Usage
  • 19 views
  • 8 downloads

Schlieren visualisation and measurement of axisymmetric disturbances.

  • Author(s) / Creator(s)
  • Abstract. Synthetic schlieren is a new technique that allowsone easily and inexpensively to visualise density variations, such as those caused by internal waves propagating in a density stratified fluid. In the special case of twodimensional internal waves (for example, those created by an oscillating cylinder), synthetic schlieren allows one to measure non-intrusively the wave amplitudes everywhere in space and time. The technique works by measuring the apparent displacement of points in a digitised image (such as a grid of horizontal lines), which is observed by a CCD camera through the experimental test section. Synthetic schlieren is sufficiently sensitive that it can measure sub-pixel-scale disturbances. In this work, we report on the first step toward measuring fully three-dimensional disturbances. We perform laboratory experiments in which internal waves are generated in a uniformly salt-stratified fluid by a vertically oscillating sphere. Theory predicts that the resulting wave-field is in the form of two cones emanating above and below the sphere. Using inverse tomographic techniques, we exploit the axisymmetry of the wave-field to relate the apparent displacement of pixels in an image to the wave amplitudes.

  • Date created
    2002
  • Subjects / Keywords
  • Type of Item
    Article (Published)
  • DOI
    https://doi.org/10.7939/R3SJ1B48P
  • License
    Attribution-ShareALike 4.0 International
  • Language
  • Citation for previous publication
    • Sutherland, B., Flynn, M., and Onu, K. (2002). Schlieren visualisation and measurement of axisymmetric disturbances.. Nonlin. Proc. Geophys., 10(3), 303-309.
  • Link to related item
    doi:10.5194/npg-10-303-2003