Inverse Design of Nacelles Using Multi-block Navier Stokes Codes

The objective of this work is to reshape a nacelle to achieve a specified nacelle pressure distribution. The nacelle may be either isolated or installed on an airplane. There are no restrictions on the attitude (toe, incidence, and roll) and position of the nacelle. The design algorithm is coupled to two different multi-block 3-D Navier Stokes flow solvers. The coupling between design and analysis is automated to the point where the design proceeds with minimal user input. Nomenclature C Local nacelle or wing chord. CDISC Constrained DISC. Cp Coefficient of pressure. DISC Direct Iteration Surface Curvature. O(..) Order of magnitude. R Local nacelle radius. X Streamwise coordinate. theta Angle running from the nacelle crown through the keel (outboard side) and back up to the crown (inboard side). Introduction Given the harsh reality of placing capital intensive products in the modern marketplace, it is an ongoing quest to improve the operational efficiency and cost effectiveness of any commercial airplane. The emergence of the current generation of large turbofans, in the 80,000 to 100,000 pound thrust class, presents anew the opportunity to optimize or reduce the drag associated with the outer surface of the engine nacelle. These large nacelles could account for a good portion of airplane drag. The problem of external cowl design may be broadly placed in two separate, yet complementary categories: (1) the design of an isolated cowl immersed in a uniform flow; and, (2) the design of an installed cowl with the attendant non-uniform flow. The former should enable the designer to derive a cowl geometry starting from a fairly rudimentary first guess. The resulting design will be inherently symmetrical about the vertical plane, thus allowing for a universal nacelle that can be installed on either side of the airplane. On the other hand, the inverse design of an installed nacelle will always result in a nacelle that is non-symmetric about the vertical plane, unless the designer can invoke special options to force symmetry. https://ntrs.nasa.gov/search.jsp?R=20040111291 2017-09-13T22:28:41+00:00Z