Sometimes in damp conditions I notice some surprising (surprising to me, anyway) behaviour of water.
I'll see moisture glistening in the heads of rivets or bolts on the top of the engine pylons - that stays there for a long time (many minutes) after take-off.
Similarly, at the front edge of my window I will see a pool of water that only very slowly diminishes, seeding little drops (that become smaller and smaller as airspeed increases). Again, this pool remains far longer than I'd expect.
I'm surprised because I'd expect the evaporative and sweeping effect of the high-speed airstream to clear this moisture extremely fast, and yet it doesn't.
I suppose that despite the speed of the airstream, there are numerous small areas on the surface of the plane that are sheltered from it very effectively.
I'm interested to know what the implications of the causes of this effect are are for aerodynamics, for example how they relate to drag on the fuselage, or - where it happens on lifting or control surfaces - how their operation is affected.