Underwater Bubbles & Hydrofoils: A Closer Look

Ever wondered how bubbles behave near underwater foils? Researchers have been studying this with advanced experiments and theories. They found that the shape and size of hydrofoils, which are used to create lift underwater, can greatly affect how bubbles change their shape and collapse. These tiny bubbles were observed between two glass plates, mimicking a confined space. Researchers used high-speed cameras to capture how the bubbles evolve near different hydrofoils. They also calculated how the bubbles' speed and shape change using a liquid velocity field and something called the Kelvin impulse.One interesting finding was that there are five main ways bubbles change shape just before they collapse. These shapes depend a lot on how thick or curved the hydrofoils are. Thicker hydrofoils made bubbles move faster and appear more rounded in cross-section. Meanwhile, more curved (cambered) hydrofoils slowed down the bubbles and made their cross-section less rounded. Another cool finding was that the fast-moving regions at the edges of bubbles can explain why bubbles sometimes dip inwards near the hydrofoil.