CFD-Based Method for Validation of DATCOMand Potential Flow Stability and Control Derivatives

Abstract

DATCOM wasuse traditionally as the method to determine the aircraft downwash, and longitudinal stability and control derivatives for small unmanned air vehicles conceptual designat the Polytechnic University of Puerto Rico. Computational fluid dynamic can be usedto validate the DATCOM and the new downwash gradient method of Dr. Mondhlerfor low aspect ratios and low Reynolds number unnamedair vehicles.The results showed that the DATCOM empiric downwash law produces significant errors inlongitudinal stability, while thedownwash method of Dr. Mondhler predicts well the downwash behaviour.A code in MATLAB was developedto compare the longitudinal stability, and generate anin-house code that accurately represent the computational fluids dynamics predictions for the conceptual design process of small unmanned air vehicles.Key Terms⎯DATCOM, Downwash gradient, Longitudinal stability, Low Reynolds number.