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prasat February 14, 2003 03:16

how to ?
 
hi, I have irregrular mesh I want too convert the mesh into regular mesh is it possible? or not

Praveen February 15, 2003 10:07

Re: how to ?
 
More descriptive subject please ? There are ways to "regularise" grids. But when you say irregular/regular, what do you mean exactly ?

prasat February 17, 2003 02:45

Re: how to ?
 
I mean I have irregular grid but I want to convert the grid into regular one.


Praveen February 17, 2003 03:25

Re: how to ?
 
1) You have a non-uniform grid which you want to map to a uniform grid. 2) You have a non-uniform grid which you want to smoothen (regularise). 3) You have an unstructured grid which you want to map to a uniform grid. 4) You have a BAD grid (bad angles, skewed cells, non-orthogonality) which you want to correct. 5) You just have an arbitrary distribution of nodes and you want to do something with that, maybe triangulate it.

prasat February 17, 2003 06:45

Re: how to ?
 
I am not sure may be the 1)You have a non-uniform grid which you want to map to a uniform grid. prasat

Praveen February 19, 2003 03:21

Re: how to ?
 
Let (a,b) be the transformed coordinates and let da, db be the constant grid spacing in the computational plane. Mapping the grid is trivial

a(i,j) = i*da b(i,j) = j*db

Now you want to solve your pde on the transformed plane. So you must first transform your pde e.g.,

df/dx = (df/da)(da/dx) + (df/db)(db/dx)

Next you must approximate (da/dx), (db/dx), ...... using finite differences (since you do not have exact transformation relations). It is easier to calculate (dx/da), ........ rather than the above quantities. For example

(dx/da)_(i,j) = [ x(i+1,j) - x(i-1,j) ]/da

Using these and some more formulae which you can find in a cfd book you can estimate the required transformation coefficients.

Lluvia Marisol Flores Tandy March 6, 2003 15:21

Re: how to ?
 
HI!

I HAVE A PROBLEM, I WAS TRYING TO FIND THIS PAPER FOR A LONG TIME AND I COLDNīT GET IT.

SOMEONE CAN HELP ME?

THANK YOU

de Vahl Davis, G., "Natural convection of air in a square cavity: a bench mark numerical solution", Int. J. Num. Meth. in Fluids, Vol. 3, pp249-264 (1983).



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