Photo Journal

    When I first attempted to take a picture of a splash on a rotating surface, I had intended to try and have it fall into a rotating liquid.  I soon found out, after trying several different cups and bowls, that it takes very little angular velocity to send milk flying wildly out in all directions.  I tried using a large, glass cylindrical bowl thinking that the steep sides would prevent the milk from traveling up and out onto me.  This worked relatively well except that the bowl was large and heavy and hard to center.  This prevented me from spinning it very quickly and I could not produce a splash that looked at all out of the ordinary.

Here is an entirely uninteresting splash from my first photo shoot.  It isn't even forming a crown.  How disappointing.  You can see in the background the milk collecting in the edge of the bowl.

    I thought maybe that I needed to place the splash at a larger radius and have it fall into milk instead on onto just a surface to produce interesting results.

    It proved difficult to move the rotator and have a wide enough band of spinning milk to drop into.  If i put enough milk in the bowl, it would be very unstable on the rotator.  If  I didn't put enough milk in the bowl, I would only be able to have the drop fall on the edge of the milk as in the above picture.  Interesting, but not what I intended to do.

    Out of frustration, thinking that splashes don't care whether the rotate or not, I decided to risk life, limb and bowl, and increase the rpms for short periods of time with little to no milk in the bowl to see if I could observe something interesting.

    Success!  You can see in the first picture, as slight asymmetry in the formation of the crown.  You can also see that the milk in the bowl was pinned up the side of the dish due to the speed of rotation.  You can also see the ring of tape and one of the pieces of duct tape used to secure the bowl to the rotator.  This proved to be a very secure mount that resulted in the whole rotator vibrating at high rpms.  The second picture is the one that let me know that more speed was the answer.  In this picture a clear crown can be seen on one side and a suppressed crown can be seen on the other.  

    I decided to change the focus of my setup from preventing mess, to achieving speed.  I decided to build a spray curtain that drained into a plastic tub to deal with the mess, and replace the the heavy glass bowl with a lightweight plastic one that was easily centered and secured with hot glue.

    With the lightweight bowl I could easily take the rotator up to (I'm modestly estimating) ten times the rotational velocity as I could with the glass bowl.  You can see the very thin line of milk spray across the plastic curtain in the back that resulted from the fast flying milk coming off the side of the bowl.  You can also see the photogate used to trigger the flash, the flash, and the bottle with stopcock that I used in my experiment.

    With this setup I was able to observe very interesting splashes.  After taking several good picture of splashes further out on the bowl, I decided to see how a splash on the middle of the bowl behaved.  Since nothing especially interesting happened there, and it wasn't part of my main goal, I decided to go back to what I was doing.

    I then decided to see what happened later in the progression of a rotating splash.  This picture and the second to last photo in the series in the gallery, show that as the rest of the splash pulls out from underneath the crown, everything goes slightly chaotic.  You can still see the edge of the crown with its peaking drops hanging in the air on the left side of the splash as the rest careens away on the bowl.

    This project presented its challenges and its rewards.  I had a great time fiddling and adjusting to get the right pictures and finally getting great pictures of rotating splashes.