Drop Dynamics
The project is based on analyzing acceleration induced water removal from ear canals. I started working in this project from Jan, 2019 in Bio-Inspired Fluids Laboratory, Cornell University.
Baskota, A., Kim, S. Kang, H.& Jung, S. (2019) “Acceleration-induced water ejection in the human ear canal”. 72nd Annual Meeting of the APS Division of Fluid Dynamics , Seattle, Washington.
Principal Investigator: Prof. Sunghwan Jung
Members: Dr. Suengho Kim
Abstract:
Water entering the ear canal is a common problem during swimming, showering or other water sports. The trapped water can lead to an ear infection as well as damage to the ear canal. A common strategy for emptying water from the ear canal is to shake the head, where the force created due to the head jerk helps push the water out. One-end closed hydrophobic glass tubes of varying diameters were used as a simplified model of the ear canal. Then, the tube is dropped onto a spring to mimic the shaking strategy. Results revealed that the critical acceleration to remove the water from the ear canal strongly depends on the volume and the position of trapped liquid inside the tube. We found that the critical acceleration is on the order of 10 g, which may cause serious damage to the human brain. The critical acceleration tends to be much higher in smaller sized tubes which indicates that shaking heads for water removal can be more laborious to children due to their small size of the ear canal, compared to adults.
Acceleration causing the water to be ejected from the hydrophobic tube in different accelerations (5g, 9g, 14g).
Water ejection from 3D printed wax tubes in different accelerations.
The whole motion of the water inside these tubes in different accelerations are recorded using high quality slow motion cameras. Through these videos, vertical acceleration is obtained with the aid of tracker software.
Figures: Top left: TRACKER using point mass to track each pixel of the video. Top right: Velocity vs Time graph after tracing the pixel's displacement per unit time.
We developed a theoretical model to explain the behavior of the water ejection from the tube.
The findings of this research demonstrate that the critical acceleration required would range from 1g to up to 20g based on different conditions (diameter, liquid volume, air volume) demonstrates. Comparing these values with several scientific works which describe that linear acceleration during sports collision, indirect vehicle clash, and other incidents, there is an overlap. Therefore, it is not advisable to shake our head to remove the trapped water, especially for children as their ear canal diameter is smaller. Surface tension plays an important role to determine the critical acceleration according to our theoretical model. It is suggested that using safe liquids with lower surface tension (rubbing alcohol, vinegar) would help to reduce the surface tension force and thus makes it easier for the water to be ejected.
There are several articles published based on this research. Here are some links:
https://phys.org/news/2019-11-ears-brain-physicists.html
https://scitechdaily.com/warning-shaking-head-to-get-rid-of-water-in-ears-could-cause-brain-damage/
https://medium.com/luminate/common-way-to-remove-water-from-ears-could-cause-brain-damage-25ed60de3427
https://www.sciencealert.com/shaking-water-from-blocked-ears-might-cause-brain-damage-scientists-warnheads
https://www.dailymail.co.uk/health/article-7723589/Children-shaking-head-water-ear-damage-BRAIN.html