  We study the flow of a weakly-interacting Bose-Einstein condensate around an
obstacle by numerical solution of the Gross-Pitaevskii equation. We observe
vortex emission and the formation of bow waves leading to pressure drag. We
compare the drag law with that of an ideal Bose gas, and show that interactions
reduce the drag force. This reduction can be explained in terms of a
`collisional screening' of the obstacle.
