Ibraheem AlQadi

Numerical Investigation of Flow Asymmetry Around Slender Body at High Angles of Attack

Flow asymmetry around slender body at high angles of attack is investigated numerically. LES of the flow around an Ogive-cylinder body at high angles of attack is carried out. The asymmetric wake-vortex phenomenon was observed at angles of attack of α = 55◦ and α = 65◦. The results showed that the phenomenon is present in the absence of artificial geometrical or flow asymmetry. An investigation of the unsteady flow field was carried out using dynamic mode decomposition. The analysis identified two dominant unsteady modes; unsteady wake and unsteady shear layer. At angle of attack 45◦ the shear mode is dominant upstream and the low-frequency wake mode is dominant downstream. For α = 55◦ the high-frequency shear-layer is dominant downstream of vortex breakdown. At α = 65◦ the spectrum shows a wide range of modes. Further investigations are necessary to understand the relation between mode switching and the initiation of flow asymmetry as the angle of attack is increased.

Large Eddy Simulation of a NACA-0012 Airfoil Near Stall

Laminar separation bubble (LSB) is a phenomenon that can greatly affect the performance of wings at a low Reynolds number.

Influence of Periodic Forcing on Laminar Separation Bubble

Flow control plays an important role in enhancing aerodynamic characteristics of airfoils such as reducing skin-friction drag, advancing or delaying transition, preventing or triggering separation, and enhancing the lift coefficient. In the review paper of Gad-el-Hak and Bushnell (J Fluid Eng 113, 5–30 (1991)) [6], they provided an extensive review of flow control techniques such as blowing (J Aircr 25, 817–821 (1989)) [11], suction (AIAA J 25, 759–760 (1987)) [13] acoustic excitation (J Fluid Mech 182, 127–148 (1987)) [18], periodic forcing excitation by imposing an oscillating wire or flap upstream the separation location (AIAA J 24, 1956–1963 (1986)) [15], (Phys Fluids Fluid Dyn 2, 179–181 (1989)) [10], (AIAA J 27(6), 820–821 (1989)) [5] and utilization of magnetic field through plasma actuators as documented by Post and Corke (AIAA J 42(11), 2177–2184 (2004)) [12] and Huang et al. (AIAA J 44(7), 1477–1487 (2006)) [7].

Numerical simulation of surface porosity in presence of wing-vortex interaction

Purpose – The purpose of this paper is to identifying ways to reduce the effects of wing-vortex interaction by applying surface porosity on selected areas of the exposed surface. A number of papers recently have investigated the aerodynamic implication of free-stream vortices impinging upon airfoils. Design/methodology/approach – The free-stream disturbance in these studies were represented by planting a vortex ahead of the wing or using some other disturbance invoking mechanism like von-Karman vortices in the wake of a cylinder or using a flipping plate to invoke a discrete vortex. In the present work, a well-defined method was used to germinate a system of controlled vortices of known strength, size and frequency ahead of the wing, and the impact of the subsequent interaction was studied with and without the presence of the surface porosity. The simulations tackled a number of cases when porosities of up to 20 and 22 per cent were applied to selected regions near the leading edge, with vortices of contr...