Problem with drag coefficient calculation
 

Hi,

I'm quite new to Fluent and lately I've been facing a rather strange problem relating to drag coefficient calculation. I'm trying to simulate external flow over a sphere at Re = 100, 300 and 1.1 X 10^6. My problem is: when I select air as my fluid, my results closely matches the reported values. However, when I select water as my fluid, my results are totally off, and the values are close to zero.
I've checked that I've keyed in the corresponding velocities correctly. I even tried changing the dimensions of the sphere and running on double precision solver to ensure it is not caused by limit in precision. But to no avail.
What could be the problem? Would really appreciate any help on this!