Hromadka, Randy Boucher","doi":"10.2495/CMEM-V7-N1-1-13","DOIUrl":"https://doi.org/10.2495/CMEM-V7-N1-1-13","url":null,"abstract":"The Complex Variable Boundary Element Method, or CVBEM, was first published in Journal of Numerical Methods in Engineering in year 1984 by authors Hromadka and Guymon [1]. Since that time, several papers and books have been published that present various aspects of the numerical technique as well as advances in the computational method such as extension to three or higher dimensions for arbitrary geometries, nonhomogeneous domains, extension to use of a Hilbert Space setting as well as collocation methods, inclusion of the time derivative via coupling to generalized Fourier series techniques, examination of various families of basis functions including complex monomials, the product of complex polynomials with complex logarithm functions (i.e., the usual CVBEM basis functions), Laurent series expansions, reciprocal of complex monomials, other complex variable analytic functions including exponential and others, as well as linear combinations of these families. Other topics studied and developed include rotation of complex logarithm branch-cuts for extension of the problem computational domain to the exterior of the problem geometry, depiction of computational error in achieving problem boundary conditions by means of the approximate boundary technique, mixed boundary value problems, flow net development and visualization, display of flow field trajectory vectors in two and three dimensions for use in depicting streamlines and flow paths, among other topics. The CVBEM approach has also been extended to solving partial differential equations such as Laplace’s equation, Poisson’s equation, unsteady flow equation, and the wave equation, among other formulations that include sources, sinks and combinations of these equations with mixed boundary conditions. In the current paper, a detailed examination is made of the performance between four families of basis functions in order to assess computational efficiency in problem solving of two dimensional potential problems in a high aspect ratio geometric problem domain. Two selected problems are presented as case studies to demonstrate the different levels of success by each of the four families of examined basis functions. All four families involve basis functions that solve the governing partial differential equation, leaving only the goodness of fit in matching boundary conditions of the boundary value problem as the computational optimization goal. The modeling technique is implemented in computer programs Mathematica and MATLAB. Recommendations are made for future research directions and lessons learned from the current study effort.","PeriodicalId":36958,"journal":{"name":"International Journal of Computational Methods and Experimental Measurements","volume":"28 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2018-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89996367","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 and experimental approach on three phase gas-liquid-solid Newtonian fluid flow in horizontal pipes","authors":"Rasel A. Sultan, Serag Alfarek, M. A. Rahman, S. Zendehboudi","doi":"10.2495/CMEM-V7-N1-33-44","DOIUrl":"https://doi.org/10.2495/CMEM-V7-N1-33-44","url":null,"abstract":"This study analyses three dimensional fluid flow through horizontal pipelines with three-phase gasliquid-solid Newtonian fluids by Computational Fluid Dynamics (CFD) simulation. Validating the simulation with experimental data, the study aims to develop a versatile acceptable simulation model that can be used further for different applied cases. An experimental setup is developed in our laboratory to determine slug flow (air-water) through a horizontal pipeline. Air as gas, water as liquid and silica as solid particle is used in this work. ANSYS Fluent version 16.2 is employed to perform the simulation. The Eulerian multiphase model with the Reynolds Stress Model (RSM) turbulence closure is adopted to analyse multiphase fluid flow. Parameters are selected from experimental works to validate the simulation. After a good agreement with experimental data, sensitivity analysis is conducted to observe the three phase fluid flow characteristics through horizontal flow. Pressure gradient (pressure drop per unit length) and in situ concentration profile are used as primary parameters. This article provides a clear relationship between the different parameters of three-phase fluid flow through a horizontal pipeline.","PeriodicalId":36958,"journal":{"name":"International Journal of Computational Methods and Experimental Measurements","volume":"68 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2018-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80053331","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":"Use of equivalent celerity to estimate maximum pressure increase in serial pipes during water hammer - numerical simulations in MATLAB","authors":"A. Malesińska, M. Rogulski, P. Puntorieri, G. Barbaro, B. Kowalska","doi":"10.2495/CMEM-V7-N1-22-32","DOIUrl":"https://doi.org/10.2495/CMEM-V7-N1-22-32","url":null,"abstract":"Pipe lines are useful for transporting water for drinking, irrigation and for fire-ing over long distances, this pipe lines are called “Transmission line” and are used to carry conveying raw or treated water from a well field or remote storage (large lake, reservoir, etc.,) facility to a treatment plant and/or distribution storage tank. In water-carrying piping systems, dangerous phenomena may occur. One such phenomenon is water hammer. The water hammer has always been an area of study, which has captivated the minds of researchers due to its complex and challenging phenomena. Modeling the phenomenon in real conditions is extremely difficult. Due to the dimensions of the piping systems, conducting research at real scales is impossible. However, thanks to the development of numerical methods, the study of water hammer and its effects can be performed using simulation programs. Unfortunately, the simulation results are not always consistent with the actual course of the phenomenon. One of the parameters that describes the nature of the course of a water hammer is the velocity of propagation of the pressure wave, c, which is called celerity. The transient surge pressure, p, may be calculated from the pressure celerity c, and the sudden change in fluid flow velocity, ∆ v. In a piping system, the value of the pressure wave celerity is not equal to the individual celerity, c, for a single pipeline. Therefore for piping systems for ∆p calculations the equivalent celerity shell be used. This article presents value of the equivalent celerity calculated from equations derived using linear analysis of natural vibrations of the system. For implement of the equations, an algorithm in MATLAB has been developed that allows one to easily calculate the equivalent celerity, ce, for N pipelines connected in series with varying diameter, length and material composition.","PeriodicalId":36958,"journal":{"name":"International Journal of Computational Methods and Experimental Measurements","volume":"27 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2018-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73798067","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}