Flow Pattern on a Hydrofoil
Despite their size, humpback whales are quite agile. Studying humpback agility experimentally offers benefits for many potential applications in biomimetically-engineered systems.
The protuberances in the image below resemble the tubercles found on the flippers of humpback whales. The image shows the flow pattern on a hydrofoil with leading edge protuberances; flow is from top to bottom. The observed patterns indicate that flow on the hydrofoil with the protuberances develops quite differently from the flow on traditional hydrofoils.
These experiments were carried out in a water tunnel. Dye was released from ports on the leading edge of the hydrofoil. The dye streams originating from the peaks and troughs remain coherent (the straight lines) and flow downstream until they breakup.
On the other hand, the dye streaming from the ‘shoulders’ of the protuberances rolls up into spirals which mark vortexes in the flow direction. As the hydrofoil pitches up, the strength of these vortexes increases.
Image credit: Hamid Johari. Dr. Johari is an APS Member as well as a member of the APS Division of Fluid Dynamics.This research was performed in collaboration with Dr. Charles Henoch and Derrick Custodio, and sponsored by the United States Office of Naval Research.
