How Does a Hot Molecule Move in a Convection Current?

[ehabmozart]

Dear all,

I have a hard time in understanding the fundamentals of convection. Let's say we blow a fan over a hot surface. From fluid mechanics, I know that there is a velocity boundary layer due to the viscosity and no slip condition. The velocity gradient is kinda parabolic. Ok, let's now follow ONE particular hot molecule. This hot molecule is conducted at the surface-fluid interface. Then my question here is does it move to the right or does it move in a parabolic motion. I guess the problem stems in my understanding of boundary layer. I mean what happens next. Moreover, is it suppose there is a convection current always. If yes, how is it possible in this case. Thanks a lot to whoever contributes.

 

[Chestermiller]

You are aware that the molecules are flying in all different directions, and, that when you talk about convection, you are talking about motion relative to the average? You are also aware that, when molecules experience collisions, there is energy transfer and changes in velocity between them, correct?

Chet