DID YOU KNOW? DTIC has over 3.5 million final reports on DoD funded research, development, test, and evaluation activities available to our registered users. Click HERE
to register or log in.
Asymmetric Entrainment of 2-D Curved Jets.
WEST VIRGINIA UNIV MORGANTOWN DEPT OF AEROSPACE ENGINEERING
Pagination or Media Count:
The control of VTOL aircraft during transition from hover to forward flight is complicated by the lifting jet-airframe interaction. This analysis is concerned with the entrainment aspect of two dimensional thick curved jets. A realistic mathematical model of such jets should account for different entrainment rates and the total pressure decay in the jet. The present theoretical analysis predicts curved jet characteristics needed for an accurate mathematical modelling of two dimensional lifting jets. The present analysis performs an integral method analysis of the curved jet using incompressible, fully turbulent, curved, free jet equations. Integral methods need specified jet edge velocity distributions. This streamwise velocity distribution depends on the airfoil geometry as well as on the jet. The present theory approximately retains this ellipticity by obtaining the streamwise jet edge velocities from a nonlinear iterative potential flow analysis of a thin jet issuing from the trailing edge of a hinged flat plate. The results of the present analysis are in agreement with available straight and curved jet results. The present theory predicts significantly 10-20 different entrainment rates near the exit where the curvature is maximum. Since VSTOL lift, moment, and pressure drag are significantly affected by the jet entrainment, one should incorporate the asymmetry of entrainment rates of curved thick jets in prediction methods. Author
APPROVED FOR PUBLIC RELEASE