Ivan Komodore

Ivan Komodore

Introduction

Get wet is intended to “get our feet wet” in flow visualization where we begin to familiarize ourselves with photography techniques and equipment as well as to begin experimentation with the different flows we experience in every day life. I have ridden bicycles through just about every kind of weather and riding in wet weather has taught me that it is almost impossible to stay dry while riding a bike in the rain. I found that water would cling to the rear tire and spray along my back. I wanted to capture this effect in as controlled of an environment as possible for my Get Wet project so that I could see what is actually going on betwen the water and the tire.

Set Up

All of my attempts were run outside on a sunny day which made lighting simple and allowed me to use fast shutter speeds. A bike was hung on a bike stand with the rear tire approximately 10″ above the concrete ground. A black backdrop was hung in the background as well to reduce distractions and to amplify the effect of the water. The rear wheel was pedaled to approximately 60 RPM and left to freewheel. While the wheel was spinning, a baking dish full of water was lifted to the bottom of the spinning wheel so that the tire made contact with the surface of the water. This caused water to spray backwards for 2-3 seconds as the wheel slowed due to the loss of kinetic energy to the water. Initially, a mountain bike was used with some success but the knobby tires caused the water to splash chaotically and it was difficult to capture any kind of interesting flow. The final shot was captured using a road bike, the smooth tire profile created a more interesting flow that will be discussed later in this report.

Photograph Details

The final image was captured using a Sony A6300 camera with a 16-50mm zoom lens. The best results were achieved using manual focus as auto focus would hunt during the shot and create unpredictable results. A fast burst shutter mode was used since the actual event took place so quickly. Burst mode allowed for the best possible image to be selected. The final shot was taken at an aperture of F3.5 with a shutter speed of 1/2000s and an ISO of 6400. The focal length was 16mm.

Image editing was done in Corel AfterShot to boost the contrast, darken the background and highlight the flow of the water. Additionally, the blues were accentuated to give the water a more aquatic look and to prevent the image from appearing in gray scale.

Flow Description

This image shows showcases some interesting fluid flow in several different stages. Initially, the water is accelerated rearward by the spinning tire and is held together by cohesion. The water begins to form a thin membrane (or sheet) as it separates from the tire and the fluid attractive force is not sufficient to continue carrying the water in a circular path. As the membrane continues to stretch, surface tension begins to take effect and the membrane breaks down into ligaments. Again, the ligaments stretch to continuously smaller diameters until surface tension comes back into play. Surface tension then breaks the ligaments up into individual drops or blobs that continue on their trajectories until they hit the ground or some other obstacle.

This kind of breakup is typically seen on flows with lower Reynolds numbers. What is happening in these flows is that the surface tension is bringing the free surface energy to a minimum. Surface tension creates instability within the sheets and membranes and amplifies the inconsistencies (called varicose perturbations) within the flow. This means that surface tension works to make the thin areas of the fluid even more thin and concentrates more mass in the thicker areas to create blobs. The thin areas of the sheets or ligaments see progressively greater local pressure which forces the fluid to the lower pressure (thicker) areas of the flow. Ultimately the thin sections become so thin that the fluid pinches off and creates separate drops. This effect is called vericose breakup.

The size of the resulting droplets has been extensively studied and has been found to primarily be a function of the viscosity and velocity of the fluid. The more quickly the fluid is moving, the smaller the droplets will be but, if the fluid is moving too quickly, it will begin to break up via different mechanisms caused by friction with the air.

References

[1] Prediction of drop-size distributions based on ligament breakup (1997); Mark Olesen; Retrieved from: http://www.nlc-bnc.ca/obj/s4/f2/dsk3/ftp05/nq22488.pdf

[2] Similarity between the primary and secondary air-assisted liquid jet breakup mechanism (2006), Y.J. Wang, Kyoung-Su Im, K. Fezzaa; Retrieved from: https://arxiv.org/ftp/arxiv/papers/0706/0706.0030.pdf

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28 Comments. Leave new

  • Chad Sloan
    Sep 24, 2018 16:42

    This is a really cool picture. I think the color is the water and the logo on the tire really go well together. The flow that was capture is something that i did not expect to happen and really cool!

    Reply
  • Ibrahim Alhajj
    Sep 21, 2018 13:16

    Great idea. The picture looks very cool. Good work on the background and the lighting

    Reply
  • Duncan Lowery
    Sep 19, 2018 22:33

    This image is very striking! The focus is tack-sharp where it needs to be and the contrast is outstanding. Lots of detail in the thin sheet of water as it is thrown off the spinning tire. Nothing important is cropped out of the image, and maintains a pleasing composition. Did you consider coloring the water or using a different liquid? If this was shot inside, how did you keep the stray water contained? The depth of field also becomes noticeable only where the water fans out in droplets – I think it makes for a cool effect.

    Reply
  • Brandon Gushlaw
    Sep 17, 2018 12:45

    This is a wonderful piece. It draws a lot of attention to what we see every day with bikes going through puddles. It great because we tend to not see the full phenomenon. I will definitely pay more attention to bikers and puddles! Thanks for the beautiful photo! If you did this again could you do it with more mud like puddles!?

    Reply
  • Christopher McFadden
    Sep 17, 2018 12:43

    The setup you described is very interesting and innovative. I think it is framed beautifully and is in pretty good focus. You could take out the logo on the wheel in post if you wanted or sell the image to AXIS.

    Reply
  • Peilin Yang
    Sep 17, 2018 12:42

    I love the color of the water and tire. They share the similar color making the image pleasing.

    Reply
  • greg collins
    Sep 17, 2018 12:41

    The image is well done. with a good use of space. I particularly like the motion across the image. The us of the stop action did well to stop the streamers and droplets. Did you think of dying the water?

    Reply
  • Justin Truong
    Sep 17, 2018 12:41

    I really liked how this photo came out. The black background with the spinning tire and liquid gave a really crisp image. It’s cool to see the direction of motion of the fluid

    Reply
  • Joseph Ryan
    Sep 17, 2018 12:40

    This is a great picture. It’s one of those things that we see all the time, while driving, biking, really doing anything in the rain, but never have the ability to carefully examine, like we can in this picture. The black background is perfect, because it makes each droplet stand out, and the blue tint is also cool. The focus is good too. The details of the highest concentration of water are crisp and clear, and the slight blurriness of outer droplets doesn’t take away from the picture at all. It would have been a cool slow-mo video, but this is still a very cool picture.

    Reply
  • Owen Brown
    Sep 17, 2018 12:40

    I really like how bright the water is in the images. The contrast puts the focus on the motion and it is interesting to see how the webs or holes form. The breakup of the flow is also very interesting.

    Reply
  • Noah Granigan
    Sep 17, 2018 12:40

    This is really cool, incorporating the wheel into the picture was done very well. The sheet of water is interesting, and the contrast is well done. The motion blur on the wheel does give a good reference for the speed of the tire.

    Reply
  • Wenjin Li
    Sep 17, 2018 12:39

    This image looks awesome. The motion of liquid is great and captured pretty good. The color, little bit blue is great as well! I like the lighting and the structure of the image. Great job.

    Reply
  • Chase Cleveland
    Sep 17, 2018 12:39

    I love the action in this photo. Such a great implementation of a cool idea. The water droplets seem fully in focus and the composition of the photo is very intriguing. Overall great job capturing the fluid flow phenomenon.

    Reply
  • Wow! I really love this image. The composition is really nice with the wheel on the right and the water spray filling the whole rest of the image. If you could get all of the spray in focus, that would be awesome, but I don’t think having some of the drops out of focus detracts from the image – you still get a good understanding of how the motion is happening.

    Reply
  • Ross Cooper
    Sep 17, 2018 12:39

    The idea, framing, and color scheme are all gorgeous in this photo. I really like how it was cropped, the wheel location, as well as how much water was in the picture. Well done.

    Reply
  • Garrett Gerchar
    Sep 17, 2018 12:39

    Love that you can see the spray and crisp rounded edge of the spray that looks like it is flying at you. Did you try cropping out the wheel in post? Any thoughts on a brighter background?

    Reply
  • Anna Lynton
    Sep 17, 2018 12:38

    Super cool. I like the dark back ground and how it is framed or cropped. Maybe you could play with the colors to see what would come out of it, but definitely not necessary as it is a very nice image as is.

    Reply
  • The shutter speed being quite quick and high focus makes a great image. It was a good job showing the lighting and dark background. I love how well it shows the gaps in the sheet flow and you can really see some interesting fluid flow properties!

    Reply
  • Chris Davidoff
    Sep 17, 2018 12:38

    This is probably my favorite image. It’s really really cool and interesting to see. It would be even cooler to have many different photos of different tire treads to see how the water gets dispersed . The black background is great and the framing is as well.
    My only critique is maybe a faster shutter speed (more light would be needed presumably)

    Reply
  • Winston Douglas
    Sep 17, 2018 12:38

    great picture, I like how you caught an image where the spokes are completely frozen . I think if the depth of field was larger then you can get all the droplets.

    Reply
  • Michael Karns
    Sep 17, 2018 12:38

    The image is very cean and sharp all around. The way you captured the water is very crisp. The pan might get in the way, but could be ineteresting to see where the water first contacts the tire.

    Reply
  • Brent T Eckles
    Sep 17, 2018 12:38

    Very detailed picture, can see the water droplets nicely. Like the background being all black. The water seems to have a nice white blue color.

    Reply
  • Jeremy Aparicio
    Sep 17, 2018 12:38

    Great idea for a photo. The focus on the bottom right under the tire is very nice. The water almost looks like it has multi-colored specks due to it being a thin film which makes for a unique effect.

    Reply
  • Charles Keely
    Sep 17, 2018 12:38

    The idea of this shot was really unique! There is a nice contrast in the image and the image is pretty clear. The curved flow is very pleasing to look at.

    Reply
  • Eli Kopp-DeVol
    Sep 17, 2018 12:38

    I pretty much love everything about this picture. The subject is framed great and in really clear focus. I also like being able to see the motion blur on the tire and the contrast between the tire and the water is neat.

    Reply
  • Maxwell Rodgers
    Sep 17, 2018 12:38

    This picture turned out fantastic. It shows a great example of the water adhering to the bike tire as well as cohering to itself. I really like the effect of the water coming off as a sheet from the tire rather than as a bunch of individual flows.

    Reply
  • Matthew Finney
    Sep 17, 2018 12:38

    This is a great image! The black background brings great contrast to the flow. The flow is very detailed and the focus on the flow is perfect.

    Reply
  • Dylan Crane
    Sep 16, 2018 13:00

    I thought about doing this as well so I’m glad you did it! It looks super cool and the fact that you got a solid black background helped it so much! Good lighting, good focus, good cropping. Only thing I see is that the wheel looks a little blurred so you could either slow it down or increase the shutter speed.

    Reply

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