Transonic Corrections for the Unsteady Compressible Source and Doublet Panel Method

The steady and unsteady aerodynamic predictions of the Doublet Lattice Method (DLM) are routinely corrected for camber, twist, and transonic effects using steady reference data obtained from experiments or higher-fidelity calculations. In this work, a novel correction technique is presented for the unsteady compressible Source and Doublet Panel Method (SDPM) in order to correct for transonic effects. Although the SDPM is more computationally expensive than the DLM, it can predict complete steady and oscillatory pressure distributions around the entire surface of the exact geometry of a wing or body. Consequently, it does not require corrections for geometric properties such as camber and twist, only for transonic flow phenomena. The corrected predictions are compared to unsteady pressure distributions measured experimentally for two experimental test cases from the literature. It is shown that that the predictions of the SDPM correction method are accurate as long as the reference pressure data are of adequate quality. Finally, the SDPM with transonic correction is applied to the prediction of the flutter boundary of the AGARD 445.6 wing, and it is demonstrated that the proposed approach is capable of predicting the transonic dip.