Editor's Note: what follows is a somewhat long stream of consciousness I wrote after an 8 AM flight. It may or may not be any good
This morning I had a fantastic opportunity: it was snowing in Wichita, which meant the airplane needed spraying down with de-ice fluid before departure. As I watched the wing become coated in a green liquid, no anger at the delay came to mind as I know it did with my fellow passengers; instead, I glued my face to the window and quietly whispered 'this is going to be cool'
It's real life flow visualization! An opportunity to observe what happens on the surface of a 737 wing at take-off! This was going to be a rare treat, and I wouldn't dare to look away.
I knew what would happen, of course. I have a degree in aerospace engineering. I've studied aerodynamics, I've applied those studies to designing aircraft. I have a strong working knowledge of exactly how air acts on a wing like this, but I've never seen it. Air is invisible after all, and besides the occasional pattern in the dirt on the surface I can never actually see it. But today it would be very visible.
As the airplane began to roll I found myself surprised even though I knew what would happen. I didn't think about the fact that we'd be going too slowly for the flow to attach, but sure enough the fluid moved backwards! Flow reversal! After a few seconds we were moving quickly enough for flow to stay attached and the liquid began to move streamwise. Of course this being a swept wing the boundary layer is supposed to push along the sweep....and there! There it goes! The fluid started moving outboard!
But there are vortex generators on the 737 wing. These are placed to prevent that boundary layer movement. The vortices provide high energy barriers to stop the boundary layer...and there it goes! A streak of naked skin begins to appear behind each vortex generator, moving directly streamwise, stopping the outboard flow of the liquid. But then I notice something I didn't expect, but immediately realized I should have: the fluid between vortex generators began to push outboard near the trailing edge, widening the clear path behind the vg's to form a nearly parabolic curve.
Eventually all the fluid had washed off except for a few spots that the air didn't quite reach: a gap between the flap track fairing and the wing, a small gap between the inboard and outboard flap. While the fluid may have washed away, my smile couldn't be any bigger. I knew what would happen, but watching it unfold before my eyes and show that the theory isn't simply theory but true understanding was nothing short of amazing.
What this moment was, more than anything, was a much needed reminder of why I became an aerospace engineer. Over 3 years of staring at a computer screen modeling airplane parts in 3D had jaded me: I had started to lose sight of the real reason I became an engineer. I had decided years ago that airplanes were fascinating enough to study, but in recent years that fascination had waned and airplanes had instead come to be a job, purely a means to earn a comfortable living.
This morning I realized that the passion that pushed me to become an engineer hasn't gone away. Airplanes are still incredible machines, and understanding how they work is still my single greatest passion in life. A 10 minute delay instead became a reaffirming of myself, and I hope that it became an inspiration to others instead of a mere inconvenience