FYFD

Tag: delta wing

  • Trails from a Delta Wing

    Trails from a Delta Wing

    Top-down view of green and red dyes streaming off a delta wing

    Rhodamine (red) and fluorescein (green) dyes highlight the complex flows around a delta wing. To visualize the flow, researchers painted the apex of the delta wing with rhodamine, which gets drawn into the core of the wing’s leading edge vortex. The green fluorescein dye was added to the wing’s trailing edge, where it gets pulled into the secondary structure of the vortices. A laser illuminates the flow, making even the most delicate wisps of dye shine. As the wake behind the wing develops, the dyes reveal growing instabilities along the vortices. Given time and space, these instabilities will grow large enough to destroy any order in the wake, leaving behind turbulence. (Image and research credit: S. Morris and C. Williamson; see also poster)

  • Flow Around a Delta Wing

    Flow Around a Delta Wing

    Colorful streaks of dye wrap like ribbons along the leading edge of a delta wing. At an angle of attack, this triangular wing forms a set of vortices that run along its edge, providing much of the low pressure–and therefore lift–on the upper surface of the wing. In contrast, the red streaks of dye in the middle of the wing demonstrate clean, laminar flow. Highly swept delta wings are popular for aircraft traveling at supersonic speeds, but they can also work well subsonically, as shown here. For more incredible and beautiful examples of flow visualizations by Henri Werlé, check out his 1974 film Courants et couleurs. (Photo credit: H. Werlé; via eFluids)

  • Flow Over a Delta Wing

    Flow Over a Delta Wing

    Fluorescent dye illuminated by laser light shows the formation and structure of vortices on a delta wing. A vortex rolls up along each leading edge, helping to generate lift on the triangular wing. As the vortices leave the wing, their structure becomes even more complicated, full of lacy wisps of vorticity that interact. Note how, by the right side of the photo, the vortices are beginning to draw closer together. This is an early part of the large-wavelength Crow instability. Much further downstream, the two vortices will reconnect and break down into a series of large rings. (Photo credit: G. Miller and C. Williamson)

  • Lift on a Paper Plane

    Lift on a Paper Plane

    In this still image from a student experiment, smoke visualization shows the formation of a vortex over the wing of a paper airplane during a wind tunnel test. This wing vortex is mirrored on the opposite wing, though there is no smoke to show it. At high angle of attack, the delta-wing shape of the traditional paper air plane creates these vortices on the upper surface, which helps generate the lift necessary to keep the plane aloft. (Photo credit: A. Lindholdt, R. Frausing, C. Rechter, and S. Rytman)

  • Vortex Cross-Sections

    Vortex Cross-Sections

    The photos above show cross-sections through the leading edge vortices on a highly swept delta wing at angle of attack.  Flow in the photos is from the upper left to lower right. Notice how the vortices grow and develop waviness as they move downstream. When perturbations enter the vortex–for example, due to the shear between the vortex fluid and the freestream–some will grow and eventually cause a break down to turbulence, as in the lower picture. (Photo credits: R. Nelson and A. Pelletier)

  • Flow Around a Delta Wing

    Flow Around a Delta Wing

    Smoke visualization in a wind tunnel shows the vortices wrapping around and trailing behind a delta wing. As with more commonly seen rectangular or swept wings, the vortices that form around delta wings affect lift, drag, and control of an aircraft. They can also be hazardous to aircraft nearby. Note that, although delta wings are often seen on supersonic aircraft, this visualization only applies at subsonic speeds. The flow field changes drastically above the speed of sound.