How to save data only of middle plane of airfoil while it calculate over whole domain
 

Dear all, I am doing LES simulation of airfoil. I am getting around 20 GB of data for each time step. In post process I need data of only middle plane of airfoil. Is there anyway to simulate for all the 9 million cells but save for data only for middle plane.

Take a look at the surfaceFieldValue function-object. I think this is probably what you want.
Possibly also of interest could be runTimePostProcessing and/or the catalyst interface, either of which would let you create images (eg, PNG files) during the simulation instead afterwards.