Friday, April 27, 2012

Friction Ahead

I've been reviewing thin airfoil theory in Aerodynamics this week.

There are two forces that act on an airfoil (think: wing) - Lift and Drag.

Lift is created from the pressure acting normal (perpendicular) to the surface of the airfoil.

Drag is created from the shear stress over the surface of the airfoil (acts tangential or parallel to surface of airfoil)

If we were to assume a world of inviscid (frictionless) flow, drag would not exist.  (Makes sense, right?  Drag is pretty much just a measure of the friction on the airfoil anyway).

And since, lift acts perpendicular to the direction that friction acts, it is independent of the friction that exists.

Wouldn't that be nice to live in world free of friction?  We'd have all the lift we wanted to soar and fly without worrying about being held down or dragged back in our progress.

But here's the clincher: If we lived in a world of perfectly inviscid flow, we would never experience lift.

Turns out that nature requires friction in order to create the environment for lift to exist.  (It gets technical here so I will spare you the details - but it involves the Kutta condition)

Likewise in our own lives: Those stresses that threaten to halt our progress and pull us back can actually be the stresses that create the environment that allows us to lift us above our present circumstances and to soar.

2 Nephi 2:11: "For it must needs be, that there is an opposition in all things.  If not so...righteousness could not be brought to pass, neither wickedness, neither holiness nor misery, neither good nor bad..."

I Can Soar by JYJ's (TVXQ's) Junsu:

Click on the CC and then on English subtitles if you have trouble understanding his English.

"A man can never know how strong he really is until he is beaten, torn, shattered...until he is broken, beyond despair, on his knees in pain...and without even knowing how or why...stands back up."
~ Thomas F. Lerchenfelt, Jr.

For my dear friends who are struggling with great forces against them,

Please remain strong.  You will rise above this.  You will.  And you will become all the better for it.  In the meantime, lean on your friends and your God and we can make it through this together.


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