FYFD

Tag: suction

  • Amphibious Adaptation

    Amphibious Adaptation

    Every year newts move to the water in the springtime to mate before returning to land for the rest of the year. This annual aquatic relocation is accompanied by changes in the newt’s body. Flaps of skin grow from their upper jaw to their lower jaw, partially closing their mouths at the corners. This can be seen in the left column of the animation compared to the center and right.

    Numerical simulation shows that this mouth change has a significant impact on the newt’s ability to hunt underwater. Newts are suction feeders, who open their jaws and expand their mouth cavity to suck in water and their prey. By closing off the corners of their mouths during their aquatic phase, the newts generate more suction, reaching peak flow velocities 10% to 50% higher than in their terrestrial form and enabling them to pull prey from 15% further away. When they leave the water, the newts lose the extra flaps so that their mouths can open wider for catching prey on land. (Image credit: S. Van Wassenbergh and E. Heiss, source)

  • Stalling

    [original media no longer available]

    At high angles of attack, the flow around the leading edge of an airfoil can separate from the airfoil, leading to a drastic loss of lift also known as stall. Separation of the flow from the surface occurs because the pressure is increasing past the initial curve of the leading edge and positive pressure gradients reduce fluid velocity; such a pressure gradient is referred to as adverse. One way to prevent this separation from occurring at high angle of attack is to apply suction at the leading edge. The suction creates an artificial negative (or favorable) pressure gradient to counteract the adverse pressure gradient and allows flow to remain attached around the shoulder of the airfoil. Suction is sometimes also used to control the transition of a boundary layer from laminar to turbulent flow.