Evaluation of potential flow models for unsteady separated flow with respect to experimental data

The wake characteristics and force production of an aspect-ratio-8 flat plate rectangular wing starting from rest at a high angle of attack (alpha = 45 degrees) were examined. The first portion of this paper presents experimental measurements that focus on circulation production at the leading edge of the wing. Circulation production is shown to be coupled to both the wing kinematics and the wake state. The second portion of the paper reviews the implementation of several pertinent potential flow models from the literature and compares the results of these models to the experimental results. Quasisteady and fixed-wake models were found to be poor predictors of both force and circulation. A similarity-solution-based model was found to make accurate predictions only at very short times. An unsteady strength two-vortex model predicted the circulation production during the acceleration portion of the kinematics, but did not predict the force. A multiple-discrete-vortex model was found to predict both the force and circulation production well, but had difficulty after the shedding of the first leading-edge vortex.