Search results

1 – 10 of over 10000
Article
Publication date: 1 October 2004

Ramji Kamakoti and Wei Shyy

The geometric conservation law (GCL) is an important concept for moving grid techniques because it directly regulates the treatments of the fluid flow and grid movement…

1308

Abstract

The geometric conservation law (GCL) is an important concept for moving grid techniques because it directly regulates the treatments of the fluid flow and grid movement. With the grid movement at every time instant, the Jacobian, associated with the volume of each element in curvilinear co‐ordinates, needs to be updated in a conservative manner. In this study, alternative GCL schemes for evaluating the Jacobian have been investigated in the context of a pressure‐based Navier‐Stokes solver, utilizing moving grid and the first‐order implicit time stepping procedure as well as the PISO scheme. GCL‐based on first and second‐order, implicit as well as time‐averaged, time integration schemes were considered. Accuracy and conservative properties were tested on steady‐state, laminar flow inside a 2D channel and time dependent, turbulent flow around a 3D elastic wing; both treated with moving grid techniques. It seems that the formal order of accuracy is not a decisive indicator. Instead, the speed of grid movement and the interplay between the flow solver and the GCL treatments make a more noticeable impact.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 14 no. 7
Type: Research Article
ISSN: 0961-5539

Keywords

Article
Publication date: 1 August 2002

E. Theuns, J. Vierendeels and P. Vandevelde

This paper describes a one dimensional moving grid model for the pyrolysis of charring materials. In the model, the solid is divided by a pyrolysis front into a char and a…

Abstract

This paper describes a one dimensional moving grid model for the pyrolysis of charring materials. In the model, the solid is divided by a pyrolysis front into a char and a virgin layer. Only when the virgin material reaches a critical temperature it starts to pyrolyse. The progress of the front determines the release of combustible volatiles by the surface. The volatiles, which are produced at the pyrolysis front, flow immediately out of the solid. Heat exchange between those volatiles and the char layer is taken into account. Since the model is used here as a stand‐alone model, the external heat flux that heats up the solid, is assumed to be known. In the future, this model will be coupled with a CFD code in order to simulate fire spread. The char and virgin grid move along with the pyrolysis front. Calculations are done on uniform and on non‐uniform grids for the virgin layer. In the char layer only a uniform grid is used. Calculations done with a non‐uniform grid are about 3 times faster than with a uniform gird. The moving grid model is compared with a faster but approximate integral model for several cases. For sudden changes in the boundary conditions, the approximate integral model gives significant errors.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 12 no. 5
Type: Research Article
ISSN: 0961-5539

Keywords

Article
Publication date: 1 December 1999

Tony W.H. Sheu and Harry Y.H. Chen

We present in this paper a finite element analysis of Navier‐Stokes equations in a time‐varying domain. The method of weighted residuals is used together with the…

1320

Abstract

We present in this paper a finite element analysis of Navier‐Stokes equations in a time‐varying domain. The method of weighted residuals is used together with the semi‐discretization approach to obtain the discrete equations. In this approach, where the physical domain is allowed to vary, care is taken to retain the space conservation law property. We describe in detail the transformation of equations between fixed and moving grids. The validity of this method has been tested against two problems which are amenable to analytic solutions. Time accurate results show favorable agreement with analytic solutions. Having verified the applicability of the Galerkin finite element code to problems involving moving grids, we consider the fluid flow in a vessel, where a portion of its boundary moves in time. Results are presented with emphasis on the depiction of vortical flow details.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 9 no. 8
Type: Research Article
ISSN: 0961-5539

Keywords

Article
Publication date: 3 October 2019

Lisha He, Jianjing Zheng, Yao Zheng, Jianjun Chen, Xuan Zhou and Zhoufang Xiao

The purpose of this paper is to develop parallel algorithms for moving boundary simulations by local remeshing and compose them to a fully parallel simulation cycle for…

Abstract

Purpose

The purpose of this paper is to develop parallel algorithms for moving boundary simulations by local remeshing and compose them to a fully parallel simulation cycle for the solution of problems with engineering interests.

Design/methodology/approach

The moving boundary problems are solved by unsteady flow computations coupled with six-degrees-of-freedom equations of rigid body motion. Parallel algorithms are developed for both computational fluid dynamics (CFD) solution and grid deformation steps. Meanwhile, a novel approach is developed for the parallelization of the local remeshing step. It inputs a distributed mesh after deformation, then marks low-quality elements to be deleted on the respective processors. After that, a parallel domain decomposition approach is used to repartition the hole mesh and then to redistribute the resulting sub-meshes onto all available processors. Then remesh individual sub-holes in parallel. Finally, the element redistribution is rebalanced.

Findings

If the CFD solver is parallelized while the remaining steps are executed in sequential, the performance bottleneck of such a simulation cycle is observed when the simulation of large-scale problem is executed. The developed parallel simulation cycle, in which all of time-consuming steps have been efficiently parallelized, could overcome these bottlenecks, in terms of both memory consumption and computing efficiency.

Originality/value

A fully parallel approach for moving boundary simulations by local remeshing is developed to solve large-scale problems. In the algorithm level, a novel parallel local remeshing algorithm is present. It repartitions distributed hole elements evenly onto all available processors and ensures the generation of a well-shaped inter-hole boundary always. Therefore, the subsequent remeshing step can fix the inter-hole boundary involves no communications.

Details

Engineering Computations, vol. 36 no. 8
Type: Research Article
ISSN: 0264-4401

Keywords

Article
Publication date: 23 June 2021

Mohammad Mehdi Razzaghi

This study aims to present a moving grid method based on the manipulation of connections.

Abstract

Purpose

This study aims to present a moving grid method based on the manipulation of connections.

Design/methodology/approach

In this study, the grid’s connections were manipulated to simulate a released store’s displacement. The selected model in this research is the EGLIN test case. In the introduced method, connections are modified in specific nodes of the grid. Governing flow equations were solved with the finite volume method. The major characteristic of this technique is using the averaging method for calculating the flux of cells.

Findings

This method maintains the grid’s quality even in large displacements of the released store. The three-dimensional simulation was carried out in transonic and supersonic regimes. Comparison of the results with experimental data were highly satisfactory.

Research limitations/implications

Using this moving grid method is recommended for simulating other models.

Practical implications

Prediction of store trajectory released from air vehicles is one of the most critical issues under study especially in the design of new stores.

Originality/value

The most prominent advantage of this method is maintaining the grid quality simultaneous with large displacements of the released store.

Details

Aircraft Engineering and Aerospace Technology, vol. 93 no. 5
Type: Research Article
ISSN: 1748-8842

Keywords

Article
Publication date: 1 December 2004

Andrzej Demenko and Dorota Stachowiak

The equivalent fixed grid and moving grid models for the finite element (FE) analysis of an induction machine are presented. The discussed transformation is the FE…

Abstract

The equivalent fixed grid and moving grid models for the finite element (FE) analysis of an induction machine are presented. The discussed transformation is the FE representation of the classical commutator transformation. The obtained fixed grid model takes into account the higher space harmonics of the flux density wave and can be used in the FE analysis of the machines with solid rotor, drug‐cap rotor, and squirrel cage winding. The models have been applied in the calculations of TEAM Workshop problem No. 30. The test problem has been solved analytically. The FE results and analytical results are very close.

Details

COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, vol. 23 no. 4
Type: Research Article
ISSN: 0332-1649

Keywords

Article
Publication date: 1 March 1994

Y.‐Y. Tsui and H.‐P. Cheng

A multidimensional calculation method is used to investigate the flow ina motored two‐stroke engine. The governing equations are written in amoving‐coordinate system such…

Abstract

A multidimensional calculation method is used to investigate the flow in a motored two‐stroke engine. The governing equations are written in a moving‐coordinate system such that the grid can move with the piston. Grid lines are added into or deleted from the computational domain, depending on opening or closure of the ports. The EPISO algorithm is modified and adopted as the solution procedure. Calculations are performed on an engine of loop‐scavenged type. Details of the gas exchange process and the flow structure in the cylinder are shown. The effects of the engine speed, inlet discharge coefficient and the angle of boost port are examined.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 4 no. 3
Type: Research Article
ISSN: 0961-5539

Keywords

Article
Publication date: 4 December 2017

Gaohua Li, Xiang Fu and Fuxin Wang

This paper aims to improve the computational efficiency and to achieve high-order accuracy for the computation of helicopter rotor unsteady flows in forward flight during…

183

Abstract

Purpose

This paper aims to improve the computational efficiency and to achieve high-order accuracy for the computation of helicopter rotor unsteady flows in forward flight during the industrial preliminary design stage.

Design/methodology/approach

The integral arbitrary Lagrangian–Eulerian form of unsteady compressible Navier–Stokes equations with low Mach number preconditioned pseudo time terms based on non-inertial frame of reference undergoing rotating and translating was derived and discretized in the framework of multi-block structured finite volume grid using three types of spatial reconstruction schemes, i.e. the third-order accurate monotonic upwind scheme for conservation laws, the fifth-order accurate weighted essentially non-oscillatory and the fifth-order accurate weighted compact nonlinear schemes.

Findings

The results show that the present non-inertial computational method can obtain comparable results with other methods, such as the dynamic overset method, and make sure that the higher-order spatial schemes can significantly improve the tip vortex resolution.

Originality/value

The computational grid used by the present method remained static during the whole unsteady computation process, with only local deformations induced by blade cyclic pitch and other operating motions, which greatly reduced the complexity of grid motion and enhanced the efficiency and robustness.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 27 no. 12
Type: Research Article
ISSN: 0961-5539

Keywords

Article
Publication date: 1 February 1992

MICHAEL J. BOCKELIE and PETER R. EISEMAN

An adaptive grid solution method is described for computing the time accurate solution of an unsteady flow problem. The solution method consists of three parts: a grid

Abstract

An adaptive grid solution method is described for computing the time accurate solution of an unsteady flow problem. The solution method consists of three parts: a grid point redistribution method; an unsteady Euler equation solver; and a temporal coupling routine that links the dynamic grid to the flow solver. The grid movement technique is a direct curve by curve method containing grid controls that generate a smooth grid that resolves the severe solution gradients and the sharp transitions in the solution gradients. By design, the temporal coupling procedure provides a grid that does not lag the solution in time. The adaptive solution method is tested by computing the unsteady inviscid solutions for a one‐dimensional shock tube and a two‐dimensional shock vortex interaction. Quantitative comparisons are made between the adaptive solutions, theoretical solutions and numerical solutions computed on stationary grids. Test results demonstrate the good temporal tracking of the solution by the adaptive grid, and the ability of the adaptive method to capture an unsteady solution of comparable accuracy to that computed on a stationary grid containing significantly more grid points than used in the adaptive grid.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 2 no. 2
Type: Research Article
ISSN: 0961-5539

Keywords

Article
Publication date: 22 August 2008

Shumei Lou, Guoqun Zhao, Rui Wang and Xianghong Wu

The purpose of this paper is to find an efficient way by using finite volume method (FVM) to simulate the aluminum alloy profile extrusion processes.

Abstract

Purpose

The purpose of this paper is to find an efficient way by using finite volume method (FVM) to simulate the aluminum alloy profile extrusion processes.

Design/methodology/approach

By assuming isotropic conditions, the hot aluminum material is described as a non‐linear Newtonian fluid material. Semi‐implicit method for pressure‐linked equations algorithm is used to calculate the physical fields, and the dynamic viscosity is updated then. Volume of fluid method and moving grid method are also used for unsteady flow to catch the free surface of the material and the moving bound.

Findings

FVM model in this paper is an accurate and efficient method for the numerical simulation of aluminum profile extrusion processes. Compared with finite element method software, FVM model is both memory and CPU efficient.

Practical implications

Provide theoretical reference for sound extrusion process and die designs, which are the key factors to produce desirable products in industrial production.

Originality/value

The paper finds an efficient way to introduce the FVM in computational fluid dynamics field into the simulation of the steady and unsteady aluminum alloy profile extrusion processes. It provides a reference for people who are interested in FVM and extrusion processes.

Details

Engineering Computations, vol. 25 no. 6
Type: Research Article
ISSN: 0264-4401

Keywords

1 – 10 of over 10000