overset grids literature review - overture

7/18/2019 Overset Grids Literature Review - Overture

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Structural Dynamics and Computer Applied Engineering (SDCAE) Lab.Gyeongsang National University (GNU), South Korea

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Overset Grids:Literature Review

Somdeb Bandopadhyay


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Benek et al (1983)

The term Chimera was used for overset grid

The interpolation was linear and non-conservative

Eulers eqn for flow over an aerofoil was solved

The results were not good due to the use of invicid Euler's eqn in computation

Henshaw et al (1994)

Fourth order N-S solver was used for overset grid

Lagrangean polynomial is used for interpolation Basic work behind the opensource CFD package: Overture

Tang et al (2003)

Provided the fact that residual error for pressure and velocity is not enough when linear interpolationis used


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Liou & Kao (1994) : Dragon Grid

New type for overset grid system scheme was used:- DRAGON GRID

Background Grid and Body grids are no longer overlapping i.e. there exists a gap between them

This gap is filled up with unstructured mesh with aligned faces at interfaces

Wang et al (1995) : Zonal Interface Generation (ZIG)

A common interface between the (major) cartesian grid and (minor) curvilinear grid was done


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Other Works

There are many other works with overset grid which couldnt be mentioned in this review in details.

Some of them are included here with a brief introduction:-

1. Kiris et al. used artificial compresibility to solve NS equation for flow in artificial heart devices.

2. Tu & Fuchsused a multigrid technique to solve for flow in Internal combustion Engine with

moving boundary

3. Perng & Streetused a predictorcorrector time advancement scheme with a multigrid algorithmfor the solution of pressure equation


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Conservation criteria during Interpolation

Burger (1984) noted that interpolation of flux is more important than the interpolation of variables

themselves.

Successfully applied her theory for 1D problem.

For 2D case the implementation of her theory was complicated and numericalexperiments were not done by her.

Chessire & Henshaw extended Burgers work to make the 2D algorithm applicable to

any number of arbitarily arranged grids. But There still existed a conservative error

Conclusion can be done as :- A conservative interpolation is typically complicated to be implemented.

Solution:- Semi conservative schemes

Mass-Flux Based Interpolation (Tang et al , 2003)

Tang enforced a 2nd order accurate approximation of a exact conservation of mass criteria

He named it : Mass Flux Based Interpolation (MFBI)


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Comparative Study of different Meshing Methods

Method Advantages Disadvantages

CartesianSmall memory and CPU requirements

Does not requires much user experience

Easy to parallelize

Difficulties in resolving boundary layersDifficulties in resolving complex boundaries

Single

Structured

Small memory and CPU requirements

Very well fitted for viscous flow computations

Restricted to simple geometries

Requires user experience

Block

Structured



Can efficiently handle complex geometries

Requires a lot of user experience

Requires block connectivity information

UnstructuredDoes not require much of user experience

Can efficiently handle very complex geometries

Allows adaptive approach and local refinement

Large memory and CPU requirements

Not suited for viscous flow computations

Overlapped



Can efficiently handle complex and moving

geometries

Requires a lot of user experience non-conservative

Interpolation issues in overlapping area


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Comparative Study of Available Codes

Code

NameSpecifications Availability

DiRTlibDonor interpolation Receptor Transaction library

It is a solver neutral library

Easy to parallelize

Not available for free

SUGGARStructured, Unstructured, Generalized overset Grid Assembler

It is used to build domain connectivity

Made for flow solvers which use DiRTlib


Chimera

GridTools

Soft-package to generate overset grid for complex geometry

Part of OVERFLOW-D general purpose NS solverCan efficiently handle complex geometries


BEGGARFlow solution environment for store separation problems

It provides automated grid assembly

Works for moving bodies simulations and 6-DOF rigid body motion


OgenCan handle structured grid generation and overlapping grids assembly

Can deal with moving body geometry and AMR for moving bodies

Freely available for academic &

research use


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Overture : Brief Information About The code

Object oriented C++ language based package

Ogen, the main grid generator is for providing structured grids which is ideal to apply

FDM, but with proper treatment FVM schemes can be used

Ugen is the unstructured grid generator which is included in Overture package

The code uses PetSclibrary to handle different quality of arrays

Lapackand blasare used as a cross compiler for FORTRAN written modules to be used

The full code is dived into main two part :- Overture.vXXand cg.vXXwhere XX stands

for the version number. The first part maiinly deals with the grid generators and the

numerical schemes for the grid to be applied during computation, while the later keeps

the Composite Solvers made by Henshaw and his team.

The solvers used in Overtureare of fourth order schemes

The published papers and other presentations from Henshaw et algives full description of thesoft-package


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Overset Grid Generation in Overture : Functional Steps

Overlapped Grid

Definition of the

Domain geometry

&

Grid componentGeneration by

user

Detection of grid

Points to be

removed by the

Grid generationtool

Confirming the

location of all grid point

s to be used for interpol

ationon the edge of

removed points


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Cut & Hole Technique in Ogen

Selection of the minor (1) and major/background (2) grid boundaries whose spacial location is

inside other grid.

The grid points of the major/background grid is marked, which shares the samespacial location as that of the minor grid

The marked points are removed by the Cut step making a hole in the background grid. This is term

ed as chimera hole

Final Step: Interpolation In this step, the interpolation of data from doner to receiver grid is done

The information are stored in the common grid points

By means of some weighted Eulerian-Lanrangean m/d, the weighted dataset are

transferred to the other grid


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Structural Dynamics and Computer Applied Engineering (SDCAE) Lab.Gyeongsang National University (GNU) South Korea

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Thank You

Questions?

overset grids literature review - overture

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