Is is possible to initialize the flow field (3d unstructured) on a cell by cell basis? I have a model I have run in another code and would like to input its solution as the initial guess for a fluent run. The model includes conjugate heat transfer and is about 2 million cells.

I guess the best thing to do is to ask a fluent support engineer if this could be done. I have found them to be very helpful in answering these type of "can we do it" questions.

You can certainly do that . . .

you might be able to read in the data somehow and get fluent to interpolate automatically onto the grid. This depends what format its in etc.

Alternatively write a execute on demand udf to read your data in and then interpolae it on to the grid. If the grids are the same then you don't have to do any interpolation so its very easy - just check the cell centroids and use the data you've read in and apply it within a loop over all cells. If the grids are different you might want to do a simple interpolation - or just pick the closest spacial point in your data and use it for the cell in fluent. This will be approximate of course, but since its an initial guess could be quite ok.

Look in both the fluent manuals and the udf manual for how to do these things.

Greg