An aerodynamic/hydrodynamic investigation of water cross-over is performed for a bionic unmanned aquatic-aerial amphibious vehicle (bionic UAAV). According to flying fish features and UAAV flight requirements of water cross-over, the bionic conceptual design of crossing over water is described and planned in multiple stages and modes of motion. A solution procedure for the numerical simulation method, based on a modified SST turbulence model and the VOF model, is expressed, and a verification study is presented using a typical case. Longitudinal-lateral numerical simulation analysis investigates the cruise performance underwater and in the air. The numerical simulation and principal experiment verification are conducted for crossing over water and water surface acceleration. The results indicate that the bionic UAAV has an excellent aerodynamic/hydrodynamic performance and variant configuration to adapt to water cross-over. The bionic UAAV has good water and air navigation stability, and the cruise flying lift-drag ratio is greater than 15 at a low Reynolds number. Its pitching moment has the phenomenon of a "water mound" forming and breaking at the water cross-over process. The present method and the bionic variant configuration provide a feasible water cross-over design and analysis strategy for bionic UAAVs.
Keywords: aerodynamic/hydrodynamic; aquatic-aerial amphibious vehicle; bionic design; experiment investigation; numerical simulation; water cross-over.