Aerodynamics in Drones

By | February 24, 2017

castleThe science behind aerodynamics was extensively evaluated and noted down in a whole set of differential equations referred to as naiver stokes. These equations are so diverse and involving that mathematicians have continuously worked on them to try and come up with assumptions that can led to a more simplifies sub set detailed enough to make the studies of aerodynamics in drones a bit easier. The most common assumption was brought up in the aim to eliminate the friction form the equation, such that only the potential flight would remain. This assumption was a bit reasonable based on the fact that friction in air is lower compared to the other factors. However this assumption suggests that no drag exist making it impossible for the drones to fly.

Aerodynamics in drones is all a matter of friction. Without this, the air particles will not have the ability to stick on to any surface, and hence would not create the boundary layer which is responsible for the lift force. Let me explain about the boundary layer. During your coffee break in the office, take a spoon and dip it half into the coffee. Then suddenly move it from right to left. You will notice that a vortex has been created separated from the spoon’s trailing edge. The vortex you see is equal to the sum of all tiny rotating vortices on the surface of the spoon which are generated by the boundary layer. Immediately you stop the spoon movement, you will notice that a new vortex appears on the opposite side separating the spinning. The total voracity remains the same and this is the key to flight.

So What makes The Drone Fly
To simplify this explanation, lets take for example an airfoil as a part of infinite long wing. Essentially, airflow around the foil separates from the nose and joins again at the trailing edge. The vortricity is the one that cause the air to change its velocity which in turn results in a net force on the body. Pressure distribution all over the foil causes a powerful suction on the upper side, that eventually integrates all over the foil leading to a lift force. On the other hand, the drag force is a total of all the forces occurring on the main stream caused by both friction and pressure. This is the same case in drones, The drone’s rotors are kept at a constant rate while at the same time, the swash plates cyclically change the blade’s pitch which in turn increases the blades’ lift.

Conclusion.
Drones are affected a lot by aerodynamics and vibration aspects, just like helicopters. In the near future, they will be the most common VTOL vehicles in aviation, and just maybe the most effective.

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