ABSTRACT: This paper presents the overall pros and cons of the effect of surface roughness elements over a NACA 4412 tapered, swept back half wing with a sweep angle of 30º and a dihedral angle of 5º. The tests were conducted at a Reynolds number of 4 × 105 in the IIUM Low Speed wind tunnel. Different roughness sizes and roughness locations were tested for a range of angle of attack. Lift, drag and pitching moment coefficients were measured for the smooth wing and with roughness elements. Surface roughness delays the stall angle and decreases the lift. The wing with the roughness elements located at 75% to 95% of mean chord from leading edge shows minimum drag and maximum lift compared to other locations. Significant increase in the pitching moment coefficient was found for flexible roughness elements. In case of rigid surface roughness, the effect on pitching moment is small.

ABSTRACT In this research, an experimental investigation was carried out at the International Islamic University Malaysia - Low Speed Wind Tunnel facility on a generic model of a hybrid lifting hull. Based on the historical trends of non-rigid airships, the fineness ratio of the said hull has been selected equal to 4. Free stream velocity was kept at 20 m/s and, along with the estimation of aerodynamic parameters, longitudinal and lateral stability characteristics were determined over a range of angles of attack from −8° to +12° and angles of sideslip from −10° to +10°. Zero lift coefficient was obtained at −4.2°, and the corresponding value was found to be greater than that at zero angle of attack. The comparison of the experimental results with the existing analytical relationships of wing has revealed that such an airfoil shaped hull cannot be considered as a wing due to 37% less analytical value of lift coefficient than that obtained by CFD simulations of the said hull. Existing equation of form factor of hull for conventional airships was also revisited, and a correction factor equal to 1.16 in the fundamental drag equation of aircraft’s fuselage was also proposed for fineness ratio equal to 4. Trends of the experimental data and mabsmoraiscomparison of the same with the theoretical calculations and computational results posed some interesting findings. The longitudinal and directional stabilities of a hybrid lifting hull were found to be statically unstable.

ABSTRACT Birds are known for their agility, manoeuvrability, and flexibility during flight. These features allow their ability to fly under a large range of flight conditions. Bio flyers and bio aerodynamic/fluid surfaces have inspired many to perform experiments and simulations as well as to relate their results to engineering applications. Wings specifically have been the most inspirational element. Aerodynamic forces, structure, unsteady flow, fluid-structure interaction, flow control, flow adaptive elements and mechanisms, flow vortices, flapping mechanisms, and hovering flight of birds are examples of research interests. This paper presents an overview of prior analyses and experiments on the aerodynamic performance and mechanical properties of birds in steady non-flapping flight.