Numerical simulation of steady and unsteady, vorticity-dominated aerodynamic interference

Abstract

The problem of modeling steady and unsteady aerodynamic interference is discussed. A configuration resembling the X-29 is used as an example. The general unsteady vortex-lattice method is used to model the flowfield. By considering the components operating alone and as members of the complete configuration, we demonstrate the importance of accurately simulating the wakes of the upstream components. The wakes of the canards as well as the canards themselves have a strong negative influence on the lift generated by the main wing; the main wing has a positive influence on the lift generated by the canards. The forward sweep of the main wing tends to focus the generated upwash in the vicinity of the canards. It is shown that the maximum influence of the vorticity shed from the canards does not develop until the shed vorticity convects downstream directly over the main wing. The general unsteady vortex-lattice method appears to be a reasonably accurate model of closely coupled, vorticity-dominated flowfields as long as the lines of the separation are known and vortex bursting does not occur near the wings.

Numerical aspects of nonlinear flexible aircraft flight dynamics modeling

“…The solution procedure leads to the creation of a shed wake, which may be allowed to evolve as a free-wake according to Helmholtz's laws of vortex motion. Hence, the UVLM is also suitable for, at least, the preliminary analysis of aerodynamic interference problems, 14 and has been used to study wake-tail interference effects on the dynamics of HALE aircraft.…”

Stability and Open-Loop Dynamics of Very Flexible Aircraft Including Free-Wake Effects

“…(28) and (31) are integrated with the unsteady aerodynamics, Eqs. (2)(3)(4)(5)(6)(7)(8). Other external forces, in particular, gravity forces, can also be introduced into the equations of motion.…”

“…The expressions for the aerodynamic loads, Eqs. (7)(8) are the output equations. Note that the derivative of the bound circulation,Γ b , appears in the evaluation of the unsteady lift and induced drag, and therefore it was included in the state vector.…”

“…An alternative procedure would have been to substitute directlyΓ n b in Eqs. (7)(8), obtained from the non-penetration boundary condition, Eq. (2), together with Eqs.…”

“…(7)(8) to forces and moments acting upon the beam nodes -any estimation of the viscous drag will be included in the inputs to the system. For that purpose, it is assumed that they can be approximated by isolated aerodynamic loads applied in the center of the leading segment of each vortex-ring.…”