Search Results

This paper describes a finite-difference method for unsteady transonic flow computation in frequency domain and transonic flutter prediction of complete aircraft configurations. The unsteady TSD equation as well as the boundary conditions are split into the in-phase and out-of-phase components in frequency domain by a nonlinear harmonic averaging technique. The resulting equations are solved by a steady flow algorithm. The unsteady pressure distributions for a rectangular wing and the ONERA M6 wing are analyzed and compared with other results to verify the code. The flutter characteristics for the AGARD I-445.6 wing, a cropped delta wing and a fighter configuration are computed and the results are discussed.

A quick, computationally inexpensive technique has been developed for the analysis of a full aircraft configuration with iced surfaces. Viscous effects for the flow field about an airfoil with an iced leading edge are accounted for in a thin-layer Navier-Stokes code (ARC2D). A panel code (PMARC) solves the flow field away from the body. The results of the airfoil analysis represent the near-field solutions and are used to modify the boundary conditions in the three-dimensional calculations with the panel code by matching the local circulation. This process is repeated until the total lift coefficient between successive iterations differs by less than a specified value. Examples showing good comparison between the 3-D calculations and experimental data are provided.

Aerodynamic effects induced from vectoring an exhaust jet are investigated using a well established thin-layer Reynolds averaged Navier-Stokes code. This multiple block code has been modified to allow for the specification of jet properties at a block face. The applicability of the resulting code for thrust vectoring applications is verified by comparing numerically and experimentally determined pressure coefficient distributions for a jet-wing afterbody configuration with a thrust-vectoring 2-D nozzle. Induced effects on the body and nearby wing from thrust vectoring are graphically illustrated.