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4.1 drag: AAD

Lets talk a bit about fluid. The more important fluid that we need to focus on is air. However we can exercise our understanding by using a different fluid for different situation. We want to understand Drag in aircraft. This doesnt seem easy to understand when we want to visualize it as the aerodynamic drag that we face in our daily life is rare. However lets talk about water as the fluid. As we go sometimes swimming or just when we wash our hands in a stream of water, we can feel the water pushing us. This is a force exerted by a fluid on a body. Just the reverse of this would be when we move our hand or body in water. Lets take an easy example of swimming pool. If we try to move within the swimming pool filled with water we feel a sense of resistance. as we try to move. what we are basically doing is moving the molecule of water and allowing that motion to take place. 

Similar phenomenon happens in aircraft when it speeds up in the run way to take off and when it fly in the cruises. So this understanding of molecular level of disturbance is important to understand. This resistance of air molecule or in our example the water molecule in the pools generating a negative acting force ie they want the motion to stop. This force is called Drag.

However it is in out best interest to minimize this Force, so that we can fly more efficiently with minimum energy. This is not an easy job to do. And this has been the lifes challenge for many scientists and researchers. Let us dive into  this topic and understand Drag a bit closely. 


So what is Drag ? 

In fluid dynamics, drag (sometimes called air resistance, a type of friction, or fluid resistance, another type of friction or fluid friction) is a force acting opposite to the relative motion of any object moving with respect to a surrounding fluid.


How can we minimize it?

Before minimizing Drag we need to understand different types of drag and their sources. Some drag are caused due to the interaction of the airstream from different component and some are simply due to the adhesive force between the air molecule and the surface o the aircraft.

friction drag

form drag

interference drag

wave drag

induced drag

viscous drag

vortex drag

parasite drag

All these drag terms will be heard in the field of aviation. however we need to be able to link then and group them for better understanding.

the drag can be classified in different way

A. Total Drag

1. Pressure Drag

induced drag

form drag


2. Friction Drag


B. Total Drag

1. induced drag

2. parasite drag

friction drag

form drag

x


C. Total Drag

1. Vortex drag

2. Wave drag

3. Viscous Drag


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