In general lots of research is going on about drag reduction and improving the aerodynamic efficiency of flight vehicles, by adopting various methods. The aim of the research is to perform a detailed study on the effects of surface roughness on flow over an aerofoil in the trailing edge.

Smooth profile of an aerofoil is altered by applying certain surface roughness in transition and turbulent boundary layer regions. This alters flow properties and results in reduced total drag and increased aerodynamic efficiency. NACA 0018 aerofoil profile in subsonic condition is considered for the study. 2-D aerofoils with and without roughness are generated using modeling software. Surface modifications are designed on both the upper and lower sides of the aerofoil from 55% to 90% of chord. The models are subjected to CFD analysis for various ? ranging from -20 to +20 degrees in the divisions of 5 degrees and with same velocity by using CFD software.

The results obtained from computational analysis justify the aim of the project. The drag has decreased substantially when the roughness is placed on the upper side and the overall lift and aerodynamic efficiency of the aero foil has been increased when roughness is on the lower side.

This surface roughness can be made as a controllable roughness which will completely eliminate the use of high lifting devices. Simply by using the surface roughness we can increase or decrease the lift and drag value. Takeoff distance will be shortened and this concept will have great impact on advanced combat air crafts.