Twin wick candle smoke rising while backlit by a color projector. Image captures moments after the flame on the wicks had been temporarily smothered by a lid and the smoke that is produced from the wicks.

Image taken in a dark, open room, close up looking at the candle with the projector up and behind beaming down. Shot with an 18-55mm variable zoom lens at 1/100″, F/5.0, ISO 800.

Post-processing in darktable. Image is cropped horizontally and has increased contrast.

Team First Report: Spectrum Smoke

                Second project, group assisted with ideas for image but captured alone. The goal of the image was to capture laminar and turbulent flow patterns in candle smoke, and the interactions of twin wicks as opposed to a single wick candle. Originally, the goal was to use fog machine smoke, but the smoke was largely turbulent and was hard to control, so candle smoke was chosen instead.

                The image captured shows candle smoke backlit by a projector. The camera was placed 5.5 inches away, and slightly lower than the candle. The flow shows the laminar and turbulent flow of candle smoke as it rises in the air. The size of the plume is about a foot high, and a few centimeters thick. The smoke begins mostly as a straight line from wicks, and that is due to the heat from the recently smothered wicks expanding the air around it evenly. Then, as the smoke rises, it loses heat and begins to interact with cooler, still air. This creates a work interaction between the smoke particles and the air particles which can be seen by the turbulent flow higher up in the image. The Reynolds number of smoke can be calculated by . . So, the Reynolds number for this flow is 32,551, which means the flow is mostly turbulent.

                The visualization technique used was marked boundary using smoke, backlight, and a dark background. The candle had two wicks and was purchased at target. The lighting was from a project that gave a flat, constant lighting. The image on the projector was just the menu screen, but each section of the menu had a bright color, so when it contacted the smoke, it gave a solid color. The color you see in the image can seem separated, but that just outlines the depth of the smoke as it rose from the candle. The camera is placed slightly below the candle, but the focus is just above the candle vase. The camera was 55mm focal length and was placed 5.5 inches away from the candle. The candle was lit and then suffocated to allow the smoke to rise as closely as possible to vertically.

                The FOV of the image was about 12 inches L and W. The distance from the object to the lens was 5.5 inches. The lens’ focal length was 55mm. The camera used was a Canon Rebel T6 DSLR. The pixel specifications are 4064 x 3461 pixels. The image was taken at 1/100 shutter speed, F/5.0, and ISO 800. The only manipulations used were a slight increase in contrast and cropping sides to reduce total blackness of the image.

The image reveals how candle smoke begins as a laminar flow due to heat flowing upwards and the velocity of the smoke particles being slower, while higher up the smoke experiences turbulent flow from moving faster into more dense air particles. I like the colors the most of this image, as I haven’t seen anything like it. I also like that the focal point of the image is right at the center. I dislike the empty space on the sides. I took other images that I enjoyed more compositionally but they were out of focus and too grainy. But the intent to have multicolored smoke was achieved. My question is should I have cropped out the black sides to improve contrast. I would like to improve the material usage in the future and try to overcome the difficulties presented by the fog fluid. To do this, I would need to find a better flume or better air circulation to be able to take multiple images without filling the room with smoke.