Global optimisation-based control algorithms applied to boundary layer transition problems

Turbulent flow has a significantly higher drag than the corresponding laminar flow at the same flow conditions. The presence of turbulent flow over a large part of an aircraft therefore incurs a significant penalty of increased fuel consumption due to the extra thrust required. One possible way of decreasing the drag is to apply surface suction to delay the transition from laminar to turbulent flow. However, in order for the gain from the reduction in drag to outweigh the extra costs associated with the suction system, the suction must be distributed in an optimum, or near optimum, manner. In this paper two practical cases are considered. In the first of these a flat plate with panels whose positions are adjustable but do not overlap is treated. Since the cost function in this case is multi-modal, non-smooth and non-convex, methods for solving the optimisation problems necessary to design multi-panel suction systems based on direct search techniques are developed. In the second case considered the problem is that of linear distributed suction over the front part of an aerofoil. For this case, the computational load increases so significantly that in some cases it is not really feasible to continue the investigation using a single processor code. To overcome this, three parallel global optimisation algorithms are developed for the design of multi-panel suction systems on an aerofoil and it is shown that good solutions can be found efficiently

Global-optimization-based methods for use in boundary layer transition control

Turbulent flow has a significantly higher drag than the corresponding laminar flow at the same flow conditions, and therefore incurs a significant penalty of increased fuel consumption due to the extra thrust required. One possible way of decreasing the drag is to apply surface suction to delay the transition from laminar to turbulent flow. In this paper an aerofoil with three non-overlapping panels covering up to 20 per cent of chord for boundary layer transition control is considered. The problem is complicated by the fact that panels can change both their positions and lengths. The complexity of the optimization problem is such that it is not practical to perform the investigation using a single processor. A constrained global parallel algorithm based on a combination of deformed configuration methods and a controlled random search method is developed. It is shown that for the problem considered, good solutions can be found efficiently

Constrained parallel global optimization for boundary layer transition control

Turbulent flow has a significantly higher drag than the corresponding laminar flow at the same flow conditions, and therefore incurs a significant penalty of increased fuel consumption due to the extra thrust required. One possible way of decreasing the drag is to apply surface suction to delay the transition from laminar to turbulent flow. In this paper an aerofoil with 3 non-overlapping panels covering up to 20% of chord for boundary layer transition control is considered. The problem is complicated by the fact that panels can change both their positions and lengths. The complexity of the optimization problem is such that it is not practical to perform the investigation using a single processor. A constrained global parallel algorithm based on a combination of deformed configuration methods and controlled random search method is developed. It is shown that for the problem considered, good solutions can be found efficiently

View Invariant Gait Recognition

Recognition by gait is of particular interest since it is the biometric that is available at the lowest resolution, or when other biometrics are (intentionally) obscured. Gait as a biometric has now shown increasing recognition capability. There are many approaches and these show that recognition can achieve excellent performance on large databases. The majority of these approaches are planar 2D, largely since the early large databases featured subjects walking in a plane normal to the camera view. To extend deployment capability, we need viewpoint invariant gait biometrics. We describe approaches where viewpoint invariance is achieved by 3D approaches or in 2D. In the first group the identification relies on parameters extracted from the 3D body deformation during walking. These methods use several video cameras and the 3D reconstruction is achieved after a camera calibration process. On the other hand, the 2D gait biometric approaches use a single camera, usually positioned perpendicular to the subject’s walking direction. Because in real surveillance scenarios a system that operates in an unconstrained environment is necessary, many of the recent gait analysis approaches are orientated towards viewinvariant gait recognition