V/STOL Fountain Force Coefficient.
MCDONNELL AIRCRAFT CO ST LOUIS MO
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The McDonnell Aircraft Company MCAIR VSTOL force and moment methodology was applied to a two-jet, a three-jet and four-jet VSTOL aircraft in hover in ground effect to determine the fraction Lambda of the impinging fountain momentum flux transferred to the airframe as a fountain impingement force. The use of potential flow panel methods was verified for the calculation of suckdown forces on VSTOL aircraft in hover, provided the jet entrainment effects are accurately modeled. In addition, an empirical two-jet fountain upwash momentum flux distribution was established for use in predicting the magnitude of the impinging fountain momentum flux. Using the MCAIR methodology, the suckdown force and the total momentum flux incident upon the aircraft were calculated, and the results were compared with experimentally measured induced lift to determine lambda for each aircraft at several heights above ground. The mass entrainment rates associated with an axisymmetric free jet were quantified in an experimental program based upon a new, indirect technique of entrainment measurement. In this new technique, the induced radial velocity field surrounding the free jet was measured using a hot film anemometer. Inverse potential flow theory was then applied to convert the measured radial velocities to free jet mass entrainment rates.
- Numerical Mathematics
- Fluid Mechanics