Investigation of ground effects on Unmanned Aerial Vehicle (UAV) are limited. The UAV''s ground effect on the water surface and irregular surfaces has not been studied well. The principal objective of this research is to apply numerical solutions to investigate the flow physics and aerodynamic characteristics of selected NACA4412 airfoil for different h/c and surface roughness conditions in the ground effect scenario. The k-ω turbulence model and compressible RANS equations are solved using the Finite Volume Method (FVM). The simulated data is authenticated with the reference data and compared with the DATCOM data. The results express that the lift coefficient variations for various surface roughness are affected by the h/c proportion. The drag coefficient for various roughness has the same pattern for different ratios and almost has the same difference from high to lower values. The result shows that the DATCOM code cannot predict the aerodynamic characteristics with ground effects.

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