Aeroelastic Modeling Using a Geometrically Nonlinear P-Version Mixed Reissner-Mindlin Plate Element

Abstract

A geometrically nonlinear Mindlin plate element with p-refinement capability is developed for use in high fidelity aeroelastic simulations. The element is tested using linear benchmark tests and performs well. The ability of the element to predict large deflections is shown through comparison with a large strain, shell element. An aeroelastic code is developed by coupling this structural mechanics solver to a second order finite difference solution of the Euler equations. Particular attention is paid to developing the methodology for coupling the fluid and structural solvers. The aeroelastic behavior of a flexible 50 delta wing at high angle of attack is investigated with this aeroelastic solver. In one simulation, the angle of attack of the delta wing is increased from 0 to 25 degrees at a rate of 1 degree every non-dimensional time unit. In the second simulation, a fluid solution is computed at 25 after which the aeroelastic calculation is started. Previous experiments for this configuration showed increased structural dynamic response in the second asymmetric mode and an accompanying region of lift enhancement starting around an angle of attack of 25 degrees. While the two different aeroelastic computations demonstrated different aeroelastic behavior, perhaps indicating some sensitivity to initial conditions, neither predicted the increased dynamic behavior or lift enhancement which was reported for the experiment. The dominant response frequency of the wing in each case was near the first structural mode which has a frequency which is too low to initiate the flow reorganization. It has been shown in previous work that it is this flow reorganization which causes a vortex to reform which results in a region of suction and subsequent lift enhancement.