I thought that the only “V for…” title that is famous is V for Vendetta but when I Googled “V for Flight” this was the search result I got. And there is something fascinating about the above searched images. Yes! you guessed it right, it is the flight pattern of the birds, swimming pattern of ducks and not only that even the fighter jets which move at huge speeds.
So why does this happens? The Answer is Wingtip Vortices. End of story. Bye!
So what is this Wingtip Vortice?
Well! if you really want to know then please! fasten your seat belts as we are about to take off to a hell of a flight.
According to Wikipedia, Wingtip vortices are circular patterns of rotating air left behind a wing as it generates lift. Even I didn’t understand it in a single time so just hang around for a while. We know that wings are essential for the flight of anything bird, planes etc (but not Iron Man ‘coz he is Iron Man). So during the flight wings experience an air lift (upward force to counter the gravity pull) due to the pressure difference developed on both sides of the wing, to be exact the pressure developed on lower surface is higher than that on the upper surface. This pressure difference gives the required air lift to the wing.
But we are living in a real world, nothing comes at a free price so how can air lift be free? It isn’t. The air from the lower side try to come up to the top (just like water flows from high pressure to lower pressure in your tap). This creates a swirling pattern which is called vortice on the edge of the wing shown in the two picture below.
This creates some insanely interesting combination of things. As a result of this vortice formation a downward force is created by the air moving from bottom to the top, this is called Downwash. However in the region sideways to the wings an upward force is created by the same movement of the air, this is called Upwash.
Now look at the movement of a bird flock.
They move in such a way that upwash generated by B1 helps to reduce the downwash of B2 and B3. In the picture shown below the upwash and downwash are shown by semi circles. Notice that upwash of B1 travel to B2 and B3 and cancel the effect their respective downwashes. Now this doesn’t happen for the bird B1 as it is moving ahead of the other two hence the upwash of B2 and B3 doesn’t reach to it.
This entire superposition effect save a lot of energy for birds B2, B3, B4 and onward during long distance flights. Migratory birds like pelicans almost all the time flies in this V shape formation with the leader of the bird (generally the strongest one) taking the central position. Researchers have even compared the heart beat rate of the leader and the rest of the flock. Unsurprisingly the heart beat of the central bird (B1) was found to be much faster as compared to the rest as it is consuming a lot of energy to counter the downwash generated.
Same analogy can be extended to the flight of Jet-planes as well but not so much to the ducks (I guess!). Anyways I’m done for the day.
One last thing, have you notice the little bend on the edge of a wing. They are used to restrict the movement of air form bottom to top resulting in less downwash being created by Wingtip Vortice.
Hope you have learned something.
Hasta la Vista!
-By a Kam-akal (Ujjwal Dubey)