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LJWorld.com weblogs Dangerous Ideas

Posted by Paul Decelles November 2, 2009 at 11:35 a.m.

So much happens to a drop of water...

Even the simplest most every day happenings reveal surprises when seen at a different scale or a different speed. Enjoy this video of falling water drops coalescing with the surface of water. There are at least two effects going on here as the video explains.

Tip of the antennae to Sarah S for the find.

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  1. Irish (Leslie Swearingen) says…

    This is extremely cool. Thanks for sharing it. I love the way the water drop popped back up, smaller and smaller.
    With better computer software who knows what we will find.
    I am looking forward to it.
    Thanks to Sarah S.

  2. devobrun (anonymous) says…

    Irish.......what does computer software have to do with this?
    Detailed mathematical descriptions have been around since the 1940s.
    High speed photography was first implemented by Doc Edgerton at MIT, also in the 1940's.
    Good film Paul. Fluid dynamics often yields surprising results. Like superheated water which boils all at once. Put those boiling chips in the pot folks.

  3. Irish (Leslie Swearingen) says…

    I know, but computer software is now necessary to science. The Hubble Telescope has computer chips so that it can be manipulated from the ground. It allows us to know what is incredibly far away and also reveals that life is like a nest of Russian dolls.

  4. devobrun (anonymous) says…

    OK, Irish....wow.

  5. justbegintowrite (Ronda Miller) says…

    This made me exceedingly thirsty. I wonder what those drops of water are bouncing off of inside of me right now (maybe that brownie)...how many bounces do you get from one swallow?

    Thanks, Paul. Intriguing per usual

  6. devobrun (anonymous) says…

    For those of you who like high speed motion pictures try this place: http://web.mit.edu/edgerton/

    Doc Edgerton is one of my heroes. Google him and see some of his photos. Paul, look for the hummingbird tape. Nature is incredible.

  7. Irish (Leslie Swearingen) says…

    Thanks for the heads up about Doc Edgerton. He is one of my heroes also.

  8. Irish (Leslie Swearingen) says…

    Wow!

  9. liggyon (David Lignell) says…

    Great video, Paul! Just when I thought I understood how the world worked, you show me another wonder. I'll not look at rain the same way again. (Now if I could only walk on water.)

  10. pdecell (Paul Decelles) says…

    Devo,

    The hummingbird video is great. Here is the link: http://www.youtube.com/watch?v=N6lbxo...

    I love how acrobatic these birds are.

    Irish, great image- the nested dolls.

  11. devobrun (anonymous) says…

    As I view the hummingbird's motion, I notice that the center of gravity (cog) is nominally at the wing pivot point. However, the bird shifts the center of gravity by tucking its tail (and butt) in or out and fanning or tilting its tail. To a lesser degree*, the head is used to move the cog as well. The combination of cog shift and dynamic airflow over the tail wing yield an ability to stay stationary, but role around.

    Another way of saying this is the aircraft's attitude is controlled by its aft section through static and dynamic stability control and to a lesser extent, the forward section shifting the cog as well.
    -----------------------------
    Edgerton was an engineer. My guess is that he collaborated with hummingbird experts and aircraft engineers to model the flight of the bird.

    When my kids were in their pre-teens, We did a lot of aircraft-based play. Everything from "White Wings" serious paper airplanes to powered flight. One of the toys that we had was a windup bird that fluttered its wings and "flew". I recall the wing motion was similar to the hummingbird's wing motion. It worked. It was fun.

    We could spread the tail and cause more tail lift to change the pitch.
    We could tilt the tail and cause a change in yaw.
    We could not change the roll. This must be a function of head roll or main wing asymmetry. Hard to see on Edgerton's film. God love him

    This was about 12 years ago and the toy was probably designed on a computer, based upon the info gleaned from the hummingbird video and modeled in a simulator. A mechanical engineer was called in to contrive a mechanical model, and "tweaking" ensued.

    The thing was fragile, but it flew a long way. My guess is that hummingbirds are far less fragile. Optimized by evolution? Dunno.

    *My estimation of "lesser" is subjective. It could be that the bird's head is massive and much more important that my evaluation.

    Quick: what is the relative mass of a hummingbird's butt and head?

    Sounds like a Monty Python skit. God love them too.

Reply 11 comments from Devobrun Paul Decelles David Lignell Leslie Swearingen Ronda Miller

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