Hi,

I am now trying to modify my code to enable the use of overset grids. I tried to test my code using a flow past cylinder but there's some unphysical velocity vectors. I wonder what could be the problems...

There's some questions which I would like to ask:

1. I've tried inverse distance and bilinear interpolation. I've read some papers which says least square Taylor series expansion is usually better. Is that so?

2. Is it better for the cylinder grid to be as big as possible, so that the interpolation region is one whereby there's least disturbance?

3. At the location of interpolation, must the cylinder and background grid be of similar size?

Thanks and happy new year!

If you are using an unstructured set of grids, then least squares does seem to provide a better interpolation scheme, based on work I have seen. In answer to questions 2 and 3, remember that when you use overset grids you are solving the equations on two different grids - thus you are generating a multiply-defined solution. Therefore interpolation works best in regions of small gradients and between meshes of similar size.

Thanks ag!

But I'm using structured grid. Is there an interpolation which is more suitable?

Thanks again

Hi,

Check these out:

A Scheme for Conservative Interpolation on Overlapping Grids, G. Chesshire and W.D. Henshaw, SIAM J. of Scientific Computing, 15, number 4, pp. 819-845 (1994).

Composite Overlapping Meshes for the Solution of Partial Differential Equations, G. Chesshire and W.D. Henshaw, Journal of Computational Physics, 90, number 1, pp. 1-64 (1990)

A Scheme for Conservative Interpolation on Overlapping Grids, G. Chesshire and W.D. Henshaw, SIAM J. of Scientific Computing, 15, number 4, pp. 819-845 (1994).

Regards, Dominic

The presentations from the latest Overset Symposium are on-line here: http://www.arl.hpc.mil/events/Overset2006/program.html. Perhaps there's something there that can help.

Also, DiRTlib is a tool that you can use to add overset capability to an existing CFD code. I don't have a URL for it, but you might want to do an internet search.

Hope this helps.