hi i cant understand that what is the need of meshing to any geometry

Spend some time with decretisation section of documentation (using the solver) you will understand the need. best of luck.

In CFD we do not solve (analytically) the governing partial diffrential equations but rather a 'numerical reprenstation' of them.

The numerical representations discretise the equation set such that relationships exist between nodes. The collection of the nodes forms the mesh/grid.

And so if we are to have any chance of solving the equation set we 'need' to know the location in space, and time also if the problem is a time dependant one, of the nodes.

Hi

I hope you'd have got the answer why we need to mesh the geometry, although nowadays the techniques are being developed where you don't need to divide the geometry into smaller elements or control volumes. They are called Meshless methods. Meshless methods begin to emerge around a decade ago, since a whole lot of time is consumed in meshing. Galerkin Method is one of the meshless methods. However, it is hardly directly used. However, it seems you are new to the field, so for the time being its better to know that meshing is a necessity and not important.

Vinod Dhiman