The effects of an oscillatory zero-net-mass-flux jet (i.e. synthetic jet) acting on a separated flow over a hump are investigated in terms of two actuation parameters – actuator position and forcing frequency. By considering the vorticity flux balance and introducing a centroid of vorticity production over the hump surface, lift and drag acting on the hump can be expressed as a function of this...

Nomenclature AoA = Angle of Attack CDF = Cumulative Distribution Function CoG = Center of Gravity CoV = Coefficient of Variation DLR = Deutsches Zentrum fuer Luftund Raumfahrt (German Aerospace Center) hb = ratio of vehicle bottom height to vehicle height hb2 = height parameter, s. Appendix A H = height of vehicle KS = Kolmogorov-Smirnov distance L = length of vehicle L/Dmax = maximum lift-to-d...

We show by computational solution of the incompressible Navier-Stokes equations with friction force boundary conditions, that the classical inviscid circulation theory by Kutta-Zhukovsky for lift and laminar viscous boundary layer theory by Prandtl for drag, which have dominated 20th century fluid dynamics, do not correctly describe the real turbulent airflow around a sail under tacking. We sho...

Wilson's storm petrel (Oceanites oceanicus) characteristically feeds by ' hovering' over the water surface, but its technique for this is unlike that of other flying vertebrates. The kinematics and aerodynamics of this ' hovering' flight were investigated to determine the possible sources of lift; various nonaerodynamic sources of lift were discounted. It is suggested that the storm petrel soar...

A viscous discrete adjoint approach to automatic aerodynamic shape optimization is developed, and the merits of the viscous discrete and continuous adjoint approaches are discussed. The viscous discrete and continuous adjoint gradients for inverse design and drag minimization cost functions are compared with finite-difference and complex-step gradients. The optimization of airfoils in two-dimen...

Bluff bodies moving in a fluid experience a drag force which usually increases with velocity. However in a particular velocity range a drag crisis is observed, i.e., a sharp and strong decrease of the drag force. This counterintuitive result is well characterized for a sphere or a cylinder. Here we show that, for an object breaking the up-down symmetry, a lift crisis is observed simultaneously ...

We report on the lift and drag forces on a stationary sphere subjected to a wall-bounded oscillatory flow. We show how these forces depend on two parameters, namely, the distance between the particle and the bounding wall, and on the frequency of the oscillatory flow. The forces were obtained from numerical solutions of the unsteady incompressible Navier-Stokes equations. For the range of param...

Some falcons, such as peregrines (Falco peregrinus), attack their prey in the air at the end of high-speed dives and are thought to be the fastest of animals. Estimates of their top speed in a dive range up to 157 m s-1, although speeds this high have never been accurately measured. This study investigates the aerodynamic and gravitational forces on 'ideal falcons' and uses a mathematical model...

This paper puts forward an aerodynamic design method to improve the high-speed performance of aircraft with low-aspect-ratio tailless configuration. The can ameliorate longitudinal moment characteristics configuration by designing and collocating key section airfoils constrains fixed parameters planform shape capacity. Firstly, effect twisting wing, fore-loading aft-reflexing on is evaluated hi...