How to write cell centred data field to an unstructred grid.

Dear sir:
I need to output my cfd data in a FVM way.How to write cell centred data field to an unstructred grid.
Regards

vtkUnstructuredGrid->GetCellData() gives you access to the collection of cell centered arrays. From there it is vtkDataArray API to edit the content of individual arrays and the unstructured grid compatible Readers and Writers to make the contents persist in files.