Free element method and its application in CFD

2019 ◽  
Vol 36 (8) ◽  
pp. 2747-2765 ◽  
Author(s):  
X.W. Gao ◽  
Huayu Liu ◽  
Miao Cui ◽  
Kai Yang ◽  
Haifeng Peng
Keyword(s):  
Fluid Mechanics ◽  
Numerical Method ◽  
Compressible Fluid ◽  
System Of Equations ◽  
Individual Element ◽  
Governing Equations ◽  
Content Type ◽  
Set Up ◽  
Free Element ◽  
Element Method

Purpose The purpose of this paper is to propose a new strong-form numerical method, called the free element method, for solving general boundary value problems governed by partial differential equations. The main idea of the method is to use a locally formed element for each point to set up the system of equations. The proposed method is used to solve the fluid mechanics problems. Design/methodology/approach The proposed free element method adopts the isoparametric elements as used in the finite element method (FEM) to represent the variation of coordinates and physical variables and collocates equations node-by-node based on the newly derived element differential formulations by the authors. The distinct feature of the method is that only one independently formed individual element is used at each point. The final system of equations is directly formed by collocating the governing equations at internal points and the boundary conditions at boundary points. The method can effectively capture phenomena of sharply jumped variables and discontinuities (e.g. the shock waves). Findings a) A new numerical method called the FEM is proposed; b) the proposed method is used to solve the compressible fluid mechanics problems for the first time, in which the shock wave can be naturally captured; and c) the method can directly set up the system of equations from the governing equations. Originality/value This paper presents a completely new numerical method for solving compressible fluid mechanics problems, which has not been submitted anywhere else for publication.

Variational multi-scale finite element method for the two-phase flow of polymer melt filling process

2019 ◽  
Vol 30 (3) ◽  
pp. 1407-1426 ◽  
Author(s):  
Xuejuan Li ◽  
Ji-Huan He
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Numerical Method ◽  
Two Phase Flow ◽  
Polymer Melt ◽  
Phase Flow ◽  
Filling Process ◽  
Two Phase ◽  
Content Type ◽  
Element Method

Purpose The purpose of this paper is to develop an effective numerical algorithm for a gas-melt two-phase flow and use it to simulate a polymer melt filling process. Moreover, the suggested algorithm can deal with the moving interface and discontinuities of unknowns across the interface. Design/methodology/approach The algebraic sub-grid scales-variational multi-scale (ASGS-VMS) finite element method is used to solve the polymer melt filling process. Meanwhile, the time is discretized using the Crank–Nicolson-based split fractional step algorithm to reduce the computational time. The improved level set method is used to capture the melt front interface, and the related equations are discretized by the second-order Taylor–Galerkin scheme in space and the third-order total variation diminishing Runge–Kutta scheme in time. Findings The numerical method is validated by the benchmark problem. Moreover, the viscoelastic polymer melt filling process is investigated in a rectangular cavity. The front interface, pressure field and flow-induced stresses of polymer melt during the filling process are predicted. Overall, this paper presents a VMS method for polymer injection molding. The present numerical method is extremely suitable for two free surface problems. Originality/value For the first time ever, the ASGS-VMS finite element method is performed for the two-phase flow of polymer melt filling process, and an effective numerical method is designed to catch the moving surface.

Application of the Conservation Element and Solution Element Method in Numerical Modeling of Three-Dimensional Heat Conduction With Melting and/or Freezing

2004 ◽  
Vol 126 (6) ◽  
pp. 937-945 ◽  
Author(s):  
Anahita Ayasoufi ◽  
Theo G. Keith ◽  
Ramin K. Rahmani
Keyword(s):  
Numerical Modeling ◽  
Heat Conduction ◽  
Fluid Mechanics ◽  
Phase Change ◽  
Numerical Method ◽  
Analytical Solutions ◽  
Three Dimensional ◽  
Solution Element ◽  
Explicit Numerical Method ◽  
Element Method

The conservation element and solution element (CE/SE) method, an accurate and efficient explicit numerical method for resolving moving discontinuities in fluid mechanics problems, is used to solve three-dimensional phase-change problems. Several isothermal phase-change cases are studied and comparisons are made to existing analytical solutions. The CE/SE method is found to be accurate, robust, and efficient for the numerical modeling of phase-change problems.

Application of the Conservation Element and Solution Element Method in Numerical Modeling of Three-Dimensional Heat Conduction With Melting and/or Freezing

2003 ◽  
Author(s):  
Anahita Ayasoufi ◽  
Theo G. Keith
Keyword(s):  
Numerical Modeling ◽  
Heat Conduction ◽  
Fluid Mechanics ◽  
Phase Change ◽  
Numerical Method ◽  
Analytical Solutions ◽  
Three Dimensional ◽  
Solution Element ◽  
Explicit Numerical Method ◽  
Element Method

The conservation element and solution element (CE/SE) method, an accurate and efficient explicit numerical method for resolving moving discontinuities in fluid mechanics problems, is used to solve three-dimensional phase change problems. Several isothermal phase change cases are studied and comparisons are made to existing analytical solutions. The CE/SE method is found to be accurate, robust and efficient for the numerical modeling of phase change problems.

Study on a Numerical Model of “Rainfall-Runoff” Process Combined with Snowmelt

2012 ◽  
Vol 518-523 ◽  
pp. 4273-4277
Author(s):  
Huang Jinbai ◽  
Wang Bin ◽  
Hinokidani Osamu ◽  
Kajikawa Yuki
Keyword(s):  
Numerical Method ◽  
Wave Theory ◽  
Large Error ◽  
Calculation Model ◽  
Surface Flow ◽  
Snow Melt ◽  
Rainfall Runoff ◽  
Surface Water Resources ◽  
Permissible Range ◽  
Set Up

In order to achieve the accurate calculation of “rainfall-runoff” process combined with snowmelt and to provide a useful numerical method for estimating surface water resources in a basin, a runoff numerical calculation model of “rainfall-runoff” process combined with snowmelt was developed for a distributive hydrological model. Numerical method on “Rainfall-runoff” process was set up by applying kinematic wave theory, and calculations on snowmelt were made using energy budget method. Validity of the model was verified through numerical simulation of the observed surface flow. Results of the error analysis indicated that a large error existed between the numerical results and the observed ones without considering snowmelt whereas the error was at the permissible range of criterion (< 3 %) by considering snowmelt. The results showed that the snowmelt calculation should be considered at snow melt area when performing the runoff calculation.

Parallel finite-element method using domain decomposition and Parareal for transient motor starting analysis

2019 ◽  
Vol 38 (5) ◽  
pp. 1507-1520 ◽  
Author(s):  
Yasuhito Takahashi ◽  
Koji Fujiwara ◽  
Takeshi Iwashita ◽  
Hiroshi Nakashima
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Parallel Computing ◽  
Domain Decomposition ◽  
Parallel Computation ◽  
Domain Decomposition Method ◽  
Space Time ◽  
Content Type ◽  
Parallel Performance ◽  
Element Method

Purpose This paper aims to propose a parallel-in-space-time finite-element method (FEM) for transient motor starting analyses. Although the domain decomposition method (DDM) is suitable for solving large-scale problems and the parallel-in-time (PinT) integration method such as Parareal and time domain parallel FEM (TDPFEM) is effective for problems with a large number of time steps, their parallel performances get saturated as the number of processes increases. To overcome the difficulty, the hybrid approach in which both the DDM and PinT integration methods are used is investigated in a highly parallel computing environment. Design/methodology/approach First, the parallel performances of the DDM, Parareal and TDPFEM were compared because the scalability of these methods in highly parallel computation has not been deeply discussed. Then, the combination of the DDM and Parareal was investigated as a parallel-in-space-time FEM. The effectiveness of the developed method was demonstrated in transient starting analyses of induction motors. Findings The combination of Parareal with the DDM can improve the parallel performance in the case where the parallel performance of the DDM, TDPFEM or Parareal is saturated in highly parallel computation. In the case where the number of unknowns is large and the number of available processes is limited, the use of DDM is the most effective from the standpoint of computational cost. Originality/value This paper newly develops the parallel-in-space-time FEM and demonstrates its effectiveness in nonlinear magnetoquasistatic field analyses of electric machines. This finding is significantly important because a new direction of parallel computing techniques and great potential for its further development are clarified.

Effects of moving lid direction on mixed convection and entropy generation in a cubical cavity with longitudinal triangular fin insertion

2017 ◽  
Vol 27 (4) ◽  
pp. 839-860 ◽  
Author(s):  
Lioua Kolsi ◽  
Hakan F. Öztop ◽  
Nidal Abu-Hamdeh ◽  
Borjini Mohamad Naceur ◽  
Habib Ben Assia
Keyword(s):  
Mixed Convection ◽  
Entropy Generation ◽  
Three Dimensional ◽  
Thermal Conductivity Ratio ◽  
Governing Equations ◽  
Content Type ◽  
Driven Cavity ◽  
Triangular Fin ◽  
Cubical Cavity ◽  
3D Problem

Purpose The main purpose of this work is to arrive at a three-dimensional (3D) numerical solution on mixed convection in a cubic cavity with a longitudinally located triangular fin in different sides. Design/methodology/approach The 3D governing equations are solved via finite volume technique by writing a code in FORTRAN platform. The governing parameters are chosen as Richardson number, 0.01 ≤ Ri ≤ 10 and thermal conductivity ratio 0.01 ≤ Rc ≤ 100 for fixed parameters of Pr = 0.7 and Re = 100. Two cases are considered for a lid-driven wall from left to right (V+) and right to left (V−). Findings It is observed that entropy generation due to heat transfer becomes dominant onto entropy generation because of fluid friction. The most important parameter is the direction of the moving lid, and lower values are obtained when the lid moves from right to left. Originality The main originality of this work is to arrive at a solution of a 3D problem of mixed convection and entropy generation for lid-driven cavity with conductive triangular fin attachments.

Washington will engage more with South-east Asia

2021 ◽  
Keyword(s):  
United States ◽  
East Asia ◽  
The United States ◽  
South East Asia ◽  
National Unity ◽  
Content Type ◽  
Key Issues ◽  
Set Up

Significance She addressed two key issues during her trip: tensions in post-coup Myanmar and China’s growing regional footprint. Shortly after she left the region, the United States announced that it would donate unused COVID-19 vaccines abroad, including to South-east Asia. Impacts Washington will tighten its sanctions on the Myanmar military while supporting ASEAN’s five-point plan to ease the country’s crisis. The National Unity Government, a parallel administration to Myanmar’s junta set up by its opponents, will try to attract greater US backing. Manila and Washington may extend negotiations over renewing their Visiting Forces Agreement to prevent the pact expiring in August.

Boundary Element Method Used in Random Response Calculation of the Plate-Beam Structure

1991 ◽  
Author(s):  
J. M. Zhu ◽  
L. Huang
Keyword(s):  
Boundary Element Method ◽  
Numerical Method ◽  
Boundary Element ◽  
Pressure Fluctuation ◽  
Random Vibration ◽  
Power Plants ◽  
Measured Data ◽  
Random Response ◽  
Beam Structure ◽  
Element Method

Abstract The furnace walls of the large boilers in power plants are combined structures consisting of orthotopic plate and equally spaced beams, which are usually submitted to random vibration under the excitation of the pressure fluctuation induced by combustion in the furnace. In this paper, a numerical method based on BEM to compute the random response of the structure is offered. The agreement between the computing results and the measured data in a practical example verifies the effectiveness of the method.

Using transfer learning for diabetic retinopathy stage classification

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Enas M.F. El Houby
Keyword(s):  
Diabetic Retinopathy ◽  
Transfer Learning ◽  
Grade Level ◽  
Design Methodology ◽  
Content Type ◽  
Stage Classification ◽  
Set Up ◽  
Retinal Fundus ◽  
Automated Methods

PurposeDiabetic retinopathy (DR) is one of the dangerous complications of diabetes. Its grade level must be tracked to manage its progress and to start the appropriate decision for treatment in time. Effective automated methods for the detection of DR and the classification of its severity stage are necessary to reduce the burden on ophthalmologists and diagnostic contradictions among manual readers.Design/methodology/approachIn this research, convolutional neural network (CNN) was used based on colored retinal fundus images for the detection of DR and classification of its stages. CNN can recognize sophisticated features on the retina and provides an automatic diagnosis. The pre-trained VGG-16 CNN model was applied using a transfer learning (TL) approach to utilize the already learned parameters in the detection.FindingsBy conducting different experiments set up with different severity groupings, the achieved results are promising. The best-achieved accuracies for 2-class, 3-class, 4-class and 5-class classifications are 86.5, 80.5, 63.5 and 73.7, respectively.Originality/valueIn this research, VGG-16 was used to detect and classify DR stages using the TL approach. Different combinations of classes were used in the classification of DR severity stages to illustrate the ability of the model to differentiate between the classes and verify the effect of these changes on the performance of the model.

Semi-analytical finite element method for simulating chemical dissolution-front instability problems in fluid-saturated porous media

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Chongbin Zhao ◽  
B.E. Hobbs ◽  
Alison Ord
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Porous Media ◽  
Chemical Dissolution ◽  
Saturated Porous Media ◽  
Content Type ◽  
Front Instability ◽  
Fluid Saturated Porous Media ◽  
Dissolution Front ◽  
Element Method

PurposeThe objective of this paper is to develop a semi-analytical finite element method for solving chemical dissolution-front instability problems in fluid-saturated porous media.Design/methodology/approachThe porosity, horizontal and vertical components of the pore-fluid velocity and solute concentration are selected as four fundamental unknown variables for describing chemical dissolution-front instability problems in fluid-saturated porous media. To avoid the use of numerical integration, analytical solutions for the property matrices of a rectangular element are precisely derived in a purely mathematical manner. This means that the proposed finite element method is a kind of semi-analytical method. The column pivot element solver is used to solve the resulting finite element equations of the chemical dissolution-front instability problem.FindingsThe direct use of horizontal and vertical components of the pore-fluid velocity as fundamental unknown variables can improve the accuracy of the related numerical solution. The column pivot element solver is useful for solving the finite element equations of a chemical dissolution-front instability problem. The proposed semi-analytical finite element method can produce highly accurate numerical solutions for simulating chemical dissolution-front instability problems in fluid-saturated porous media.Originality/valueAnalytical solutions for the property matrices of a rectangular element are precisely derived for solving chemical dissolution-front instability problems in fluid-saturated porous media. The proposed semi-analytical finite element method provides a useful way for understanding the underlying dynamic mechanisms of the washing land method involved in the contaminated land remediation.

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