The report presents the results of a potential flow study for air cushion devices in hovering. The emphasis is on the importance of pre-exit turning. In the analysis the flow issues from an infinite duct with parallel walls. The theory uses conformal transformations to relate the complex potential and the complex velocity. The resulting differential equation can then be integrated to give the flow velocity as a function of geometric coordinates. The applicability of the analysis is independent of ground clearance and hence provides a bridge between peripheral-jet and plenum theories. Results for the variation of base pressure, flow coefficient, discharge coefficient and the two components of jet reaction with ground clearance are presented for several duct angles. The effect of extending the outer lip is shown. The exit velocity profile and a streamline plot are presented for a vertical jet at a height-to-thickness ratio of 2. Comparison with other potential flow results indicates that the internal flow phenomena of pre-exit turning may alter base pressures and discharge coefficients by as much as 10%. Comparison with experimental data indicates that the pressure drop due to pre-exit turning can be as large as that due to viscous effects. ( Author )

  • Corporate Authors:

    Rensselaer Polytechnic Institute

    110 Eighth Street
    Troy, NY  United States  12180
  • Authors:
    • Cooke IV, George C
  • Publication Date: 1968-11

Media Info

  • Pagination: 37 p.

Subject/Index Terms

Filing Info

  • Accession Number: 00001626
  • Record Type: Publication
  • Source Agency: National Technical Information Service
  • Report/Paper Numbers: TR-AE-6811 PhD Thesis
  • Contract Numbers: C-117-66
  • Files: TRIS
  • Created Date: Oct 30 1972 12:00AM