On a hot, humid day, right after my class, I heard the loud noise from the engine of a Boeing 747-8, and I immediately pulled out my camera and took this picture. Obviously, there is water mist forming on the upper surface of the wing, and there are long white lines at the tips of the wing, but why?
Let’s start with the water mist that forms on the wings. This is because when the plane takes off, the air speed on the surface of the wing increases, and the air pressure above the wing is lower than in the environment, causing the internal energy of the gas to decrease, and therefore the temperature will decline. At this point, water vapor condenses on the wings, forming a white fog like this in the picture.
The white lines at both ends of the wing are tip vortex, and the high-pressure air on the lower surface of the wing tends to move up around the wing tips, so the airflow will form a vortex, resulting in tip vortex. The reason for its white color is also because it is the rapid change of the condensation of water mist in the air, and finally formed a common physical phenomenon in our lives.
So, the next time when you hear the sound of an airplane, why not look up and see if they leave any trace in the sky, and think about the principle behind them.
