[browney]

Yep, Your explanation makes sense. The diffuser acts like a wing, where a pressure has to act to accelerate the air around the curvature. It makes sense that you don't want the diffuser too steep, otherwise the boundry layer will seperate effectivly stalling the diffuser. I guess another way to think about it, is with conservation of momentum/newton's 3rd too. The air is accelerated upwards by the diffuser so the diffuser is being pushed downwards.

Are you able to tell me then, why is it then that an increase in cross sectional area causes the fluid to slow down (like in the diffuser on the exit side of a venturi), seemingly the opposite to this. I was thinking about it using the equation 'q = v1 A1 = v2 A2' Where the area was increasing so the air was slowing.

You won't confuse me (well hopefully not!) with getting complex, I'm 3/4 of the way through an automotive engineering degree, so I've done 2 years of fluid mechanics. It's funny, I've looked through my fluids text book and a text book on road vehicle aerodynamics I borrowed but the best explanation I get is on an internet forum!