Numerical investigations on the flow over NACA 0012 aerofoil are carried out to provide better understanding of the unusual lift characteristics exhibited by this aerofoil at low Reynolds numbers. Computations are carried out at Re = 10,000–100,000, for different values of angles of attack and freestream turbulenceintensity. There exists a narrow range of these parameters where the net circulation around this symmetrical aerofoil is negative, leading to the generation of negative lift at positive angles of attack. Different flow regimes are identified and physical explanations are given for this unusual behaviour of negative lift, andthe influence of different flow parameters is discussed.

This paper describes the design of a miniature air suction system to house a chemical sensor. It has been designed to improve the aerodynamic chemical sensing efficiency and to have a low weight since it is meant to be mounted on a micro air vehicle. The design is done around a readily available miniature axial flow fan by computational methods. A converging-diverging shape for the air suction system with the sensor disc having a central hole and mounted at the throat is proposed as good design concept. The systematic approach hasled to a light weight system with high aerodynamic efficiency even under extreme flow conditions that may be caused by MAV manoeuvre or cross winds.