Usefulness of Inviscid Linear Unsteady Lifting-Line Theory for Viscous Large-Amplitude Problems

Abstract

Unsteady Lifting-Line Theory (ULLT) is a low order method capable of modeling interacting unsteady and finite wing effects at low computational cost. Most formulations of the method assume inviscid flow and small amplitudes. Whilst these assumptions might be suitable for small-amplitude aeroelastic problems at high Reynolds numbers, modern engineering applications increasingly involve lower Reynolds numbers, large amplitude kinematics and vortex structures that lead to aerodynamic non-linearities. This paper establishes that ULLT still provides a good solution for low Reynolds number, large-amplitude kinematics problems, by comparing ULLT results against those of experimentally validated computational fluid dynamics simulations at Re=10 000.

Applying Frequency-Domain Unsteady Lifting-Line Theory to Time-Domain Problems

“…The Re=10 000 cases were computed following the experimentally-validated RANS method used in Bird et al [45],…”

“…The meshes are the same as those used in Bird et al [45]. In this paper, two rectangular wings of chord length…”

“…To solve for the aerodynamics in research areas such as micro air vehicles, unmanned aerial vehicles [10] or energy harvesting devices [12], solutions for low-Reynolds number, high-amplitude kinematics problems are required. The linear, potential-flow based model used in the derivation of Sclavounos' ULLT obtains surprisingly good results for frequency-domain problems in this regime [45] given that the assumptions used in its derivation are broken. Here, time-domain cases are explored using the UCoFD method.…”

Applying frequency-domain unsteady lifting-line theory to time-domain problems

“…The Re=10 000 cases were computed following the experimentally-validated RANS method used in Bird et al [39],…”

“…The meshes are the same as those used in Bird et al [39]. In this paper, two rectangular wings of chord length…”