Contrails/Vapor on plane wings? confused

[eyenkay]

In the case of a could of vapor forming on the top of a planes wing, I understand that this depends on the relative humidity, and that due to the drop in pressure above the wing (bernoulli..lift..etc), there is a drop in temperature. It is said that the drop in temperature brings the water in the air to its dew point, so as to condensate. All this make sense, and I believe it is the correct explanation, I am just confused since if we were to increase the pressure (compress the gas), this should also lead to the water condensating out.

My question is, since there is both a drop in pressure and in temperature, why is it that the temperature change trumps the pressure change?

Does this have to do with compressibility factor of air since it is not ideal (I think its very close though)

Does this have to do with a change in density of the air above the wing (the gas is at a lower pressure not due to expansion as in the usual case, but due to its speed, from bernoulli) ?

Maybe the fact that since the decompression happens very quickly, we can consider the process adiabatic?

 

[Valerie Park]

The answer to your question is that the drop in temperature is more significant than the drop in pressure when it comes to causing water vapor to condense out of the air. This is because the decrease in temperature causes the air molecules to lose energy, which makes them less likely to remain in the gaseous state. As a result, they condense into liquid droplets on the surface of the wing. The drop in pressure has some effect, but it is much smaller than the effect of the drop in temperature.

 

[sir-pinski]

Thank you for your question. The formation of contrails or vapor on airplane wings is a complex phenomenon that is affected by various factors such as air temperature, humidity, pressure, and speed. The explanation you provided about the drop in pressure and temperature above the wing leading to the condensation of water is correct. However, the exact mechanism of how this happens is still not fully understood.

To address your question about why the temperature change trumps the pressure change, it is important to understand that the temperature change is not the only factor at play here. The decrease in pressure above the wing also causes a decrease in the air's saturation point, making it easier for water vapor to reach its dew point and condense. Additionally, the decrease in pressure also leads to a decrease in air density, which can affect the formation of contrails.

The compressibility factor of air does play a role in this process, as air is not an ideal gas and its properties can change under different conditions. However, the exact impact of this factor on the formation of contrails is still being studied.

As for the adiabatic process, it is possible that the rapid decrease in pressure above the wing can be considered adiabatic, but this is just one aspect of the complex phenomenon. There are other factors at play, such as the mixing of warm and cold air and the presence of particles in the air, that can also impact the formation of contrails.

Overall, the formation of contrails is a combination of various factors and is still not fully understood. Scientists continue to study this phenomenon to gain a better understanding of its mechanisms and effects. I hope this helps to clarify your confusion.