If you make a cylinder, shell it, then make a split line to give you left and right sides, you can define one side as your velocity and the other as your pressure.
You can change the angle of attack by leaving your cylinder in place and rotating the barn inside of it. Or if the barn requires complex mesh settings you'd have to rotate the cylinder and alter the vector definition for each.
Thanks for the suggestion - I'll give that a try. I think I might have stumbled on another possible solution - setting up the Vx, Vy, and Vz values in the initial conditions dialog using F(time) tables - it seems to respect these values up to the maximum time set in the table.
why not keep the flow the same direction and rotate the barn? like you would in a wind tunnel