2-D Flow Numerical Solution for Airfoil and Hovercraft in Ground Effect
Abstract
A proposal has been made to compute a 2-D numerical solution to the stream function - vorticity equation to analyze the flow field, both of an airfoil in ground effect and of an air cushion vehicle of arbitrary geometry supported by peripheral jets. This report is an investigation of both problems. Finite difference solutions of the stream function-vorticity equation are computed on a body fitted coordinate system. The Laplace equation for streamlines around an airfoil in ground effect is solved, and results are compared to an analytic finite singularity solution. Comparison of Cl and Cma.c at varying angles of attack and ground distance indicate good agreement. The finite difference method is found to be sensitive to grid point distribution about the leading edge, for which a criterion is established. Since an air cushion vehicle acts as a flow source within the field, the finite difference expression is modified to accommodate a branch cut. The presence of vorticity is essential to definition of the peripheral jets. The vorticity distribution, derived from arbitrary velocity distribution at jet outlets and assumed to be constant along streamlines, leads to a stable solution of the stream function- vorticity equation.
Document Details
- Document Type
- Technical Report
- Publication Date
- Dec 01, 1978
- Accession Number
- ADA081902
Entities
People
- Itzhak Dvir
Organizations
- Air Force Institute of Technology